7.4 Populations in ecosystems Flashcards
Define community
All the different species that live in one area and interact with each other
Define ecosystem
All the living organisms found in one area, combined with non-living aspects of their environment. Can vary from very large to very small
Describe biotic factors, giving examples
Biotic = living features of an ecosystem, e.g. predators, disease
Describe abiotic factors, giving factors
Abiotic = non-living features of an ecosystem, e.g. light, temperature
Define habitat
The place where an organism lives within an ecosystem
Define a niche
The role of a species within its habitat, consisting of both its biotic interactions
e.g. what it eats, and abiotic interactions, e.g. time of day its active
What is meant by carrying capacity?
The maximum size of population an ecosystem can support
Name four abiotic factors that affect population growth
- Temperature
- Light
- pH
- Water
What is meant by intraspecific competition
Competition between organisms of the same species
What is meant by interspecific competition?
Competition between organisms of different species
What resources might organisms compete for?
Food, water, shelter, minerals, light, mates (intraspecifc only)
Describe the pattern of a typical predator-prey relationship in terms of population change
- Prey is eaten by predator, resulting in predator population increasing and prey population decreasing
- Fewer prey means increased competition for food, so predator populations decreases
- Fewer predators means more prey survives, and the cycle begins again
How are quadrats used for estimating population size?
Can be placed on grid coordinates, or at intervals along a belt transect. Results reported as either percentage cover or frequency. For slow-moving or non-motile organisms
How is mark-release-recapture used for estimating population size?
- A sample of a species is captured, marked, then released back into the same area they were caught
- After a certain period of time another sample is captured, and the number of marked organisms are counted
What is the equation for mark-release-recapture?
Estimated population size = total no. of individuals in 1st sample x total no. of individuals in 2nd sample / no. of marked individuals recaptured