Module 4 : Section 3 - The Theory of Evolution Flashcards
When did Darwin publish his theory of evolution by natural selection
1859
What were Darwin’s observations
- Organisms produce more offspring than survive
- There’s variation in the characteristic of members of the same species
- some of these characteristic can be passed on from one generation to the next
- individuals that are best adapted to their environment are more likely to survive
Darwin wrote his theory of evolution by natural selection to explain his observations. The theory consisted of:
- individuals within a population show variation in their phenotypes (their characteristics)
- selection pressures (environmental factors e.g. predators, disease and competition) create a struggle for survival
- Individuals with better adaptations are more likely to survive and have reproductive success so they pass their advantageous adaptations to their offspring
- Over generations this leads to evolution as the favourable adaptation s become more common in the population
Who is Alfred Russel Wallace
A scientist working at the same time as Darwin, Wallace played an important part in developing the theory of evolution by natural selection
What did Wallace contribute to the theory of evolution
- He independently came up with the idea of natural selection and wrote to Darwin about it
- He and Darwin published their papers in evolution together and acknowledged each other’s work, although they didn’t always agree about the mechanisms involved in natural selection
- Wallace’s observations provided lots of evidence to support the theory of evolution by natural selection
- e.g. realised that warning colours are used by some species to deter predators from eating them and that this was an example of an advantageous adaptation that had evolved by natural selection
What different types of evidence support evolution
- Fossil evidence
- DNA evolution
- Molecular evidence
How does Fossil record evidence support evolution
- Fossils are remains of organisms preserved in rocks
- By arranging fossils in chronological order, gradual changes in organisms can be observed that provide evidence of evolution
Give an example of fossil record evidence supporting evolution
The fossil record of the horse shows a gradual change in characteristics, including increasing size and hoof development
How does DNA evidence support evolution
- theory of evolution suggests that all organisms have evolved from shred common ancestors
- closely related species diverged more recently
- evolution is caused by gradual changes in the base sequences of an organisms’ DNA
- organisms that diverged away from each other more recently, should have more similar DNA, as less time has passed for changes in the DNA sequence to occur
What does it mean for something to diverge
Evolve to become different species
Give an example of fossil record evidence supporting evolution
Humans, chimps and mice all evolved from a common ancestor. Humans and mice diverged a long time ago but humans and chimps diverged quite recently. The base sequence of human and chimps is 94% the same, but human and mouse DNA is only 85% the same
What do scientists analyse specifically when looking for DNA evidence to support evolution
- they look at the cell’s nucleus as most DNA is found there
- but they also look at difference into mitochondrial DNA as eukaryotic organisms have DNA in their mitochondria
How does Molecular evidence support evolution
- in addition to DNA, the similarities in other molecules provide evidence
- scientists compare the sequence of amino acids in proteins and compare antibodies
- organisms that diverged away from each other more recently have more similar molecules as less time has passed for changes in proteins and other molecules to occur
What are pesticides
Chemicals that kill pests (e.g. insects that damage crops).
Populations of insects can…
Evolve resistance to pesticides
