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A Trip to Africa

You have just arrived in Ghana, on the west coast of Africa. You step off the plane and a swarm of mosquitoes surrounds you. Before you get in your cab to go to your hotel, you notice at least five mosquito bites starting to itch on your arm. You don’t think much about it--after all, you’ve had hundreds of mosquito bites before. You’re not going to let a few bites keep you from seeing the elephants and wild boars, after all. About ten days later, though, you wake up feeling AWFUL! You have a headache, a high fever, and you feel sick to your stomach. Your African guide takes you to a local clinic where a blood test is done. Diagnosis? MALARIA.

Malaria is a disease carried by mosquitoes in some parts of Africa. These mosquitoes have a tiny parasite in their saliva. When the mosquito bites a human, it injects some saliva into the blood--and along with it comes the parasite. These parasites invade your red blood cells and multiply inside them. The red blood cells burst and die--sending more parasites into your blood. This happens over and over, making you very sick! Some of the symptoms are vomiting, diarrhea, and headache, to name a few. If left untreated, it could kill you.

Your guide is sorry to see you so sick. After taking the medication the doctor prescribed, you start to feel better, and, after a week or so, you are almost back to normal. “Have you had malaria?” you ask your guide. He smiles and explains, “I have sickle-cell anemia. Malaria does not make me sick.”

Why would this be?

A normal red blood cell (like would be found in your body) looks similar to this:



In a person with sickle-cell anemia, such as your guide, some of the red blood cells look like this:

It is common that people who have sickle-cell anemia are more resistant to the malaria parasite.

Answer the following questions:
1. How does having sickle-cell anemia increase your chance of survival if you live in Ghana?
2. Is there an advantage to having sickle-cell anemia if you live in the U. S.? Why?

 

Now, how does this apply to other organisms? Let's look at specific traits which may help an organism survive in the location where it lives.

Seagulls have adapted, with webbed feet for a life near the shore and wings and feathers for a life in the air.

Organisms can have many traits, which are qualities or features. The traits can be either inherited or acquired. When animals inherit traits, they sometimes are very helpful for survival. Sometimes the traits they inherit aren’t useful, and they can actually prevent the animal from surviving at all. Over a long period of time, the traits of a group of organisms in an area become more and more beneficial to their survival in that specific area.

 

Animals that live in deserts usually have some common traits, regardless of what desert they live in. They all get by on very little water. They prefer being active when the temperature is coolest, usually around dusk and just after dawn. In the same way, animals that live in cold climates have similar adaptations. They may be active only during the middle of the day, when the temperature is warmest. They may have thicker fur or more feathers than similar animals that live in warmer areas. Plants have the same tendency to have traits adapted to a specific environment. Cactus plants have a thick, waxy skin to prevent the loss of water.

 

Traits of an organism aren’t much good to anyone but that organism unless that organism can give those traits to someone else. Reproduction is all about giving traits to someone else. When an organism reproduces, it passes on its traits to its offspring. Animals that reproduce sexually can combine traits from different animals, and sometimes the combinations are better than either parent. Sometimes, however, they are worse. Imagine your lawn. Every spring you go out and mow it. You may have noticed some dandelions. If you never spray for dandelions, will they survive? Some will. Which ones? You may have predicted, “The short ones.” The short ones may have advantage in your lawn, since you cut it with a lawnmower. The only flowers that would survive to reproduce would be the ones which are too short to be cut by the lawnmower. In another environment, maybe only the tall ones survive. They may be better able to get sunlight or water or some other requirement for life. All organisms function this way.

 

You may have heard the phrase, "Survival of the fittest." It brings up images of big, strong, capable organisms struggling to beat each other out for food. It can sometimes be that, but fittest doesn’t mean the most physically fit, rather it means the organism that “fits” best in its environment. As stated above in the section on reproduction, the organisms that have traits that best suit them for survival are the organisms that will reproduce. Organisms that don’t “fit” in their environment don’t always die immediately, but often they don’t reproduce or don’t reproduce as often or as well, and so they have less offspring. On the other hand organisms that are more fit for their environment often have more offspring. Traits that help an organism survive become more and more common, and traits that aren’t useful become less and less common.

 

Analysis:

You are to use the knowledge you have about how traits help organisms survive. In doing this, you will create a children's story to explain this information. You can view an example of a possible children's story related to this topic.

 

You will be writing and illustrating a children’s book about that possible situation. Your children's story needs to include the following list to plan your story.

cover (front and back)     
pages  
one organism and two different environments  
traits of your organism  
advantages of natural environment  
disadvantages of new environment  
illustrations  
text  
overall quality  

You should do your planning on something called a story board (a rough draft of your story.) To create a storyboard, take a regular piece of white paper and fold it in half three times to make eight frames.

In each of these frames, plan a page of your children’s story. Include the type of illustration, the text you may use, and other elements. This storyboard is like a rough draft. It will help you organize your final story. Use it to plan how to include all the items in the above chart.

You may need to go to the library or use the Internet or an encyclopedia to research an organism you are interested in and the two environments. Use the information to design your story.

Review science safety rules here.

Get the plug-ins: Get Adobe Acrobat Reader , and Get Quicktime Player. (The Quicktime plug-in is needed to play sounds and movies correctly.)

Want to share photos of you or your friends doing this activity? Send it in an e-mail with the following information:

  1. The title of the activity
  2. The URL (Internet address)
  3. Your name.

Remember that no pictures can be used that show student faces or student names on it. 

Teachers should view the Teacher Site Map to relate Sci-ber text and the USOE 7th grade science core.


Updated October 24, 2008 by: Glen Westbroek

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