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LGS A-Level OCR Biology - Unit 6 - Ecosystems Part 2

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This deck covers key concepts from Unit 6 of the OCR Biology curriculum, focusing on ecosystems, succession, and energy transfer.

Loss of biomass in endotherms vs ectotherms

Ectotherms use less energy in maintaing body heat so there is more biomass availabe
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Key Terms

Term
Definition
Loss of biomass in endotherms vs ectotherms
Ectotherms use less energy in maintaing body heat so there is more biomass availabe
Saprotrophs
Secrete extracellular enzymes onto dead/waste materials | Digest the materials into small molecules which are then absorbed and stored/respired
Why is the producer efficiency v. low
Approx 90% of light is reflected, unusable wavelength and transmitted through leaf Limiting factors; Energy used for photosynthetic reactions
Succession
Progressive change in the structure and species composition in a community Affects vegetation first but then brings about corresponding changes in bac...
Climax community
Final, stable community that exists after the process of succession has occurred Usually woodland communities
Deflected succession
Happens when succession is stopped/interfered w/ e.g. grazing so a plagioclimax develops as the species are stuck in that one stage of succession

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TermDefinition
Loss of biomass in endotherms vs ectotherms
Ectotherms use less energy in maintaing body heat so there is more biomass availabe
Saprotrophs
Secrete extracellular enzymes onto dead/waste materials | Digest the materials into small molecules which are then absorbed and stored/respired
Why is the producer efficiency v. low
Approx 90% of light is reflected, unusable wavelength and transmitted through leaf Limiting factors; Energy used for photosynthetic reactions
Succession
Progressive change in the structure and species composition in a community Affects vegetation first but then brings about corresponding changes in bacteria, fungi, insects, birds and mammals
Climax community
Final, stable community that exists after the process of succession has occurred Usually woodland communities
Deflected succession
Happens when succession is stopped/interfered w/ e.g. grazing so a plagioclimax develops as the species are stuck in that one stage of succession
Pioneer species
Species that begin the process of succession, often colonising an area as the first living thing there
Primary succession
If a community is developed from bare ground e.g. volcanic eruptions Pioneer communities start succession ---> conditions change (build up or organic material /nutrients) and other species succeed them; Larger plants continuously succeed small plants until a climax community is formed
Secondary succession
Does not start from bare ground | Takes place on a previously colonised but damaged/disturbed habitat
Why are sand dunes helpful in terms of succession
Shows us the stages of succession in order of occurrence whereas usually we only see the current stage
How does succession affect species diversity
Increases it however dominant species may outcompete the smaller species killing whole species off
Weathering
Breakdown or decomposition of rock in situ
How does weathering contribute to succession
Decomposition of rock increases soil depth/ changes soil composition; Favouring new species
Calculating net primary production
Gross primary production = npp - products of respiration
Calculating efficiency of energy transfer
Net production/ food intake x 100
Plagioclimax
Sub-climax community when succession has been deflected
Ways to deflect succession
Mainly agriculture and human activity e.g. Grazing; Burning; Application of fetilisers; Application to herbicide; Exposure to excessive amounts of wind
How does succession affect biomass
Increases it due to more organisms in the ecosystem
Why should sub-climax communities be conserved
Higher species diversity than climaxx communities - still contain some sub-climax species and climax species; Results in conserving a much wider range of plants and animals that dont live in the climax community
Pioneer species on sand dunes
Species that can tolerate salty water, lack of fresh water and stable sand e.g. sea rcket
Pioneer species on bare rock
Algae and lichens as they don't need to be anchored into the soil
Increasing primary productivity
Some crops are planted early; Irrigating crops; Drought resistant crops; Using greenhouses; Crop rotation; Fertilisers (provides inorganic ions); Pesticides/ pest resistant crops
How does planting some crops early increase primary productivity
Provides a longer growing season to harvest more light
How does irrigating crops increase primary productiviy
Water is readily available for the light dependent stage of photosynthesis even when rainfall is below average
How does growing crops in a greenhouse increases primary productivity
Provides a warmer temp ---> increases the rate of photosynthesis