7. genetics, populations, evolution and ecosystems P2

Question 1

INHERITANCE
define genotype

Answer 1

the genetic constitution of an organism

Question 2

INHERITANCE
define phenotype

Answer 2

The expression of an organisms genetic constitution combined with its interaction with the environment

Question 3

INHERITANCE
what’s an allele?

Answer 3

different forms of a particular gene found at the same locus on a chromosome.

Question 4

INHERITANCE
what is meant by codominant alleles

Answer 4

two dominant alleles are both expressed/ both contribute to the phenotype,
either by showing a blend of both characteristics or the characteristics appearing together.

Question 5

INHERITANCE
define monohybrid inheritance

Answer 5

the inheritance of characteristics is controlled by a single gene.

Question 6

INHERITANCE
define dihybrid inheritance

Answer 6

inheritance of 2 characteristics which are
controlled by different genes.

Question 7

INHERITANCE
what is meant by sex linkage?

Answer 7

where an allele is located on one of the sex chromosomes, meaning its expression depends on the sex of the individual.

Question 8

INHERITANCE
why are males more likely to express a recessive sex-linked allele?

Answer 8

most sex-linked alleles are located on the X chromosome. Therefore males only get one copy of the allele, so will express the characteristic even if it’s recessive.

Question 9

INHERITANCE
define autosomal linkage?

Answer 9

where two or more genes are located on the same chromosome.

Question 10

INHERITANCE
define epistasis

Answer 10

where two non linked genes interact with one gene either masking or suppressing the other.

Question 11

POPULATIONS
define species

Answer 11

a group of organisms that can interbreed to produce fertile offspring.

Question 12

POPULATIONS
define population

Answer 12

all the organisms of a particular species that live in the same place.

Question 13

POPULATIONS
define gene pool

Answer 13

the sum of all the alleles of the genes of a population (of a single species) at a particular time

Question 14

POPULATIONS
define allele frequency

Answer 14

the proportion of a certain allele within a gene pool

Question 15

POPULATIONS
give the Hardy Weinberg equations

Answer 15

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

p + q = 1

Question 16

SPECIATION
give genetic factors that cause phenotypic variation within a species.

Answer 16

mutation of alleles

random fertilisation by gametes

random assortment of genetic material during meiosis.

Question 17

SPECIATION
how does natural selection cause a change in a populations gene pool over generations?

Answer 17

Organisms with advantageous characteristics are more likely to survive and pass their favourable alleles to offspring. Frequency of unfavourable alleles decrease.

Question 18

SPECIATION
what is stabilising selection?

Answer 18

Occurs when environmental conditions stay the same. Individuals closest to the mean are favoured and any new characteristics are selected against.

results in low diversity.

Question 19

SPECIATION
what is directional selection?

Answer 19

occurs when environmental conditions change. Individuals with phenotypes suited to the new conditions will survive and reproduce and pass on their genes.

Over time the mean of the population will move towards these characteristics.

Question 20

SPECIATION
what is disruptive selection?

Answer 20

the opposite of stabilising selection. both extremes of the normal distribution are favoured over the mean.

Over time, the population becomes phenotypically divided

Question 21

SPECIATION
define speciation

Answer 21

where a population is split and isolated, there are different selective pressures on the two groups. If the genetic makeup changes to the extent the two groups can no longer interbreed, they have become two separate species.

Question 22

SPECIATION
define allopatric speciation

Answer 22

speciation resulting from a physical barrier, e.g. river, mountains.

The environments occupied by the two groups are different, and therefore different alleles are favoured.

Question 23

SPECIATION
define sympatric speciation?

Answer 23

speciation resulting from a non physical barrier, e.g. a mutation that no longer allows two organisms to produce fertile offspring. Any changes to anatomy or behaviour may also prevent breeding

Question 24

SPECIATION
define genetic drift

Answer 24

a change in a populations allele frequencies that occurs due to chance rather than selective pressures

Question 25

**SPECIATION** why does genetic drift affect small populations more than large ones?

Answer 25

the gene pool is smaller, so there are less alleles available and any change in frequency becomes pronounced very quickly

Question 26

**POPULATIONS IN ECOSYSTEMS** define community

Answer 26

all the different species that live in one area and interact with each other.

Question 27

**POPULATIONS IN ECOSYSTEMS** define ecosystem

Answer 27

all the living organisms found in one area, combined with non-living aspects of their environment

Question 28

**POPULATIONS IN ECOSYSTEMS** describe biotic and abiotic factors, giving examples

Answer 28

Biotic - living features of an ecosystem, e.g. predators, desease abiotic - non-living features of an ecosystem e.g. light, temperature.

Question 29

**POPULATIONS IN ECOSYSTEMS** define habitat

Answer 29

the place where an organism lives within an ecosystem.

Question 30

**POPULATIONS IN ECOSYSTEMS** define a niche

Answer 30

the role of a species within its habitat consisting of both its biotic interactions, e.g. what it eats and abiotic interactions, e.g. time of day it is active.

Question 31

**POPULATIONS IN ECOSYSTEMS** define carrying capacity

Answer 31

the maximum size of a population an ecosystem can support

Question 32

**POPULATIONS IN ECOSYSTEMS** name four abiotic factors that affect population growth

Answer 32

temperature light PH water/humidity

Question 33

**POPULATIONS IN ECOSYSTEMS** what is meant by intraspecific and interspecific competition?

Answer 33

intraspecific - competition between organisms of the same species. interspecific - competition between organisms of different species

Question 34

**POPULATIONS IN ECOSYSTEMS** what resources might organisms compete for?

Answer 34

food water shelter light mates

Question 35

**POPULATIONS IN ECOSYSTEMS** describe the pattern of a typical predator-prey relationship in terms of population change

Answer 35

prey is eaten by predator, resulting in predator pop increasing and prey pop decreasing. fewer prey means increased competition for food, so predator pop decreases. fewer predators means more prey survives and the cycle begins again

Question 36

**POPULATIONS IN ECOSYSTEMS** how are quadrats used for estimating population size?

Answer 36

can be placed on gird coordinates or at intervals along belt transect. For slow moving or non-motile organisms

Question 37

**POPULATIONS IN ECOSYSTEMS** how is mark-release-recapture used for estimating population size?

Answer 37

a sample of a species is captured, marked, then released back into the same area they were caught. after a certain period of time, another sample of the species is captured, and the number of marked organisms are counted. for motile organisms

Question 38

**POPULATIONS IN ECOSYSTEMS** what is the equation for mark-release-recapture?

Answer 38

estimated pop size = total number of individuals in first sample **X** total number of individuals in the second sample **divided by** the number of marked individuals recapture’s

Question 39

**POPULATIONS IN ECOSYSTEMS** what assumptions does the mark-release-recapture method make?

Answer 39

- no migration in or out of the population - no deaths or births - method of marking doesn’t affect survival - mark does not come off - marked individuals distribute evenly

Question 40

**POPULATIONS IN ECOSYSTEMS** why are ecosystems described as being dynamic?

Answer 40

populations constantly rise and fall any small change can have a large effect biotic and abiotic factors may alter the conditions of the ecosystem.

Question 41

**POPULATIONS IN ECOSYSTEMS** what is meant by primary succession?

Answer 41

where an area previously devoid of life is colonised by a community of organisms

Question 42

**POPULATIONS IN ECOSYSTEMS** summarise the process of primary succession

Answer 42

pioneer species can survive harsh conditions and colonise the area. they change abiotic factors of their env, e.g. decomposition adds nutrients to ground. over time, this allows more complex organisms to survive

Question 43

**POPULATIONS IN ECOSYSTEMS** what is the climax community and how is it reached?

Answer 43

the final stage of succession, where the ecosystem is balanced and stable. it is reached when soil is rich enough to support large trees or shrubs and the environment is mo longer changing

Question 44

**POPULATIONS IN ECOSYSTEMS** how might a species alter the environmental that develops during succession?

Answer 44

a species may improve the environment to make it more suitable for other species. Or a species may worsen the environment by making it less suitable for other species.

Question 45

**POPULATIONS IN ECOSYSTEMS** define conservation

Answer 45

the protection and management of species and habitats, in order to maintain biodiversity. methods need to be adapted to the ecosystem in question

Question 46

**POPULATIONS IN ECOSYSTEMS** how might succession be managed in order to aid conservation?

Answer 46

sometimes succession needs to be prevented in order to preserve an ecosystem at a certain point.