Genetics, Populations, Evolution and Ecosystems- Topic 7

Question 1

Explain what it means when two genes are linked.

Answer 1

Genes on the same chromosome

Question 2

The breeder had expected equal numbers of …. explain why actual numbers were different to those expected

Answer 2

As the fusion of gametes is random

Question 3

What sample is sufficiently large enough for a Chi-squared test?

Answer 3

sample of at least 20

Question 4

Define a population

Answer 4

group of organisms of the same species occupying

a particular space at a particular time that can potentially interbreed.

Question 5

Give Hardy Weinberg equation used to determine allele frequency

Answer 5

p + q = 1

Question 6

What do the letters stand for in Hardy Weinberg equation?

Answer 6

q = recessive homologous
p = dominant homologous
2pq = heterozygous

Question 7

What is a gene pool?

Answer 7

All the alleles of all the genes of all the individuals in a population at a given time

Question 8

What is allele frequency?

Answer 8

Number of times an allele occurs within the gene pool

Question 9

Individuals within a population of a species may show a wide range of variation in phenotype. What is this due to?

Answer 9

Genetic factors: mutations, meiosis, random fertilisation of gametes
and environmental factors: pH, temperature, food availability

Question 10

What is the primary source of genetic variation?

Answer 10

Mutation

Question 11

What is evolution?

Answer 11

The frequency of an allele in a population changing over time

Question 12

How is differential survival and reproduction, ie natural selection created?

Answer 12

Predation, disease, and competition (selection pressures)

Question 13

Why do a greater proportion of the next generation inherit the beneficial alleles?

Answer 13

Individuals with phenotype that inc chance of survival = more likely to survive, reproduce and pass on their genes. (therefore freq of beneficial alleles in the gene pool increases from generation to generation)

Question 14

Name 3 types of selection.

Answer 14

Stabilising selection, Directional selection and disruptive selection

Question 15

What is stabilising selection?

Answer 15

individuals with alleles for characteristics towards middle of range more likely to survive and reproduce e.g. MEDIUM fur length
- occurs when environment ISN’T changing

Question 16

What is directional selection?

Answer 16

Individuals with alleles for extreme phenotype are more likely to survive and reproduce. Could be in response to environmental change

Question 17

what is disruptive selection?

Answer 17

extreme phenotypes at either end of the range are more likely to survive and reproduce. (middle characteristics lost) occurs when environment favours more than one phenotype

Question 18

Define community

Answer 18

all populations of different species living and interacting in a particular place at the same time

Question 19

Define a Habitat

Answer 19

place where an organism normally lives and is characterised by physical conditions and the other types of organisms present.

Question 20

Define Ecological niche

Answer 20

where an organism lives and what it does there

Question 21

Define carrying capacity

Answer 21

certain size of population of a species that an ecosystem supports

Question 22

What is an abiotic factor and can you give an example?

Answer 22

non-living factor in environment e.g. temperature

Question 23

What is a biotic factor and can you give an example?

Answer 23

a living environmental factor e.g. competition and predation

Question 24

What is an Ecosystem?

Answer 24

A community plus all the non-living conditions in the area in which it lives.

Question 25

What is interspecific Competition?

Answer 25

Organisms of different species compete with each other for the same resources e.g. food and habitat

Question 26

What is intraspecific competition?

Answer 26

Organisms in the same species compete with each other for the same resources

Question 27

What are the 2 ways that you can estimate the size of a population?

Answer 27

Randomly placing quadrats

Mark-release-recapture

Question 28

What equation can you use to determine the estimated population size?

Answer 28

total no.of individuals in 1st * total in 2nd /

number of marked individuals recaptured

Question 29

When using quadrats how can results be made more reliable?

Answer 29

The larger the no.of sample quadrats the more reliable the results will be

Question 30

What is succession?

Answer 30

The process by which an ecosystem changes over time. Biotic and abiotic conditions change.

Question 31

Primary succession

Answer 31

when species colonise new land. First species to colonise the area = pioneer species (e.g. seeds/spores)

Question 32

Secondary succession

Answer 32

Already soil layer so succession starts at later stage (pioneer species in secondary succession are larger plants e.g. shrubs)

Question 33

What is the final stage of succession and what happens?

Answer 33

Climax community - ecosystem is largest and most complex. Won’t change much, in a steady state

Question 34

Why do some species become dominant species?

Answer 34

Better adapted for improved conditions and out-compete plants and animals that are already there.

Question 35

As succession goes on the ecosystem becomes more ….. which means that ………. increases

Answer 35

As succession goes on the ecosystem becomes more complex which means that biodiversity increases

Question 36

What is a benefit of using a transect?

Answer 36

They ensure every community is sampled

Question 37

What is conservation?

Answer 37

management of resources so that they have maximum use in future

Question 38

Why is conservation important?

Answer 38

to maintain our planet

value of organisms

Question 39

How does speciation occur?

Answer 39

Speciation (development of the new species) when 2 populations are reproductively isolated

Question 40

What is allopatric speciation

Answer 40

Where species are geographically separated and experience slightly different conditions e.g. climate.
therefore also different selection pressures (changes in allele frequency)

Question 41

What is sympatric speciation?

Answer 41

mutation can occur increasing no. of chromosomes. individuals with different numbers of chromosomes can’t produce fertile offspring, making organism reproductively isolated.

Question 42

Name and describe ways reproductive isolation can occur

Answer 42

Seasonal- individuals from same population develop different mating seasons/ sexually active at different times of year
Mechanical- changes in genitalia prevent successful mating
Behavioural- a group of individuals develop courtship rituals that aren’t attractive to main population

Question 43

What is genetic drift?

Answer 43

When chance dictates which individuals survive, breed and pass on their alleles

Question 44

genetic drift has greater effect in ….. populations

Answer 44

greater effect in smaller populations where chance is greater

Question 45

How can genetic drift lead to speciation?

Answer 45

By chance allele A passed on more often than others so number of individuals with allele increases. changes in allele frequency in 2 isolated populations could eventually lead to reproductive isolation and speciation.

Question 46

Give the Hardy Weinberg equation used to determine the frequency of genotypes or phenotypes

Answer 46

p2 + 2pq + q2 = 1