7. Genetics, Populations, evolution and ecosystems

Community

populations of different species in an ecosystem

Ecosystem

community and the non-living components of its environment together

Niche

what governed by

• role in an ecosystem, where it lives, what it eats, abiotic impact and biotic impact

• governed by adaptation to both abiotic and biotic factors

What does the competitive exclusion principle signify?

no two species can occupy the same niche

How can you use log scales to plot population data?

turn actual values into log number by doing log10 (number)

convert back to actual value by doing 10^log number

What is demographic transition?

Stage 1 - small and stable: high birth and death rate

Stage 2 - early expansion: high birth rate decreasing death rate

Stage 3 - late expansion: decreasing birth rate low death rate

Stage 4 - low birth rate low death rate

carrying capacity

maximum population of a species an ecosystem can sustain

Factors effecting population sizes

temperature - optimum for enzyme activity

light - photosynthesis plants, food sources animals

pH - optimum - enzyme activity

Water/humidity - depending on adaption - scarce only small well adapted populations

describe link to carrying capacity

ask about population demographic pyramids

Competition types

intraspecific - natural selection

interspecific - less fierce , increase niche to avoid

what to measure abundance what to measure distribution?

abundance - random quadrats

distribution - transect

Mark recapture equation

Lincoln index

total no individual in sample 1 x total in sample 2

all divided by number marked and recaptured

assumptions of mark recapture method

• marked individuals have enough time to redistribute

• marking does not harm / increase predation

• population size does not change

• mark not rubbed off

succession

process by which an ecosystem changes over time. happening in stages

primary succession key terms

• succesion on land without life initially

• pioneer species, change abiotic environment, humus, outcompete, climax community

pioneer species

first species to appear

What is monohybrid inheritance?

• one trait is controlled by one allele

What is dihybrid inheritance?

• two characteristics controlled by 2 different genes on different chromosomes

• the patterns in traits when interbred

What is sex-linkage?

a trait inherited by allele on non-homologous region of a sex chromosome.

What is autosomal linkage?

• two different alleles for different traits on the same chromosome

• increases likelihood of being inherited together

• only not inherited together due to crossing over

What is epistasis? what is dominant vs recessive epistasis ratios?

when one gene locus affects the expression of another gene locus

dominant = 12:3:1

recessive = 9:3:4

What are the Hardy-Weinberg principles?

• no mutations

• large sample size

• no selection

• random mating

What are the Hardy-Weinberg equations?

p² + 2pq + q² = 1 and p + q = 1

What causes genetic variation?

random fertilisation

mutation

meiosis

environmental factors like minerals in soil

What is selection?

The process where better suited individuals to their environment are more likely to survive and breed

Explain the speciation process?

• mutation causes variation

• allopatric (separated by physical barrier) sympatric (reproductive separation) - mutations affecting courtship behaviour or anatomy or nondisjunction

• acquire genetic mutations over generations i.e accumulation of difference in gene pools

• increase biodiversity

• until species unable to breed to produce fertile offspring