Evolution pt 1

Chapter 22 of textbook

When did the Earth form?

3.8 Billion years ago

Cambrian Diversification:

The rapid appearance of multicellular, diverse, and complex organisms about 500 million years ago. Scientists still don’t know why.

Humans:

Appeared 5-10 million years ago, forming in the “last seconds” of the “clock”

Principal of Uniformitarianism:

The physical forces of nature are timeless, and the fundamental laws of nature have remained unchanged, and will always happen. (Charles Lyell)

Examples of Uniformitarianism:

Erosion and plate tectonics.

These small processes have always happened, and always will

Gradualism:

Small changes add up to make large evolutionary changes.

Species:

In the simplest sense, different types of organisms.

Species undergo modification through….

Successive generations, with time

Changes in a certain species leads to….

The formation of a new species

Population:

All individuals of the same species occupying a specific area at a certain point in time

Fitness:

A measure of successful reproduction represented in the next generation. i.e, who eats, survives, and reproduces the best

Natural Selection:

The process by which a trait that has a reproductive advantage spreads over generations

Common Descent with modification:

•All species have descended from species that existed before them

•Natural selection is based on fitness and a crucial mechanism for change in populations

Natural Selection Is:

An AGENT of evolution / a mechanism that CAUSES evolution

Potential of Populations:

Most populations are capable of producing more offspring than can be supported by their environment. Basically, most populations create more than they need because some will die early

Heritability:

A trait has genetic basis, and can be passed down to offspring

Competition:

Required for natural selection. Individuals with a higher fitness will survive, while “lesser” individuals will not.

Evolution Defined:

Evolution is a genetically based change of phenotype in a population over successive generations

What evolves?

Populations evolve