Population Size And Ecosystems Flashcards
What factors make ecosystems dynamic?
- intensity of energy
- biological cycles( nitrogen cycle)
- habitats change- succession
- new species and extinction
What determines the size of a population?
- birth rate/ natality
- death rate/ mortality
- immigration
- emigration
Describe fugitive species
- poor at competition
- rely on large capacity for reproduction and dispersion
- invade new environment rapidly
Describe equilibrium species
Competition within a stable habitat
One step growth curve
Definition of carrying capacity
The maximum number around which a population fluctuates in a given environment
What are density dependent factors?
More affect in larger population
- biotic factors: parasites, disease, food supply
What are density independent factors?
Not affected by population density
Due to sudden change in abiotic factors: temperature
Definition of abundance
Measure of how many individuals exist in a habitat
Ways to measure abundance in animals
- capture mark recapture
- kick sampling
Ways to measure abundance in plants
- Quadrat
- percentage cover
- percentage frequency
Definition of distribution
Area or volume in which a species is found
How to measure distribution in uniform habitat
Outermost plants are marked and area inside is measured
Describe belt transects
Show abundance data for a given area at measured distances along the transect
Quadrat placed at each coordinate along the transect and a reading taken
Definition of ecosystem
A characteristic community of interdependent species interacting with the abiotic components of their habitat.
Definition of habitat
The place in which an organism lives
Definition of community
Interacting populations of two or more species in the same habitat
Gross primary productivity
The rate of production of chemical energy in organic molecules by photosynthesis in a given area in a given time. KJ m-2 y-1
Net primary productivity
Energy in the plants biomass which is available to primary consumers.
KJ m-2 y-1
Equation for NPP
NPP= GPP- respiration
Primary productivity
The rate at which producers convert energy into biomass.
Secondary productivity
The rate at which consumers convert the chemical energy of their food into biomass.
Definition of succession
The change in structure and species composition of a community over time
Definition of climax community
A stable community that has reached equilibrium with its environment and no further change occurs
Definition of primary succession
The change in structure and species composition of a community over time in an area that has not previously been colonised
Definition of pioneer species
The first species to colonise a new area in an ecology succession
Definition of secondary succession
The changes in a community following the disturbance or damage to a colonised habitat
What effects the length of a food chain?
- more energy enters at first level
- energy transferred efficiently
- predator and prey populations
- larger ecosystems
- 3D environment
Why is some light that falls on plants not absorbed?
- wrong wavelength
- reflected
- transmitted straight through leaf
How energy is lost at each tropic level
- molecules that are egested
- lost as heat
- parts of animal not eaten
Disadvantages of pyramid of numbers
- no size of organisms
- no juvenile and adults
- difficult to draw to scale
- may be inverted
Disadvantages of pyramid of biomass
- difficult to measure
- doesn’t indicate amount of energy
- may be inverted
Ammonification
Proteases digest proteins into amino acids
Deaminases remove NH2 groups from amino acids and reduce them to ammonium ions
Nitrification
Addition of nitrites and nitrates to the soil
Nitrosomonas converts ammonium ions to nitrites
Nitrobacter converts nitrites to nitrates
Denitrification
Loss of nitrate from the soil
Pseudomonus converts nitrate to nitrogen
Human impact on nitrogen cycle
- ploughing fields- soil aeration
- draining land
- haber process - artificial nitrogen fixation
- animal waste
- slurry
Planting legumes
