OCR Biology Ecosystems 6.3.1 Revision Summary - By A* Student
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Course
Ecosystems 6.3.1 (H420)
Institution
OCR
A revision summary of OCR A level Biology Ecosystems 6.3.1
Made by a student who achieved A* in A level Biology.
Covers all the points within the OCR Biology Specification.
Condenses 3 OCR specification books and class notes.
Ecosystem – all biotic & abiotic factors that interact within a defined area. Transfer of Biomass – mass of living material present
- Large scale = African grassland - Energy = cannot be recycled
s
- Medium scale = playing field - Materials = recycled.
- Small scale = rock pool Food Chain Simple
Habitat – place where organism lives Food Web Complex & show interdependent relationships
Population – all organisms of one species who live & breed together Producer – supply all chemical energy for all other organisms
Community – populations of different species who live & interact with each Primary consumer – herbivore
other Secondary consumer – carnivore
Niche – role of each species in an ecosystem Tertiary consumer – carnivore
Biotic (living) Abiotic (non-living) Decomposers (fungi & bacteria) – break down dead
Competition, Light, Temperature, Water availability, humidity, organisms releasing nutrients back into the ecosystem
Consumption, Predation Oxygen availability, Soil factors – pH, Biomass decreases with each trophic level
Dynamic – constantly changing - Respiration, movement, excretion, maintaining body temp.
- Cyclic change = predator-prey - Not all biomasses can be consumed; bones, cellulose.
- Directional – erosion. Biomass present at trophic level = Biomass or organism
x total no. of organisms
Nitrogen Cycle – needed to make proteins & aa. Decomposers Dry Organisms killed ↑accuracy Unethical.
1. Nitrogen Fixation produces Ammonium, NH3 (saprotrophs) Mass & heated Small sample
- Azobacter (in the soil) 1. secrete enzymes Wet Living organism No killing Presence of water
- Rhizobium (in root nodules) onto dead/ waste mass measured ↓accuracy
2. Ammonification material
- Pyramid of Numbers = not always a pyramid (lots of
- Nitrosomonas oxidise ammonia 2. enzymes digest &
organisms with small biomass).
(chemoautotrophs) break down material
- Pyramid of Biomass = always pyramid, ↑accuracy,
- Ammonia, NH3 nitrites, NO2 into small molecules
energy avalibale after transfer
3. Nitrification 3. Saprotroph absorbs Efficiency of transfer = x 100
- Nitrobacter oxidise nitrites (chemoautotrophs) molecules. energy availale before transfer
- Nitrites, NO2- nitrates, NO3- GPP = NPP + R
4. Denitrification Gross Primary production (GPP) = energy taken in from
- Pseudomonas in anaerobic conditions sunlight & converted into product
- nitrates (NO2-) Nitrogen (N2) - Limited: Used in R, low light, low nutrient available, pests
remove biomass, fungal disease.
Net Primary Production (NPP) = energy stored in plants as
biomass
Respiration (R) = energy used in respiration.
Human manipulation – conserve maximum energy.
In plants In animals
Remove competition (weeds) Reduce movement
2.
Green houses = optimal Remove predators
3. conditions Antibiotics prevent
1. Crop rotation – stops disease
reduction in soil of inorg ions Keep body temp warm &
used by plants. constant
Pesticide removes pests
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