Topic 1.5 Populations & Ecosystems (Populations) Flashcards
Define ‘Population’
An interbreeding group of organisms of the same species occupying a particular habitat.
Define ‘Birth Rate’
The reproductive CAPACITY of a population; the number of new individuals from reproduction per unit of time.
Define ‘Immigration’
The MOVEMENT of individuals into a population of the same species.
Define ‘Equilibrium Species’
Equilibrium species control their population by COMPETITION rather than reproduction and dispersal (FUGITIVE species).
What does ‘dynamic’ mean?
We describe ecosyems as dynamic as the factors that affect organisms in an ecosystem constsantly change.
Dynamic means something that is characterised by CHANGE, activity or progress.
What FACTORS highlight the reasons why ecosystems are dynamic?
- The INTESISTY of energy flowing through an ecosystem.
- Biological cycles
- The change of habitats over time
- Climate changes
- Species change over time
These factors contribute to why the number of individuals in a population differs.
What determines the size of a population at a given time? Give 4…
-Birth rate - increases population
-Death rate - decreases population
-Immigration - increases population
-Emmigration - decreases population
How do fugitive species regulate their population number?
Provide an example…
Fugitive species are POOR at competition, thus their strategy is to rely on a large capacity for REPRODUCTION and dispersal to increase their numbers. They INVADE a new environment RAPIDLY. Algae is a good example, they colonise bare rock.
How do fugitive species regulate their population number?
Provide an example…
Fugitive species are POOR at competition, thus their strategy is to rely on a large capacity for REPRODUCTION and dispersal to increase their numbers. They INVADE a new environment RAPIDLY. Algae is a good example, they colonise bare rock.
What curve highlights the pattern of growth used by equilibrium species?
Sigmoid curve - one-step growth curve
What are the 4 parts of the one-step growth curve?
Go in order…
- Lag phase
- Exponential growth phase
- Stationary phase
- Death phase
Describe the lag phase…
Population number does NOT increase in the INITIAL stages - it’s a period of SLOW growth.
This phase is a period of adaption and PREPRATION for growth.
Describe the exponential growth phase - 1 sentence…
What is the other name for it?
It is also called the ‘log phase’.
In this section the numbers increase as long as there is no factor limiting growth.
Why can the rate of growth/increase not be maintained indefinelty? What kicks in?
Environmental resistance kicks in…
This is where environmental factors slow down population growth.
3 Examples of Environemtnal Resistance…
- Food availability
- The higher the conc. of waste products the more TOXIC the environment/living space becomes…
- NOT enough space/nesting sites…
What is the STATIONARY phase? Explain the term ‘carrying capacity’…
This is where birth rate and death rate are equivalent. The population has reached its MAXIMUM size. This is called the ‘carrying capacity’ for that specific environment - i.e the value/number of individuals that an area can handle/support. This number is dependent on the bundance of resources vital for survival…
The population count does not remain constant but rather fluctuates around this value in response to environmental changes such as the number of predators present.
What is the ‘death phase’?
Factors that slow population growth at the end of the log phase become more significant here causing the population to decrease where death rate exceeds birth rate - causing a negatve gradient to occur.
What are BIOTIC and ABIOTIC factors?
- Biotic factors are parts of the environment of an organism that is living - such as parasites & predators…
- Abiotic factors are parts of the enivronment of an orgnism that are non-living - such as temperature & oxygen availability
What 2 factors REGULATE population increase?
- Density-Dependent Factors - some environmental factors have more effect if the population in a given area is more dense/larger.
- Density-Independent Factors - these factros DON’T rely on the density of a population. Their effect is the SAME regardless of the size of the population…
