3.4 Adaptation, natural selection and the evolution of species

Question 1

Describe the order of events that occur during speciation

Answer 1

• isolation barrier is introduced
• organisms are now exposed to different conditions(climate, food competition…)
• random mutations occur
• -favourable mutations survive and are passed onto the next generation
• unfavourable mutations are killed and die
• this happens for many generations
• eventually the two subpopulations are so different that they can no longer interbreed and produce fertile offspring

Question 2

Name 3 isolation barriers

Answer 2

• geographical
• ecological(change in abiotic factors)
• behavioural(organisms may select different food sources or mating)

Question 3

Give examples of mutagenic agents

Answer 3

• ionising radiation(x-rays, nuclear fallout)
• ultraviolet radiation(from the sun)
• chemical mutagen(mustard gas)

Question 4

Explain the process of natural selection using the peppered moth as an example

Answer 4

• soot covered the trees and the light variety weren’t able to camouflage and were killed
• the dark variant survived and passed their characteristics onto the next generation
• the abundance of the dark variety increased and the species survived as a result

Question 5

What is natural selection?

Answer 5

the process in which the weak are “weeded out”. organisms that are better adapted to their environment have a better chance of passing these favourable characteristics onto the next generation
it ensures that the best adapted individuals survive

Question 6

What is an adaptation?

Answer 6

an inherited characteristic that makes an organism suited for survival in its environment

Question 7

What is speciation?

Answer 7

the formation of a new species due to natural selection and changing environmental conditions

Question 8

Give examples of special adaptations that allow organisms to survive in extreme environments

Answer 8

• camouflage
• long necks in giraffes
• insulated fur

Question 9

How may mutations affect the phenotype?

Answer 9

neutral-no effect on the phenotype

disadvantageous-have a negative effect(cystic fibrosis)

advantageous-has a positive effect(pepperd moth example)

Question 10

Give examples of behavioural, physiological and structural adaptations

Answer 10

Behavioural - hibernation, migration
Physiological - temperature regulation
structural - camouflage

Question 11

What do variations allow organisms to do?

Answer 11

to evolve over time in response to changing environmental conditions

Question 12

What are mutations?

Answer 12

a change to the structure or composition of an organisms genetic mater

Question 13

What is a selective advantage?

Answer 13

a favourable characteristic which gives an organism an increased chance of survival

Question 14

What are selection pressures?

Answer 14

a factor that affects a population resulting in the death of some individuals and survival of others

Question 15

What is an ecological barrier?

Answer 15

a isolation barrier caused by adaptation to living conditions

Question 16

What is a behavioural barrier?

Answer 16

an isolation barrier caused by differences in timing, location or complexity of mating rituals that prevents members of the populations from mating even if they are not geographically separated

Question 17

What is an isolation barrier?

Answer 17

barrier that prevents interbreeding and gene exchange between sub-populations of a species

Question 18

Name 3 environmental selection pressures

Answer 18

• predation
• food shortage
• disease