Ecosystems Flashcards
What is an ecosystem?
All the organisms living in a community plus all the abiotic conditions in a habitat
What is a niche?
The role of a species within an ecosystem. This includes its biotic relationships (intraspecific competition for resources, what it eats) and abiotic relationships (shade, oxygen, minerals)
Why each species has its own niche
- If two species had the same niche they would compete for everything
- Species can have similar niches, causing interspecific competition
- The abundance of a species in an ecosystem will vary depending on how much competition for resources exists
- The distribution of a species will vary because an organism can only exist where its niche exists
What is the carrying capacity?
The maximum stable population size of a species that an ecosystem can support
Biotic factors affecting population size
- Intraspecific competition (same species occupy same niche so compete for everything)
- Interspecific competition (abundance of one species affects the other)
- Predation (organisms only distributed where able to survive)
How can we investigate population growth of bacteria?
- Prepare broth culture (liquid containing bacteria + nutrients needed to grow)
- Use a spectrophotometer to measure amount of light passing through culture
- The more bacteria, the less light passing through, the higher the absorbance
- Plot an exponential graph of absorbance and time
What is abundance?
The number of individuals of a single species in an ecosystem/habitat
What is distribution?
Where a species is found in an ecosystem/habitat
Using quadrats
- Use a random number generator to generate coordinates to place quadrat (random sampling)
- Record the number of individuals of each species in the quadrat (species frequency)
- Repeat 10 times at different coordinates and calculate mean species frequency
- Divide area of habitat by area of quadrat and multiply answer by mean species frequency to record abundance
- Instead could record percentage cover (count square if covers over 50%) as quicker
Using transects
- Run a tape measure between two points
- At regular intervals (systematic sampling) record number of individuals that touch the tape (point) of in quadrat (belt)
- Record how distribution of species changes along transect
Mark-release-recapture method
- Capture organisms
- Mark in a way that doesn’t harm them
- Release organisms back into habitat and wait
- Take 2nd sample
- Count how many organisms in second sample are marked
- Use equation to estimate total population size / abundance
Mark-release-recapture equation
Total population = (number caught in 1st sample x number caught in 2nd sample) / number of marked in 2nd sample
What is succession?
A series of changes in a species composition in a given place over time
What is a climax community?
The final stage of succession where few species dominate and there is a stable equilibrium of species. Different ecosystems have different abiotic conditions so develop into different climax communities
Succession process
- Area is colonised by pioneer species
- Pioneers change environmental conditions, making habitat less hostile for other species
- Other species to outcompete the preceding species
- Biodiversity increases
- Continues until climax community is reached
