4.3.5 evidence for natural selection

Question 1

natural selection

Answer 1

term used to explain how features of the environment apply a selective force on the reproduction of individuals in a population

Question 2

who was charles darwin

Answer 2

• naturalist
• spent much of life studying & observing living organisms
• proposed mechanism for evolution = natural selection
• theories developed during 5-year trip on HMS beagle
• visited galapagos islands where many species on each island were similar but had clear variation eg. wide variety of bird species was actually closely related finches
• published ‘the origin of species’

Question 3

who was alfred russel wallace

Answer 3

• naturalist
• independently came to same conclusions as darwin
• collections in south east asia & amazon
• darwin & wallace first publication = joint papers together on subject of evolution by natural selection

Question 4

4 particular observations darwin made

Answer 4

1. offspring generally appear similar to their parents
2. no 2 individuals are identical
3. organisms have ability to produce large numbers of offspring
4. populations in nature tend to remain fairly stable size

Question 5

3 conclusions by darwin

Answer 5

1. there’s a struggle to survive
2. better-adapted individuals survive & pass on characteristics
3. over time, a number of changes may give rise to new species

Question 6

2 evidence for evolution

Answer 6

• fossil evidence
• biological molecules

Question 7

interesting facts shown by fossils

Answer 7

1. in the past, the world was inhabited by species different from those today
2. old species have died out & new species have arisen
3. the new species that have appeared are often similar to older ones found in same place

Question 8

strong evidence provided by bio molecules for evolution

Answer 8

• certain molecules are found throughout living world –> if 1 species gave rise to another, both are likely to have same biological molecules which suggests all species arose from 1 original ancestor
• 2 closely related species will have separated only relatively recently
  –> their bio molecules likely to be identical/very similar
• in species which took separate evolutionary paths a while ago, the biological molecules are likely to differ more
• evidence from molecules eg. cytochrome c & other proteins (show pattern of changes)

Question 9

percentages for comparison of human DNA with other organisms - showing evolutionary relationships

Answer 9

• 1.2% of coding sequence different from chimpanzees
• 1.6% different from gorillas
• 6.6% different from baboons