Category: Biology (Page 29 of 40)

Weekend Science Fun: Beavers

Beavers are amazing animal architects.

Have you seen a beaver dam? We saw one in northern Arizona last summer.

We figured out it was a beaver dam because we saw their webbed footprints in the mud, we saw where trees had been gnawed off, plus we found a skull. How did we know it was a beaver skull? We recognized it because the four front chewing teeth were bright orange. The orange color comes from the iron that strengthens a beaver’s teeth.

Beavers build dams to create deeper pools of water — called the beaver ponds — within a shallow creek. The structure where the beaver lives is called the beaver lodge. We didn’t see anything that looked like a traditional beaver lodge near the dam we found, but a book we read suggested if the conditions are right, beavers may simply use holes in the stream bank for homes.

Activity 1. Find out more about beavers.

Have you ever seen a real beaver?

Beavers are large rodents. A big one can weigh up to one hundred pounds. They are brown and have a large flat tail. Their feet are webbed for swimming. They eat plants, especially bark and twigs from the trees that grow around their ponds.

Check these beaver facts.

Building Behaviors
A new dam is started by a young pair of beavers. Young beavers set out on their own at roughly two years old. Beavers mate for life, and the mother beaver has babies each year. The yearlings from the first year stay and help with the new babies. Once their mother has her second batch of young, however, it is time to leave.

Photo by Steve at Wikimedia

If you think about it, not only do these young beavers go on to build dams and lodges in a new place and under different conditions than their original home, but also their only previous experience has been to help their parents repair the structures that had been already in place before they were born. They have never built a dam before, yet they are able to do so. That’s pretty incredible!

Activity 2. Build a model of a lodge or dam, or even a complete diorama in a shoebox.

Gather:

  • Pencils and colored pencils
  • Twigs and small branches
  • Chenilles
  • Blue construction paper or plastic wrap to represent water
  • Glue
  • Modelling clay
  • Pebbles
  • Age-appropriate scissors
  • Cardboard for base/support

Research how a beaver lodge is made, and then draw or build a model. Draw some beavers in the pond, and add some trees for them to build with and eat. If you do an entire diorama, be sure to include the beaver dam. You might even want to add the canals that beavers use to float the trees to the lodge or dam.

Check out videos online that show beavers at work for ideas. Here’s a short one from PBS:

The BBC has a longer video narrated by David Attenborough.

Beavers generally have at least two entrances to their lodges that are underwater. Under a pile of branches and stems, there is a space for them to eat and sleep. At the top is a chimney for air circulation.


Public domain image from Wikimedia.

 Have fun and let us know if you have any questions or comments.

Weekend Science Fun: Honey Bees

Happy 2011!

Now it is time to sweep the cobwebs from the blog, check all the old links, delete the posts that are no longer relevant, and spruce up Growing With Science for the New Year. Time to reflect on what we have accomplished and plan where to go from here. Always a fun time of year.

A special thanks to all the regular followers who have made this blog such a wonderful experience! Please let me know if you have any comments/suggestions/questions to help us become even better in 2011.

How Honey Bees Keep Warm

In the last bug of the week blog post I mentioned that honey bees have a way to keep warm that is different from that used by butterflies. It turns out that the radio show Science Friday had a discussion last week (Friday, December 24th, 2010) all about honey bees called Buzz on Bees. One of the show’s guests, Dr. Thomas Seeley from Cornell University, explained that even when it is very cold outside honey bees keep the temperature within their hives up to 90° F. That’s pretty warm! No wonder the worker bees are able to fly when no other insects are moving.

(Photograph taken December 28, 2010 in San Diego, California.)

How do the bees keep warm? They feed on the honey they have stored in the honeycomb, which gives them energy to shiver. Basically, honey bee shiver and shake to create warmth. They use about a pound of honey per week to accomplish this (you can hear the podcast here.)

Honey Bees Swarming

Dr. Seeley also talked about how honey bees make new colonies, a process called swarming. During the time that the scout  honey bees are looking for a place to make their new home.

Vocabulary:

  • queen honey bee – the large bee that lays all the eggs in a bee colony
  • swarm – a group of honey bees moving from a colony to find and start a new nest, usually contains a queen and about 10,000 worker bees
  • scout bees- worker bees that search for new nests for the swarm, pick the most promising, and lead the rest of the bees to the new site
  • waggle dance – the way the scout bees communicate with each other on the surface of the swarm
  • piping- a sound scout bees make to rouse the rest of the bees in the swarm to get ready to fly
  • buzz run- the actions and sounds of the scout bees letting the swarm bees know it is time to take off
  • wax glands- glands on the underside of the honey bee worker’s abdomen that produce wax for the new honeycomb in the new nest
  • aggregation pheromone- special odors produced by the honey bees to bring the swarming bees back together in a cluster

Making Honey

The other guest on the show was Dr. May Berenbaum 
from the University of Illinois. She explained how bees make honey from nectar and some of the special properties of honey. Basically the bees gather nectar from flowers, carry it back to their nest in a special stomach called a crop and then pass it to other bees for processing. The worker bees dry the moisture from the nectar, add some special enzymes to change the chemistry of the nectar and over time it becomes honey. When it is done, the bees cap the cells that contain honey with wax. The honey can stay fresh in the cells almost indefinitely.

Activity:

Make a Sweet Honey Book

First discuss how bees collect nectar and make honey.

Information Sheet: What Bees Eat

Secondly, explain that humans have long used honey for food and as a sweetener. Have your children gather stories and poems about honey bees, and recipes using honey from their relatives and family friends and /or the library (like these) or make up their own. Group stories, poems and recipes together to create a small book, decorate with honey bee artwork, and print for distribution.

For more honey bee-related activities and information, see this previous post.

Both Dr. Seeley and Dr. Berenbaum have new books out, written for adults.

Tom Seeley’s is Honeybee Democracy (Princeton University Press, 2010)
.

May Berenbaum is the 
editor of Honey, I’m Homemade: Sweet Treats from the Beehive Across the Centuries and Around the World (University of Illinois Press, 2010).

And for kids our growing list of children’s books about bees at Science Books for Kids.

Note: If any of the links are broken for you, please leave a comment and I will try to retrieve them.

Genes and DNA for Kids

I am excited to report that the experiment for this week are inspired by a new book, You Can’t Wear These Genes by my friend Shirley Duke, who blogs at SimplyScience. Be sure to look for my interview with Shirley and more about the book over at Wrapped In Foil. Shirley will be celebrating her 100th blog post this week at SimplyScience, so you might want to stop over and say hello.

About the book:
You Can’t Wear These Genes is an easy-to-understand overview of genetics for children in grades 4-7. Reading this book is a perfect way to introduce a lesson on genes and DNA.

Shirley starts out with an idea a child can relate to, how we inherit traits from our parents. Further inside are explanations of common terms, like chromosomes, alleles, and what a genome is. The crisp clear, illustrations of the structure of DNA, for example, complement the text. Not only does Shirley review the background of what we know so far in the field of genetics, but she also gives us a glimpse of the future by looking at the Human Genome Project, genetic engineering and cloning.

I know I will be using this book when I present the following activity to a group of children next month.

Activity: DNA Extraction From Strawberries and/or Bananas

Believe it or not, these days you can extract DNA from common fruits and vegetables right in your own home.

You’ll need:

  • strawberries, bananas or both (these fruit contain extra copies of DNA making extraction easier)
  • plastic bags that seal (or something to mash the fruit in)
  • water, preferably distilled
  • a device to measure liquids in ml (optional for a single test, see 1 below)
  • dish detergent
  • table salt and measuring spoon
  • a container to mix the extraction buffer in
  • isopropyl alcohol and a way to keep it cold. Most recipes call for 90%, but 70% is acceptable.
  • glass container, like a beaker
  • funnel (optional)
  • filter material such as cheesecloth, coffee filter, paper towel or any old piece of cloth
  • test tube or spice jar, and some type of holder to keep it upright
  • A medicine dropper (optional)
  • wooden stick that will fit in the test tube, such as a craft stick or wooden skewer

Method:

Before you start, put the isopropyl alcohol in the fridge or on ice so that it is cold when you need to use it. Note:  you can use ethanol, but isopropyl (rubbing) alcohol is cheaper and easier to obtain.

1. If you are working with a group you will need to make the extraction buffer, which is the solution that helps break down the strawberry cells and release the DNA. The basic ingredients are water, dish detergent (or shampoo) and table salt. One common formula is 300 ml water, 25 ml dish detergent, and 1 Tablespoon table salt. Note:  Stir this mixture gently. Excessive bubbles will interfere with the extraction process later on.

If you are doing a single test on one strawberry or one piece of banana, there’s no need to make up a big container of buffer. Try 2 tsp water, 1 tsp soap, and 1 pinch salt for each berry.

2. Place a single strawberry or 1/2 a banana in the plastic bag, seal and mash it up. You can do one kind of fruit, or do both separately and then compare your results. The plastic bags works well if you are doing this with a group of children because each child can mash his or her own. You can simply mash the fruit in a bowl, too. This should only take a minute or two. If the banana is somewhat green, you can add a bit of water to make it easier to mash.

3. Add up to 10 ml of the extraction buffer to the bag, and mash some more. Again, try not to create excessive bubbles. Remind small children not to taste the fruit after this step.

4. Set up some sort of filtration system. This can be a simple as a coffee filter over a cup or cheesecloth over a funnel. The idea is to separate the fruit juice from the pulpy material. The DNA should now be in the juice that passes through the filter. You can throw away the pulpy remains. The videos have more details about filtering if you have never done it before.

5. Pour your juice into the test tube or spice jar. If you have a lot of bubbles on top, remove these with a medicine dropper. Now slowly pour in 8 to 10 ml of the cold isopropyl alcohol. It should form a layer on the top of the juice.

6. With the wooden stick, stir at the interface of the alcohol and juice. A thick, globby material should form on the stick, which is your DNA. If it doesn’t appear right away, give it a minute or two and try again.

There’s nothing like being able to watch someone do a demonstration to help you figure out what to do. Here are two videos that show how to extract DNA, each using slightly different techniques.

DNA Extraction from Strawberry Video

DNA Extraction from a Banana Video

These are sure to give you some ideas for further experiments. What happens when you add the alcohol to the test tube first versus second. Does the order change the amount of DNA you obtain?

Once you are confident of your technique, go ahead and try other fruit or vegetables, such as kiwi or onions. You can also compare room temperature versus cold alcohol to see whether it really needs to be cold. Have fun and I’d love to hear what you find out.

For more information about genetics online, try Learn Genetics at The University of Utah.

You Can’t Wear These Genes

Reading level: Ages 9-12
Paperback: 48 pages
Publisher: Rourke Publishing (FL) (August 2010)
Language: English
ISBN-10: 1615905634
ISBN-13: 978-1615905638

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