4.4 variation and Evolution

Question 1

Evolution: definition

Answer 1

a change in the average phenotype of a population

Question 2

Speciation: Definition

Answer 2

formation of a new species

Question 3

species: definition

Answer 3

group of organisms that can interbreed to form fertile offspring

Question 4

when will evolution not occur

Answer 4

if the conditions under which the Hardy Weinberg principles apply

Question 5

Can be speciation be due to

Answer 5

-genetic drift (in isolated populations)
-founder effect in small populations
-natural selection

Question 6

what is the founder effect

Answer 6

when a small population has become separated from the original population and so an allele in the small population becomes more frequent in future generations

Question 7

what is allopatric speciation

Answer 7

where a new species evolves as a result of geographical isolation/ physical barriers (mountains, deserts)
prevented from interbreeding

Question 8

what is the isolating mechanisms in allopatric speciation

Answer 8

geographical isolation

Question 9

what is sympatric speciation

Answer 9

when organisms living in the same niche become reproductively isolated into 2 groups for non-geographical reasons

Question 10

what are non-geographical reasons

Answer 10

pre-sygotic
post-zygotic

Question 11

example of a pre-zygotic reason

Answer 11

can be behavioural, morphological, gametic or seasonal

Question 12

example of post-zygotic reason

Answer 12

hybrid in viability/sterility and breakdown

Question 13

6 steps of natural selection

Answer 13

1. mutation
2. variation
3. competition advantage
4. survival of the fittest
5. reproduction
6. Pass on advantageous alleles

Question 14

what does mutation in alleles lead to
speciation by natural selection

Answer 14

lead to changes in allele frequency

Question 15

speciation by natural selection

Answer 15

how phenotypes can be changed or maintained to be optimal in the environment

Question 16

reason for variation in phenotypes
speciation by natural selection

Answer 16

due to different alleles

Question 17

after many offsprings are produced what happens?
speciation by natural selection

Answer 17

there is a competition for limited resources

Question 18

what is selection pressure
speciation by natural selection

Answer 18

some phenotypes get a survival advantage (long enough to breed)

Question 19

what happens to successful phenotypes
speciation by natural selection

Answer 19

they pass on their alleles increasing their frequency in the population

Question 20

purpose of a T test

Answer 20

whether the difference between the mean of 2 groups is down to chance or another factor

Question 21

Deme: definition

Answer 21

group of individuals within a population who breed with one another, it is possible for individuals from different deems to interbreed

Question 22

genetic drift: definition

Answer 22

the change in allele frequency in a population by chance, (more noticeable in small populations )

Question 23

what is the variation in genetic drift

Answer 23

it is by chance

Question 24

gene pool: definition

Answer 24

all the alleles present in a population at a given given time

Question 25

when will a gene pool remain constant

Answer 25

if: -population is large -no selection pressure -mating is random -no mutations occur -all genotypes are equally fertile -no emmigration/immigration

Question 26

explain the Hardy-Weinberg Principle

Answer 26

-the frequency of alleles and genotypes within a population will remain constant from one generation to the next

Question 27

what is needed for Hardy Weinberg equillibrium

Answer 27

certain conditions are needed: -large population -no selection for/against any phenotype -random mating - no mutations -isolated population

Question 28

what is the H.W equation

Answer 28

-estimate the frequency of dominant/recessive or of different genotypes within a population

Question 29

H.W equation p=

Answer 29

frequency of dominant alleles (A)

Question 30

H.W equation q=

Answer 30

frequency of recessive allele (a)

Question 31

H.W equation p+q=

Answer 31

1.0

Question 32

H.W equation p2=

Answer 32

frequency of AA

Question 33

H.W equation 2pq=

Answer 33

frequency if Aa

Question 34

H.W equation q2=

Answer 34

frequency of aa

Question 35

variation: definition

Answer 35

the phenotypic difference between organisms of the same species

Question 36

2 types of variation

Answer 36

heritable/non-heritable

Question 37

what is heritable variation

Answer 37

due to genetic reasons (by crossing over, independent assortment, sexual reproduction, epigenetics) can be passed on to offspring

Question 38

what is non-heritable variation

Answer 38

due to environmental reasons, cannot be passed on

Question 39

what is continuous variation

Answer 39

-characteristics have many possible values - no distinct categories -generally polygenic (controlled by many genes) -gene expression influence by the environment -forms a normal distribution curve

Question 40

example of continuous variation

Answer 40

height, weight, finger length, leaf length

Question 41

what is discontinuous variation

Answer 41

-no intermediate types -only a small number of possibilities -characteristics are distinct -monogenic (controlled by a single gene) -gene expression not influenced by the environment -bar chart

Question 42

example of discontinuous variation

Answer 42

blood group, eye colour

Question 43

what factors affect population of organisms

Answer 43

biotic factors- predationm parasites, disease, competition

Question 44

2 types of competition

Answer 44

intraspecific interspecific

Question 45

what is intraspecific competition- what is competed for

Answer 45

between members of the same species (competition for mates/space)

Question 46

what is interspecific competition- what is competed for

Answer 46

between different species (compete for for the same resources)

Question 47

role of advantageous alleles

Answer 47

increase the likelihood of survival, organism survives and passes on the successful allele

Question 48

explain selection pressure

Answer 48

the effect of selective agencies on the phenotypes in a population (can alter the frequency of alleles) i.e food availability, climate, human impact

Question 49

FOR selection pressure

Answer 49

phenotypes have an advantage in competition so the alleles that code for them are selected FOR

Question 50

AGAINST selection pressure

Answer 50

phenotyoes do not have an advantage and are unable to compete successfully. alleles that code for them are selected against.

Question 51

different types of selection types

Answer 51

stabilising directional disruptive

Question 52

definition of stabilising selection types

Answer 52

the average trait is selected for

Question 53

does stabilising selection lead to speciation

Answer 53

unlikely no

Question 54

examples of stabilising speciation

Answer 54

tail size for a cat too small=lack balance too long= drags on the floor average size=aid survival

Question 55

what is directional selection type

Answer 55

one extreme is selected for change the characteristics of the population

Question 56

does directional selection lead to speciation

Answer 56

unlikely no

Question 57

examples of directional selection

Answer 57

lizard tail length, long tail is selected as it looks like a snake so will scare off predators

Question 58

what is disruptive selection

Answer 58

either extreme is selected, average trait is selected against

Question 59

does distruptive selection lead to speciation

Answer 59

Yes

Question 60

example of disruptive selection

Answer 60

rabbits. small rabbits may run faster, fit down smaller holes. large rabbits are able to fight back better. both selected over average size rabbits