Populations within Ecosystems Flashcards
(26 cards)
What is a community?
all the populations of different species in the same area at the same time
What is an ecosystem?
The interaction between a community biotic and the abiotic parts of the environment.
What is a habitat?
part of an ecosystem in which a particular organism lives
What is a niche?
organisms role within their ecosystem (e.g their position within the food web and habitat)
- each species occupies their own niche, no two species can share niche OR they’ll go into competition with each other
What is a species?
A group of organisms that can interbreed to produce fertile offspring
How do abiotic factors affect biodiversity?
The changes that species produce in their abiotic environment can actually result in a less hostile environment
As a result, this can change or sometimes increase the biodiversity within that environment
What is carrying capacity?
The maximum stable population size of a species that an ecosystem can support.
What abiotic factors limit population size?
- light availability
- water supply
- temperature
- amount of space available
- soil pH
What biotic factors limit population size?
- interspecific competition → members of different species competing for the same resource that is limited in supply
- intraspecific competition →members of the same species in competition for resources and a mate
- predation → in a stable community, the numbers of predators and prey rise and fall in cycles, limiting the population sizes of both predators and prey
how to ensure samples are accurately represent a population?
- random sampling in uniform areas to avoid bias
- line transects to examine a change over a distance
- large number of samples (30+)
How to estimate size of population? (non-motile organisms)
Transects + Quadrats
1. Lie two tape measures at a right angle to create a gridded area
2. Use a random number generator to generate co- ords
3. place the quadrat and collect data
4. repeat 30+ times and calculate a mean
Calculate this as a percentage (i.e. percentage cover)
3 Factors of Predator Prey Relationships over time
-
Size of the predator prey population fluctuate: increase in prey is more food for predators- predators get more food so reproduce more SO MORE PREDATORS
- population of prey decreases causing SO not enough food for predator SO predator decreases - There will be more predators than prey: Prey populations will always peak at higher point → predators are further along the food chain what they eat will contain less energy due to energy loss at each trophic level) SO predator would need to eat multiple prey
- Size of the populations will always change first in the prey and then in the predators: increase in predator population after a while due to lag time.
How to estimate size of population? (motile organisms)
Mark - Release - Recapture
1. The first large sample is taken. As many individuals as possible are caught, counted and marked in a way that won’t affect their survival
2. The marked individuals are returned to their habitat and given sufficient time to randomly mix with the rest of the population
3. The number of marked and unmarked individuals within the second sample are counted
4. The proportion of marked to unmarked individuals is used to calculate an estimate of the population size
N = (n1 × n2) ÷ n2
n1 = number of marked released
n2 = number of individuals in second sample
m2 = number of marked in second sample
What is succession?
the change in the ecological community overtime
What is a seral stage?
each stage where there is a noticeable change in the community
What is primary succession?
The process that occurs when newly formed or newly exposed land (with no species present) is gradually colonised by an increasing number of species.
Outline the stages of primary succession.
- pioneer species colonises bare rock or sand
- As these pioneer species die and decompose, humus forms a basic soil
- this changes the abiotic factors and they become less hostile allowing smaller plants to survive
- environment stability increases, the new soil becomes deeper and more nutrient-rich, allowing larger plants and shrubs
- climax community is reached
How does the environment change as a result of succession?
- deeper soil
- more nutrient rich soil
- increased species biodiversity
- more water content in soil
How to manage succession?
- conservation of intermediate species in succession
- grazing animals
- managed burning
Outline the stages or primary succession
- Pioneer species are adapted to survive in harsh/hostile abiotic factors → through death and decomposition they change the abiotic factors to become less harsh/hostile and form a thin layer of soil called humus
- mosses and smaller plants can now survive & change environment further
- more nutrient in the soil allow larger plants to grow
- eventually climax community is reached
general trend of primary succession
- changes that organisms produce in abiotic environment results in a less hostile environment & increased biodiversity- environment is more stable, abiotic factors are now favourable
- each species changes the environment making it less suitable for previous species SO each existing species is outcompeted by a new species colonising
What is a climax community?
the stable, final community that makes uo a final stage of succession
- abiotic factors overtime
What is secondary succession?
climax community gets disrupted and plants are destroyed
- succession starts again but doesn’t start from bare rock seral stage
what is interspecific competition?
members of different species competing for the same resource that is in limited supply
