7 Genetics: 19 Populations in Ecosystems Flashcards
What is the definition of a community?
Populations of different species.
What forms an ecosytem?
A community and the abiotic components of its environment.
What niches could a species occupy?
Biotic - the organisms it eats, and is eaten by.
Abiotic - oxygen and carbon dioxide.
What is the carrying capacity of an ecosystem?
A certain size of population of a species that an ecosystem can support.
How can a population size vary due to abiotic factors?
When the environmental conditions are optimal for a species, they can grow fast and reproduce successfully.
How can a population size vary due to biotic factors (interactions between organisms)?
Interspecific competition,
intraspecific competition,
and predation.
What is interspecific competition?
Competition between different species for the same resources.
If one species is better adapted to its surroundings, the other species is likely to be out-competed.
What is intraspecific competition?
Competition within a species for the same resources.
What is predation?
An organism kills and eat other organisms.
As prey population increases, predator population grows but prey population decreases so predator population decreases.
How can the size of a population be estimated?
What techniques?
Randomly placed quadrats or belt transects for slow-moving or non-motile organisms.
Mark-release-recapture method for motile organisms.
What are the assumptions made when using the mark-release-recapture method?
- The marked sample has had enough time to mix back in with the population.
- The marking hasn’t affected the chances of survival.
- The marking will stay on and won’t be rubbed off.
- There are no changes in population due to births, deaths, and migration during the study period.
What are ecosytems decribed as?
Dynamic systems.
What is the process of succession?
Primary succession:
- happens on newly formed or exposed land
- a pioneer species colonises new land.
- they are well adapted to the hostile conditions
- as they die and saprobionts decompose them, a basic soil is formed.
- new organisms can grow
- as they die, more nutrients are released
- larger organisms can grow, also attracting larger animals
- a climax community is reached
Secondary succession:
- there’s already a soil layer so the pioneer species is larger
- at each stage, better adapted organisms out-compete the organisms, becoming the dominant species.
- biodiversity increases.
Climax community:
- the final stage.
- the ecosystem is supporting the largest and most complex community it can.
- stable.
What does conservation of habitats involve?
Management of succession.
e.g. grazing animals keeps vegetation low as plants can’t establish themselves.
Managed fires are lit so secondary succession ensues.
What is an example of a conflict between human needs and conservation?
Some tribes need to raise cattle which overgraze, destroying grassland for wildlife.
