topic 7 - inheritence, succession etc!

Definition of genotype

The genetic constitution of an organism (the allele it has for a gene)

recessive allele definition

an allele only expressed if no dominant allele is present

definition of phenotype

The expression of the genes and its interaction with the environment

homozygous definition

a pair of homologous chromosomes carrying the same alleles for a single gene

heterozygous definition

a pair of homologous chromosomes carrying two different alleles for a single gene

dominant allele

allele that is always expressed in the phenotype

codominant definition

both alleles equally dominant and expressed in phenotype

sex linkange

a gene whose locus is on the X chromosome

autosomal linkage definition

genes that are located on the same chromosome

epistasis definition

when one gene modifies or masks the expression of a different gene at a different locus

gene pool definition

all the alleles of all the genes within a population at one time

population definition

all the individuals of one species in one area at one time

allele frequency

the proportion of an allele within the gene pool

What are some assumptions of hardy qeinburgs model

Assumes there are no migration to introduce or remove alleles from population

no mutations to create new alleles

no selection

mating is random

the population is large

hardy weinberg equation

p2+ 2pq = q2

what is speciation

the process that results in the creation of a new species. This occurs when one original population of the same species becomes reproductively isolated. this isolation then means there are now 2 populations of the same species but they cannot breed together - unable to interbreed and make fertile offspring therefore are classed as 2 different species

what is allopatric speciation

Populations become separated geographically resulting in reproductive isolation, unable to reproduce, bkth separate populations will continue to accumulate different beneficial mutations over time to help them survive in their own environments. Due to the accumulation of dna differences over time the two become so genetically different they become unable to interbreed and create fertile offspring

what is sympatric speciation

This could be due to a random mutation within the population which could impact reproductive behaviour, for example different courtship ritual or individuals to be fertile at different times of the year. Due to this they do not reproduce together and there will be no gene flow between the two groups. Overtime these reproductively isolated populations accumulate different mutations and their dna is so different they cannot interbreed to produce fertile offspring so are classed as 2 different species

what is genetic drift

Change in allele frequency within a population between generations.

Continual substantial genetic drift results in evolution

Smaller population equals bugger impact allele frequency has proportionally

community definition

All the populations of different species in the same area at the same time

what is niche

an organisms role within an ecosystem, including their position in food web & habitat. Each species occupied their own niche

Carrying capacity defintion

The maximum population size an ecosystem can support

What is interspecific competition

when members of a different soecies are in competition for same resource which is in limited supply eg : habitat water or food. the individual better adapted to the environment is more likely to succeed

what is intraspecific competition

when members of the same species are in competition for resources and a mate links to the courtship ritual.

what is succession

The change in an ecological community over time

What is pioneer species

first species colonising rock or sand etc.

Example of primary succession

-Pioneer species which are adapted to live in harsh abiotic factors, through death and decomposition change the abiotic factors to become less harsh and form a thin layer of soil.

-Mosses and smaller plants can now survive and increase depth and nutrient content of soil, abiotic factors become less harsh so larger plants can survive and change environment further.

-each new species changes environment in a way that becomes less suitable for previous species, therefore existing species outcompeted by new species colonising.

-less hostile environment and increases biodiversity. Final stage is climax community and is dominated by trees

what is final stage in succession

Climax community

what is secondary successiong

succession is disrupted and plants destroyed. Succession starts again but soil is already created so it does not start from bare rock seral stage.

Summary of what happens in succession

species richness and number of organisms increase (biodiversity increases)

• as succession occurs larger plants species and animals colonise area

• food webs become more complex

method of conservation of havitats

by naintaining earlier stages in succession and preventing a climax community, so a greater variety of habitats are conserved so greater range of species