Genetic diversity and adaptation

Question 1

Genetic diversity

Answer 1

Number of different alleles of a gene in a population

Question 2

Population

Answer 2

A group of interbreeding individuals of the same species

Question 3

The principles of natural selection in the evolution of populations

Answer 3

Variation of alleles exists in population due to random DNA mutations eg some bacteria contain the gene for antibiotic resistance due to a mutation

Change in environment eg antibiotic introduced; those with an advantageous allele have an increased chance of survival and reproduction – differential survival/reproductive success eg bacteria with gene for resistance survive and reproduce whilst those without it die

Those surviving/reproducing pass advantageous allele to offspring so that the frequency of advantageous allele and (named) characteristic increases in the population

This occurs over many generations (evolution: change in allele frequency over time)

Question 4

Directional selection

Answer 4

A change in the environment causes selection pressure to act on one side of the mean.

One extreme phenotype is more likely to survive and reproduce so the mean phenotype changes

Question 5

Stabilising selection

Answer 5

A stable environment causes selection pressure to act on either side of the mean

Both extremes of the phenotype are less likely to survive and reproduce so the mean phenotype remains the same

Question 6

Anatomical adaptations that increase an organisms chance of survival

Answer 6

Structural features of organisms body/observed structures

eg whales thick layer of blubber helps keep warm in cold sea

Question 7

Physiological adaptations that increase an organisms chance of survival

Answer 7

Processes inside the body

eg brown bears hibernate in the winter and have a lower metabolism to conserve energy so they don’t need to look for food when its scarce

Question 8

Behavioural adaptations that increase an organisms chance of survival

Answer 8

Ways an organism acts

eg a possum plays dead if they’re being threatened by a predator in order to escape attack

Question 9

Species and offspring

Answer 9

If two organisms belong to the same species they are able to produce fertile offspring

Offspring from 2 different species may be infertile because they will have an odd number of chromosomes; meiosis cannot occur to produce (haploid) sex cells (gametes)

Question 10

Courtship behaviour and species recognition

Answer 10

Allows recognition of members of the same species as courtship behaviour is species specific, so that fertile offspring is produced.

It also indicates sexual maturity and helps organisms recognise members of the opposite sex.

Stimulates the release of gametes and establishes a pair bond to raise young.

It also synchronises mating so that it takes place when there is the maximum probability of the sperm fertilising the ovum.

Question 11

Phylogenetic classification system

Answer 11

Arranges species into groups based on their evolutionary origins (common ancestor) and relationships

Arranges the groups into a hierarchy, in which the groups are contained within larger composite groups with no overlap

Each group within a phylogenetic biological classification is called a taxon

Question 12

Hierarchy that comprises the taxa

Answer 12

Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 13

The binomial system

Answer 13

Each species is universally identified by a binomial consisting of the name of its genus and species

It is a universal system; leads to no confusion as many organisms have more than one common name

Question 14

Genome sequencing

Answer 14

Compares the order of the base sequences of the whole genome of different species

A higher percentage match between two species means that they are more closely related

Question 15

Immunology

Answer 15

The sequence of amino acids in proteins is determined by mRNA which, in turn, is determined by DNA.

The tertiary structure of a protein tells us about the sequence of DNA

If the same antibody binds to a specific antigen, then they are closely related

Question 16

Biodiversity

Answer 16

The variety of living organisms in an area. It has 3 components:

Species diversity – the number of different species and the number of individuals of each species within a community

Genetic diversity

Ecosystem diversity

Question 17

Habitat

Answer 17

Places where an organism lives

Question 18

Community

Answer 18

All the populations of different species within a habitat

Question 19

Local biodiversity

Answer 19

The variety of species living in a small habitat eg pond/meadow

Question 20

Global biodiversity

Answer 20

The variety of species living on earth

Question 21

Species richness

Answer 21

The number of different species in a community

Question 22

Index of diversity what is it

Answer 22

Describes the relationship between the number of species within a community and the number of individuals in each species

The greater the species richness and species evenness, the higher the number (lowest possible value is 1)

Index of diversity is a more useful measure of species diversity than species richness

As well as measuring the number of species, it also measures the number of individuals in a species (different proportions of species) so it takes account for the fact that some species may be present in low/high numbers

Question 23

Index of diversity formula

Answer 23

d = N(N-1) / Σn(n-1)

d = Index of diversity
N = Total number of organisms of all species
n = total number of organisms of each individual species
Σ = the sum of

Question 24

How do farming techniques reduce biodiversity

Answer 24

The removal of woodland and hedgerows so there are fewer habitats/niches and a lesser variety of food sources

Creating monocultures eg replacing natural meadows with cereal crop so there is a lower diversity of plants

The use of pesticides, herbicides and inorganic fertilisers kills insects

Crops are a better competitor for resources eg light/nutrients

Question 25

The balance between conservation and farming

Answer 25

Humans need to make a balanced judgement between the demands for increased food production due to a rapidly growing human population and the need to conserve the environment Ways to increase biodiversity without unduly raising food costs or lowering yields: - Use crop rotation of nitrogen fixing crops instead of fertilisers - Maintain existing hedgerows and plant new hedges instead of using fences - Reduce the use of pesticides It is recognised that these practices will make food slightly more expensive to produce, so to encourage farmers there are a number of financial incentives e.g. from the Department for Environment, Food and Rural Affairs (DEFRA) and the European Union.

Question 26

Variation

Answer 26

Differences (in characteristics) between individuals within a species (intraspecific variation) or between different species (interspecific variation) Variation within a species could be the result of genetic factors (ie alleles), environmental factors, or a combination of both

Question 27

Continuous variation

Answer 27

No distinctive categories and the data tends to be quantitative. It is controlled by many genes and is strongly influenced by the environment eg height

Question 28

Discontinuous variation

Answer 28

There are distinct, discrete categories and the data tends to be qualitative It is controlled by a single gene or a few genes and it is unaffected/not strongly influenced by the environment eg blood groups

Question 29

Genetic diversity

Answer 29

Number of different alleles in a population

Question 30

Genetic diversity within, or between species, and how it can be made by comparing different things

Answer 30

The frequency of measurable/ observable characteristics indicates genetic diversity because is based on the fact that different alleles determine different characteristics, so the higher the variety of a characteristic, the higher the variety of alleles of that gene and hence the greater the genetic diversity The base sequence of DNA and mRNA The amino acid sequence of the proteins encoded by DNA and mRNA

Question 31

Comparison of observable characteristics to measure genetic diversity and limitations of this

Answer 31

Early estimates of genetic diversity were made by looking at the frequency of measurable/observable characteristics within a population Many observable characteristics are coded for by more than one gene (polygenic) so they vary continuously; it is difficult to distinguish one from another Characteristics could be modified by the environment so differences may be a result of different environmental conditions rather than different alleles

Question 32

How gene technology caused a change in the methods of investigating genetic diversity

Answer 32

Gene technologies have made it possible to directly obtain DNA sequences. These technologies can be used to give more accurate estimates of genetic diversity within a population/species because: Different alleles of the same gene have slightly different base sequences. If you compare DNA base sequences of the same gene in different organisms in a population, you can find out how many alleles of that gene are in a population Different alleles are transcribed into slightly different mRNA base sequences and may produce polypeptides with slightly different amino acid sequences which can also be compared

Question 33

Taking a representative sample: random sampling and example

Answer 33

Random sampling eliminates bias Example of random sampling in a field: - Divide the area into a grid of numbered lines - Using random numbers from a table, obtain a series of coordinates - Take samples at the intersection of each pair of coordinates ie using quadrats

Question 34

Taking a representative sample: a large sample size

Answer 34

Minimises effects of chance (lower probability that chance will influence the data) Anomalies have less influence and can be identified Analyse results with a statistical test to see if variation observed is or isn’t due to chance

Question 35

Taking a representative sample: mean

Answer 35

Mean = (sum of all measurements)/(total number of measurements) It can show if there is variation/ differences between samples. It is useful for comparison, but provides no info about the range of values

Question 36

Taking a representative sample: standard deviation

Answer 36

Shows the spread of values around the mean. 68% of all measurements lie within ±1 standard deviation and about 95% of all measurements lie within ±2 standard deviations (only true for normal distribution) The higher the value standard deviation, the higher the variation If standard deviations overlap, causing values of each set of data to be shared, any difference between the two may be due to chance.