Family Pedigree

Thursday February 7, 2019

A pedigree analysis chart, usually used for families, allow us to visualize the inheritance of genotypes and phenotypes (traits). In this chart, the P, F1, and F2 generation are represented by the numerals I, II, and III respectively. Notice that those carrying the trait are colored red, and those not carrying the trait (the normal-looking ones) are in blue. The normal, non-trait carrying organisms on the chart are called the wild-type.


The term wild-type is used in genetics often to refer to organisms not carrying the trait being studied. For example, if we were studying a gene that turns house-flies orange, we would call the normal-looking ones the wild-type.


Let’s make a pedigree for your family. Here’s what you need:


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Materials:
• Paper
• Pen
• Access to a photocopier (optional)


Before starting this science project, you should go through your reference material and familiarize yourself with the proper way to draw a human pedigree (shown below)



To start this project, draw a pedigree showing the different members of your family.


a. Include as many family members as you can get data from. The more people and generations you include, the more likely it is that you’ll have enough information to determine the mode of inheritance.


b. You might need help from your parents to figure out all the relationships.


2. If you have access to a photocopier, make four copies of the pedigree—one for each trait you are going to evaluate. If photocopying isn’t an option, manually copy the pedigree.


3. Determine the phenotype of each person on your pedigree for each of the four traits. Use a separate pedigree for each trait. Examples are: eye-color, hair color, widow’s peak, height. Note: Widow’s peak can vary considerably; score any sort of V-shaped hairline as positive.


4. From your pedigrees, can you deduce the mode of inheritance for each trait? For which traits is your pedigree informative? If you don’t have enough information to determine the mode of inheritance of a particular trait, try making a pedigree for another family.




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Extracting DNA in your Kitchen

Monday May 2, 2011

If the cell has a nucleus, the DNA is located in the nucleus.  If not, it is found in the cytoplasm.  DNA is the genetic material that has all the information about a cell.


DNA is a long molecule found in the formed by of two strands of genes. DNA carries two copies—two “alleles”—of each gene. Those alleles can either be similar to each other (homozygous), or dissimilar (heterozygous).


We’re going to learn how to extract DNA from any fruit or vegetable you have lying around the fridge. Are you ready?


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Materials:


  • pumpkin OR apple OR squash OR bananas OR carrots OR anything else you might have in the fridge
  • dishwashing detergent
  • 91% isopropyl alcohol
  • coffee filter and a funnel (or use paper towels folded into quarters)
  • water
  • blender
  • clear glass cup


Download Student Worksheet & Exercises


Procedure:


Step 1: First, grab your fruit or vegetable and stick it in your blender with enough water to cover. Add a tablespoon of salt and blend until it looks well-mixed and like applesauce. Don’t over-blend, or you’ll also shred the DNA strands!


Step 2: Pour this into a bowl and mix in the detergent. Don’t add this in your mixer and blend or you’ll get a foamy surprise that’s a big mess. You’ll find that the dishwashing detergent and the salt help the process of breaking down the cell walls and dissolving the cell membranes so you can get at the DNA.


Step 3: Place a coffee filter cone into a funnel (or use a paper towel folded into quarters) and place this over a cup. Filter the mixture into the cup. When you’re done, simply throw away the coffee filter. Note: Keep the contents in the cup!


Step 4: Be careful with this step! You’ll very gently (no splashing!) pour a very small about of alcohol into the cup (like a tablespoon) so that the alcohol forms a layer above the puree.


Step 5: Observe! Grab your compound microscope and take a sample from the top. You’ll want a piece from the ghostly layer between the puree and the alcohol – this is your DNA.


What’s going on?


Veggies and fruits are made of water, cellulose, sugars, proteins, salts, and DNA. To get at the DNA, you first need to get inside the cells and separate it out from the other parts. The blender breaks up the fibers that hold the cells together.


The salt and detergent are added next so they can break down the cell walls. Cell walls of plants are made of cellulose. Inside that cellulose is another cell wall (cell membrane). This membrane has an outer later of sugar and an inner layer of fat.


The detergent is a special molecule that has an attraction to water and fats (which is why it works to get your dishes clean). The end of the molecule that is attracted to fat attaches to the fat part of the cell membrane. When you stir up the mixture, it breaks up the membrane (since the other end likes water). It wedges itself inside and  opens the cell up… which causes the DNA to flow out.


Since DNA dissolves in water, it stays in the vegetable juice. When alcohols is added, the DNA “comes out” of solution as the ghostly white strands seen at the bottom of the alcohol layer.


For Advanced Students:


For advanced students, here’s a set of videos that detail the cell walls, the basic biological molecules, DNA and RNA and how everything works together.


First watch this video below to see how we broke down the cell walls in the DNA extraction experiment:



Here’s a video on how DNA and RNA work:



Here’s a video that describes how the four biological molecules (proteins, lipids, carbohydrates, and nucleic acids) work:



Exercises


  1. What are fruits and veggies made of?
  2.  What does DNA stand for?
  3.  What is DNA?
  4.  What is a gene?
  5.  Describe the structure of DNA.

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Tracking Traits

Monday May 2, 2011

Why do families share similar features like eye and hair color? Why aren’t they exact clones of each other? These questions and many more will be answered as well look into the fascinating world of genetics!


Genetics asks which features are passed on from generation to generation in living things. It also tries to explain how those features are passed on (or not passed on). Which features are stay and leave depend on the genes of the organism and the environment the organism lives in. Genes are the “inheritance factors “described in Mendel’s laws. The genes are passed on from generation to generation and instruct the cell how to make proteins. A genotype refers to the genetic make-up of a trait, while phenotype refers to the physical manifestation of the trait.


We’re going to create a family using genetics!


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Materials
• Paper or use this Genetics Table
• Two different coins
• Scissors
• Glue or Tape



Download Student Worksheet & Exercises


Step one: Creating the Parent Generation

  1. First you’re going to create the genetic make-up of the parents. Here’s how:
  2. Take out the Genetics Data Table, and flip the first coin to create the genetic profile for the mother.
  3. Flip the coin and in the Mother’s Hair trait column, write D for dominant if the coin reads heads, and R for recessive if tails in the table.
  4. Flip the coin again. In the Mother’s Hair trait column right after the first trait, write D for dominant if the coin reads heads, and R for recessive if tails in the table.
  5. If you flipped heads the first time and tails the second, you’d write “DR” in the Mother’s Hair box.
  6. Continue this process for all of Mother’s traits. You should have two letters in each box for the entire column.
  7. Repeat steps 3-6 for Father. When you’ve completely filled out Mother’s and Father’s columns, you’ve completed the paternal genetic profile. Now you’re ready for the next part:

Step two: The Child

  1. Will the child be a boy or a girl? To determine this, flip the second coin. Heads for a boy, tails for a girl. After this is decided, circle boy or girl under “child 1” on the Genetics Data Table.
  2. Now the first coin will represent the gene from the mother and the second coin will represent the gene from the father.
  3. Start with the Hair trait: Flip both coins. If the first coin is tails, take the first trait from the mother. If the first coin is heads, take the second trait.
    1. For example, if the first coin is tails, and the mother’s code is DR, then write “D” in the child one column for hair.
    2. Do the same thing for the father’s traits with the second coin. For example, if the second coin is heads, and the father’s code is DR, then write “R” in the Hair Trait column of child 1.
    3. By the end of this step, child 1 should have one letter from the mother, and one letter for the father in child 1’s hair trait column.
  4. Use the same steps used to find the genetic code for the hair trait to find the code for the rest of the traits. By the end all the traits should have one letter from the mother’s genetic code and one letter from the father’s genetic code.

Step 3: What the Child Looks Like

Grab a sheet of paper and start drawing the child. If the genetic code for a trait has a “D” in it, then the dominant trait is used.


For example, if the hair color is DD, DR, or RD then the hair color is dark. If the hair color code is RR, then the hair color is light. Draw the traits on your paper!


You can repeat this for as many children as you would like in your family.


Step 4: Make another family and compare!

Are all families alike? What if you try this process again for another family? Do you see any similarities or differences? Do similar features come from dominant genes? Do differences come from recessive genes? What other traits would you include? Write this in your science journal!


Conclusions:

In fact, most similarities should come from the dominant genes because they are expressed more often. The recessive genes are expressed less often, so the create the differences.


Extra credit:

What percent of the children expressed the dominant allele of each trait? Did you get Mendel’s results? Do the calculations and check it out!


Exercises


  1. What is the difference between a genotype and a phenotype?
  2. What is a dominant trait?
  3. What is a recessive trait?
  4. Assume B=Black hair and b=blond hair.  Make a Punnet square to cross Bb with bb. Tell what the possibilities are for offspring hair color.
  5. Why don’t traits simply average out in offspring.  For example, why does a tall plant crossed with a short plant not yield a bunch of average-sized plants?
  6. In your activity, what percent of the children expressed the dominant allele of each trait? Did you get Mendel’s results? Do the calculations and check it out!

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Family Pedigree

Monday May 2, 2011

A pedigree analysis chart, usually used for families, allow us to visualize the inheritance of genotypes and phenotypes (traits). In this chart, the P, F1, and F2 generation are represented by the numerals I, II, and III respectively. Notice that those carrying the trait are colored red, and those not carrying the trait (the normal-looking ones) are in blue. The normal, non-trait carrying organisms on the chart are called the wild-type.


The term wild-type is used in genetics often to refer to organisms not carrying the trait being studied. For example, if we were studying a gene that turns house-flies orange, we would call the normal-looking ones the wild-type.


Let’s make a pedigree for your family. Here’s what you need:


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Materials:
• Paper
• Pen
• Access to a photocopier (optional)


To start this project, draw a pedigree showing the different members of your family.


a. Include as many family members as you can get data from. The more people and generations you include, the more likely it is that you’ll have enough information to determine the mode of inheritance.


b. You might need help from your parents to figure out all the relationships.


2. If you have access to a photocopier, make four copies of the pedigree—one for each trait you are going to evaluate. If photocopying isn’t an option, manually copy the pedigree.


3. Determine the phenotype of each person on your pedigree for each of the four traits. Use a separate pedigree for each trait. Examples are: eye-color, hair color, widow’s peak, height. Note: Widow’s peak can vary considerably; score any sort of V-shaped hairline as positive.


4. From your pedigrees, can you deduce the mode of inheritance for each trait? For which traits is your pedigree informative? If you don’t have enough information to determine the mode of inheritance of a particular trait, try making a pedigree for another family.



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Cell in Action

Monday May 2, 2011

Cells make up every living thing. Take a look at all the living things you can see just in your house. You can start off with you and your family. If you have any pets, be sure to include them. Don’t forget about houseplants as well – they’re alive. Now take a walk outside. You’ll likely see many more plants, as well as animals like birds and insects. Now imagine if all those living things were gone. That’s how it would be if there were no cells, because cells are what all those living things are made of.


Animals, plants and other living things look different, and contain many different kinds of cells, but when you get down to it, all of us are just a bunch of cells – and that makes cells pretty much the most important thing when it comes to life!


Here’s a video on the difference between animal and plant cells:



Are you wondering what all the different organelles are inside the cell? Here’s a video that goes into all the cool detail (note – this video is more for advanced students):



Now pull out your science journal! As you watch this video below, write down the organelles you see and describe what you think is happening.



What’s going on?


The endoplasmic reticulum, shown in red, transports proteins to the Golgi Apparatus, shown in blue. The Golgi Apparatus packages proteins and sends them where they are needed, either in the cell, or to the cell membrane for transport out of the cell.


Protozoa in the Grass

Monday May 2, 2011

This experiment allows you to see protozoa, tiny-single celled organisms, in your compound microscope. While I can go in my backyard and find a lot of interesting pond scum and dead insects, I realize that not everybody has a thriving ecosystem on hand, especially if you live in a city.


I am going to show you how to grow a protozoa habitat that you can keep in a window for months (or longer!) using a couple of simple ingredients.


Once you have a protist farm is up and running, you’ll be able to view a sample with your compound microscope. If you don’t know how to prepare a wet mount or a heat fix, you’ll want to review the microscope lessons here.


Protozoa are protists with animal-like behaviors. Protists live in almost any liquid water environment. Some protists are vital to the ecosystem while others are deadly.


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Download Student Worksheet & Exercises


Here’s how you can grow your own to look at under a compound microscope:


1. Leave a glass of water out overnight, to get rid of chlorine. If you are in a hurry, use filtered water (not distilled) instead.


2. Add dead grass to the glass of water. Stir.


3. Add yeast to the glass. Stir again.


4. Allow the glass to sit overnight in a warm place. For best results, let grow and ferment for several weeks.


5. Each day for a week, observe a sample of water and/or grass under the microscope, after the first 24 hours.


6. Sketch the protozoa you see, and note if there are more or less of a certain type as time goes on in your science journal.


Exercises


  1. What is a cell?
  2.  Why are cells so small?
  3.  What is a protozoa?
  4.  How does it develop?

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Celery Stalk Water Race

Monday May 2, 2011

If you think of celery as being a bundle of thin straws, then it’s easy to see how this experiment works. In this activity, you will get water to creep up through the plant tissue (the celery stalk) and find out how to make it go faster and slower.


The part of the celery we eat is the stalk of the plant.  Plant stalks are designed to carry water to the leaves, where they are needed for the plant to survive.  The water travels up the celery as it would travel up any plant.


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Download Student Worksheet & Exercises


1. First, find four celery stalks about the same size with leaves still attached.


2. Mix up a four-cup batch of colored water (try purple).


3. Place your celery stalks in the water, leaf-end up. After an hour or two, take it out and place it on the paper towel. Label your celery stalk with the each time length it was in the water.


4. Repeat this for different increments of time. Try one overnight!


5. Use a ruler and measure how high the water went. Record this in your science journal.


6. Now make a graph that compares the time to distance traveled by placing the time on the horizontal axis and the distance traveled on the vertical.


7. What happens if you start with hot water? Ice cold water? Salt water?


8. What happens if you cut the celery stalk at the base high enough so it straddles two cups of different colors?


Exercises


  1. What two types of transport move substances into a cell?
  2. How does water get into the celery?
  3. What are the tubes in celery called?
  4. In what direction does air flow? Hint: Think of the balloon example.
  5. What happens to the water after it travels through a plant?
  6. Use answers 1-4 to describe the process of water traveling through a celery stalk.

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Bacteria in Humans and Dogs

Monday May 2, 2011

Some organisms, like bacteria, consist of only one cell. Other organisms, like humans, consist of trillions of specialized cells working together. Even if organisms look very different from each other, if you look close enough you’ll see that their cells have much in common.


Most cells are so tiny that you can’t see them without the help of a microscope. The microscopes that students typically use at school are light microscopes.


Robert Hooke created a primitive light microscope in 1665 and observed cells for the very first time. Although the light microscope opened our eyes to the existence of cells, they are not useful for looking at the tiniest components of cells. Many structures in the cell are too small to see with a light microscope.
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In this experiment, you will get to observe single-celled organisms (bacteria, actually) that live in the mouths of both humans and dogs using your compound microscope.


1. You’ll need to get your materials together. Be sure to label the Petri dishes and have your other equipment out: the cotton swabs, the canine volunteers and the human volunteers.


2. First, scrape the inside of a volunteer’s cheek use the cotton tip to swab. Swirl the cotton swab onto a Petri dish.


3. Repeat this for the rest of your human and dog volunteers.


4. Find a dark, warm spot for your Petri dishes to live in that won’t be disturbed for at least 24 hours.


5. After a day, remove the Petri dishes and place it next to your compound microscope.


6. Use a fresh swab to move the bacteria from the Petri dish to the slide and use a staining technique (covered in the Microscope Lab).


7. View each of your specimens, recording everything as you go along.


8. So what do you think? Whose mouth is cleaner – dogs or people?


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Colored Flowers

Monday May 2, 2011

When plants are watered, the water travels up the roots of the plant, and to all of the plant’s parts.  So, with sunlight and time, the colored water eventually made to the plant’s flowers, creating the color change you observed.


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1. Mix the food color in the water.


2. Pour the colored water into the glass.


3. Take the flowers (with intact stalks) and place them in the flask, so that half of the stalk is submerged under water.


4. Place the flask in the window, or any other place, which will provide sufficient sunlight for the plant.


5. Observe the color of the flowers over a period of time


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Cell Walls of Cotton

Monday May 2, 2011

cotton-plantThe cell wall organelle supports and protects the cell.  Cell walls have small holes, called pores, in them.  This lets water, nutrients, and other substances into the cell.


Here’s what you do:


First, take out your science journal. Write down how many cotton balls you think will fit into a full glass of water without spilling any water.


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1. Fill a glass of water so it is completely full. No spilling!


2. Take a cotton ball and try to add it to the glass of water without spilling any water.


(Hint: Scrunch up the cotton ball, and slowly get it wet, then allow it to fall in.)


3. Get as many cotton balls into the cup as you can.


What’s going on?


In this experiment, you were able to get the cotton balls in the water because cotton balls are mostly air. Even the strands of cotton are mostly air, because the strand is just the cell wall from the cotton plant.


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Osmosis in Potatoes & Beans

Monday May 2, 2011

One way substances can get into a cell is called passive transport. One special kind of passive transport is osmosis, when water crosses into the cell. This experiment allows you to see the process of osmosis in action. Are you ready?


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Download Student Worksheet & Exercises


1. Cut two thin slices of potato. The pieces should be about the same thickness and be slightly flimsy.


2. Place both slices in separate glasses of water.


3. Add salt to one of the glasses.


4. Wait about 15 minutes.


5. Pull out the two pieces of potato and make observations in our science journal.


Did you notice that the potato slice in the fresh water became a little stiffer, while the potato in salt water became rather flimsy?  Remember that cells are made of water, and that the water in the cells flows from areas of low salt concentration to high salt concentration.  That means that if the water outside the cell is saltier than the water inside, water will move from the inside of the cell to the outside. As the water left the cell it was like letting the air out of a balloon. As more and more of the cells lost water, the slice of potato became soft and flexible.  If the water inside was saltier, the opposite happens, and some water goes into the cells, stiffening them up.


Osmosis is the diffusion of water molecules through a membrane, where the water molecules move from high water concentration to areas of low water concentration.


Salt starts osmosis by attracting water and causing the water to move toward and across the membrane. Remember that salt is a solute, and when water is added to a solute, it spreads out (diffuses) the concentration of salt, and that creates a chemical solution.


Imagine the salt concentration inside a cell being the exact same as the salt concentration outside the cell – what would happen? Right – the water level will stay the same and nothing would happen. Now imagine there’s more salt inside of a cell than outside it. What happens now? The water moves through the membrane into the cell causing it to swell with water.


If the cell is placed in a higher concentration of salt (like sticking a carrot in a salt bath), the water will leave the cell, and that’s why the plant cells shrink and wilt. This is also why salt kills plants, because it takes water from the cells. This doesn’t just happen in plants, though. Animals can also get dehydrated if they drink ocean water.


Questions to Ask:


  1. How was the concentration of salt different in each cup?
  2. Which direction was water flowing in each cup?
  3. Why did one potato become stiff, while the other became flimsy?

Let’s do this experiment again, but use beans instead of potatoes.


1. Place enough beans and water in a glass to completely fill it


2. Place the glass on a cookie sheet


3. Leave the glass alone for several hours… even overnight!


4. While you wait, take out your science journal and write about what you expect to happen. When your experiment is ready, record what you found.


Questions to Ask:
1. The beans should begin to fall out of the water. If you look at them, you will see that they have expanded. What happened?


2. Where was the concentration of water greater – inside or outside of the beans? Explain.


Exercises


For Potatoes


  1. How was the concentration of salt different in each cup?
  2. Which direction was water flowing in each cup?
  3. Why did one potato become stiff, while the other became flimsy?

For Beans


  1. If you look at the beans, you will see that they have expanded. What happened?
  2. Where was the concentration of water greater – inside or outside of the beans? Explain.

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Carbon Dioxide and Photosynthesis

Monday May 2, 2011

Photosynthesis is a process where light energy is changed into chemical energy.  As we said in the last section, this process happens in the chloroplast of plant cells.  Photosynthesis is one of the most important things that happen in cells.


In fact, photosynthesis is considered one of the most important processes for all life on Earth.  It makes sense that photosynthesis is really important to plants, since it gives them energy, but why is it so important to animals?  Let’s learn a little more about photosynthesis and see if we can answer that question.


There are many steps to photosynthesis, but if we wanted to sum it up in one equation, it would be carbon dioxide (CO2) + water (H2O) makes glucose (C6H12O6) and oxygen (O2).  These words can be written like this:


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6CO2 + 6H2O + Light Energy –> C6H12O6 + 6O2


Carbon dioxide, water, and energy combine to form glucose and oxygen.


We learned in the last section that glucose is a kind of sugar.  This sugar is important for energy, so the plant stores all the glucose it creates.  However, the plant releases the oxygen it creates.


Now we can see two reasons why photosynthesis is so important not just to plants, but to animals too.  First, all animals need oxygen to live.  Photosynthesis produces oxygen, so without this process, animals could not survive.  Also, don’t forget that since animals can’t make their own food, they have to eat plants, or eat other animals that have eaten plants.  So without plants, animals would quickly run out of food.


This experiment will demonstrate that carbon dioxide is necessary in photosynthesis.


Materials:


  • candle
  • lighter with adult help
  • large glass jar
  • stopwatch
  • leafy plant (weeds work also)

Optional: sodium hydroxide and iodine



Download Student Worksheet & Exercises


1.Light your candle. invert the glass over it and time how long it takes the candle to use up all the oxygen and extinguish itself. Write this number down in your journal.


2. Find a young plant or bush, preferably with a lot of growth and leaves. Place your candle next to the plant (don’t burn your plant!) and invert the jar over it again.  Use your stopwatch to time how long the candle stays lit. Write this number down in your journal.


3. Which one do you expect to take longer? What actually happened?


OPTIONAL BUT DANGEROUS…


Place the caustic soda on a disposable plate. Don’t get this on  your hands or eyes – it’s very corrosive. Handle this chemical ONLY with gloves and keep away from small children and pets like dogs and cats.


Place the caustic soda next to the plant and cover with the glass. Leave this setup undisturbed for a few hours. When you’re done, take a leaf from the plant and do an iodine test on it to find out if there is starch present. Simply place a drop of iodine on the leaf. Iodine changes to dark blue when starch is present.


Exercises


  1. Describe the process of photosynthesis in words.
  2. Write the chemical equation for photosynthesis.
  3. What is glucose?
  4. Why is glucose important for plants?
  5. Why are plants necessary for animals?
  6. Does the result of the experiment depend on how large the plant is? Why or why not?

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Onion Mitosis

Monday May 2, 2011

In eukaryotes there is a nucleus, so a more complex process called mitosis is needed with cell division. Mitosis is divided into four parts, or phases:


Phase 1 – Prophase: In this phase the nuclear membrane begins to break down and the DNA forms structures called chromosomes.


Phase 2 – Metaphase: In this phase the chromosomes line up along the center of the parent cell


Phase 3 – Anaphase: In this phase, the chromosomes break apart, with a complete set of DNA going to each side of the cell


Phase 4 – Telophase: In this phase, a new nuclear membrane forms around each of the sets of DNA


The four stages of mitosis (the cell at the top has not started mitosis) lead to two daughter cells.


A little after telophase, the cytoplasm splits and a new cell membrane forms.  Once again, two daughter cells have formed.  Take a look at this animation for a good overview of mitosis and see if you can identify all the phases.


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Cells continue to divide until a protein tells them to stop.  As they divide, they become different and specialized, eventually making the tissues and organs found in the many different living things we see every day.



Download Student Worksheet & Exercises


Mitosis is part of the cell cycle, a larger process that living organisms use to repair damage, grow, or just maintain condition. In this experiment, we’re going to figure out the time it takes for a cell to go through each of the four mitosis states.


Grab your science journal and here’s what you do:


Materials:


  • Compound microscope with slides and coverslip
  • Onion (the root tip, not the onion itself) – you can grow your own if you can’t find any at the store (see image at above left). Place the bottom of an onion in a glass of water for a couple of days and you’ll see the roots grow to the size you need (about 2 cm long).
  • Science journal

First, set up your microscope.


Next, prepare an onion sample. Take it from the root tip called the meristematic zone (use the picture on the right), just above the root cap at the very end of the tip.


Use the staining technique we show in our Microscope Lab. Cut the sample lengthwise before placing it on the slide.


If you want to stop the cell division process while you watch the slide, you’ll need to prepare a heat fix mount instead (make sure you don’t boil the liquid when you use the candle or you’ll ruin your slide). You can add a drop or two of stain after the heat fix and blot the excess with a paper towel. Add a drop of water and a coverslip and you’re ready to look!


Try different powers of magnification to find the four different stages of mitosis. Count the number of cells found at each stage of mitosis and figure out the percentage. (Total up the number of cells and use this number to divide each count by. Don’t forget to multiply by 100 for percentage!)


Out of all four stages of mitosis, which one takes the most time to complete? The shortest time? What happens to the process if we skip metaphase?


Cell division. Mitosis.


Exercises


  1. What is mitosis?
  2.  What are the four stages of mitosis?  Briefly describe what happens in each.
  3. Out of all four stages of mitosis, which one takes the most time to complete? The shortest time? What happens to the process if we skip metaphase?

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Cool Carrot Osmosis

Monday May 2, 2011

The carrot itself is a type of root—it is responsible for conducting water from the soil to the plant. The carrot is made of cells. Cells are mostly water, but they are filled with other substances too (organelles, the nucleus, etc).


We’re going to do two experiments on a carrot: first we’re going to figure out how to move water into the cells of a carrot. Second, we’ll look at how to move water within the carrot and trace it. Last, we’ll learn how to get water to move out of the carrot. And all this has to do with cells!


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Osmosis is how water moves through a membrane. A carrot is made up of cells surrounded by cell membranes. The cell membrane’s job is to keep the cell parts protected. Water can pass through the membrane, but most things can’t.


And water always moves through cell membranes towards higher chemical concentrations. For example, a carrot sitting in salt water causes the water to move into the salty water. The water moves because it’s trying to equalize the amount of water on both the inside and outside of the membrane. The act of salt will draw water out of the carrot, and as more cells lose water, the carrot becomes soft and flexible instead of crunchy and stiff.


You can reverse this process by sticking the carrot into fresh water. The water in the cup can diffuse through the membrane and into the carrot’s cells. If you tie a string around the carrot, you’ll be able to see the effect more clearly! Here’s what you do:



Download Student Worksheet & Exercises


Experiment #1: Water moving INTO the carrot via osmosis and UP the carrot.

In this experiment we will see the absorption of water by a carrot. Make note of differences between the carrot before the experiment, and the carrot afterward.


Materials


  • 2 carrots
  • Sharp knife (be careful!)
  • Cutting board
  • Glass
  • Water
  • Food coloring

Procedure :


Step 1: Cut the tip off of a carrot (with adult supervision).


Step 2: Place the carrot in a glass half full of water


Step 3: Place the carrot somewhere where it can get some sunshine.


Step 4: Observe the carrot over several days.


What’s going on?

When surrounded by pure water, the concentration of water outside the carrot cells is greater than the concentration inside. Osmosis makes water move from greater concentrations to lesser concentrations. This is why the carrot grows in size—it fills with water!


Procedure:

Step 1: Re-do the four steps above in a new cup, and this time put several (10-12) drops of food coloring into the water.


Step 2: With the help of an adult, cut the carrot in half length-wise.


What’s going on?

Carrots are roots. They conduct water from the soil to the plant. If we were to repeat this experiment several times—first cutting the carrot at half a day, then one day, then one day and a half, etc—we would see the movement of the water up the root.


Experiment #2: Water moving OUT of the carrot via osmosis

In this experiment we answer the question “what if the concentration of water is greater inside the carrot?”


Materials


  • Large carrot
  • 3 tablespoons of salt
  • Two glasses
  • String
  • water

Procedure

Step 1: Snap the carrot in half and tie a piece of string around each piece of carrot (make sure they’re tied tightly).


Step 2: Place each half in a glass half full of warm water.


Step 3: In one of the glasses, dissolve the salt.


Step 4: Leave overnight.


Step 5: The next morning pull on the strings. What do you observe?


What’s going on?

The salt-water carrot shrunk while the non-salt-water carrot bloated!


This is because of osmosis. Carrots are made up of cells. Cells are full of water. When the concentration of water outside the cell is greater than the concentration of water inside the cell, the water flows into the cell. This is why the non-salt-water carrot bloated—the concentration was greater outside the cell than inside. The concentration of water was greater inside the salt-water carrot than outside (because there was so much salt!) so the water flowed out of the cell. This made the salt-water carrot shrink.


Questions to Ask:

  1. What happens if you try different vegetables besides carrots?
  2. How do you think this relates to people? Do we really need to drink 8 glasses of water a day?
  3. What happens (on the osmosis scale) if humans don’t drink water?
  4. Use your compound microscope to look at a sample and draw the cells (both before and after taking a bath in the solution) in your science journal.
  5. What did you expect to happen to the string? What really happened to the string?
  6. Which solution made the carrot rubbery? Why?
  7. Did you notice a change in the cell size, shape, or other feature when soaked in salt water? (Check your journal!)
  8. Why did we bother tying a string? Would a rubber band have worked?
  9. What would happen to a surfer who spent all day in the ocean without drinking water?
  10. What do you expect to happen to human blood cells if they were placed in a beaker of salt water?

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Genetics Exercises

Monday May 2, 2011

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.


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1. Define “genetics” in your own words.
2. Describe Mendel’s experiments with peas.
3. What do P, F1, and F2 represent?
4. What were Mendel’s findings regarding tall vs short crosses?
5. According to Mendel’s law of segregation, what are dominant and recessive traits?
6. What is a Punnett Square?
7. An orange amoeba and a red amoeba walk into a bar. Several years later they get married and have a batch of beautiful, red kids. The kids then marry each other and have kids. 75% of that last generation is red, and 25% is orange. According to Mendel’s theories, which color is dominant? Which is recessive? How do we know?
8. What are genes?
9. What is the difference between phenotypes and genotypes?
10. What is the difference between incomplete dominance and codominance?
11. What are genetic disorders?
12. If a gene is sex-linked, which chromosomes could it be found on?
13. In a study on the gene that gives flies wings, 30 of the F1 generation were wingless, and 100 looked like normal flies. How many were wild-type?
14. What are restriction enzymes?
15. What did the Human Genome Project accomplish?
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Cells Exercises

Monday May 2, 2011

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.


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1. Why are cells called the “building blocks” of life?
2. Anton van Leeuwenhoek discovered animals no one had ever seen before. How was he able to do this?
3. You leave some bread on your counter. After a few days, you notice some mold growing on the bread. According to the cell theory, where did the cells that make this mold come from?
4. How does the shape of a nerve cell help it do its job?
5. If a cell had no cell membrane, what might happen to it? Why?
6. Where are the organelles found in a cell?
7. If a cell was making proteins, but the proteins were not the type the cell needed, what organelle is most likely not working properly? Why?
8. How are prokaryotes different from eukaryotes?
9. What are three places ribosomes are found?
10. How is the endoplasmic reticulum like a freeway?
11. What might happen in a cell if the Golgi Apparatus was not working properly?
12. What does the mitochondrion do in the cell?
13. How are vesicles and vacuoles similar? How are they different?
14. Name two organelles found in plant cells, but not animal cells.
15. What might happen to a plant if its cells didn’t have cell walls?
16. Thinking about the organelles they have, why can’t animals undergo photosynthesis?
17. Imagine that the wall of a dam breaks, and water begins rushing through the hole in the wall. Explain this in terms of concentration.
18. Nutrient X has a higher concentration inside a cell than outside a cell. Will active or passive transport be required to get nutrient X into the cell? Explain.
19. Is it possible for a protein to assist something cross the cell membrane, and have it still be considered passive transport? Explain.
20. Why is photosynthesis important to plants? Why is it important to animals?
21. Your friend tells you that photosynthesis “creates” energy for plants. How would you correct this statement?
22. How is glucose used differently than ATP in the cell?
23. What is the purpose of cellular respiration?
24. Name two types of cell division used by prokaryotes.
25. Why does the nucleus need to break down during mitosis?


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Answers to Cells Exercises

Monday May 2, 2011

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!


Simply click here for printable questions and answers.


Answers:
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1. All living things are made of them
2. Using his microscope, he was able to see things smaller than those things that can be seen with the naked eye
3. All cells come from other cells, so the mold cells must have come from cells in the bread itself
4. By having long extensions, the nerve cell can send messages to other cells
5. The cell could not survive because there would be nothing to stop harmful substances from entering.
6. In the cytoplasm
7. The nucleus, because it is the organelle that determines which proteins are made
8. Prokaryotes do not have nuclei; eukaryotes do
9. Alone, in groups, or on the endoplasmic reticulum
10. The ER transports proteins and lipids throughout the cell.
11. Proteins would not get to the correct destination
12. Provide energy
13. Both of these organelles hold and transport proteins and other nutrients. Vesicles are smaller than vacuoles.
14. Chloroplast and cell wall
15. The plant would lose its structure and rigidity
16. Chloroplasts are needed for photosynthesis, and animal cells don’t have them.
17. The water is moving from an area of high concentration, behind the dam, to an area of low concentration, on the other side of the wall
18. Active, because we are going from an area of low to high concentration
19. Yes, as long as energy is not used, it is passive transport
20. Photosynthesis provides energy for plants and oxygen for animals
21. Energy cannot be created, but photosynthesis does change light energy into chemical energy that can be used by the plant.
22. Glucose is the form in which the energy is stored. ATP is the form in which it is used.
23. To change chemical energy in glucose to ATP
24. Binary fission and budding
25. A complete set of DNA, which is found in the nucleus, needs to go to each daughter cell.


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Answers to Genetics Exercises

Monday May 2, 2011

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!


Simply click here for printable questions and answers.


Answers:
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1. Something close to: the science of heredity, dealing with resemblances and differences of related organisms resulting from the interactions of their genes and the environment.
2. Mendel observed traits in pea plants over many generations. He kept careful note of which traits appeared in each generation.
3. P represents the parental generation, F1 represents the generation of the offspring of P, and F2 represents the generation of the offspring of F1.
4. In the F1 generation was 100% tall, and the F2 generation was 75% tall and 25% short.
5. Dominant traits are always expressed when present, recessive traits are only expressed when they both alleles are recessive.
6. A table used for keeping track of the inheritance of genes.
7. Red. Orange. Mendel’s law of segregation predicts that dominant genes when crossed with the recessive allele will only express the dominant genes in the F1 generation, then express the dominant gene 75% of the time in the F2.
8. The individual codes for making proteins located in the DNA.
9. Phenotypes are the appearance of the organism—the physical traits. Genotypes are the genes that produce the trait.
10. Incomplete dominance is a shared expression of two traits. Codominance is the duel expression of two dominant traits.
11. Inherited genetic disorders—defective genes or chromosomes.
12. X or Y.
13. 100.
14. Enzymes used to cut specific sequences of DNA.
15. The Human Genome Project successfully sequenced over 20,000 human genes and mapped them on the 23 human chromosomes.


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Exercises for Living Organisms

Monday May 2, 2011

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.


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1. What is science?
2. What do scientists do if their conclusions go against what they used to think?
3. What are some observations you have made today?
4. Why are hypotheses sometimes called educated guesses?
5. Your friend has a hypothesis that some plants die because witches cast evil spells on them. Is this a good hypothesis? Why or why not?
6. If a scientist’s hypothesis is wrong, does that mean their experiment was bad?
7. Why should you do research before starting an investigation?
8. How can you tell if you can trust a particular web site, when doing research?
9. A student does an experiment to see if rap music helps plants grow. She takes 10 plants, waters them, gives them sunlight, and plays rap music for them. They all grow beautifully. Has she proven that rap music helps plants grow? Why or why not?
10. In question 9, what important group is missing? Describe what the student would (or would not) do to this group?
11. What are some ways scientists communicate results?
12. Why is it important to communicate results?
13. Why do scientists use models?
14. What is one thing our body does to keep a constant temperature?
15. Why do offspring tend to look like their parents?
16. What are cells?
17. How are autotrophs and heterotrophs different?
18. Why do we need to classify organisms?
19. If two animals were in the same phylum, would they be more or less similar than two animals in different phyla? (Phyla is the plural of phylum.)
20. What is the first word in an organism’s scientific name?
21. Why are scientific names useful?


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Answers to Living Organisms Exercises

Monday May 2, 2011

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!


Simply click here for printable questions and answers.


Answers:
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1. A method of answering questions based on evidence
2. They must change their way of thinking
3. Answers could include anything noticed using the five sentences
4. They are guesses because they haven’t been proven, but they are educated because they are based on some research.
5. No, because it is not provable (Remember that the problem is not that you might think this hypothesis is silly. If you could somehow prove it, it would be a valid hypothesis to test.)
6. No
7. This allows you to see what scientists already know about the topic
8. It is useful to look at what person or organization made the site, and determine if they are trustworthy and knowledgeable.
9. No, they plants might have grown just as well without the rap music
10. It is missing a control group. This group of plants should get the sunlight and water, but not the rap music.
11. Creating web sites, writing scientific articles, or giving lectures
12. This allows other scientists to do their own experiments based on the first scientist’s results.
13. To represent things that can’t easily be seen
14. Answers could include reducing blood flow, sweating, or shivering.
15. Parents pass on traits to their offspring
16. The smallest parts of living things still considered alive
17. Autotrophs create their own food; heterotrophs do not
18. Because there are so many of them, they have to be organized in some way
19. More similar
20. The genus
21. They are the same everywhere in the world, no matter what language is spoken


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Is It Alive?

Monday May 2, 2011

How can you tell if something is alive or not? For this activity, grab a pencil and paper and watch the video below. Write down whether you think it is alive or not, and what action is going on to make you think it’s alive. Ready?




Walk Around the House

Monday May 2, 2011

cookiesWalk around your house. In each room, make an observation by using your senses (sight, sound, smell, touch and taste). Based on this observation, ask a question.


For example, if you observe that the kitchen smells like cookies, you might ask, “Has someone been baking cookies?”


Create a testable hypothesis that answers each of your questions. Feel free to test any of your hypotheses.


Conducting Research

Monday May 2, 2011

Think of an organism (bacteria, fish, reptiles…) that interests you. With adult help, search the Internet to find five web pages about this organism.


Answer the questions below about each web site in your science journal:


1. Who wrote the site? (If unknown, write “unknown.”)


2. If the site has an author, does the site list his or her qualifications for writing about the organism?


3. Is there an organization that created the site? If so, who are they?


4. Does the site give you a way to contact the author and/or organization if you have questions?


5. Based on your answers to questions 1-4 above, do you trust this site as being a good source for information about the organism? Why or why not?


Thumb War Hypotheses

Monday May 2, 2011

thumb-warDifferent people have different sized thumbs and wrists. Do you think this will affect people’s success at winning a thumb war?


Open up your science journal and write a hypothesis to answer this question.
Now, find as many volunteers as you can. Measure everyone’s wrist and thumb circumference by wrapping the string around it and measuring the string used with the ruler. Write this down in your journal also.


Have each volunteer have a thumb war with each of the other volunteers three times.


Keep track of his or her victories and record all results in your journal.


You can create a graph of your results, with wrist circumference on the horizontal and number of victories on the vertical axis.


How does your data compare with your hypothesis?


Observing the Placebo Effect

Monday May 2, 2011

boy drinking a glass of waterYou’ll need a couple of volunteers for this experiment, but it’s totally worth it. Make sure you’ve got your science journal to record your results.
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Prepare 12 cups with liquid – 3 should have plain water, 3 should have water with sugar, 3 should have water with red food coloring, and 3 should have water with red food coloring and sugar.


Label the cups in such a way that only you will know what is in each one.


Get a few volunteers. Tell them that in this experiment you will either be giving them water or punch. (Really you are giving them sugar water, but that’s basically all punch is.)


Give each person a cup, ask him or her to drink it, and then tell you, based on taste, if they had water or punch.


Record your results, and compare it to reality. How many people guessed wrong? Did these people’s drinks have anything in common?


What’s Happening: You will likely see a version of the placebo effect. People with red drinks will likely think they are drinking punch, even if they only have water with food coloring. People with clear drinks will likely think they are drinking water, even if their cup has sugar in it too.
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Classifying Objects

Monday May 2, 2011

silverwareGrab a handful of buttons. Make sure there are all different kinds and colors.


If you don’t have buttons, use any pile of objects, like matchbox cars, coins, nuts, etc.


Now group the buttons according to size, color, texture, number of holes, shape, etc.


You can do this activity with shells, peanuts, plant leaves, or the back of your desk drawer. Is it easier to organize the non-living or the living things?


Similar and Different Organisms

Monday May 2, 2011

We're going to access another website (Seaworld) that has a HUGE catalog of living organisms and their scientific names. Here's how you do it:
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First, visit this website: https://seaworld.org/animals/facts/

Select an animal from the list.

Now, you should see the kingdom, phylum, class, order, family, genus, and species of the animal. Write this down in your science journal.

Next to this entry in your journal, list five animals that you think are similar to the animal you chose. Now go back to the website and write down the information for each one.
For each of the five animals, determine how close they are to the animal you chose. For example, are they in the same family, but not the same genus? The same order but not the same family? Have fun!
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Membranes

Monday May 2, 2011

Here’s a fun experiment that shows you how much stuff can pass through a membrane. Scientist call it the  semi-permeability of membranes.


Before we start, take out your science journal and answer this question: What do you think will happen when we stick a piece of celery into a glass of regular water. Anything special?


What if we add a teaspoon of salt to the water? Now do you think anything will happen?
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Let’s find out. First, you’ll need:


  • 2 pieces of celery stalk
  • salt
  • 2 glasses
  • a sensitive scale to weigh the celery

Note: If you don’t have a scale, you can rig up a balance by suspending two cups from a either end of of a pencil. Balance the center on a point (like another pencil) and you’ll be able to tell which is heavier at the end of this experiment (see image below).


You’ll need to measure the celery both before and after this experiment since you won’t be able to “read” the weight.


Trim your celery to be the same weight before you start your experiment.



Download Student Worksheet & Exercises


  1. First, weigh the celery (both pieces) and record this in your journal.
  2. Next, make your hypotonic solution (plain water). Fill a glass with water and stick your celery in for ten minutes.
  3. Remove the piece of celery and pat dry. Weight it again and record your results. If you don’t see a weight difference, dip it in again for ten more minutes. Pat dry and weigh again.
  4. Now make your hypertonic solution (salt water). Add a small amount of salt to the water (keep adding until no more can be dissolved and a small amount remains on the bottom).
  5. Weight the second celery stalk and record it in your journal. Add this new celery stalk to the water. Wait impatiently for ten minutes. Remove and record the weight. Did you notice a difference? (Note – if you left the first one in for 20 minutes, make sure to leave this one in for the same amount of time.)

What effect did the salt solution have on the celery?  Did it change in appearance?  Did it feel different? Record your results in your journal!


Osmosis is the diffusion of water molecules through a membrane, where the water molecules move from high water concentration to areas of low water concentration.


Salt starts osmosis by attracting water and causing the water to move toward and across the membrane. Remember that salt is a solute, and when water is added to a solute, it spreads out (diffuses) the concentration of salt, and that creates a chemical solution.


Imagine the salt concentration inside a cell being the exact same as the salt concentration outside the cell – what would happen? Right – the water level will stay the same and nothing would happen. Now imagine there’s more salt inside of a cell than outside it. What happens now? The water moves through the membrane into the cell causing it to swell with water.


If the cell is placed in a higher concentration of salt (like sticking a carrot in a salt bath), the water will leave the cell, and that’s why the plant cells shrink and wilt. This is also why salt kills plants, becaise it takes water from the cells. This doesn’t just happen in plants, though. Animals can also get dehydrated if they drink ocean water.


Exercises


  1. In what direction does water move?
  2. What is the process by which water crosses membranes by itself?
  3. What are all living things made of?
  4. Did the celery in the fresh water weigh more or less? Why?
  5. Did the celery in the salt water weigh more or less after a few minutes?

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Microscope Shopping List

Saturday July 31, 2010

This lab is an introduction to the microscope. We're going to cover how to use a compound microscope, the basics of optics, slide preparation, and why we can see things that are invisible to the naked eye.

What's a compound microscope? Compound microscopes are basically two lenses put together to make things appear larger. If you've ever used magnifying glass, you've noticed how the lens makes words easier to read. If you were to look through two magnifiers (one stacked on top of the other with space in between), you've seen this effect multiply to create an even larger image. That's exactly what a compound microscope does. It uses stacked lenses to greatly increase the magnification.

I'll show you how to get the most out of your investment by learning how to operate a microscope and prepare specimen slides. Click here for a printer-friendly version of this page.

Selecting a Microscope

The first thing you need to do is select a compound microscope. Cheap microscopes are going to frustrate you beyond belief, so we've provided recommendations that will get last your kids through college.

It can be a daunting task to find high quality microscopes and accessories at affordable prices. Here are a couple of recommendations for microscope and equipment that will last your kids through college. You'll also need additional items like slides, coverslips, tweezers, and other basic equipment.

The microscope you select will last a long time. Expect to pay at least $100 for a decent microscope that will provide many years of use. Here are ones we recommend investing in...

Economy Model: The Kids Microscope is a great entry level microscope for under $110. It meets the optical requirements to do our microscope labs but has only single intermediate focusing. It is also available in a cordless LED model that you can use in the field. If your children are young, this may be a good scope to start out with.
Student Model: The Home Microscope is an excellent 5th - 12th grade level microscope with fluorescent lighting that will really meet all the microscope needs of most families. It is well built with very good optics and will stand up to many years of use. I recommend the additional mechanical stage, as stage clips can be frustrating when working at high power!
Advanced Model: There is a Serious Student Model that includes the mechanical stage, iris diaphragm for lighting control, extra 100x oil immersion objective for 1,000x magnification, and immersion oil. This one will take you far in your studies of the micro world. Using the 100x objective with immersion oil is more challenging but also very rewarding as your child is able to see more and develop advanced microscope skills.
All-the-Bells-and-Whistles Model: The Ultimate Home Microscope is really a great microscope (and very similar to the one I personally use with the teaching head attached). This is a university/lab level microscope that is built to withstand the rigors of daily use. This scope is heavier, sturdier, and has all the advanced features like 100x oil immersion objective, iris diaphragm lighting control and a mechanical stage with very easy to use controls. It is also available in a binocular model that is more comfortable to use.When your microscope arrives, keep it in its packaging until you watch the next video. I'll show you how to handle it, store it, and where not to touch.
No matter which microscope you select, you'll want to be sure it meets these criteria: at least three objectives (40X, 100X, 400X) and the optics are all glass to provide better quality images and the microscope frame construction is metal to provide the durability you want. Most microscopes include a dust cover and custom fit styrofoam box for safe storage. Optional additions include a mechanical stage (which we highly recommend), a fourth 100x objective lens (for 1,000x magnification), and adjustable iris diaphragm for better lighting/contrast control.
By the way, if you're considering the the fourth 100x lens, make sure you get the special “oil immersion” objective. Light tends to do weird things when you magnify it that much, and to avoid these kinds of problems, scientists use a drop of oil on the slide to connect the objective with the slide. However, you can't do this trick with just any objective lens - you need to have a special kind of lens that won't get mussed up when contacted with oil (hence the “oil immersion” type).

Where to Find Other Essentials

In addition to a microscope, you'll also need additional items like slides, cover slips, tweezers, and other basic equipment. Here's what you need to complete the labs in this section:

Supplemental Equipment:

These items are not required for this lab, however if your budget allows for these items in the future, they are very nice to have...

Prepared Slide Sets: Using our labs you will learn to make different kinds of microscope slide mounts and examine a variety of samples that you can easily collect. Prepared slides contain specimens that have been professionally stained and prepared so that you can expand your microscope studies to a great variety of plant and animal life that you would otherwise not have access to. The general slide set and the biology slide set are two sets that contain a great variety of specimens to expand your microscopic studies.
Microscope Case: While the dust cover and styrofoam box that come with your microscope provide a good degree of protection, you may want to consider a microscope case to provide greater protection and convenience in carrying and storing your microscope. These cases have the added advantage of also storing your microscope accessories with your microscope in one location.
Digital Microscope: This one is actually cheaper than most optical models listed above, and I've used it when teaching kids. The best part is, all kids can view at the same time, and you can take both pictures and video of your specimens while viewing. It's really a great deal for the price. The one I really like is the Celestron 44340 LCD.

Can’t afford a microscope?

I’ll show you how to build a very simple microscope using two handheld magnifying lenses! All you need is an afternoon, a few kids, and two magnifiers per kid. Now it doesn't come close to any of the microscopes above, but it will allow you to do some basic experimentation. (The magnifiers do not need to be the same magnification.) Gather up a few coins, dead bugs, and plant specimens and you’ll be all set for a microscope adventure.


Microwhat?

Saturday July 31, 2010

Welcome to our unit on microscopes! We’re going to learn how to use our microscope to make things appear larger so we can study them more easily. Think about all the things that are too small to study just with your naked eyeballs: how many can you name?


Let’s start from the inside out – before you haul out your own microscope, we’re going to have a look at what it can do. I’ve already prepared a set of slides for you below.  Take out a sheet of paper and jot down your guesses – here’s how you do it:


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What is it?

Take a peek and see if you can figure out what each one is. Record your guess on a piece of paper. Don’t spend more than 90 seconds on each one. If you’re working with others, have everyone write down their answers individually, and then work together and discuss each one. Come up with a final group conclusion what’s on each slide before peeking at the answers.


plant cells
Paramecium Respiratory Tissue Hair Follicle
Green Algae Water Flea Pine Wood

Need answers? Hover your mouse over each slide to reveal the title.


More questions you can ask:

1. List the ways that microscopes are used. Why bother using them anyway? (Can you name four?)


2. What do you already know about microscopes? List two things.


3. What would you really like to learn about microscopes? Name three, at least.


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Anatomy of the Microscope

Saturday July 31, 2010

Nose? Objective? Stage? What kind of class is this?  Well, some of the names may sound a bit odd, but this video will show you what they are and how they are used. As you watch the video, touch the corresponding part of your microscope to get a feel for how it works.


NOTE: Be very careful NOT to raise the stage too high or you’ll crack the objective lens!  Always leave a space between the stage and the lens!! Anytime you use the coarse adjustment knob, always look at the stage itself, NOT through the eyepiece (for this very reason). When you use the fine adjustment knob, that’s when you look through the eyepiece.




More questions to ask:

1. After you’ve learned the different parts of the microscope, swing around and teach it to a nearby grown-up to test your knowledge. See if you can find all these parts: eyepiece, base (legs), objective lens, eyepiece, diaphragm (or iris), stage, fine and coarse adjustment knobs, mirror/lamp, nose.


2. Show your grown-up which parts never to touch with your fingers.


3. What’s the proper way to use the coarse adjustment knob so you don’t crack the objective lens?


Care and Cleaning

1. Pick up the microscope with two hands. Always grab the arm with one hand and the legs (base) with the other.


2. Don’t touch the lenses with your fingers. The oil on your fingers will smudge and etch the lenses. Use an optical wipe if you must clean the lenses. Steer clear of toilet paper and paper towels – they will scratch your lenses.


3. When you’re done with your scope for the day, reset it so that it’s on the lowest power of magnification and lower the stage to the lowest position. Cover it with your dust cover or place it in its case.


How to Use a Microscope: Optics, Observing, and Drawing Techniques

Saturday July 31, 2010

How do the lenses work to make objects larger? We’re going to take a closer look at optics, magnification, lenses, and how to draw what you see with this lesson. Here’s a video to get you started:




Here’s what you do:


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1. Take a look at the eyepiece of your microscope. Do you see a number followed by an X? That tells you the magnification of your microscope. If it’s a 10X, then it will make objects appear ten times larger than usual.


2. Peek at the objective lenses. They’re on the nose of the microscope, and there’s usually 3 or 4 of them. Do you see the little numbers printed on the side of the lenses, also followed by an X? Find the one that says 4. if you look through just that lens by itself, objects will appear 4 times as large. However, it’s in a microscope, so you’re actually looking through two lenses when you use the microscope. What that means is that you need to multiply this number by the eyepiece magnification (in our example, it’s 4 * 10 = 40) to get the total power of magnification when you use the microscope on this power setting. It’s 40X when you use the 10X eyepiece and 4X objective. So objects are going to appear 40 times larger than in real life.


3. Practice these with your microscope – here are the settings on my microscope – help me fill out the table to figure out how to set the lenses for the different magnification powers:


Eyepiece
Objective
Total Magnification
10X
4X
10X
100X
40X
400X
10X
1000X



Questions to Ask:

1. What does this table above look like for your microscope?


2. Your microscope may have come with an additional eyepiece. If so, add it to your table and figure out the range of magnification you have.


3. What is your highest power of magnification? Set it now.


4. List three possible combination of eyepiece and objective lenses if the power of magnification is 100X.


Learning to Look

Do how do you use this microscope thing, anyway? Here’s how you prepare, look, and adjust so you can get a great view of the micro world:




Download Student Worksheet & Exercises


1. Carefully cut a single letter (like an “a” or “e”) from a printed piece of paper (newspaper works well).


2. Use your tweezers to place the small letter on a slide and place a coverslip over it (be careful with these – they are thin pieces of glass that break easily!) If your letter slides around, add a drop of water and it should stick to the slide.


3. Lower the stage to the lowest setting using the coarse adjustment knob (look at the stage when you do this, not through the eyepiece).


4. Place your slide in the stage clips.


5. Turn the diaphragm to the largest hole setting (open the iris all the way).


6. Move the nose so that the lowest power objective lens is the one you’re using.


7. Bring the stage up halfway and peek through the eyepiece.


8. If you’re using a mirror, rotate the mirror as you look through the eyepiece until you find the brightest spot. You’ll probably only see a fuzzy patch, but you should be able to tell bright from dim at this point.


9. Use the coarse adjust to move the stage slowly up to bring it into rough focus. If you’ve lowered the stage all the way in step 7, you’ll see it pop into focus easily. (Be careful you don’t ram the stage into the lens!)


10. Use the fine adjust to bring it into sharp focus. What do you see?


Drawing What You See

Learning to sketch what you see is important so that the view is useful to more than just you. Here’s the easy way to do it: get a water glass and trace around the rim on a sheet of paper with your pencil. This gives you a nice, large circle that represents your scope’s field of view (what you see when you look into the microscope). Now you’re ready for the next step:




1. Draw a picture of that the letter looks like under the lowest power setting in your first circle and label it ‘right side up’. Then give the slide a half turn and draw another picture in a new circle. Label this one ‘upside-down’.


2. If you’re using a mechanical stage (which we highly recommend), twist one of the knobs so that the slide physically moves to the right as you look from the side (not through the eyepiece) of the microscope. If you’re using stage clips, just nudge the slide to the right with your finger. Now peek through the eyepiece as you move the slide to the right – which way does your letter move?


3. Now do the same for the other direction – make the slide move toward you. Which way does the letter appear to move when you look through the eyepiece?


4. What effect do the two lenses have on the letter image as you move it around? (Need a hint? Look back at the Microscope Optics Lesson from Unit 9)


Look back at your two drawings above. Let’s make them so they are totally useful, the way scientists label their own sketches. We’re going to add a border, title, power of magnification, and more to get you in the habit of labeling correctly. Here’s how you do it:


Border You need to frame the picture so the person looking at it knows where the image starts and ends. Use a water glass to help make a perfect circle every time. When I sketch at the scope, I’ll fill an entire page with circles before I start so I can quickly move from image to image as I switch slides.


Title What IS it? Paramecia, goat boogers, or just a dirty slide? Let everyone (including you!) know what it is by writing exactly what it is. You can use bold lettering or underline to keep it separate from any notes you take nearby.


Magnification Power This is particularly useful for later, if you need to come back and reference the image. You’ll be quickly and easily able to duplicate your own experiment again and again, because you know how it was done.


Proportions This is where you need to draw only what you see. Don’t make the image larger or smaller – just draw exactly what you see. If it’s got three legs and is squished in the upper right corner, then draw that. Most people draw their image smaller than it really is when viewed through the eyepiece. If it helps, mentally divide the circle into four quarters and look at each quarter-circle and make it as close to what you see as you can.


Exercises


  1. Why do we use microscopes?
  2. What’s the highest power of magnification on your microscope? Lowest?
  3. Where are the two places you should NEVER touch on your microscope?
  4. Fill in the blanks with the appropriate word to describe care and cleaning of your microscope:fingers       lowest                                               handsarm                                       toilet paper                                    legs                        dust cover
    1. Pick up the microscope with two ________.  Always grab the _________with one hand and the _______(base) with the other.
    3. Don’t touch the lenses with your _________. The oil will smudge and etch the lenses. Use an optical wipe if you must clean the lenses. Steer clear of ____________ and paper towels – they will scratch your lenses.
    5. When you’re done with your scope for the day, reset it so that it’s on the _________ power of magnification and lower the stage to the lowest position. Cover it with your __________ or place it in its case.
  5.  What things must be present on your drawing so others know what they’re looking at?
  6.  What’s the proper way to use the coarse adjustment knob so you don’t crack the objective lens?
  7.   List three possible combination of eyepiece and objective lenses if the power of magnification is 100X.
  8.  Briefly describe how to dry mount a slide.
  9.  How could you view a copper penny with your microscope?

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Preparing a Dry Mount Slide

Saturday July 31, 2010

Make sure you’ve completed the How to Use a Microscope activity before you start here!


This is simplest form of slide preparation!  All  you need to do is place it on the slide, use a coverslip (and you don’t even have to do that if it’s too bumpy), and take a look through the eyepiece.  No water, stains, or glue required.


You know that this is the mount type you need when your specimen doesn’t require water to live. Good examples of things you can try are cloth fibers (the image here is of cotton thread at 40X magnification), wool, human hair, salt, and sugar. It’s especially fun to mix up salt and sugar first, and then look at it under the scope to see if you can tell the difference.


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Here’s what you do:



1. Pull a hair from your head and lay it on a slide. If it’s super-curly, use a bit of tape at either end, stretching it along the length of the slide. Keep the tape near the ends so it doesn’t come into your field of view when you look through the microscope.


2. Lower the stage to the lowest setting and rotate the nose piece to the lowest magnification power.


3. Place the slide on the stage in your clips.


4. Focus the hair by looking through the eyepiece and slowly turning the coarse adjustment knob. When you’re close to focus, switch to the fine adjustment knob until it pops into sharp view.


5. Open your science notebook and draw a circle. Sketch what you see (don’t forget the title and mag power!)


6. When you’re done, lower the stage all the way and insert a new slide… and repeat. Find at least six things to look at. We’re not only learning how to look and draw, but hammering a habit of how to handle the scope properly, so do as many as you can find.


Don’t forget to check the windowsills for interesting bits. Use baby food jars or film canisters to collect your specimens in and keep them safe until you need them.


TIP: If you want to keep your specimen on the slide for a couple of months, use a drop of super glue and lay a coverslip down on top, pressing gently using a toothpick (not your fingers) to get the air bubbles out. Let dry.


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Preparing a Wet Mount Slide

Saturday July 31, 2010

Make sure you’ve completed the How to Use a Microscope activity before you start here!


Anytime you have a specimen that needs water to live, you’ll need to prepare a wet mount slide. This is especially useful for looking at pond water (or scum), plants, protists (single-cell animals), mold, etc. When you keep your specimen alive in their environment, you not only get to observe it, but also how it eats, lives, breathes, and interacts in its environment.


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The first thing you need to do is collect your pond water. Make sure it has lots of good stuff in it! You’ll need a 20mL sample. Once you have it, place it on a table along with your microscope, slides, cover slips, tweezers, and dropper. If you’re using Protoslo (if critters are too fast, this slow them down for easier viewing), get that out, too. Open up your science notebook, draw a bunch of circles for drawing borders, and then watch this video:



Download Student Worksheet & Exercises


1. Place a slide on the table.


2. Fill the eyedropper with pond water and place a drop on the slide.


3. Place the edge of the cover slip on the pond water drop, holding the other edge up at an angle. Slowly lower the end down so that the drop spreads out. You want a very thin film to lay on the slide without any air bubbles or excess water squirting out. If you go have bubbles, gently press down on the cover slip to squish them out or start over.


4. Take time practicing this – you want the water only under the coverslip. Dab away excess water that’s not under the slide with a paper towel.


5. Lower the stage to the lowest setting and rotate the nose piece to the lowest magnification power.


6. Place the slide on the stage in your clips.


7. Focus by looking through the eyepiece and slowly turning the coarse adjustment knob. When you’re close to focus, switch to the fine adjustment knob until it pops into sharp view.


8. Adjust the light level to get the greatest contrast so you can see better.


9. Move the slide around (this is where a mechanical stage is wonderful to have) until you spot something interesting. Place it in the center of your field of view, and switch magnification power to find a great view (not too close, not to far away). Adjust your focus as needed.


8. Open your science notebook and draw a circle. Sketch what you see (don’t forget the title and mag power!)


9. When you’re done, lower the stage all the way and insert a new slide… and repeat. Find at least six things to look at. We’re not only learning how to look and draw, but hammering a habit of how to handle the scope properly, so do as many as you can find.


NOTE: If the critters you’re looking at move too fast, add a drop of Protoslo to the edge of your slide to slow them down (by numbing them). The Protoslo will work its way under the cover slip.


Exercises


  1. Why do we use a wet mount slide?
  2. Give one example of a specimen that would use a wet mount slide?
  3. How do you prepare a wet mount slide?
  4. Why do we stain specimens?
  5. Give one example of a specimen that would use a stain.
  6. What type of stain can we use (give at least one example).

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Slide Preparation: Staining

Saturday July 31, 2010

Make sure you’ve completed the How to Use a Microscope and also the Wet Mount activities before you start here!


If your critter is hard to see, you can use a dye to bring out the cell structure and make it easier to view.  There are lots of different types of stains, depending on what you’re looking at.


The procedure is simple, although kids will probably stain not only their specimens, but the table and their fingers, too.  Protect your surfaces with a plastic tablecloth and use gloves if you want to.


We’re going to use an iodine stain, which is used in chemistry as an indicator (it turns dark blue) for starch. This makes iodine a good choice when looking at plants. You can also use Lugol’s Stain, which also reacts with starch and will turn your specimen black to make the cell nuclei visible. Methylene blue is a good choice for looking at animal cells, blood, and tissues.


In addition to your specimen, you’ll need to get out your slides, microscope, cover slips, eye dropper, tweezers, iodine (you can use regular, non-clear iodine from the drug store), and a scrap of onion. If you can find an elodea leaf, add it to your pile (check with your local garden store). Here’s what you do:


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Download Student Worksheet & Exercises


1. Fill a container with water and add a small piece of elodea leaf and onion. You’ll want the onion to be a thin slice, no more than a quarter of an inch thick.


2. Practice making a wet mount first.  Put a fresh slide on the table. Using tweezers, pull off a thin layer of onion (use a layer from the middle, not the top) and place it on your slide. Gently stretch out the wrinkles (use a toothpick or tweezers) and add a small drop of water and cover with a cover slip. Take a peek at what your specimen looks like on low power – do  you notice it’s hard to see much?  Draw what you see in your notebook.


3. Now increase the power and look again.  Draw a new sketch in your notebook.


4. Now we’re going to highlight the cell structure using iodine.  Lugol’s is also iodine, but the regular brown stuff from the drug store works, too. Grab a bottle of the one you’re going to use.


5. To stain the specimen, we’re going to add the stain to one side of the cover slip and wick away the water from the other side. Use a folded piece of tissue paper and touch it lightly to one side of the cover slip as you add a single drop of stain to the other side. When the stain has flowed through the entire specimen, take a peek and draw what you see in a a fresh circle.


6. Do the same thing with the elodea leaf. And anything else plant-based from your backyard. Or refrigerator.  Draw what you see and don’t forget to label it with a title and power of magnification!


Exercises


  1. Why do we use a wet mount slide?
  2. Give one example of a specimen that would use a wet mount slide?
  3. How do you prepare a wet mount slide?
  4. Why do we stain specimens?
  5. Give one example of a specimen that would use a stain.
  6. What type of stain can we use (give at least one example).

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Slide Preparation: Heat Fixes

Saturday July 31, 2010

Make sure you’ve completed the How to Use a Microscope and also the Wet Mount and Staining activities before you start here!


If you tried looking at animal cells already, you know that they wiggle and squirm all over the place. And if you tried looking when using the staining technique, you know it only makes things worse.


The heat fix technique is the one you want to use to nail your specimen to the slide and also stain it to bring out the cell structure and nuclei. This is the way scientists can look at things like bacteria.


You’re going to need your microscope, slides, cover slips, eyedropper, toothpicks or tweezers, candle and matches (with adult help), stain (you can use regular iodine or Lugol’s Stain), sugar, yeast, and a container to mix your specimen in. Here’s what you do:


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Download Student Worksheet & Exercises


1. Fill your container with warm water.  Add about a tablespoon of yeast (one packet is enough) along with a teaspoon of sugar.  The warm water activates the yeast and the sugar feeds it.  You should see a foam top form in about 10 minutes.


2. Using your eyedropper, grab a bit of your sample (you want the liquid, not the foam) and place a drop on a fresh slide. Spread the drop out with a toothpick.  You want to smear it into a thin layer.


3. Light the candle (with adult help). Heat the slide in the flame by gently waving it back and forth. Don’t stop it in the flame, or you’ll get black soot on the underside of the slide and possibly crack it because the glass heats up and expands too fast. You also don’t want to cook the yeast, as it will destroy what you want to look at. Just wave it around to evaporate the water.


4. Add a drop of iodine (or stain) to the slide. Wait 15 seconds.


5. Rinse it under water. (You can optionally stain it again if you find it’s particularly difficult to see your specimen, but make sure to look at it first before repeat staining.)


6. Place a drop of water (use a clean eyedropper) on the specimen and add the cover slip.


7. Lower the stage to the lowest setting and rotate the nose piece to the lowest magnification power.


8. Place the slide on the stage in your clips.


9. Focus by looking through the eyepiece and slowly turning the coarse adjustment knob. When you’re close to focus, switch to the fine adjustment knob until it pops into sharp view.


10. Adjust the light level to get the greatest contrast so you can see better.


11. Move the slide around (this is where a mechanical stage is wonderful to have) until you spot something interesting. Place it in the center of your field of view, and switch magnification power to find a great view (not too close, not to far away). Adjust your focus as needed.


12. Open your science notebook and draw a circle. Sketch what you see (don’t forget the title and mag power!)


NOTE: What other things can you look at?  You can scrape the inside of your cheek with a toothpick and smear it on a fresh slide, take a mold sample from last week’s leftovers in the fridge, or…? Have fun!


Exercises


  1. Why do we use heat fixes?
  2. Briefly describe how to do a heat fix.
  3. What is a specimen that needs a heat fix?

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Microscopes and Telescopes

Wednesday February 3, 2010

Hans Lippershey was the first to peek through his invention of the refractor telescope in 1608, followed closely by Galileo (although Galileo used his telescope for astronomy and Lippershey’s was used for military purposes).  Their telescopes used both convex and concave lenses.

A few years later, Kepler swung into the field and added his own ideas: he used two convex lenses (just like the ones in a hand-held magnifier), and his design the one we still use today. We're going to make a simple microscope and telescope using two lenses, the same way Kepler did.  Only our lenses today are much better quality than the ones he had back then!

You can tell a convex from a concave lens by running your fingers gently over the surface – do you feel a “bump” in the middle of your hand magnifying lens?  You can also gently lay the edge of a business card (which is very straight and softer than a ruler) on the lens to see how it doesn't lay flat against the lens.

Your magnifier has a convex lens – meaning the glass (or plastic) is thicker in the center than around the edges.  The image here shows how a convex lens can turn light to a new direction using refraction. You can read more about refraction here.

A microscope is very similar to the refractor telescope with one simple difference – where you place the focus point.  Instead of bombarding you with words, let’s make a microscope right now so you can see for yourself how it all works together. Are you ready?

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How to Make a Microscope

Materials:

  • 2 hand held magnifiers
  • dollar bill
  • penny - Note: The penny used in this video shows the Lincoln Memorial, which was shown on pennies minted between 1959 - 2008.

Here's what you do: Hold one magnifying glass in each hand.  Focus one lens on a printed letter or small object.  Add the second lens above the first, so you can see through both.  Move the lens toward and away from you until you bring the letter into clear focus again.   You just made a microscope!  The lens closest to your eye is the EYEpiece.  The lens closest to the object is the OBJECTive. The image here is of the objective part of a compound microscope.  The different silver tubes have different sizes of lenses, each with a different magnification, so the same scope can go from 40X to 1,000X with the flip of a lens.

How do I determine magnification power for my microscope? Simply multiply the powers of your optics together to get the power of magnification. If you’re using one lens at 10X and the other at 4X, then the combined effect is 40X. You’ll usually find the power rating stamped in tiny writing along the magnifier.

So now you've made a microscope.  How about a telescope? Is it really a lot different?

The answer is no.  Simply hold your two lenses as you would for a microscope, but focus on a far-away object like a tree.  You just made a simple telescope… but the image is upside-down!

microscope1We don’t fully understand why, but every time we teach this class, kids inevitably start catching things on fire.  We think it’s because they want to see if they really can do it – and sure enough, they find out that they can!  Just do it in a safe spot (like a leaf on concrete) if that’s something you want to do. Click here for a detailed instructional video on how to do this safely.

How do I connect the flaming shrubbery back to the main optics lesson? Ask your child why the leaf catches on fire… and when the shrug, you can lead them around to a discussion about focus points of a lens.  It’s hard for kids to visualize the light lines through a lens, so you can shine a strong light through a fine-tooth comb as shown in the image above.  Use clear gelatin (or Jell-O) shapes as your “lenses” and shine your rays of light through it.  If your room is dark enough, you’ll get the image shown above.

The point where all the lines intersect is where things catch fire, as the energy is most concentrated at this point. Note how the lines flip after the focus point – this is why the telescope images are inverted.  The microscope image is not flipped because you’ve placed the image (and/or your eye) before the focus point.  Play around with it and find out where the focus point is.  Slide your lenses along a yardstick to easily measure distances.

How to Make a Telescope

Materials:

  • 2 hand held magnifiers
  • window

Want to experiment further? Then click for the Optical Bench experiment and also sneak a peek at the Advanced Telescope Building experiment where you will learn about lenses, refractor, and newtonian telescopes.

Ready to buy your own professional-quality instrument that will last you all the way through college? Click here for our recommendations on microscopes, telescopes, and binoculars.
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Laser Microscope

Wednesday February 3, 2010

Did you know that you can use a laser to see tiny paramecia in pond water? We’re going to build a simple laser microscope that will shine through a single drop of water and project shadows on a wall or ceiling for us to study.


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Here’s how it works: by shining a laser though a drop of water, we can see the shadows of objects inside the water. It’s like playing shadow puppets, only we’re using a highly concentrated laser beam instead of a flashlight.


If you’re wondering how a narrow laser beam spreads out to cover a wall, it has to do with the shape of the water droplet. Water has surface tension, which makes the water want to curl into a ball shape. But because water’s heavy, the ball stretches a little. This makes the water a tear-drop shape, which makes it act like a convex lens, which magnifies the light and spreads it out:


Here’s how to make your own laser microscope:


Materials:


  • red or green laser (watch video for laser tips)
  • large paperclip
  • rubber band
  • stack of books
  • white wall
  • pond water sample (or make your own from a cup of water with dead grass that’s been sitting for a week on the windowsill)


Download Student Worksheet & Exercises


Exercises


  1. Does this work with other clear liquids?
  2.   What kind of lens occurs if you change the amount of surface tension by using soapy water instead?
  3.   Does the temperature of the water matter? What about a piece of ice?
  4.  Does this work with a flashlight instead of a laser?
  5.  Do lasers hurt your eyes? How?

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