Evolution - M6

Question 1

2 types of variation and their causes

Answer 1

Continuous = Genetic + Environment

Discontinuous= Genetic , environment has little or no effect

Question 2

how to represent continuous data biology

Answer 2

Histogram

Question 3

how to represent discontinuous data biology

Answer 3

Bar chart

Question 4

Gene pool =

Answer 4

The sum total of all the genes in a breeding population at any given time

Question 5

Allele frequency =

Answer 5

The relative frequency of a particular allele in a population

Question 6

is The frequency with witch an allele occurs in a population related to weather it is dominant or recessive ?

Answer 6

No

Question 7

Population genetics

Answer 7

The study of the gene pools, and the allele and genotype frequencies of populations of organisms

Question 8

The environment influences the expression of polygenetic traits ____ than monogenetic traits

Answer 8

More

Question 9

Stabilising selection

Answer 9

When environment isn’t changing much, indivs with alleles for characteristics towards the middle of the range (e.g: short fur to long fur) are more likely to survive + reproduce.
Thus reducing range of possible phenotypes. keeping allele frequencies constant
maintenance of the intermediate

Stabilising selection is natural selection that keeps allele frequencies relatively constant over generations
This means things stay as they are unless there is a change in the environment

Question 10

Directional selection

Answer 10

Directional selection is natural selection that produces a gradual change in allele frequencies over several generations
This usually happens when there is a change in environment (and therefore a change in selection pressures) or a new allele has appeared in the population that is advantageous

Question 11

Process of directional selection

Answer 11

• There is always phenotypic variation within a population
• There is a selection pressure that favours a particular phenotype
• The phenotype is produced by particular alleles
• Individuals with the favoured phenotype are fitter and so more likely to reproduce and pass on the advantageous alleles to their offspring
• Those who do not possess the advantageous allele or phenotype are less likely to survive and pass on their alleles to their offspring
• So over time and several generations the frequency of the advantageous allele increases and the frequency of other alleles decreases

Question 12

Disruptive selection

Answer 12

When change in environment, indivs with alleles for characteristics of TWO extreme typeS are more likely to survive + reproduce

Question 13

Howe is evolution via genetic drift different to evolution via natural selection?

Answer 13

Characteristics become more common by chance, rather than (In natural selection) they increasing an organisms likelihood of survival

Question 14

Process of Evolution via genetic drift

Answer 14

-Indivs in population show variation in their genotypes
-By chance , the allele for one genotype is passed on to the offspring more than others. So the number of indivs with that allele increases
-if by chance , the same allele is passed on more often again and again, it can lead to evolution as the allele becomes more common in the population

Question 15

Three factors affecting genetic drift

Answer 15

-Population size
-Genetic Bottleneck
-The founder effect

Question 16

How does Population size effect Genetic drift

Answer 16

-Genetic drift usually has a greater effect on smaller populations where chance has a greater influence

-In larger populations, any chance variations in allele frequency even out across whole population

Question 17

How does Genetic Bottleneck effect Genetic drift

Answer 17

An event (e.g: natural disaster) causes big reduction in pop. size = reduce gene pool.

Evolution via genetic drift has higher effect here.

-Takes thousands of years for genetic diversity to develop in a population thru slow accumulation

Question 18

An example of a smaller change to a population size

Answer 18

Gene flow caused by mutation

Question 19

How does The founder effect effect Genetic drift

Answer 19

-Indivs in a pop. show variation in genotype
-Some indivs start new pop. + by chance have mostly one genotype
-Now further ‘gene flow’ new pop. will grow with reduced genetic variation
-As pop. is small, more heavily influenced by genetic drift than larger pop.

Question 20

Hardy-Weinberg principle stastes

Answer 20

in a stable population with no disturbing factors, the allele frequencies will remain constant from one generation to the next and there will be no evolution

Question 21

when does Hardy Weinberg principle not apply

Answer 21

any situation which disrupt genetic equilibrium

when assumptions (on other fc) are not applied)

Question 22

Conditions for Hardy-Weinberg principle to apply

Answer 22

1) No selection (pressure)
2) No mutations
3) Large population size
4) Random mating

No migration

Question 23

Formula for prediction ALLELE frequency

Answer 23

P + q = 1

Dominant = p
Recessive = q

Question 24

Formula for prediction GENOTYPE frequency

Answer 24

P^2 + pq + q^2 = 1

P^2 = Homozygous Dominant

pq = heterozygous

q^2 = homozygous recessive

Question 25

Artificial selection

Answer 25

When humans select individuals in a pop. to breed together to get desirable traits
(selection over many generations leeds to new breeds.)

Question 26

how are cattle artificially selected

Answer 26

-Farmers select a female with a very high milk yield + male who’s mother had a very high milk yield + breed these two together
-offspring with highest milk yield bred together
-Continued over several generations

Question 27

outline 2 Problems with Artificial selection

Answer 27

Reducing gene pool

Organism’s health

Question 28

Artificial selection on Reducing gene pool

Answer 28

-Only animals with similar traits and therefore alleles are bred together therefore decrease number of alleles in gene pool.
= less chance of alleles offering resistance to new diseases being present in the population

Question 29

When the genetic differences lead to an inability of members of the populations to interbreed and produce fertile offspring, ………. has occurred

Answer 29

speciation

Question 30

2 types of Speciation

Answer 30

Allopatric speciation

Sympatric speciation

Question 31

Allele frequency

Answer 31

How often a particular allele occurs within a population

Question 32

Allopatric speciation

Answer 32

New habitat due to separation
-different selection pressures
-Those with that allele are more likely to survive and reproduce (potentially less favourable in previous habitat)
-Change in allele frequency in gene pool
- no genetic exchange (between separated groups)
-Characteristics are accumulated until a new species is formed

Question 33

Sympatric speciation

Answer 33

no geographical barrier
Reproductive isolation.
no gene flow occurs between two populations

occurs within same habitat

can occur via:
Ecological separation: different environments in same area (e.g: soil pH)
Behavioural separation: e.g: diff eating which leads to diff attraction to mate, so no reproduction

by mating preferences, Disruptive selection

Commonly caused by a rapid genetic change which causes changes in
-Morphology
-behaviour
-habitat preferences

Question 34

polyploidy

Answer 34

more than 2 sets of homologous chromosomes

more common in plants

result in
higher yield, improved flavour?, best resistance

(having multiple coppies of same gene reduces risk of recessive mutations causing detrimental effects)