IB Biology A4.1 Notes

Topic 4 focuses on ecosystems and changes within them. In the context of organisms, the changes they undergo are mostly due to evolution. This is the change in heritable characteristics of a species over time.

Given evolution's previously controversial history since its proposition of theory in the mid 19th-century by Charles Darwin and Alfred Russel Wallace, it is important to understand the process.

The theory of evolution by natural selection is governed by four tenets:

1. More offspring are produced than can survive.
2. Morphology, physiology, and behavior greatly varies between individuals.
3. Different traits results in different rates of survival and reproduction.
4. Traits are passed down generations.

The evidence for evolution is provided by several key pieces of information, including:

1. Base sequences
2. The fossil record
3. Selective breeding
4. Homologous structures