Genetics and Variation - Ecosystems Flashcards
define discontinuous variation
organisms fit into distinct categories with no overlaps
controlled by a small number of genes
largely unaffected by environment
define environmental variation
variation where the environment determines where an organism lies within the limits
genes also set limits
usually due to polygenes
what is an example of environmental variation?
height or weight
define continuous variation
no categories to place individuals
controlled by polygenes
significantly affected by environment
forms a normal distribustion curve
define selection pressure
factors that cause competition for survival eg predators, disease
define genetic drift
the change in frequency of an allele in a population over time
where does genetic drift occur most often?
in smaller populations
what is the difference between the founding population and new population in genetic drift?
founding population has a small no. individuals with small no. alleles
new population has non-representative allele frequencies compared to parent population
define speciation
the evolution of a new species
what are the 3 steps of speciation?
gene pool isolation
evolution due to environment
reproductive isolation - organisms can no longer breed with members of original species to produce fertile offspring
what are the 2 causes of speciation?
allopatric speciation
sympatric speciation
when does allopatric speciation occur?
when organisms are geographically separated and each population experiences different selection pressures
when does sympatric speciation occur?
random mutations occur that cause an organism to be reproductively isolated from other organisms
normally requires organism to be able to reproduce asexually
what are the 4 causes of reproductive isolation?
seasonal changes
mechanical changes
behavioural changes
chromosomal changes
define ecology
the study of organisms in their environment
define abiotic factors
non-living parts of an environment
define biotic factors
living parts of an environment
define a community
a group of different species that live in the same place at the same time
what is an ecosystem?
biotic and abiotic factors and a community of organisms in a specific area
what is an environment?
the conditions that surround an organism, including both abiotic and biotic factors
what is a habitat?
the location where an organism lives
define niche
the role a species has in its environment, governed by adaptation to both biotic and abiotic conditions
what is a population?
all of the members of a species living together in the same place at the same time
what is a species?
organisms that look similar and can breed together to produce fertile offspring
when is random sampling used?
to estimate a population size where organisms are evenly distributed
what is the method for using quadrats?
- divide the area into a grid by placing 2 tape measures along the sides, assign each square coordinates
- use random number generator to choose coordinates
- estimate % cover, count organisms present or indicate if organism is present
- repeat
what are the 2 types of quadrats?
frame quadrats and point quadrats
when is transect sampling used?
when organism distribution has spatial variation
what is spatial variation?
when organisms are distributed over two environments
what is the method for using transect sampling?
- place line marked at regular intervals across the area
- place a quadrat at each interval
- count or calculate % cover of organisms within the quadrat
- repeat with more transects and calculate average of organisms at each interval
what does quadrat sampling measure?
the abundance of species in a given area
what is the mark-release-recapture method of sampling?
- catch, count and mark a sample of animals
- release the animals back into their habitat
- after a period of time, catch a new sample
- count number of marked animals recaptured
- calculate population size - (total of 1st sample x total of 2nd sample) divided by no. marked animals recaptured
when can mark-release-recapture sampling be used?
when there is a large sample size
when between the 2 samples:
there is little to no migration, immigration and reproduction
marked organisms can effectively re-mi with the rest of the population
marking does not influence behaviour or increase predation risk
what is the carrying capacity?
the maximum sustainable size of a population
