Lecture 2 - The Diversification of Life

What are the two main historical explanations for the diversification of life, and how do they differ?

Supernatural: life was created by a supernatural being, w/ a “true form”

Organic: species evolve over time through natural processes

What is "typological thinking," and how does it differ from Darwin's understanding of species?

Typological thinking is the belief that there is one "true" form for each species, which remains unchanged over time; his view was different because he acknowledged that species are not unchanging, and he emphasized the significance of variation within species (allows natural selection to occur)

How did the work of Erasmus Darwin contribute to the development of evolutionary theory

Proposed that species change gradually over time, and he suggested that each species evolves from a simpler ancestor into a more complex and perfect form.

How did the work of Jean-Baptiste Lamarck contribute to the development of evolutionary history?

Proposed that species evolve through natural processes and suggested the inheritance of acquired characteristics, meaning traits gained during an organism’s lifetime could be passed on to offspring.

What was the key contribution of Charles Darwin to the theory of evolution?

The mechanism of Natural selection: demonstrated that organisms with advantageous traits are more likely to survive and reproduce, passing those traits on to future generations

What are the five components of Darwin's theory of evolution?

• Steady Change: The world is constantly changing, and species do not remain the same forever.

• Gradualism: Evolution occurs gradually over long periods of time.

• Common Ancestry: All species share a common ancestor.

• Natural Selection: Evolution occurs through the differential survival and reproduction of organisms better adapted to their environment.

• Multiplication of Species: New species can evolve from existing ones through speciation.

What is natural selection?

The process by which certain traits become more common in a population because individuals with those traits have a better chance of surviving and reproducing

What are the 4 observations that Darwin’s theory of natural selection was based on?

• There is variation among individuals in a species.

• Some of this variation is heritable.

• Species produce more offspring than can survive.

• Individuals with advantageous traits (better adapted to the environment) are more likely to survive and reproduce, passing these traits on to future generations.

What is the famous case study of natural selection involving the peppered moth (Biston betularia), and what did it demonstrate?

• With industrial pollution, tree trunks became darkened, favoring dark-colored moths because they blended in better and had a survival advantage.

• Over time, the frequency of dark-colored moths increased in polluted areas, while light-colored moths remained more common in rural, unpolluted areas.

This case demonstrates how environmental changes (e.g., industrial pollution) can drive natural selection, leading to changes in the population's traits over time.

How did Kettlewell's experiments on the peppered moths support the theory of natural selection?

He conducted two key tests:

1. He released and recaptured moths in both urban (polluted) and rural (non-polluted) areas. He found that dark-colored moths were more likely to be recaptured in urban areas, while light-colored moths were more likely to be recaptured in rural areas.

2. He placed dead moths of both color forms on tree trunks and observed bird predation. Birds ate more of the lighter-colored moths in urban areas, supporting the idea that camouflage influences survival.

These experiments provided strong evidence that natural selection, driven by predation, favored the dark-colored moths in industrial areas, supporting Darwin's theory.

List Lamarck’s possible explanations for how organisms evolved

1. Species change gradually over time

2. Each species represents a stage in its evolution from a simple ancestor to a more complicated and perfect form

3. Each new species arose through spontaneous generation from non-living matter