3.5 Population Size And Ecosyetms Flashcards
Factors affecting population size
-Birth rate
-Death rate
-Immigration
-Emigration
Strategies for population growth
-Fugitive species
-Equilibrium species
Fugitive species
-Can tolerate competition
-Reproduce rapidly
-Invade new environments
-E.g algae and weeds
Equilibrium species
-Competition within a stable habitat
-S shaped curve (one step growth curve)
Environmental resistance factors
Abiotic
Biotic
Abiotic factors
Temp, pH, light intensity, water availability
Biotic factors
Competition for resources (intro and inter), disease, parasites, increase in predator numbers
Predator-prey interactions cause both populations to oscillate due to
Negative feedback mechanisms
Carrying capacity
Maximum population size of a species that can be sustained by an environment
Population crash
Decrease in population number when carrying capacity is exceeded
Population growth =
Death + Emigration
Density dependent factors which limit population size
Competition
Predation
Disease
Parasitism
Density independent factors
Abiotic
Earthquakes
Volcanoes
Wildfire
Extreme weather
Abundance
Number of individuals of the same species in a give area
Animal abundance can be measured by
Capture-mark-recapture
Kick sampling
Sessile abundance can be measured by
-Random sampling (quadrat to find density)
-Systematic sampling (transect to determine change in percentage cover)
Quadrats show
Density of an organism in a given area
Transects show
Change in percentage cover of species
Competitive exclusion principle
-When two species occur in the same habitat, one will outcompete the other
-Two species cannot occupy the same niche
Ecosystem
-Community of interdependent species and their habitat
-Made up of biotic and abiotic elements
-Changes over time
Producers
-Autotrophic
-Absorb light energy and convert to simple inorganic compounds into more complex organic compounds (carbohydrates)
Consumer
-Heterotrophic
-Must ingest or absorb organic carbon from other organisms
Detritivores
-Feed on dead organic matter
-Earthworms, woodlice and maggots
Decomposers
-Break down organic compounds into simpler inorganic compounds
-These see soluble and can be absorbed by plants
-Bacteria and fungi
Why is light not absorbed
-Reflected from leafs surface
-Wrong wavelength
