Chapter 22: Descent with Modification

Objectives

1. Understand Darwin’s general observations

2. Define Evolution

3. Understand how descent with modification explains adaptations of organisms and unity and diversity of life.

4. Understand how observations (evidence) has contributed to the theory of evolution.

Darwin’s work was based on other scientist’s work

-Geology-Life Sciences-Classification-Paleontology-Population

Darwin’s Trip-Traveled on a ship called the Beagle around South America-Darwin studied Geology and inferred current data didn’t support a static, young earth-Studied geographic distribution of species-Main focus was on species adaptation - Characteristics that enhance species’ survival and reproduction in a specific environments.

Darwin observed beak differences based on the bird’s major food source.

Darwin wrote an essay but didn’t publish

When he realized others were following his research he decided to finish and publish “The Origin of Species”

Artificial and Natural Selection

-Darwin used the word selection

-Darwin related nature to selective breeding of plants and animals or artificial selection Darwin’s Observations that led

him to the idea of natural selection

1. Organisms within a population have variation of traits

2. Traits are inherited3. Species are capable of over

producing offspring4. Many offspring don’t survive

Darwin’s Inferences from observations

1. Individuals whose inherited traits give them a better chance of surviving and reproducing in a given environment leave more offspring

2. This unequal ability to survive and reproduce leads to an accumulation of favorable (selected) traits over generations.

Natural Selection Summary

-Natural Selection was the first mechanism of evolution

-Process in which certain organisms with certain traits survive and reproduce at a higher rate then others

- Over Time the process of selection can increase the match between traits and an organism’s niche

-If an environment changes selection of new traits/adaptations may occur with the possibility of speciation

Key points1. Individuals don’t evolve2. Only inherited traits are selected3. Environments change constantly

and natural selection is constantly happening

p. 460

The theory of evolution is based on data collected from many fields of study.

1. Direct observations (p. 161 conclusions) - Guppies experiment - Viral evolution (HIV)- Bacterial evolution

2. Geology and Paleontology (fossil Record)

3. Anatomy/Embryology (Homology)-Homologous structures are variations on a similar structuratl theme-Vestigial structures are remnant structures == Wouldn’t expect with organism’s current niche.-Homologies are used to create an evolutionary tree -- the closer the organisms are the more characteristics they share.-Genetic Homology

4. Biogeographical-Distribution of organisms is determined by geographical separation.

5. Population Genetics -Will discuss next chapter (23)

** Evolution is considered a theory due to the massive amounts of data to support as well as constant data that is still to come.

The Farm Fox Experiment

Directions: Read the article and type a one page paper that discusses the following.

1. Description of domesticated traits that are shared across species.

2. Description of the hypothesis of the experiment.

3. Description of how variables were controlled.

4. Brief description of the results.

5. Summary of the conclusions made from the experiment

6. Summary of how the data gained in this experiment contributes to the theory of evolution.