Process
OCR A-Level Biology H420
Cell Structure
Biological Molecules
Nucleotides and Nucleic Acids
Enzymes
Biological Membranes
Cell Division, Cell Diversity and Cellular Organisation
Exchange Surfaces
Transport in Animals
Transport in Plants
Communicable Diseases, Disease Prevention and the Immune System
Biodiversity
Classification and Evolution
Communication and Homeostasis
Excretion as an Example of Homeostatic Control
Neuronal Communication
Hormonal Communication
Plant and Animal Responses
Topic overviewTropisms and plant responses to stress and herbivoryPlant hormones and their commercial usesThe nervous system and the brainReflex actions and the knee jerk reflexFight or flight and the control of heart rateThe structure of skeletal muscleThe neuromuscular junction and the sliding filament model
Photosynthesis
Respiration
Cellular Control
Patterns of Inheritance
Manipulating Genomes
Cloning and Biotechnology
Topic overviewNatural plant cloning and taking cuttingsMicropropagationAdvantages and disadvantages of plant cloningAnimal cloning: embryo twinning and nuclear transferAdvantages and disadvantages of animal cloningMicroorganisms in food productionAseptic techniqueFermentation and its conditionsThe microbial growth curveImmobilised enzymes
Ecosystems
Populations and Sustainability
Practical Skills and Mathematical Requirements
Ecosystems
- 4 subtopics
- 9 things to know
- Components 02 and 03
What Ecosystems covers
Ecosystems is the fifth section of Module 6. It covers the biotic and abiotic factors that shape an ecosystem, why so little biomass passes between trophic levels, the nitrogen and carbon cycles, succession from pioneer species to climax community, and how distribution and abundance are estimated.
Where it is assessed
Components 02 and 03
Module 6 is examined on Biological Diversity, then the unified paper.
Check the OCR specification ↗The 4 subtopics
Each one has its own page.
- Ecosystems, biotic and abiotic factorsWhat an ecosystem is at every scale and what makes one dynamic, with examples of the biotic and abiotic factors acting within it.Open →
- Biomass transfer between trophic levelsHow biomass is measured, why roughly a tenth passes to the next level, the efficiency calculation, and how farming manipulates the transfer.Open →
- The nitrogen and carbon cyclesDecomposers, nitrogen fixation, nitrification, assimilation, ammonification and denitrification with the bacteria involved, and the movement of carbon between reservoirs.Open →
- Succession, distribution and abundancePioneer species, climax communities and deflected succession, and estimating abundance with quadrats, transects, percentage cover and mark-release-recapture.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Process
Explain primary succession.
Process
How is population size estimated for mobile animals?
Key term
What is biomass?
Key term
Define decomposers and state the main types of organism involved.
Process
What is assimilation in the nitrogen cycle?
Key term
Describe how random sampling is carried out using quadrats.
Key term
What is denitrification?
Key term
What is an ecosystem, which biotic and abiotic factors act in it, and does it stay the same over time?
Take Ecosystems further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Habitat vs Niche
Habitat: the physical place where an organism lives. Niche: the role an organism occupies and how it uses the place it lives.
Gross primary productivity vs Net primary productivity
Gross primary productivity: the total chemical energy fixed by producers in a given area and time. Net primary productivity: what remains of it after the producers' own respiration.
Primary succession vs Secondary succession
Primary succession: colonisation of ground that has never supported a community. Secondary succession: recolonisation of ground where a community has been cleared but soil remains.
Questions from this topic
Each one with the model answer underneath.
- 1
Define the term ecosystem.
Model answer
A community of living organisms interacting with each other and with their abiotic environment.
- 2
Give an example of a very small ecosystem.
Model answer
A rock pool.
- 3
Give an example of an intermediate-sized ecosystem.
Model answer
A large tree and its associated organisms.
- 4
Give an example of a large ecosystem.
Model answer
A playing field.
- 5
What does it mean to say that ecosystems are dynamic?
Model answer
They change over time in response to environmental conditions and species interactions.
- 6
Define biotic factors.
Model answer
Living components that influence ecosystems.
What is inside Levo
Six ways to work the same material.
Ecosystems revision questions
- What does Ecosystems cover in OCR A-Level Biology?
- 4 subtopics: ecosystems, biotic and abiotic factors, biomass transfer between trophic levels, the nitrogen and carbon cycles and succession, distribution and abundance. Each one has its own page with questions and model answers.
- How is Ecosystems organised?
- By the OCR H420 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Ecosystems, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
Or £46 a year, about £3.83 a month. Cancel anytime.