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Unit 2

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Concepts/Objectives | Vocabulary/Background | Activity | Extension


Lesson Plan 2




Evolution: a gradual process in which something changes into a different form; life forms changing over time.
Convergence: to meet; to approach the same point from different directions.
Adaptation: a feature that allows an animal to survive in its environment.


Evolution is the gradual change in a species over geologic time, many thousands or millions of years. Natural selection refers to the fact that an organism which has the most effective way of dealing with the environment is most likely to survive. An example is sea otters; those with warmer thicker fur will survive cold northern waters better than another with less thick fur. The sea otters with thicker fur will survive to pass this trait on to their offspring, so that over time all sea otters end up with thicker fur.

An adaptation is a feature that an animal has that allows it to survive in its environment. Sometimes these adaptations are very similar among different animals. In fact, entirely different species can have the same type of adaptation to survive in similar environments. As mentioned above, wings (to fly and escape) and fins (to swim) are good examples. Other examples include:

armor (for protection)
elongated Snouts (for sucking up food)
horns (for combat and protection)
large Ears (for both predator and prey to hear better in an environment where hearing is more important than sight)
large Eyes (for seeing well at night)
long Necks (for reaching food sources)
spines (for protection)
stripes (for predator/prey camouflage)
tusks (for rooting and digging, protecting or fighting)

To help in you discussion here are some criteria to determine valid examples of convergent evolution. In order to be considered an example of convergent evolution the animals must

1) be ancestrally unrelated
2) have structurally similar characteristics
3) are using these characteristics for the same function.

In essence they must have similar structures with similar functions. For instance "tails" would not be a good example of convergent evolution because they are something shared by almost all vertebrates in their life cycle and also because they are not necessarily used for the same function. For example, horses use tails to swish flies and monkeys use tails for balance and certain monkeys use them to hang from trees.

Convergent Evolution is what occurs when two different species evolve similar structures from similar lifestyles.