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The organism , environment and feeding relationships IGCSE Biology Edexcel
Definitions
Ecosystem |
1. distinct self supporting |
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2. system of organisms |
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3. interacting with each other and the environment |
individual |
1. a single member of a species |
Population |
1. a particular species |
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2. in the same area |
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3.at a certain time |
community |
1. multiple populations |
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2. living and interacting |
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3. in an ecosystem |
Habitat |
1. where an organism lives at any one time |
Producers |
plants which photosynthesize to produce food |
Consumers |
animals that eat plants or other animals |
Decomposers |
organisms that break down dead material and help to recycle nutrients by saprotrophic nutrition (extracellular enzymatic digestion ) |
Biodiversity |
1. amount of variation shown by species |
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2. species richness |
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3.abundance of species and even distribution |
Biotic factors
availability of food |
1. more food means more organisms can survive and reproduce |
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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 |
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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 |
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2. population may decline or wipe out |
competition |
1. if 2 species compete for the same resource and one is better adapted then that species will outcompete the other |
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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 |
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4. excretory products - some of the energy is transferred to the decoposer food chain |
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5. some parts are inedible |
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efficiency of energy |
useful energy output / total energy input x100 |
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importance of biodiversity
species depend and compete with each other for: |
1) food |
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2)shelter |
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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 |
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2. more light->more phs ->more plant growth |
Temperature |
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 |
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2. higher wind intensity -> greater rate of transpiration |
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3. affects rate of photosynthesis as it ensures water and mineral ions are transported to the leaves |
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1. phs in plants |
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2. increase in CO 2
-> increase in ph s |
O 2
concentration , salinity |
some aquatic animals can only survive in certain conditions |
flow rate of river |
pollution |
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 |
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