Topic 7- Genetics, populations, evolution and ecosystems Flashcards
what is genotype?
alleles that make up an organism
what is a phenotype?
observable characteristics of an organism resulting from the interaction between genotype and the environment
what is a gene?
length of DNA that codes for a particular polypeptide
what is the locus?
position of a gene on a particular DNA molecule
what is an allele?
different form of a gene
homozygous
two alleles the same
heterozygous
two different alleles
dominant allele
allele that expresses itself in the phenotype
recessive allele
allele not expressed
co dominant alleles
both contribute to phenotype
monohydrid inheritance
inheritance of singular gene
law of segregation
in diploid organisms, characteristics are determined by alleles that occur in pairs. Only one of each pair of alleles can be present in a single gamete
dihybrid inheritance
two characteristics determined by two different genes located on different chromosomes are inherited
law of independent assortment
each member of a pair of alleles may combine randomly with either of another pair.
codominance
both alleles expressed in phenotype
multiple alleles
gene may have more than two alleles, but only 2 can be present in an individual
sex linkage
females- XX- same gametes
males- XY- two different gametes
any gene carried by X or Y chromosome is said to be sex-linked
autosomomes
other 22 chromosomes other than sex chromosomes
autosomal linkage
two or more genes carried on the same autosome
all linked genes remain together during meiosis assuming there is no crossing over
do not segregate according to Mendel’s law of independent assortment
epistasis
allele of one gene affects or masks the expression of another in the phenotype
chi-squared test
used to test null hypothesis
is a means of testing whether any deviation between the observed and expected numbers is significant or not
when can the chi-squared test be used?
sample size relatively large
data falls into discrete categories
only raw counts used
degrees of freedom
number of categories — 1
used to find critical value
compare to 0.05 (5%)
gene pool
all the alleles of all the genes of all the individuals in a population at a given time
allele frequency
number of times an allele occurs within the gene pool
hardy-weinberg principle
used to calculate frequencies of alleles of a particular gene in a population
assumptions of hardy -weinberg principle
no mutations arise
population isolated
no selection
population is large
mating in population is random
hardy-weinberg equations
p+q=1
p^2+2pq+q^2=1
what causes genetic variation?
mutations
meiosis
random fertilisation of gametes
selection pressures
environmental factors that limit the population of a species
examples of selection pressures
predation
disease
competition
factors that natural selection rely on
1) organisms produce more offspring than can be supported by available food, light, space
2) genetic variety within the population of all species
3) variety of phenotypes that selection operates against
intraspecific competition
competition amongst individuals
interspecific competition
competition between different species
natural selection
those with the more advantageous allele survive
they reproduce to produce more offspring with the advantageous allele
allows population to evolve and adapt
stabilising selection
preserves average phenotype of population by favouring average individuals
selection against extreme phenotypes
directional selection
changes the phenotypes of a population by favouring phenotypes that vary in one direction from the mean of the population
selection for one extreme phenotype
disruptive selection
favours individuals with extreme phenotypes rather than those with phenotypes around the mean of the population
abiotic factors
non-living
biotic factors
living
ecosystems
dynamic systems made up of a community and all the non-living factors of its environment
population
group of individuals of one species that occupy the same habitat at the same time and are potentially able to interbreed
carrying capacity
size of population of species an ecosystem supports
community
all the populations of different species living and interacting in a particular place at the same time
habitat
place where an organism lives
microhabitats
smaller units of a habitat with their own microclimate
niche
how an organism fits into the environment, including all the biotic and abiotic factors
competitive exclusion principle
no two species occupy exactly the same niche
abiotic factors influencing population
temperature
light
pH
water
humidity
predator
organism that feeds on another organism (prey)
predation
one organism consumed by another
effect of predator-prey relationship
predators eat prey reducing population of prey
with fewer prey available the predators are in greater competition with each other for the prey left
predator population reduced as some unable to obtain enough prey for survival
fewer prey eaten so more survive and reproduce
predator population increases with more prey available
point quadrant
horizontal bar supported by 2 legs
ten holes at set intervals
pin dropped through
each species touching pin recorded
frame quadrant
square frame divided by string or wire into equally sized subdivisions
placed in different locations
abundance of each species in the quadrant recorded
mark-release-recapture
used to measure abundance of motile organisms
known number caught and marked before being released back into the community
given number of individuals collected randomly and the number of marked individuals recorded
estimated population size
(first sample x second sample)/number of marked individuals recaptured
assumptions of mark-release-recapture
1) proportion of marked to unmarked individuals in second sample is same as proportion of marked to unmarked as a whole
2) marked individuals distribute themselves evenly amongst remainder
3) few deaths or births
4) mark or label is not lost or rubbed off
succession
changes in species that occupy an area over time
stages of succession
1) colonisation of pioneer species in inhospitable environment
2) climax community created as biodiversity increases/ species flourish
features that emerge during succession
non-living factors become less hostile
greater variety of habitats
increased biodiversity
more complex food webs
increased biomass
secondary succession
occurs when land already occupied has been altered in some way
conservation
management of earths natural resources by humans in such a way that maximum use of them can be made in the future
main reasons for conservation
personal
ethical
economic
cultural
aesthetic
