A4.1 Evolution & speciation

Question 1

Evolution

Answer 1

Change in heritable characteristics of a population over time

Question 2

What are the 2 main theories of evolution?

Answer 2

Lamarck — acquired characteristics are not inherited & passed onto future generations, not supported by genetics

Darwin — favourable traits are passed onto offspring (causes evolution over time), supported by genetics, variation is present in a population due to presence of alleles

Question 3

Evidence for evolution

Answer 3

• DNA, RNA & proteins
• Homologous structures
• Selective breeding

Question 4

What are mutations caused by?

Answer 4

Errors in base sequences of DNA

Question 5

Why are DNA, RNA & proteins evidence for evolution?

Answer 5

Same genes are present in organisms which have evolved from a common ancestor

Question 6

Selective breeding

Answer 6

Humans choosing plants or animals with desirable traits to breed together & produce offspring with those traits

Question 7

Example of an animal which has undergone selective breeding

Answer 7

Dogs

Question 8

Example of a plant that has undergone selective breeding

Answer 8

Brassica Oleracea

Question 9

Why are homologous structures an evidence for evolution?

Answer 9

It is present in organisms that have descended from a common ancestor as a result of evolution

Question 10

Why are pentadactyl limbs an example of homologous structures?

Answer 10

All organisms with pentadactyl limbs that evolved from a common ancestor
—> Structure of limb is similar in all species but have evolved for variety of purposes

Question 11

Convergent evolution

Answer 11

Evolution of similar structures in species not related due to a recent common ancestor

Question 12

Analogous structures

Answer 12

• Differing structure
• similar function
• do not form from a common ancestor
• evolved by convergent evolution

Question 13

Examples of animals with analogous structures

Answer 13

Birds, bats, insects —> can all fly but do not share a common ancestor

Question 14

Speciation

Answer 14

Formation of new species through evolution

Question 15

Extinction

Answer 15

Occurs when there are no living members of a species remaining

Question 16

When does reproductive isolation occur?

Answer 16

When there is a barrier which prevents individuals from reproducing

Question 17

What is the condition for speciation?

Answer 17

Can only occur if a populations of a species are reproductively isolated

Question 18

Geographic isolation

Answer 18

When 2 populations of the same species are prevented from reproducing because of geographical features (Ex. River, mountains, islands)

Question 19

Example of animals that have been evolved due to geographic isolation

Answer 19

Chimpanzees & Bonobos
- Share a common ancestor
- Lived in Central Africa
- Congo river became wider —> got split into 2 distinct populations
- Selective pressures were different on the 2 sides of the river