3.7 Genetics, populations, evolution and ecosystems

Question 1

Genotype

Answer 1

The complete set of genes/genetic constitution of an organism

Question 2

Phenotype

Answer 2

Expressed characteristics caused by the genotype and its interaction with the environment

Question 3

Chi squared equation

Answer 3

Σ (O-E) / E

Question 4

Sex linkage

Answer 4

when a gene is found on the X/Y chromosome

Question 5

Autosomal linkage

Answer 5

Two or more genes that are on the same autosomal chromosome, so must be expressed together. Can be heterozygous or homozygous

Question 6

Autosomal Chromosome

Answer 6

A non-sex/numbered chromosome (1-22)

Question 7

Epistasis

Answer 7

When one gene affects the expression of another gene

Question 8

Recessive epistasis

Answer 8

The presence of a recessive allele prevents the expression of another allele at a second locus. Recessive epistasis gives the ratio of 9:3:4.

Question 9

Dominant epistasis

Answer 9

When a dominant allele at one locus completely masks the alleles at a second locus. Dominant epistasis gives a ratio of 12:3:1.

Question 10

Population

Answer 10

A group or organisms of the same species occupying a particular space at a particular time that potentially can interbreed

Question 11

Gene pool

Answer 11

Total number of alleles that are present in population

Question 12

Allele frequency

Answer 12

The proportion of a specific allele in a gene pool

Question 13

Hardy Weinberg Equation (2 of them)

Answer 13

1. p + q =1
2. p² + 2pq + q² = 1

Question 14

Hardy Weinberg assumptions (5)

Answer 14

1. No mutations
2. No movement of alleles into or out of population by migration
3. Population is large
4. No selection - every allele has equal chance of being passed on
5. Mating is random

Question 15

Reasons for variation in phenotype (5)

Answer 15

1. Meiosis - crossing over of homologous chromosomes
2. Meiosis - segregation of homologous chromosomes
3. Mutation
4. Random fertilisation
5. Environmental factors

Question 16

Factors influencing natural selection

Answer 16

Predation
Disease
Competition

Question 17

Natural selection 5 marker

Answer 17

1. Variation in ______ poluation
2. Due to mutation
3. Causing an allele for _______
4. Reference to selection
5. Organisms with _______ survive and breed better
6. Increase in allele frequency

Question 18

Natural selection definition

Answer 18

Those organisms with phenotypes providing selective advantages are likely to produce more offspring and pass on their favourable alleles to the next generation

Question 19

Evolution

Answer 19

A change in allele frequencies in a population over time

Question 20

Stabilising selection

Answer 20

When natural selection favours the average allele
Allele frequency remains constant
Example: Human birth weight

Question 21

Directional selection

Answer 21

When natural selection favours the extreme allele
Example: Abiotic resistance in bacteria

Question 22

Disruptive selection

Answer 22

When both extremes of alleles are favoured over intermediate ones.
Example: Cuttlefish mating

Question 23

Allopatric speciation process

Answer 23

1. Allopatric speciation
2. reproductive isolation
3. Different selection pressures
4. Variation due to mutation
5. Advantageous alleles passed on
6. Allele frequency increases
7. Eventually the groups will not be able to breed to produce fertile offspring so are not the same species

Question 24

Sympatric speciation process

Answer 24

1. Sympatric speciation
2. reproductive isolation
3. Different selection pressures
4. Variation due to mutation
5. Advantageous alleles passed on
6. Allele frequency increases
7. Eventually the groups will not be able to breed to produce fertile offspring so are not the same species

Question 25

Genetic drift

Answer 25

The change in allele frequencies in a population from generation to generation that occurs due to chance events.

Question 26

Why is genetic drift important in smaller populations

Answer 26

Smaller populations have less variation and, therefore, a lower ability to respond favorably — that is, adapt — to changing conditions.

Question 27

Community

Answer 27

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

Question 28

Ecosystem

Answer 28

The dynamic interaction between all the living (biotic) and non-living (abiotic) factors in a given area

Question 29

Niche

Answer 29

The role of a species within its habitat. Only one species may occupy a specific niche.

Question 30

Abiotic factors

Answer 30

Non-living: - Temperature - Soil pH - Light intensity - Water and humidity - CO2 concentrations

Question 31

Biotic factors

Answer 31

Living: - Predation - Competition - Disease

Question 32

Interspecific competition

Answer 32

Competition between members of different species

Question 33

Infraspecific competition

Answer 33

Competition between members of the same species

Question 34

Size of a population experiment (slow/non-motile organisms)

Answer 34

Quadrat / belt transect 1. Separate area into a grid 2. Use a random coordinate generator to determine where to place the quadrat 3. Count frequency of organism in quadrat / estimate percentage cover 4. Use a large sample (50) and calculate the average 5. Multiply average by number os squares in grid

Question 35

Size of a population experiment (fast/hidden animals)

Answer 35

Capture recapture method 1. Capture a set or animals 2. Mark them in such a way that it does not affect their survival or the experiment 3. Release organisms back into area they were captured from 4. After a set amount of time capture another set of those animals 5. Count the number of animals that have been marked 6. Calculate estimated size of population Population size = Initial set x second set / Marked second set

Question 36

Carrying capacity

Answer 36

The number of members of a population an ecosystem can support

Question 37

Assumptions of mark-release method (5)

Answer 37

- Marked individuals distribute evenly - Few deaths/births - No migration in or out of population - Method does not reduce chance of survival for individuals of the population - Proportion of marked to non marked individuals represents the whole population

Question 38

Predation cycle

Answer 38

1. Prey is eaten by predator 2. Predator population increases 3. Not enough food to sustain large population 4. predator population decreases 5. Prey population increases 6. More food for predator population REPEAT

Question 39

Succession (5)

Answer 39

1. Colonisation by pioneer species 2. Pioneer species causes change in environment NAMED 3. Environment becomes less hostile for other organisms 4. Change in biodiversity 5. To climax community

Question 40

Sympatric speciation definition

Answer 40

The formation of two species from one original species due to reproductive isolation whilst occupying the same geographical location.

Question 41

Allopatric speciation definition

Answer 41

The formation of two species when populations of a species become separated from each other by geographical barriers

Question 42

In fruit flies, males have the sex chromosomes XY and the females have XX. In fruit flies, a gene for eye colour is carried on the X chromosome. The allele for red eyes, R, is dominant to the allele for white eyes, r. Male fruit flies are more likely than female fruit flies to have white eyes. Explain why [2]

Answer 42

1. Males have one allele; 2. Females need two recessive alleles

Question 43

The allele for grey body colour, G, is dominant to the allele for black body colour, g. The allele for long wings, L, is dominant to the allele for short wings, l. Grey body and long wings - 223 Black body and short wings - 218 Explain the results [3]

Answer 43

1. Genes are linked - autosomal linkage 2.No crossing over 3. No Gl or gL