Populations And Ecosystems Flashcards
What are the factors controlling population size
Intensity of energy flowing through the ecosystem varying
Biological cycles e.g nitrogen cycle causing mineral availability to vary
Succession causing habitats to change
Arrival /removal of new species
Climate change altering habitats
What factors determine the population size in a particular time of a habitat
Birth rate or natality
Death rate /mortality
Immigration
Emigration
What are fugitive species
Species that are poor at competition so rely on a large capacity for reproduction and dispersal to increase numbers they invade new environments rapidly e.g algae colonising rock
How do equilibrium species control their populations
Through competition within a stable habitat
Usual pattern of growth is an s shaped curve (one step growth curve )
What is a population
An interbreeding group of organisms of the same species occupying a particular habitat
What is a birth rate
Reproductive capacity of a population ; number of new individuals derived from reproduction per unit time
What is immigration
Movement of individuals into a population of the same species
What is an equilibrium species
Species that control their population by competition rather than reproduction and dispersal
What are the four phases in the one step growth curve
Lag phase
Exponential phase
Stationary phase
Death phase
What happens during the lag phase
Initially there is no growth which then turns to slow growth
Adaptation or preparation for growth intense metabolic activity e.g enzyme synthesis
In sexually reproducing animals it is the time taken to reach sexual maturity
What happens in the exponential /log phase
Numbers increase and more individuals become available for reproduction
What factors can affect rate of increase the exponential phase
Environmental resistance eg
Less food available
Conc of waste product becomes toxic not enough space / nesting sites
Biotic factors e.g predation , disease and parasitism and competition
For bacteria : accumulation of toxic waste , available food , overcrowding
What is the stationary phase
Occurs when birth rate is equal to death rate , population has reached its carrying capacity
Population not absolutely constant and fluctuates around environmental factors
What is the death phase
Factors that slow population growth at the end of the log phase become more significant and population size decreases until death rate is greater than birth rate and graph has negative gradient
How would you measure abundance of plants
Estimating percentage cover
Estimating percentage frequency
Using quadrat to calculate mean
What is a habitat
The place where an organism lives
What is a community
Interacting populations of two or more species in the same habitat at the time
What is a trophic level
Feeding level at which the number of times that energy has been transferred between the sun and successive organisms along the food chain
What is biomass
The mass off biological material In living or recently living organisms
What is gross primary productivity
The rate of production of chemical energy in organic molecules by photosynthesis in a given area at a given time
What is net primary productivity
Energy in the plants biomass that is available to primary consumers
What is primary productivity
The rate at which energy is converted by producers into biomass
What is secondary productivity
The rate at which consumers convert the chemical energy of their food into biomass
What is the issues with pyramid of numbers
Doesn’t take into account size of organisms
May be so large it might have hard to draw to scale
