Show Menu

Ecosystems IGCSE Biology Cheat Sheet by

The organism , environment and feeding relationships IGCSE Biology Edexcel


1. distinct self supporting
2. system of organisms
3. intera­cting with each other and the enviro­nment
1. a single member of a species
1. a particular species
2. in the same area a certain time
1. multiple popula­tions
2. living and intera­cting
3. in an ecosystem
1. where an organism lives at any one time
plants which photos­ynt­hesize to produce food
animals that eat plants or other animals
organisms that break down dead material and help to recycle nutrients by saprot­rophic nutrition (extra­cel­lular enzymatic digestion )
1. amount of variation shown by species
2. species richness
3.abun­dance of species and even distri­bution

Biotic factors

availa­bility of food
1. more food means more organisms can survive and reproduce
2. increase in population size
new predators
1. in balanced ecosystems , predators catch enough prey to survive but not many that they wipe out the population
2. if a new predator is introduced ecosystem may become unbalanced
new pathogens
1. if a new pathogen enters an ecosystem , the population will have no immunity or resistence
2. population may decline or wipe out
1. if 2 species compete for the same resource and one is better adapted then that species will outcompete the other
2. may continue until there are too few members of the lesser adapted species to breed succes­sfully

pyramid of energy

illust­rates the amount of energy contained within the biomass
area of each box represents the quantity of energy
wide base , as you move up the energy decreases
only 10% of the energy is passed on
only a small proportion is absorbed by the producers , most energy is relfected

energy transfer

1. producers use glucose from respir­ation to produce their own biomass
energy losses
2.primary consumers eat producers they digest the biomass and use the chemical energy to increase or sustain their own biomass
1. during movement
chemical energy is transfered , biomass is also transf­erred
2. as heat during respir­ation
only the energy from assimi­lation remains with the organism to be passed on
3. egestion e.g. cellulose in faeces
4. excretory products - some of the energy is transf­erred to the decoposer food chain
5. some parts are inedible
efficiency of energy
useful energy output / total energy input x100

importance of biodiv­ersity

species depend and compete with each other for:
1) food
3)main­tenance of physical enviro­nment
High biodiv­ersity ->s­tab­ility of ecosystems ->r­educing dependence
more resilient to enviro­nmental impact or disease

Abiotic factors

Light intensity
1. needed for photos­ynt­hesis
2. more light-­>more phs ->more plant growth
affects rate of phs due to KE of enzymes
Moisture levels
living organisms require water to survive
soil pH, mineral ion , clay content
different species of plants are adapted to different condit­ion­s(m­ention them !)
wind intensity
1. affects rate of transp­iration in plants
2. higher wind intensity -> greater rate of transp­iration
3. affects rate of photos­ynt­hesis as it ensures water and mineral ions are transp­orted to the leaves
concn for plants
1. phs in plants
2. increase in CO
-> increase in phs
concen­tration , salinity
some aquatic animals can only survive in certain conditions
flow rate of river
toxic waste

food chains and food webs

represents the transfer of energy from producer through a sequence of organisms
source of all energy in a food chain is the light energy from the sun
food web: when an organism is both a primary or secondary consumer

pyramid on numbers and biomass

to show how many organisms are in a habitat you need to draw a pyramid of numbers
pyramid of biomass shows the total mass the organisms at each level would have
the larger an individual is the fewer of them there are
always pyramid shaped
width of box indicates the number of organisms at that trophic level
refers to dry biomass , after water has been removed
not always pyramid shaped


No comments yet. Add yours below!

Add a Comment

Your Comment

Please enter your name.

    Please enter your email address

      Please enter your Comment.

          Related Cheat Sheets

          AP Biology Unit 6: Ecology and Animal Behavior Cheat Sheet
          GCSE BIOLOGY: Cells and Biological Molecules Cheat Sheet

          More Cheat Sheets by lito.p

          Polymers IGCSE D&T Cheat Sheet