Evolution and populations

Question 1

phenotype meaning

Answer 1

an organisms observable charecteristics

Question 2

what is phenotypic variation

Answer 2

the differences in these traits among individuals of the same species

Question 3

what factors can affect phenotypic variation

Answer 3

genetic, environmental or a mixture of the two

Question 4

how does genetic variation occur

Answer 4

small differences in DNA structure

Question 5

how can genetic variation initially arise

Answer 5

from random mutations, creating new alleles which can be beneficial or harmful.

Question 6

3 ways in which genetic variation occurs through sexual reproduction

Answer 6

crossing over of sister chromatids

independent assortment

random fertilization

Question 7

how does independant assortment affect genetic variation

Answer 7

random alignment of chromosomes results in different combinations of chromosomes and therefore different allele combinations

Question 8

how does crossing over affect genetic variation

Answer 8

genetic material is exchanged between non sister chromatids, leading to new alleles

Question 9

how does random fertilisation affect genetic variation

Answer 9

and male gamete can fuse with any female gamete and therefore the genetic info passed on is random

Question 10

how does mutation affect genetic variation

Answer 10

random change in DNA base structure results in the generation of a new allele.

Question 11

what are selection pressures

Answer 11

environmental factors that affect an individuals chances of survival

Question 12

biotic

Answer 12

living factorsab

Question 13

abiotic

Answer 13

non living factors

Question 14

how may a selective advantage occur

Answer 14

random mutation results in an advantageous allele = live longer and pass allele onto futire generations and this allele frequency increases.

Question 15

evolution definition

Answer 15

the formation of new species from pre-existing species over time, as a result of changes to gene pools and allele frequencies from generation to generation

Question 16

what are the 3 types of selection pressures

Answer 16

stabilizing, directional, disruptive.

Question 17

what is stabilizing selection

Answer 17

favours the average phenotype and removes extremes

Question 18

what is directional selection

Answer 18

favours individuals at one extreme

Question 19

what is disruptive selection

Answer 19

maintains high frequencies of 2 different sets of alleles

Question 19

why does disruptive selection cause polymorphism

Answer 19

there are 2 different ways a population may morph into eg. small and large beak size in birds.

Question 20

what is reproductive isolation

Answer 20

when allelels or phenotypes prevent certain individuals from breeding succesfully with others in the same population

can lead to speciation

Question 21

what is genetic isolation

Answer 21

when the alleles in a population which have been reproductively isolated (FOR EXAMPLE) now stop exchanging genes and the allele frequencies of the groups change only within each group

occurs unto a point in which the 2 groups can no longer reproduce to produce fertile offspring.

Question 22

what is allopatrick speciation

Answer 22

when a population is split by a geographical barrier.

Question 23

how does allopatrick speciation occur

Answer 23

2 groups are isolated by a geographical barrier

this means they are reproductively isolated and no gene flow between the groups occurs

the 2 groups have different selection pressures

natural selection occurs

over time phenotype and genotypes become so different that the 2 can no longer interbreed to produce fertile offspring.

Question 24

what is sympatrick speciation

Answer 24

speciation without a geographical barrier

Question 25

examples of sympatrick speciation

Answer 25

ecological - 2 different environments behavioral - groups develop different behaviors eg. courtship.

Question 26

what is genetic drift

Answer 26

when chance affects which individuals in a population survive and reproduce.

Question 27

what does genetic drift lead to

Answer 27

the loss of alleles purely by chance

Question 28

is genetic drift more likely to affect large or small populations and why

Answer 28

small as in large populations, chance variations in allele frequencies even out over the whole population

Question 29

what is a species

Answer 29

a group of similar organisms that can reproduce to produce fertile offspring

Question 30

genetic reason why 2 species cant interbreed

Answer 30

different number of chromosomes odd numbers of chromosomes cannot line up properly in meiosis

Question 31

what is a population

Answer 31

a group of organisms of the same species occupying a particular space at a particular time

Question 32

what is a gene pool

Answer 32

sum of all the alleles of the genes of a population at a particular time

Question 33

allele frequency meaning

Answer 33

how often different alleles occur in the gene pool of a population

Question 34

what is phenotypic frequency

Answer 34

the number of individuals in a population showing a particular observable trait

Question 35

equation for phenotype frequency

Answer 35

total individuals with phenotype/ total individuals x 100

Question 36

what does the hardy weinburg principle state

Answer 36

allele frequencies in a population will remain constant from one generation to the next.

Question 37

what is assumed in the hardy weinburg principle

Answer 37

organisms are diploid reproduce by sexual reproduction mating is random population is large there is no mutation

Question 38

first hardy weinburg equation

Answer 38

p + q = 1

Question 39

what do p and q respresent

Answer 39

the frequency of dominant and recessive allele

Question 40

second hardy weinburg equation

Answer 40

p^2 + q^2 + 2pq = 1 p^2 = homozygous dominant q^2 = homozygous reccesive 2pq = heterozygous