7.4 Populations in Ecosystems Flashcards
What is an ecosystem?
A community and the non-living components of the environment put together
What happens within a habitat?
A species occupies a niche
Controlled by biotic and abiotic factors
What affects the size of a population?
Initially no limiting factors
Then
Biotic and abiotic factors
What are some abiotic factors?
Temperature
Light
pH
Water and humidity
What does humidity affect?
Transportation in plants - needs high transpiration
What an ecosystem supports is called?
The carrying capacity
What factors affect intraspecific competition?
Food Water Mates Shelter Minerals Light
What is intraspecific competition? Example?
Competition within a species
Male robins stealing food from other males territories when food is short in winter
What is interspecific competition? Example?
Competition between different species
Red and grey squirrels have the same niche
What is predetation?
When one species is caught and eaten by another species
What occurs in a predator-prey relationship?
Prey is eaten by a predator - population of the prey falls as the predator population increases
= increases competition between predators for prey
Lack of food for predators means their population falls so less prey eaten
Population of prey recovers - cycle occurs in an oscillating manner
How can the size of population be estimated for slow moving organisms? Method and measurement?
Methods
Randomly placed quadrats
Quadrats along a transect
Measurements
Percentage cover
Frequency
How can the size of population be estimated for fast moving organisms? Method?
Mark-release-recapture
Known number of species is captured and marked - so their chance of survival doesn’t change
They are released where they were caught
After a length of time another known number of organisms are captured - the number of these marked are recorded
How is population estimated from mark-release-recapture?
Estimated population =
Total in the first sample x Total number in the second sample ————————————————— Number of marked individuals
What does mark-release-recapture rely on?
The proportion of marked to unmarked is the same
The marked individuals have time to distribute evenly
Definite boundary - no immigration/emigration
Few/no births or deaths
Marking isn’t toxic and doesn’t reduce survival chance
Marks don’t rub off during the investigation
What is succession?
The change of one community of organisms into the other
What is primary succession?
When an area previously devoid of life is colonised by communities of organisms
Eg the eruption of a volcano
What is the stages of succession?
Pioneer species
Early coloniser
Late coloniser
Climax community
Describe succession?
Pioneer species (eg lichen) survive in harsh conditions
They decompose forming humus (leading to the formation of soil)
The soil becomes rich in minerals for more complex organisms
Each stage of succession tend to out compete the previous one
What is secondary succession?
When a previously colonised area has been cleared (eg forest fire) is recolonised
As a soil layer is already present, succession begins at a later stage
What is conservation? Example?
The human management of the earth’s resources - typically the managing of succession
Eg the controlled burning of land to stop the formation of a climax community
