7. Genetics, Populations, Evolution and Ecosystems

Question 1

Genotype

Answer 1

the genetic constitution of an organism (all the genes an organism possesses)

Question 2

Phenotype

Answer 2

the expression of the genetic constitution of an organism and its interaction with the environment

Question 3

Homozygous

Answer 3

two copies of the same allele for a gene

Question 4

Heterozygous

Answer 4

two different alleles for a gene

Question 5

Recessive allele

Answer 5

only expressed in the phenotype when no dominant alleles are present

Question 6

Dominant allele

Answer 6

always expressed in the phenotype

Question 7

Codominant allele

Answer 7

both expressed in the phenotype

Question 8

Monohybrid cross

Answer 8

shows the likelihood of inheriting one gene, expected phenotypic ratio of 3:1 but 1:2:1 with codominant alleles

Question 9

Dihybrid cross

Answer 9

shows the likelihood of inheriting certain combinations of two genes, expected phenotypic ratio of 9:3:3:1 but 1:1:1:1 with autosomal linkage

Question 10

Multiple alleles

Answer 10

more than two alleles for one gene

Question 11

Sex linkage

Answer 11

gene is located on the X chromosome, males only need one recessive allele to express the characteristic, females need two recessive alleles to express the characteristic

Question 12

Autosomal linkage

Answer 12

genes are located on the same non-sex chromosome, genes stay together during independent segregation, genes unlikely to be separated by crossing over as it is rare, genes are likely to be inherited together

Question 13

Epistasis

Answer 13

when one gene masks the expression of another gene

Question 14

Recessive epistatic alleles

Answer 14

only mask the expression of another gene if no dominant alleles are present, expected phenotypic ratio of 9:3:4

Question 15

Dominant epistatic alleles

Answer 15

always mask the expression of another gene, expected phenotypic ratio of 12:3:1

Question 16

Population

Answer 16

all the organisms of the same species occupying a particular habitat at a particular time that can potentially interbreed

Question 17

Gene pool

Answer 17

all the genes and alleles in a population at a particular time

Question 18

Hardy-Weinberg principle

Answer 18

a mathematical model used to estimate the allele frequencies within a population, assumes allele frequencies within a population won’t change over generations as long as there is a large population, random mating, no mutations, no selection, no migration

Question 19

Hardy-Weinberg calculation

Answer 19

p^2 + 2pq + q^2 = 1

Question 20

Intraspecific variation

Answer 20

variation in phenotype within a species, can arise from genetic factors (mutation, meiosis, random fertilisation) and environmental factors

Question 21

Interspecific variation

Answer 21

variation in genotype and phenotype between different species, can arise from genetic factors (mutation, meiosis, random fertilisation) and environmental factors

Question 22

Evolution

Answer 22

gradual change in allele frequency over time

Question 23

Genetic drift

Answer 23

gradual change in allele frequency over time due to random chance, greater effect in small populations

Question 24

Natural selection

Answer 24

variation exists in the population due to mutation, a selection pressure creates a struggle for survival, individuals who are better adapted to their environment are more likely to survive and reproduce (differential reproductive success), passing the beneficial allele onto their offspring, over many generations frequency of the beneficial allele increases

Question 25

Stabilising selection

Answer 25

individuals with alleles for the middle range phenotype are more likely to survive and reproduce, mean remains the same but range decreases

Question 26

Directional selection

Answer 26

individuals with allele for an extreme phenotype are more likely to survive and reproduce, occurs when there is a change in environment, mean changes but range stays the same

Question 27

Disruptive selection

Answer 27

individuals with allele for either extreme phenotype more likely to survive and reproduce, leads to speciation

Question 28

Speciation

Answer 28

the development of a new species from an existing species

Question 29

Allopatric speciation

Answer 29

two populations become geographically isolated, different environments have different selection pressures leading to natural selection of the advantageous phenotype, eventually the two populations can no longer breed to produce fertile offspring

Question 30

Sympatric speciation

Answer 30

two populations become reproductively isolated through seasonal, mechanical or behavioural changes, eventually the two populations can no longer breed to produce fertile offspring

Question 31

Community

Answer 31

all different species occupying a particular habitat at a particular time

Question 32

Ecosystem

Answer 32

all the organisms living in a community and all the abiotic conditions of the environment

Question 33

Niche

Answer 33

the organism’s specific role within an ecosystem, includes its biotic (competition, predation) and abiotic (light, oxygen) interactions

Question 34

Carrying capacity

Answer 34

maximum stable population size an ecosystem can support

Question 35

Investigating population growth

Answer 35

prepare broth culture containing bacteria and sufficient nutrients to grow, use a spectrophotometer to measure absorbance (higher absorbance indicates more bacteria), plot an exponential graph of absorbance and time

Question 36

Sampling

Answer 36

quantitative investigation allowing estimation of the number of individuals in a habitat, use a large sample size so representative and random sampling to avoid bias

Question 37

Quadrat

Answer 37

frames used to record abundance of non-mobile species, use a grid and random number generator to generate coordinates, count number of individuals of each species in the quadrat, repeat at least 20 times, calculate mean species frequency, divide area of habitat by area of quadrat and multiply by mean species frequency

Question 38

Transect

Answer 38

line used to record distribution of non-mobile species, run a tape measure between two points, at regular intervals place a quadrat beside the transect and count number of individuals of each species in the quadrat, repeat along the transect

Question 39

Mark-release-recapture

Answer 39

method used to estimate population size of a mobile species, capture initial sample, mark individuals in a harmless way, release individuals and wait for them to reintegrate, capture second sample and count how many are marked

Question 40

Mark-release-recapture equation

Answer 40

(number caught in first sample x number caught in second sample) divided by number marked in second sample

Question 41

Succession

Answer 41

change in an ecosystem over time, can be primary (on newly formed land) or secondary (on land cleared of all plants)

Question 42

Succession process

Answer 42

area is colonised by pioneer species, pioneer species change environmental conditions, making the habitat less hostile for other species, new species may outcompete the preceding species, biodiversity increases, continues until climax community is reached

Question 43

Climax community

Answer 43

final stage of succession where few species dominate and there is a stable equilibrium of species

Question 44

Conservation

Answer 44

protection and management of ecosystems in a sustainable way (eg. preventing succession, seed banks, captive breeding, fishing quotas, restricting urban development)