The Theory of Evolution - Dearborn Public Schools



The Theory of Evolution

In science, theories are statements or models that have been tested and confirmed many times.

Theories have some important properties:

• They explain a wide variety of data and observations

• They can be used to make predictions

• They are not absolute, they serve as a model of understanding the world and can be changed as the world view changes

In science, the term "Theory" does not express doubt.

In science, the term theory is used to represent ideas and explanations that have been confirmed through tests and observations

The theory of evolution remains one of the most useful theories in biology because it explains many questions and observations.

Some questions that can be answered by evolution:

• Why do so many different animals have the same structures, the arm bones in a human are the same bones as a flipper in a whale?

• Why do organisms have structures they no longer use, like the appendix in a human? Non functioning wings in penguins

• Why are there bones and fossil evidence of creatures that no longer exist? What happened to these creatures?

• Why do so many organisms' morphology and anatomy follow the same plan?

• Why is the sequence of DNA very similar in some groups of organisms but not in others?

• Why do the embryos of animals look very similar at an early stage?

|The Theory of Evolution is considered a Unifying Theory of Biology, because it answers many of these questions |

|and offers and explanation for the data. |

Lamarck's Theory of Acquired Characteristics

Lamarck thought that you would gain or lose features if you overused or didn't use them, and you could pass these new traits onto your offspring.

This was known as the Inheritance of Acquired Characteristics

• A lizard that didn't use it legs would eventually not have legs and its offspring wouldn't have legs

• A giraffe stretched its neck to reach higher leaves, and this stretched neck would be a trait inherited by its offspring

Lamarck's Theory was eventually discarded - PROVEN TO BE WRONG!

Why? Logically it doesn't work. Imagine if you were in a car accident and had a leg amputed. This does not mean that your children will only have one leg. Features gained during life are not passed on to children.

Darwin's Theory of Evolution by Natural Selection

Darwin was a naturalist who observed many species. He is famous for his trips to the Galapagos Islands, his observations of the finches (and other animals) and the book he wrote: "The Origin of Species”:

There are four parts of natural selection:

1. Variation exists among individuals in a species.

2. Individuals of species will compete for resources (food and space)

3. Some competition would lead to the death of some individuals while others would survive

4. Individuals that had advantageous variations are more likely to survive and reproduce.

The favorable variations are called Adaptations.

|Darwin's Finches: |

|Darwin noted that all the finches on the galapagos island looked about the same except for the shape of their |

|beak. His observations lead to the conclusion that all the finches were descendents of the same original |

|population. The shape of the beaks were adaptations for eating a particular type of food (Ex. long beaks were |

|used for eating insects, short for seeds) |

Evidence of Evolution

1. Fossils

• Fossils are the remains or impressions left by plants or animals that lived a very long time ago.

• Fossils may look the same as when the plant or animal was alive but have now changed to stone.

• If today's species came from ancient species, then we should be able to find remains of those species that no longer exist.

• We have tons of fossils of creatures that no longer exist but bear striking resemblance to creatures that do exist today.

• Carbon dating--gives an age of a sample based on the amount of radioactive carbon is in a sample.

• Fossil record- creates a geologic time scale.

2. Anatomy

• Homologous Structures-- structures that are similar in origin, but have different functions.

o Example: The wing of a bird and the forearm of a human

• Analogous Structures-- structures that are not similar in origin, but have same functions.

o Example: The wing of a bird and the wing of a butterfly.

• Vestigial Organs-- seemingly functionless parts, snakes have tiny pelvic and limb bones, humans have a tail bone

3. Embryology

• Embryological development--Embryos of different species develop almost identically

4. DNA

• Evidence of Common Ancestry -- organisms that are more distantly related would be expected to accumulate a greater number of evolutionary differences, whereas two species that are more closely related should share a greater portion of their DNA.

WRITE ANSWERS ON SEPARATE SHEET OF PAPER!

The Theory of Evolution Guided Reading Questions

Answer the following questions on a separate sheet of paper. Please restate.

1. In science, what are theories?

2. What are the three important properties of theories?

3. In science, the term theory is used to what?

4. What theory remains one of the most useful theories in biology because it explains many questions and observations?

5. List 3 questions that can be answered by evolution?

6. Lamarck’s theory related to evolution was called Inheritance of Acquired Characteristics. Describe his theory and what he thought.

7. Describe one example of Lamarck’s Inheritance of Acquired Characteristics.

8. Eventually, what happened to Lamarck’s theory and why?

9. Darwin was a naturalist who observed many species. Where did Darwin observe finches and many other animals to create his ideas for the theory of evolution?

10. What was the book called that Darwin wrote about

evolution?

11. List the four parts of Natural Selection.

12. What are adaptations?

13. Darwin noted that all the finches on the Galapagos island looked about the same except for the shape of their beak. What was the conclusion he came up with based on his observations

14. What are the 3 types of evidence of evolution?

15. What are fossils?

16. What is the difference between homologous and analogous structures? List one example for each. ``

17. What are vestigial organs?

18. List an example of a vestigial organ.

19. Describe embryology.

20. How is DNA evidence of evolution?

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