Genetic Diversity, Adaptation and Biodiversity

population

all the organisms of one species that live in a habitat

gene pool

all the alleles in a population

species

group of organisms that are able to produce fertile offspring

community

the organisms of all the different species that live in one habitat, and interact with each other

species richness and how can it be determined

the number of different species in a community

1. use random number generator to select sampling site at random

2. use quadrat

3. count number of different plant species in each quadrat

method to determine the total number of the beetle species in the meadow

• determine the area of plot 1

• calculate the total area of the meadow

• divide the area of the meadow by the area of the plot

• multiply by the number of beetles

What is the difference b/w species richness and an index of diversity?

Species richness only measures the number of different species, it does not measure the number of individuals

give 2 ways that the students would have ensured their index of diversity was representative of each habitat

• random samples

• large numbers

suggest how to get a more precise value for the index of diversity for a habitat

• take more samples and find mean

• use a random number generator to pick coordinates and collect species data at those points

The index of diversity of the insects was higher in the hedge than in the barley field. Explain why.

• more plant species

• more food sources

• more habitats

what is biodiversity and how can it be measured?

The variety of living organisms

It can be measured in terms of:

- species diversity (number of species in a community)

- ecosystem diversity (range of different habitats)

- genetic diversity

What is global biodiversity?

the variety of species on earth

What is local biodiversity?

the variety of species living in a (small) habitat close by

- e.g. a pond or woodland

What is ecosystem diversity?

The range of different habitats in an area

abiotic factors

non-living factors

how can resistance appear in an isolated population of organisms

mutation

genetic diversity

total number of different alleles in a population

What advantage does a high genetic diversity provide?

ability to adapt to change in environment

• allows natural selection to occur

How can genetic diversity of a population be increased?

1. Mutation of DNA, causing new alleles to be formed

2. New alleles can be introduced if a new population of that species migrates to the area (gene flow)

niche

the role of a species within its environment

• species sharing the same niche will compete with each other

how could you determine if two organisms from different populations belongs to the same species

breed together

• if fertile offspring: then same species

evolution

• variation present in original population

• mutation occurs

• individuals with advantageous alleles more likely to survive and reproduce

  • become better adapted for survival

  • differential reproductive success

  • greater reproductive success

• allele frequency changes

• pass on allele to offspring

• frequency of allele increases in offspring and next generation

  • takes many generations for favourable allele to become the most common allele

allopatric speciation

• geographical isolation

• gene pools are separate and no interbreeding

• variation present in population

• variation due to mutation

• different selection pressures

• differential reproductive success

• leads to change/increase in allele frequency & gene pools over time

sympatric speciation

• speciation occurs in the same habitat/environment/population

• mutation occurs

• mutation causes difference in reproductive/mating habits (usually mentioned in the questioned)

• reproductive isolation (e.g. different breading seasons)

  • no interbreeding

  • gene pools remain separate

  • no gene flow

• change in frequency of alleles

  • different alleles passed on

• eventually become different species & unable to produce fertile offspring

  • divergence of gene pools

  • gene pools become increasingly different until they cannot interbreed to produce fertile offspring

directional selection

• dominant allele confers advantage

  • dominant allele more likely to survive and reproduce

• recessive allele confers disadvantage

stabilising selection

only few organisms survive at the extreme

• most survive from middle of the range

Explain how resistance to an antibiotic could become widespread in a bacterial population following a gene mutation conferring resistance in just one bacterium.

1. frequent use of antibiotic kills bacteria & creates selection pressure

2. bacteria with mutation have selective advantage over others

3. these bacteria are more likely to survive and reproduce than other types of bacteria, allowing them to pass on advantageous alleles in greater numbers

4. frequency of advantageous alleles increases in subsequent generations

5. therefore frequency of resistant types of bacteria increase in subsequent generations

how succession occurs

• colonisation by pioneer species

• change in the environment, which enables the other species to survive and colonise

• change in biodiversity

• stability increases

  • becomes a less hostile environment

  • climax community

what does the Hardy-Weinberg principle predict?

that the frequency of alleles will stay constant/the same, provided that theres no mutation

5 assumptions that must be made when using the hardy-weinberg equation

1. no selective advantage

2. large population

3. random mating

4. no mutation

5. no immigration/emigration

give 4 conditions necessary for results from mark-release-recapture investigations to be valid.

1. no migration/immigration

2. no reproduction

3. large enough sample size

4. marking doesn’t increase vulnerability to predation

capture-recapture method

• capture/collect sample

• mark and release

• ensure that method of marking doesn’t:

  1. harm lizard

  2. makes it more visible to predators

• leave sufficient time for lizards to randomly distribute in island, before collecting a second sample

• population = number in first sample x number in second sample / number of marked lizards in 2nd sample

Give 5 ways in which courtship behaviour increases the probability of successful mating

1. Can recognise and attract the same species

2. Stimulates the release of gametes

3. Recognition of a mate: attracts opposite sex

4. Indicates sexual maturity/fertility

5. Can form a bond so the pair can reproduce several times

What is traditional taxonomy and its limitations?

The comparison of the frequency of observable characteristics

- limited by polygenic (coded for by more than one gene) features and environmental effects

How are organisms compared in modern taxonomy?

Through the similarities/differences of their:

1. DNA base sequences

2. mRNA base sequences

3. Amino acid sequences

classification

The process of arranging organisms into groups

What is artificial classification?

Division of organisms based on obvious differences (e.g. colour,size etc.)

Can be based on analogous characteristics

Explain what is meant by a heirarchy/hierarchical classification

1. Groups within groups;

2. No overlap (between groups);

Describe Domain Eukarya

1. Mainly multicellular

2. Cells contain membrane-bound organelles

3. Membranes contain fatty acids linked to glycerol via ester binds

4. 80S ribosomes

5. Cell walls made of chitin/cellulose

Describe Domain Archaea

1. Genes similar to eukaryotes

2. No murein in cell walls

3. More complex RNA polymerase

4. 70S ribosomes

Describe Domain Bacteria

1. Unicellular

2. Murein cell walls

3 no membrane-bound organelles

4. 70S ribosomes

5. Single loop of DNA, but no histones

how are phylogenetic groups created

Grouped according to evolutionary links and common ancestry

What impact does agriculture have on species diversity?

decreases species richness

• farmland is typically used for only 1 species (monoculture)

• use of pesticides/ herbicides

List 5 agricultural practices that reduce biodiversity

1. Removing hedgerows

2. Clearing large woodlands

3. Use of pesticides

4. Use of herbicides

5. Monoculture

How does monoculture reduce biodiversity?

Monoculture means growing only one type of plant, so other plants that are natural to the area are killed and removed to make space

Fewer organisms can be supported

How does the use of herbicides reduce biodiversity?

1. Plants are killed - biodiversity is reduced

2. Species that prey on these plants lose their food resources

• so their species number could also fall

How does the use of pesticides reduce biodiversity?

1. Pesticides are chemicals used to kill the organisms that feed on crops

• so the pests are killed, biodiversity is reduced

2. Species that prey on the pests lose food sources

• so species numbers could also fall

How does the clearing of woodlands reduce biodiversity?

1. The number of trees, and the number of species of trees are both damaged

• this means that habitats are destroyed

2. The land is used for farming, so the species living there cannot use it for shelter or as a food source (esp. if pesticides are used)

• so the species must migrate or they will die

advantages and disadvantages of replanting hedges

advantages

• greater biodiversity so increase in predators of pests

• increase in pollinators so more yield

disadvantages

• increase in pests which could damage crops

• reduced land area for crop growth

• more difficult to farm therefore less income

What impact does agriculture have on genetic diversity?

decreases

• farmers select certain characteristics, which reduces number of different alleles in the population

What are the 2 factors affecting genetic variation?

1. Genetic factors (genes and alleles present)

2. Environmental factors (food/climate/lifestyle)

How can biodiversity be increased in areas of agriculture?

1. Use hedgerows instead of fences.

2. Rotate crops every season

3. Limit use of pesticides and herbicides.

3 reasons why a population might show very low levels of genetic diversity

1. Genetic bottleneck: population might've been very small

2. Founder effect: population may have been started by a small number of organisms

3. Inbreeding