BSC2010 Unit 3 Lecture 1

Evolution

Change in genetic composition of populations over time

Theory

A scientifically acceptable or plausible general principle based on data and offered to explain phenomena

Scientific theories are…

-Supported by evidence

-Parsimonious

-Falsifiable

Evolutionary theory

Our understanding of the mechanisms that resultin genetic changes in populations through generations

What did Erasmus Darwin suggest?

All warmblooded animals have a common ancestor

What did Jean-Baptiste Lamarck propose?

The inheritance of acquired characteristics (a potential mechanism of evolution)

What works was Darwin strongly influenced by?

1. Lyell’s Principles of Geology

2. Malthus’s An Essay on the Principle of Population

Lyell’s Principles of Geology

Proposed that forces we see today are also responsible for events in the past and have caused the geological features of the earth (wind, rain, etc); earth is “indefinitely old”

Malthus’s An Essay on the Principle of Population

Populations have the potential for rapid increase but are kept in check by limited resources

Artificial selection

Darwin bred pigeons and recognized similarities between selection by breeders and selection by nature → increases favored trait

Limited resources + overproduction of offspring =

“struggle for existence”

Darwin’s great insight

Individuals that fit the environment better wil be more likely to survive and reproduce.

What did Darwin realize from Galapagos finches?

They likely came from a common ancestor and were “modified for different ends.”

Darwin’s theory for evolutionary change

-Species change over time

-Descent with modification

-Mechanism for change is natural selection

Three conditions for natural selection

1. A population must have variation in a trait.

2. That variation must be heritable.

3. Some variants must have higher fitness

Who also independently discovered natural selection?

Alfred Russel Wallace

B

Four pieces of evidence for evolution

1. Comparative morphology

2. Development (embryology)

3. Fossil record

4. Molecular biology (DNA comparisons)

Why do whales have vestigial hind limbs?

Common ancestor with other mammals

Evidence for evolution in cetaceans

Homologous bone structures with humans, embryonic similarities with humans, tetrapod fossils,

E