9.4- TYPES OF SELECTION

Question 1

What is selection?

Answer 1

process by which organisms that are better adapted to their environment tend to survive + breed, while those that are less well adapted tend not to

Question 2

What is directional selection?

Answer 2

selection may favour individuals that vary in one direction from mean of population

Question 3

What does directional selection do?

Answer 3

changes characteristics of population

Question 4

What is stabilising selection?

Answer 4

selection may favour average individuals

Question 5

What does stabilising selection do?

Answer 5

preserves characteristics of population

Question 6

What are most characteristics influenced by?

Answer 6

more than one gene (polygenes)

Question 7

What are the characteristics that are influenced more than one gene, more influenced by?

Answer 7

more influenced by environment than ones determined by single gene

Question 8

What does the effect of the environment on polygenes produce?

Answer 8

individuals in population that vary about the mean

Question 9

What is phenotype?

Answer 9

observable physical + biochemical characteristics of organism

Question 10

Who are most likely to survive if the environmental conditions change? (directional selection)

Answer 10

phenotypes that are best suited to new conditions are most likely to survive

Question 11

What will happen to the mean overtime? (directional selection)

Answer 11

mean will move in direction of individuals with phenotypes best suited to new conditions

Question 12

Directional selection: bacterial resistance to penicillin- what was the mutation? #1

Answer 12

spontaneous mutation occurred in allele of gene in bacterium that enabled it to make new protein

Question 13

Directional selection: bacterial resistance to penicillin- what was the new protein that the bacterium was able to make? #2

Answer 13

new protein was enzyme that broke down antibiotic penicillin before it was able to kill bacterium
enzyme called penicillinase

Question 14

Directional selection: bacterial resistance to penicillin- what did the mutation give the bacterium? #3

Answer 14

advantage in being able to use penicillinase to break down antibiotic + so survive while rest of population of bacteria were killed by it

Question 15

Directional selection: bacterial resistance to penicillin-what was the bacterium that survived able to do? #4

Answer 15

able to divide by binary fission to build up small population of penicillin-resistant bacteria

Question 16

Directional selection: bacterial resistance to penicillin- what were the members of the small penicillin-resistant population more able to do? #5

Answer 16

more able to survive, + so multiply in presence of penicillin than members of non-resistant population

Question 17

Directional selection: bacterial resistance to penicillin- what happens to the population of penicillin-resistant bacteria? #6

Answer 17

population of penicillin-resistant bacteria increased at expense of non-resistant population
so frequency of allele that enables production of penicillinase increased in population

Question 18

Directional selection: bacterial resistance to penicillin- what happens to the population’s normal distribution curve? #7

Answer 18

population’s normal distribution curve shifted in direction of population having greater resistance to penicillin

Question 19

Directional selection: bacterial resistance to penicillin- do the bacteria mutate because of the presence of bacteria?

Answer 19

NO- mutations occur randomly + very rare

Question 20

What does directional selection result in?

Answer 20

phenotypes of one extreme of population being selected for + those at other extreme being selected against

Question 21

If environmental conditions remain stable, who are favoured? (stabilising selection)

Answer 21

individuals with phenotypes closest to mean that are favoured

Question 22

What does stabilising selection tend to eliminate?

Answer 22

phenotypes at extremes

Question 23

What does stabilising selection result in?

Answer 23

phenotypes around mean of population being selected for and those at both extremes being selected against

Question 24

What does natural selection result in?

Answer 24

species that are better adapted to environment they live in

Question 25

What may be the adaptations for natural selection? (3)

Answer 25

anatomical
physiological
behavioural