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
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller hyaldridge. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £5.48. You're not tied to anything after your purchase.
