Predator-prey relationship causes both populations to oscillate
Sigmoid growth: usual
pattern of growth= 1
step growth curve
Density-Dependent
Factors
Environmental factors that
have more effect if the
populations in a given area
is large
Disease, parasitism,
predation, depletion of
food supply
Biotic
Density-Independent
Factors
Abiotic
Effect is the same regardless
of population size
Temperature
Ecosystems: A characteristic community of
interdependent species interacting with
the abiotic components of their habitat
A sequence of
energy changes
Abundance: The number of individuals
in a species in a given area or volume
Capture-mark-recapture
Kicksampling
Quadrat
Kite diagrams
Distribution: The area/volume in which
the organism of a species are found
Transect
Belt transect
Line transect
Food Chains
Energy leaves the
system as heat
Length is
dependent on
Annotations:
-The energy that enters the food chain at the 1st trophic level
-Efficiency of energy transfer between trophic levels
-Predator and prey population
-Size of the ecosystem: larger=longer
Photosynthetic efficiency: A measure
of the ability of a plant to trap light
energy
Annotations:
-Wrong wavelength of light
-Light can be reflected
-Light can be transmitted straight through the leag
Efficiency of energy transfer= Energy incorporated into biomass after
transfer/ Energy available in biomass before transfer
There is a loss from the
food chain at each level
Annotations:
-There is energy in molecules that are egested
-Energy is lost as heat due to respiration
- Energy remains in molecules in parts of animal that may not be eaten e.g. horns
Ecological Pyramids
Pyramid of Numbers
Does not take into account
the size of the organisms
Area of the pyramid bar is
proportional to the total
number at each trophic level
Pyramid of Energy
=feeding relationships
Area of bar decreases =energy loss from
the ecosystem
Easy to compare the efficiency of
energy transfer between trophic levels
Pyramid of
Biomass
Inverted pyramid
Hard to measure accurately
Succession
Climax community
equilibrium
GPP=Respiration
Constant quantity of humus
Complex food web
Bare rock ---> Deciduous forest
1. Algae and lichen colonise the rock=pioneer
community
2. Formation of primitive soil
3. As soil develops, herbaceous plants outcompete mosses.
Seeds that can germinate in direct sunlight are favoured
4.Tall grass starts to grow. Shade-tolerant species are established
5. Soil thickens as plants and animals start to die
6. Shrubs outcompete herbaceous plants
7. Soil deepens which increases the quantity
of minerals and humus in the soil
8. Large trees outcompete shrubs
Secondary succession
Annotations:
Same sequence as primary succession but it's more rapid
Factors affecting
succession
Human interference
Over-grazing
Farming of land
Deforestation
Migration
Arrival of
spore, seeds
and animals
Competition amongst organisms
Intraspecific-between
individuals of the same species
Interspecific- between
individuals of different species