Genetics, Populations, Evolution and Ecosystems- Topic 7 Flashcards
Explain what it means when two genes are linked.
Genes on the same chromosome
The breeder had expected equal numbers of …. explain why actual numbers were different to those expected
As the fusion of gametes is random
What sample is sufficiently large enough for a Chi-squared test?
sample of at least 20
Define a population
group of organisms of the same species occupying
a particular space at a particular time that can potentially interbreed.
Give Hardy Weinberg equation used to determine allele frequency
p + q = 1
What do the letters stand for in Hardy Weinberg equation?
q = recessive homologous p = dominant homologous 2pq = heterozygous
What is a gene pool?
All the alleles of all the genes of all the individuals in a population at a given time
What is allele frequency?
Number of times an allele occurs within the gene pool
Individuals within a population of a species may show a wide range of variation in phenotype. What is this due to?
Genetic factors: mutations, meiosis, random fertilisation of gametes
and environmental factors: pH, temperature, food availability
What is the primary source of genetic variation?
Mutation
What is evolution?
The frequency of an allele in a population changing over time
How is differential survival and reproduction, ie natural selection created?
Predation, disease, and competition (selection pressures)
Why do a greater proportion of the next generation inherit the beneficial alleles?
Individuals with phenotype that inc chance of survival = more likely to survive, reproduce and pass on their genes. (therefore freq of beneficial alleles in the gene pool increases from generation to generation)
Name 3 types of selection.
Stabilising selection, Directional selection and disruptive selection
What is stabilising selection?
individuals with alleles for characteristics towards middle of range more likely to survive and reproduce e.g. MEDIUM fur length
- occurs when environment ISN’T changing
What is directional selection?
Individuals with alleles for extreme phenotype are more likely to survive and reproduce. Could be in response to environmental change
what is disruptive selection?
extreme phenotypes at either end of the range are more likely to survive and reproduce. (middle characteristics lost) occurs when environment favours more than one phenotype
Define community
all populations of different species living and interacting in a particular place at the same time
Define a Habitat
place where an organism normally lives and is characterised by physical conditions and the other types of organisms present.
Define Ecological niche
where an organism lives and what it does there
Define carrying capacity
certain size of population of a species that an ecosystem supports
What is an abiotic factor and can you give an example?
non-living factor in environment e.g. temperature
What is a biotic factor and can you give an example?
a living environmental factor e.g. competition and predation
What is an Ecosystem?
A community plus all the non-living conditions in the area in which it lives.
What is interspecific Competition?
Organisms of different species compete with each other for the same resources e.g. food and habitat
What is intraspecific competition?
Organisms in the same species compete with each other for the same resources
What are the 2 ways that you can estimate the size of a population?
Randomly placing quadrats
Mark-release-recapture
What equation can you use to determine the estimated population size?
total no.of individuals in 1st * total in 2nd /
number of marked individuals recaptured
When using quadrats how can results be made more reliable?
The larger the no.of sample quadrats the more reliable the results will be
What is succession?
The process by which an ecosystem changes over time. Biotic and abiotic conditions change.
Primary succession
when species colonise new land. First species to colonise the area = pioneer species (e.g. seeds/spores)
Secondary succession
Already soil layer so succession starts at later stage (pioneer species in secondary succession are larger plants e.g. shrubs)
What is the final stage of succession and what happens?
Climax community - ecosystem is largest and most complex. Won’t change much, in a steady state
Why do some species become dominant species?
Better adapted for improved conditions and out-compete plants and animals that are already there.
As succession goes on the ecosystem becomes more ….. which means that ………. increases
As succession goes on the ecosystem becomes more complex which means that biodiversity increases
What is a benefit of using a transect?
They ensure every community is sampled
What is conservation?
management of resources so that they have maximum use in future
Why is conservation important?
to maintain our planet
value of organisms
How does speciation occur?
Speciation (development of the new species) when 2 populations are reproductively isolated
What is allopatric speciation
Where species are geographically separated and experience slightly different conditions e.g. climate.
therefore also different selection pressures (changes in allele frequency)
What is sympatric speciation?
mutation can occur increasing no. of chromosomes. individuals with different numbers of chromosomes can’t produce fertile offspring, making organism reproductively isolated.
Name and describe ways reproductive isolation can occur
Seasonal- individuals from same population develop different mating seasons/ sexually active at different times of year
Mechanical- changes in genitalia prevent successful mating
Behavioural- a group of individuals develop courtship rituals that aren’t attractive to main population
What is genetic drift?
When chance dictates which individuals survive, breed and pass on their alleles
genetic drift has greater effect in ….. populations
greater effect in smaller populations where chance is greater
How can genetic drift lead to speciation?
By chance allele A passed on more often than others so number of individuals with allele increases. changes in allele frequency in 2 isolated populations could eventually lead to reproductive isolation and speciation.
Give the Hardy Weinberg equation used to determine the frequency of genotypes or phenotypes
p2 + 2pq + q2 = 1
