topic 7 - genetics, population, evolution and ecosystems Flashcards
define dominant allele
only a single allele is required for the characteristic to be expressed in the phenotype
define recessive allele
two copies of the allele are required for the characteristic to be expressed in the phenotype
this means it is only expressed in a homozygous individual
define homozygous and heterozygous
homozygous is an individual that carries two copies of the same allele
heterozygous is an individual that carries two different alleles
define phenotype
the observable characteristics of an organism expressed as a result of the genotype and its interaction with the environment
what is monohybrid inheritance?
the inheritance of a characteristic controlled by a single gene
the phenotypic ratio of the F2 generation is 3:1
what is a dihybrid cross?
it considers the inheritance of two different genes at the same time
the phenotypic ratio of the F2 generation is 9:3:3:1
what is codominance?
both alleles are expressed in the phenotype
neither allele is dominant or recessive
what are the rules of codominance?
when writing the genotype for codominance the gene is symbolised as a capital letter and the alleles are written as superscript letters e.g. Cᴿ
define sex linked
a gene whose locus is on the X chromosome
why are males more likely to develop as sex linked disorder
-there x chromosome is longer than y
-no homologous Y area for most of X
-hence males only require 1 copy of a recessive allele for expression on the phenotype
define autosomal linkage
two or more genes that are located on the same chromosome which is not a sex chromosome
this means they are less likely to be seperated during crossing over so are inherited together
define epistasis
when one gene modifies or masks the expression of a different gene at a different locus
what is the hardy weinberg principle
it is a mathematical model which can be used to predict the allele frequencies within a population
what are the five assumption for the hardy weinberg equation
-no migration to introduce or remove alleles from the population
-no mutations to create new alleles
-no selection which would favour particular alleles
-the mating is random
-the population is large
define gene pool
all the alleles of all genes within a population at one time
define allele frequency
the proportion of alleles within a gene pool
what is the equation for the hardy weinberg principle
p^2 + 2PQ + Q^2 = 1
the equation is simultaneously used with the equation P + Q = 1
either p or q must be identifies before using the first equation
p is the frequency of the dominant allele
q is the frequency of the recessive allele
p2 is the frequency of the homozygous dominant genotype
2pq i the frequency of the heterozygous genotype
q2 is the frequency of the homozygous recessive genotype
how is variation introduced
-the primary source of genetic variation is mutation
-meiosis and random fertilisation of gametes
-predation, disease and competition for the meals of survival and reproduction in natural selection
explain allopatric speciation
-geographical isolation
-separation of gene pools so no interbreeding
-variation arise due to mutation
-different selection pressures cause differential reproductive success
-this leads to a change in the allele frequency
-the two populations cannot interbreed and produce fertile offpsring so they are considered two different species
explain sympatric speciation
-occurs in the same habitat
-mutation causes variation
-populations become reproductively isolated due to difference in their behaviour such as performing a different courtship ritual
-due to this the two populations will not reproduce and different alleles are passed on to their offspring
-the two populations cannot interbreed and produced fertile offspring so two different species produced
describe genetic drift
-random change in allele frequency in a gene pool
-the effect is much more drastic in small populations
-it is driven by chance not selection
define community
all of the populations of different species in the same area at the same tim e
define ecosystem
a community of biotic and abiotic factors of an area and their interactions
why is an ecosystem described as dynamic
-populations constantly fall and rise
-any small change can have a large effect
-the biotic and abiotic factors may alter the conditions of an ecosystem
define niche
an organisms role within an ecosystem including their psotion in the food web and habitat
define carrying capacity
the maximum population size an ecosystem can support
give examples of abiotic factors
-the non living features of an ecosystem
give examples of biotic factors
-the living features of an ecosystem
-such as predation, diease and food supply
what is interspecific competition
-when members of different species are in competition for the same resources that is in limited supply
what is intraspecific competition
when members of the same species are in competition for the same resources and a mate
outline the method for random sampling
-two numbered axis are laid out over sample area
-random number generator provides coordinates for the area of study
-quadrat is placed and dates is collected
-repeat at least 30 times to get a mean
-this method removes bias, allows use of statistical tests and the data is representative
outline the process of mark capture release method
-capture a known sample and mark them without causing harm and must be weather resistant
-release back into the community
-allow time for reintegration
-the community is revisited and a given number of individuals are caught again
-the number of marked individuals is counted
-population size is estimated using equation
estimated population = number of organisms initially caught x number of marked organisms recaptured
describe the steps in primary succession
-colonisation occurs by a pioneer species
-the pioneer specie cause a change in the environment
-this enables other species to colonise once there is a change
-this increase species diversity
-the stability increases the environment is less hostile
-climax community is reached
