Population ecology Flashcards
Community
Population of living species living and interacting at the same time in a particular place.
Habitat
Place where organism lives
Niche
How organism fits into an environment. Abiotic and biotic factors that the organism is adapted to to survive.
Population size varies as a result of…
Effect of abiotic factors, interactions between organisms (interspecific competition and predation).
Abiotic factors
Temperature - can affect enzymes.
Light - increase speed of growth or how many seeds produced.
pH - effects enzymes
Water and humidity - effects transpiration
Intraspecific competition
Competition between individuals of same species
Interspecific competition
Individuals of different species. Normally one has competitive advantage over other, leading to increase of one and decrease of other population. No two species can occupy same niche.
Effect of predator-prey relationship on population size
- Predators eat prey, reducing population of prey
- Fewer prey, predators in greater competition.
- Predator population reduced.
- Fewer prey eaten, population increase.
- Cycle
What to consider when using quadrats
Size - larger species need larger quadrats and where possible when population is spread out using more smaller quadrats.
Number of sample quadrats- more = more reliable results but more time.
Random sampling
How to random sample
Two long tape measures at right angles.
Get coords using random number gen.
Place quadrat at coord.
Systematic sampling
Stretch tape and placing a quadrat regularly.
How to ensure reliable results
Large sample size (many quadrats used), mean taken of all samples.
Release and recapture formula
Pop size = (number in first sample * number in second) / number of MARKED individuals recaptured
Release and recapture assumptions
Proportion of unmarked is same in sample as population.
Marked individuals distribute themselves evenly.
Population has definite boundary so no immigration or emigration.
Few deaths and births.
Marking is not toxic or washed off.
How does one stage link to another in succession
Alters environment in a way less suitable for existing species so new species outcompete existing one.
Alters environment to be more suitable for other species with different adaptations.
First stage of succession
Pioneer species make up pioneer community.
Characteristics of pioneer species
Asexual reproduction. Wind dispersed seeds or spores to reach isolated situations. Rapid germination. Photosynthesis. Fix nitrogen from atmosphere. High tolerance to extreme conditions.
Climax community
Stable equilibrium with climate, depends on place.
During succession, common features are…
Abiotic environment becomes less hostile.
More habitats and niches
Increased biodiversity.
Higher biomass
Secondary succession
Land is altered and succession to a climax community happens more rapidly.
Conservation
Preventing succession to another stage. E.g. a countryside of fields prevented from turning into woodlands by grazing.
Species
Group of individuals that can breed to produce fertile offspring
Why is most of sun’s energy not converted to organic matter by photosynthesis
Much of sunlight reflected
Not all wavelengths of light can be absorbed
Limiting factor of photosynthesis limits rate
The light does not hit chlorophyll molecule
GPP (gross primary production)
The chemical store of energy in a plant in a given area over given time
NPP (net primary production)
GPP - respiratory losses
Why is low amount of energy transferred at each stage in food chain
Some of organism not consumed.
Some is not digestible and left in faeces.
Some lost in urine.
Heat from respiration
Why do most food chains have at most 5 tropic levels
Relative inefficiency of energy transfer.
How does speciation occur
Two groups become separated and reproductively isolated so that gene flow is reduced. Each group experiences different selection pressure so frequency of alleles changes due to natural selection and 2 populations can no longer interbreed.
