Topic 3.2 Natural Selection

Question 1

Define natural selection

Answer 1

the process by which the organisms that are best adapted in a particular environment are most likely to survive and reproduce, passing on their advantageous alleles to their offspring

Question 2

Why does natural selection occur?

Answer 2

1. predation
2. disease
3. competition
   all resulting in differential survival and reproduction

Question 3

Explain how natural selection results in the development of new characteristics

Answer 3

• random mutations result in new alleles
• some alleles give the organism an advantage over the rest of the species, making them more likely to survive and reproduce
• their offspring receive the new allele, and frequency continues to increase over many generations

Question 4

What are the 3 types of adaptation?

Answer 4

• anatomical (changes to body structure) e.g. oily fur
• physiological (changes to body processes) e.g. venom production
• behavioural (changes to actions) e.g. hibernation

Question 5

What’s a genotype?

Answer 5

the genetic make-up of an organism with respect to a particular feature

Question 6

What’s a phenotype?

Answer 6

the physical traits (including biomechanical characteristics) expressed as a result of the interactions of the genotype with the environment

Question 7

Define allele

Answer 7

an allele is a version of a gene, a variant

Question 8

What is ecology?

Answer 8

the study of the interactions of organisms with each other and with the environment in which they live

Question 9

Define a niche

Answer 9

the role of an organism within the habitat in which it lives, species sharing the same niche will compete with each other

Question 10

Define speciation

Answer 10

the formation of a new species

Question 11

What is allopatric speciation?

Answer 11

speciation that takes place when populations are physically and geographically separated and there can be no interbreeding or gene flow between the populations

Question 12

What is sympatric speciation?

Answer 12

speciation that takes place between populations of a species living in the same place. They become reproductively isolated by mechanical, behavioural or seasonal mechanisms and gene flow continues between the populations to some extent as speciation takes place

Question 13

How does speciation occur?

Answer 13

when a population is split and reproductively isolated, there are different selective pressures on the 2 groups. if the genetic makeup changes to the extent that the 2 groups can’t interbreed, they have become separate species

Question 14

How does evolution relate to bacteria resistance?

Answer 14

bacteria can develop mutations that make them resistant to antibiotics, which they will then pass on when they reproduce

Question 15

Name the different types of isolation (5)

Answer 15

• geographical
• ecological
• seasonal
• behavioural
• mechanical

Question 16

Define geographical isolation

Answer 16

occurs when a physical barrier e.g. river or mountain range separates individuals from an original population

Question 17

What is ecological isolation?

Answer 17

occurs when 2 populations inhabit the same region, but develop preferences for different parts of the habitat

Question 18

Define seasonal isolation

Answer 18

occurs when the timing of flowering or sexual receptiveness in some parts of the population drifts away from the norm of the group, which can eventually lead to the groups reproducing months apart

Question 19

What is behavioural isolation?

Answer 19

happens when changes occur in the courtship ritual, display or mating pattern so that some animals do not recognise others as being potential mates, which may be due to mutations causing changes in markings e.g. colour or pattern

Question 20

What is mechanical isolation?

Answer 20

happens when a mutation occurs that changes the genitalia of animals making it physically impossible for them to mate successfully, or it changes the relationship between the stigma and stamens

Question 21

State the 4 concepts of the theory of evolution

Answer 21

1. living organisms that reproduce sexually show great variety in their appearance
2. organisms produce an excess of offspring so there is always a struggle to survive which means there is competition between the same species
3. advantageous characteristics are passed down to offspring
4. organisms that inherit disadvantageous characteristics are likely to die before reproducing