Genetics, populations, evolution and ecosystems Flashcards
What is the effect of predator-prey relationship on population of size?
Predator feeds on prey- reduces prey population
Due to the reduction of prey population- predators are in competition to each other for food
Predator population decreases-
due to less prey being available as food for predator to survive and reproduce
With reduction of predators-
few prey are taken as food; death rate of prey decreases as more can survive and reproduce
Prey population increases so more prey available as food, more predators survive.
Why a predator population often exterminates its prey population in a laboratory but rarely does so in natural habitats?
Because in a natural habitat, prey have more hiding spaces to hide from a predator so they can survive
What can be used to investigate non motile populations?
Quadrats and belt transects
What makes the use of quadrats more reliable?
Use more quadrats, use larger quadrats for larger species, take a mean value of your abundance, make sure quadrats are placed randomly (use a number generator for coordinates)
What are transects useful for?
Useful for measuring a gradual change in communities of plants and animals
What are the two ways to measure abundance?
Frequency- measures how many quadrats the species occur in
Percentage cover- estimation in the area within a quadrat that a plant species is abundant in
Mark release recapture technique?
Take a sample of individuals, mark them all with a non harmful tag release them
Give the individuals time to disperse
then after a period of time recapture a similar sized sample and count how many of those that are marked
Use this equation : (no in the first sample * no in 2nd sample)/ (no. marked in the second sample)
Assumptions made during mark release recapture method (4)
That are no/few births or deaths
No immigration or emigration into the population
Mark is not lost or rubbed off during the investigation
Marked individuals in the first sample distribute themselves evenly amongst the remainder of the population
What is the effect on the estimated population size is the birth rate increases or the tag makes the sample more conspicuous to prey?
The estimation goes up (overestimation)- this is because less marked individuals would collected the second sample making the portion of unmarked to marked much larger
What is the effect of intraspecfic competition on population sizes ?
population of species increases when resources are plentiful;
more organisms compete for the same amount of space and food;
resources become limited;
population thus decreases;
smaller population means less competition so better growth and reproduction
What is the effect on interspecific competition on population sizes ?
Resources available to both populations are reduced;
Populations limited by low amounts of food;
Less energy for growth and reproduction; reduced population sizes;
Species better adapted to its surroundings will survive.
Process of speciation (sympatric))
Groups are geographically isolated
Individuals in group are varied due to mutations
Different environments have different selection pressures
organisms with advantageous alleles are selected for so they survive and reproduce
Increase frequency of allele in gene pool
Process of succession
Pioneer species colonise the area and change the environmet
Makes the environment less hostile
Other species become better competitors
Decline in pioneer species; rise in other species
There’s an increase in biodiversity
Sucession occurs until a climax community is formed
What does Hardy-Weinberg principle predict?
Proportion of alleles will stay constant from one generation to the next
Assumptions of Hardy-Weinberg principle (5)
No mutations of any genes Mating is random Population is isolated Each gene has an equal chance of being inherited Population is large
definition of gene pool
all the alleles of all the individuals in a given population at a given time
definition of allele frequency
how often a gene appears in a gene pool
definition of disruptive selection
when both extreme phenotypes are selected for whilst mean phenotypes are selected against
definition of directional selection
When one extreme phenotype is selected for when the environmental conditions are changing
A new optimum mean is formed
definition of stabilising selection
when the average phenotype is selected for and extreme phenotypes are selected against
genetic factors that result in diversity
Meiosis- crossing over and random segregation
Random fertilisation
Mutations
features of a climax community
populations remain stable
aboitic factors remain constant
same species present
how do you know if a disease is NOT sex linked?
If a child has a disease but the father does not
If the disease was sex linked, the father would have passed on the recessive allele
how do you know if a disease is recessive?
if the parents do not have the disease but a child does
the parents thus were heterozygous for the disease
