3.7 Genetics, Population, Evolution And Ecosystems Flashcards
What is a population?
Group of all organisms of the same species living in the same habitat, that can interbreed to produce fertile offspring
What is a habitat?
Part of an ecosystem in which particular organisms live in
What is a community?
All the populations of the different species in the same area at the same time
What is an ecosystem?
A community and the non-living components of an environment (biotic and abiotic factors)
What is a niche?
An organisms role within an ecosystem, including position in the food web and habitat. Each species occupies its own niche
What is carrying capacity?
Maximum population size an ecosystem can support
What are abiotic factors and examples?
•Non-living conditions
e.g temperature, oxygen, CO2 and light intensity
What are biotic factors and examples?
Living conditions (impact of interactions between organisms)
e.g competition, predation, disease
What are the different types of competition?
Interspecific: members of different species compete for the same limited resources and better adapted individuals survive
Intraspecific: members of the same species compete for resources and mates. Fitter individuals attract a mate
What does a predator-prey relationship show?
•both population sizes will fluctuate
•at most times, more prey than predators so prey no. peaks more
•size of population changes in prey and then predators due to lag time
How can you accurately represent a population?
•large no. of samples (representative 30+)
•random samples (avoids bias)
Outline a random sampling method
1.lie 2 tape measures at a right angle to create a gridded area
2.use a random number generator to generate 2 coordinates e.g calculator
3.place a quadrat and collect data e.g total no.
4. Repeat at least 30 times (or until running mean as more reliable and allows for a statistical test to be done)
5.multiply to give estimate for total field area
What are the 2 types of transects?
Belt: quadrat placed at every position along tape measure
Interrupted: quadrat placed at uniform intervals along the tape measure
Outline a method for a line transect
1.place tape measure at right angles to e.g the shore line
2.place quadrat every 1 metre along the tape measure
3. Collect data
4. Repeat by placing another 30 transects along each e.g the beach at right angles to the shore line (randomly)
What is local frequency and ad/dis of using it to estimate abundance?
•% of squares in quadrat with species
Ad: •quick for large areas
•useful if too many to count or hard to identify individual
Dis: •poor accuracy as it doesn’t consider overlapping plants or size of plants
What is density and ad/dis of using it to estimate abundance?
•no. of one species in a given area
Ad: •more accurate
•used to estimate species richness
Dis: •more time consuming
What is % cover and ad/dis of using it to estimate abundance?
•proportion of ground occupied by the species
Ad: •quicker method than density
•useful if too many to count or difficult to identify
Dis: •subjective so limiting accuracy
•doesn’t consider overlapping plants or the size of the plant
How is mark-release-recapture done to estimate population?
1.collect sample in each area and mark unobtrusively
2.allow time to re-integrate with rest of the population
3.collect second sample and count no. marked
4.estimate using equation =
S1X S2
———-
no. marked in S2
What assumptions are made in mark-release-recapture?
•no immigration/migration
•no reproduction
•marking doesn’t increase predation
•population is large enough
What is meant by uniformly distributed?
Same no. of organisms in each region/equally spread
What is ecological succession?
Process by which communities change over time as a result of interactions between abiotic and biotic factors.
Proceeds with a series of stages with one community of organisms being replaced by another
What is primary and secondary succession?
1)occurs in environment where there is no pre-existing vegetation or soil
2)occurs on substrate that previously supported vegetation before and ecological disturbance
What is the process of succession?
1.pioneer species colonise first as they can tolerate hostile abiotic conditions
2.pioneer species reproduce, grow and die, this changes abiotic conditions to make it less hostile e.g increase the mineral nutrients in soil
3.less hostile environment for new species to colonise and eventually outcompete the pioneer community and outcompete each other
4.over time new communities continue replacing previous communities and biodiversity increases (biomass and productivity increase)
5.eventually a stable climax community is reached
What is deflected succession and what does it produce?
•occurs when the climax community is prevented from being reached e.g due to coppicing and grazing by animals
•it intervenes and prevents succession completing as large trees are prevented from growing
•this produces a sub-climax community called plagioclimax
What are features of climax communities?
•same species present over a long time
•stable population
•abiotic conditions remain stable
Why does a population decrease when temperatures in environment decreases?
•use more energy to maintain right internal temperature
•less energy for growth and reproduction
What is the genotype?
2 alleles an individual possess for a particular gene
What is the phenotype?
The expression of the genes and its interactions with the environment
What is homozygous?
Pair of homologous chromosomes carrying the same alleles for a single gene
What is heterozygous?
Pair of homologous chromosomes carrying 2 different alleles for a single gene
What is a recessive allele?
An allele only expressed if no dominant allele is present
What is a dominant allele?
An allele that will always be expressed in the phenotype
What is a codominant allele?
Neither allele is recessive or dominant over the other. Alleles of the same gene are expressed separately to yield different traits in an individual when heterozygous genotype is inherited
(Equally dominant and equally expressed)
What causes multiple alleles?
Mutations in a gene that occur at different positions in the gene
What are the alleles for blood group?
IAIO IAIA = A
IBIO IBIB = B
IAIB = AB (codominant)
IOIO = O
What is a dihybrid cross?
Inheritance of 2 different genes considered at the same time
Why are males more likely to have recessive conditions?
•some genes are on the X or Y = sex linked
•Y is shorter than X where X has an inequivalent portion (non-homologous portion)
•only need one copy of a recessive mutant allele on X to give disease
•females need 2 recessive alleles
After a genetic cross, why are observed ratios not the same as expected ratios?
•Sample size is too small so doesn’t tend to expected value
•random fertilisation of a gametes
•epistasis
•crossing over
How can you tell from a pedigree that the condition is not sex linked?
•if dominant disease the dad would have an X with the dominant allele
•female would hence have to inherit dominant allele from dad (XX = one mum/one dad)
•if daughter is unaffected it is not sex linked
Why do X and Y chromosomes not form typical bivalents?
•X and Y are different sizes
•they have non-homologous sections which cannot form pairs
In dihybrid crosses what will the ratio be for offsprings if the parents that are both heterozygous for both genes?
9:3:3:1
In dihybrid crossing what will the offsprings be if you cross a homozygous recessive and homozygous dominant parents?
All will be heterozygous for both genes
What is epistasis and in what type of crosses does it occur in?
•form of gene interaction in which one gene masks or modified the phenotypic expression of another
•no new phenotype produced
•dihybrid crosses
What is autosomal linkage?
When 2 genes are located on the same chromosome so the alleles for each gene linked on the same chromosome will be inherited together
How are results from autosomal linkage be explained?
1.mention linked genes
2.mention gametes formed from the linked genes
3.recombinant phenotypes produced from crossing over (rare)
/mention the genotypes
Why is chi squared used for inheritance questions?
•determine whether observed results were significantly different from expected results
•differences between frequencies in categories (categoric data)
What does the hardy-Weinberg principle predict?
Frequency of alleles remains constant from one generation to the next, providing:
•no mutation
•no selection pressure
•population is large
•population is genetically isolated
•mating at random
•no migration
What is the hardy-Weinberg equation and what do the letters stand for?
/2= squared
P/2 + 2pq + q/2= 1
p+q=1
p=frequency of dominant allele
q=frequency of recessive allele
p/2=homozygous dominant genotype
q/2=homozygous recessive genotype
2pq=heterozygous genotype (carriers)
What is disruptive selection and what does it lead to?
•individuals which contain alleles coding for either extreme trait are more likely to survive, reproduce and pass on their alleles. The allele frequency will change and extreme allele frequency increases. If this continues it can lead to speciation where 2 populations can no longer interbreed (reproductive isolation)
Why does reproductive isolation occur?
•allopatric=geographically isolated
•sympatric=changes in reproductive mechanism, where organisms are initially of the same population in the same area (without geographical isolation)
What is allopatric speciation?
•geographical isolation of same species
•there will be no gene flow/interbreeding
•random mutation causes allele variation in the organism
•each will have different environmental conditions so will have different selection pressures
•some have beneficial alleles that allows survival, reproduction and allele is passed onto offspring (differential reproductive success)
•which leads to change/increase in allele frequency
•form species where populations can no longer interbreed to produce fertile offspring
What is sympatric speciation?
•organisms in a population in the same area become reproductively isolated due to e.g different behaviours/courtship rituals/habitat preferences/fertile at different times of the year due to mutation
•no gene flow between the 2 groups so accumulate different mutations/allele frequencies change so form species = cannot interbreed to produce fertile offspring
What is genetic drift?
•change in the allele frequency within a population between generations. Where impact of bigger in smaller populations
•founder effect (few individuals colonise a new region)
and genetic bottleneck (small surviving population have less variety in alleles so less diversity)
Why would the observed results of a genetic cross be different from the expected results?
•genes have autosomal linkage= certain combo of alleles in gametes more likely
•genes exhibit epistasis=some genotypes hidden in phenotypic ratio
•genes could be sex-linked so phenotypes could be more likely in males than females
Why is there a specific allele in an isolated population?
•isolated so inbreeding/small gene pool (no interbreeding with other populations)
•allele inherited from common ancestor
What is an autosome?
Any chromosome that is not a sex chromosome
What stat test is used for population Qs?
•chi squared as data is categoric
•allows for the probability of the differences being due to chance being found out
