AQA GCSE Biology notes Topic 7 – Ecology
Topic 7 – Ecology
Table of Content
7.1 Adaptations, interdependence and competition ......................... 2
7.1.1 Communities ................................................................................................................... 2
7.1.2 Abiotic factors ................................................................................................................. 2
7.1.3 Biotic factors ................................................................................................................... 2
7.1.4 Adaptations ..................................................................................................................... 2
7.2 Organisation of an ecosystem ..................................................... 3
7.2.1 Levels of organization ..................................................................................................... 3
7.2.2 How materials are cycled ................................................................................................ 4
7.2.3 Decomposition (biology only) ......................................................................................... 4
7.3 Biodiversity and the effect of human interaction on ecosystems . 6
7.3.1 Biodiversity ..................................................................................................................... 6
7.3.2 Waste management........................................................................................................ 6
7.3.3 Land use .......................................................................................................................... 7
7.3.4 Deforestation .................................................................................................................. 7
7.3.5 Global warming ............................................................................................................... 8
7.3.6 Maintaining biodiversity ................................................................................................. 8
7.4 Food Trophic levels in an ecosystem (biology only) ..................... 9
7.4.1 Trophic levels .................................................................................................................. 9
7.4.2 Pyramids of biomass ....................................................................................................... 9
7.4.3 Transfer of biomass ...................................................................................................... 10
7.5 Food production (biology only) ................................................. 11
7.5.1 Factors affecting food security ..................................................................................... 11
7.5.2 Farming techniques ...................................................................................................... 11
7.5.3 Sustainable fisheries ..................................................................................................... 11
7.5.4 Role of biotechnology ................................................................................................... 11
1
, AQA GCSE Biology notes Topic 7 – Ecology
7.1 Adaptations, interdependence and competition
7.1.1 Communities
Ecosystem - interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their
environment
Competition
Plants Animals
• Light • Food
• Space • Mates
• Water • Territory
• Mineral ions
Interdependence - within a community each species depends on other species for food, shelter,
pollination, seed dispersal etc. If one species is removed it can affect the whole community
Stable community
• All species & environmental factors are in balance → population sizes remain fairly constant
• No of predators & prey rise & fall in cycles
7.1.2 Abiotic factors 7.1.3 Biotic factors
• Light intensity • Availability of food
• Temperature • New predators arriving
• Moisture levels • New pathogens
• Soil pH & mineral content • One species outcompeting another so the
• Wind intensity & direction numbers are no longer sufficient to breed
• CO2 levels for plants
• O2 levels for aquatic animals
7.1.4 Adaptations
Structural Behavioural Functional
Definition Shape or colour of a part of an Way an organism behaves Reproduction / metabolism
organism
Description • Sharp teeth of a carnivore • Play dead → avoid • Late implantation of
• → tear meat apart predators embryos
• Camouflage • Basking in sun → • Conservation of water
• → avoid being spotted by absorb heat by producing little
prey • Courting → attract sweat
• Thick layer of fat mate
→ insulation
2
, AQA GCSE Biology notes Topic 7 – Ecology
Extremophiles - organisms live in extreme environments eg high temp, pressure, salt concentration
• Eg Bacteria living in deep sea vents
Suggest how needing less O2 helps animal to conserve water (2)
• Less breathing rate
• Less water lost through breath
• Less water from respiration
7.2 Organisation of an ecosystem
7.2.1 Levels of organization
Photosynthetic organisms - producers of biomass for life on Earth
Food chains - feeding relationships within a community
• Producers → primary consumers → secondary consumers → tertiary consumers
• Producer – synthesises molecules eg green plant or alga which makes glucose by photosynthesis
• Consumers – kill & eat other animals are predators
• Prey – eaten by consumers
Stable community – no of predators & prey rise and fall in cycles
Practicals
Quadrats - slow / non-motile organisms
Uniformly distributed - organisms equally spread
Randomly placed quadrats (population size that are uniformly distributed)
Describe how you could estimate the number of bluebells in a small woodland (5)
1. Use tape measures to create a grid
2. Use random no. generator to generate coordinates
3. Count number of individuals in quadrat
4. Repeat at least 30 times and calculate mean
!". "% &'(&)&(*+, "% + -./0&/-
5. 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 = 1"2+, +3/+
Belt transect (population changes over distance)
1. Place tape measure down shore in a straight line at a right angle
2. Place quadrat next to tape measure every 5m
3. Count frequency of species in quadrat
4. Repeat by placing another 30 transects at each interval
Types of abundance measurements
𝑵𝒐. 𝒐𝒇 𝒔𝒒𝒖𝒂𝒓𝒆𝒔 𝒊𝒏 𝒒𝒖𝒂𝒅𝒓𝒂𝒕 𝒄𝒐𝒏𝒕𝒂𝒊𝒏𝒊𝒏𝒈 𝒔𝒑𝒆𝒄𝒊𝒆𝒔
• 𝑭𝒓𝒆𝒒𝒖𝒆𝒏𝒄𝒚 = × 𝟏𝟎𝟎%
𝑵𝒐. 𝒐𝒇 𝒔𝒒𝒖𝒂𝒓𝒆𝒔
𝑵𝒐. 𝒐𝒇 𝒊𝒏𝒅𝒊𝒗𝒊𝒅𝒖𝒂𝒍 𝒐𝒇 𝒂 𝒔𝒑𝒆𝒄𝒊𝒆𝒔
• 𝑫𝒆𝒏𝒔𝒊𝒕𝒚 = 𝑻𝒐𝒕𝒂𝒍 𝒂𝒓𝒆𝒂
𝑵𝒐. 𝒐𝒇 𝒔𝒒𝒖𝒂𝒓𝒆𝒔 𝒄𝒐𝒗𝒆𝒓𝒆𝒅
• % 𝒄𝒐𝒗𝒆𝒓 = 𝑻𝒐𝒕𝒂𝒍 𝒏𝒐. 𝒐𝒇 𝒔𝒒𝒖𝒂𝒓𝒆𝒔
× 𝟏𝟎𝟎%
3
, AQA GCSE Biology notes Topic 7 – Ecology
7.2.2 How materials are cycled
Carbon cycle
• Returns carbon from organisms via
respiration to the atm as CO2 is used by
plants in photosynthesis
• Burning produces CO2
• Decomposition of dead organisms
o Microbial respiration → CO2
o Anaerobic respiration → mineral
ions in soil / convert to fossil fuels
How microorganisms help to recycle materials?
• Microorganisms decay
• Return carbon to atm as CO2 by microbial respiration and mineral ions to soil by anaerobic respiration
Water cycle
• Evaporation, Condensation, Precipitation
• Interception - precipitation caught by the vegetation
• Transpiration - water from vegetation transferred back to atmosphere
• Overland flow (surface runoff) - water flowing over ground surface
• Throughflow - sideways movement of water through soil towards river
• Groundwater flow - sideways movement of water through permeable rock towards river
• Infiltration - downward movement of water into soil
• Percolation - downward movement of water through permeable rock
7.2.3 Decomposition (biology only)
Factor How factor affects rate of decay
• Low temp - ↓ chemical reactions involving enzymes, ↓rate of decay
Temp • Warm temp - ↑ reactions involving enzymes, ↑rate of decay
• Too high – enzymes denature, ↓rate of decay
4
Topic 7 – Ecology
Table of Content
7.1 Adaptations, interdependence and competition ......................... 2
7.1.1 Communities ................................................................................................................... 2
7.1.2 Abiotic factors ................................................................................................................. 2
7.1.3 Biotic factors ................................................................................................................... 2
7.1.4 Adaptations ..................................................................................................................... 2
7.2 Organisation of an ecosystem ..................................................... 3
7.2.1 Levels of organization ..................................................................................................... 3
7.2.2 How materials are cycled ................................................................................................ 4
7.2.3 Decomposition (biology only) ......................................................................................... 4
7.3 Biodiversity and the effect of human interaction on ecosystems . 6
7.3.1 Biodiversity ..................................................................................................................... 6
7.3.2 Waste management........................................................................................................ 6
7.3.3 Land use .......................................................................................................................... 7
7.3.4 Deforestation .................................................................................................................. 7
7.3.5 Global warming ............................................................................................................... 8
7.3.6 Maintaining biodiversity ................................................................................................. 8
7.4 Food Trophic levels in an ecosystem (biology only) ..................... 9
7.4.1 Trophic levels .................................................................................................................. 9
7.4.2 Pyramids of biomass ....................................................................................................... 9
7.4.3 Transfer of biomass ...................................................................................................... 10
7.5 Food production (biology only) ................................................. 11
7.5.1 Factors affecting food security ..................................................................................... 11
7.5.2 Farming techniques ...................................................................................................... 11
7.5.3 Sustainable fisheries ..................................................................................................... 11
7.5.4 Role of biotechnology ................................................................................................... 11
1
, AQA GCSE Biology notes Topic 7 – Ecology
7.1 Adaptations, interdependence and competition
7.1.1 Communities
Ecosystem - interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their
environment
Competition
Plants Animals
• Light • Food
• Space • Mates
• Water • Territory
• Mineral ions
Interdependence - within a community each species depends on other species for food, shelter,
pollination, seed dispersal etc. If one species is removed it can affect the whole community
Stable community
• All species & environmental factors are in balance → population sizes remain fairly constant
• No of predators & prey rise & fall in cycles
7.1.2 Abiotic factors 7.1.3 Biotic factors
• Light intensity • Availability of food
• Temperature • New predators arriving
• Moisture levels • New pathogens
• Soil pH & mineral content • One species outcompeting another so the
• Wind intensity & direction numbers are no longer sufficient to breed
• CO2 levels for plants
• O2 levels for aquatic animals
7.1.4 Adaptations
Structural Behavioural Functional
Definition Shape or colour of a part of an Way an organism behaves Reproduction / metabolism
organism
Description • Sharp teeth of a carnivore • Play dead → avoid • Late implantation of
• → tear meat apart predators embryos
• Camouflage • Basking in sun → • Conservation of water
• → avoid being spotted by absorb heat by producing little
prey • Courting → attract sweat
• Thick layer of fat mate
→ insulation
2
, AQA GCSE Biology notes Topic 7 – Ecology
Extremophiles - organisms live in extreme environments eg high temp, pressure, salt concentration
• Eg Bacteria living in deep sea vents
Suggest how needing less O2 helps animal to conserve water (2)
• Less breathing rate
• Less water lost through breath
• Less water from respiration
7.2 Organisation of an ecosystem
7.2.1 Levels of organization
Photosynthetic organisms - producers of biomass for life on Earth
Food chains - feeding relationships within a community
• Producers → primary consumers → secondary consumers → tertiary consumers
• Producer – synthesises molecules eg green plant or alga which makes glucose by photosynthesis
• Consumers – kill & eat other animals are predators
• Prey – eaten by consumers
Stable community – no of predators & prey rise and fall in cycles
Practicals
Quadrats - slow / non-motile organisms
Uniformly distributed - organisms equally spread
Randomly placed quadrats (population size that are uniformly distributed)
Describe how you could estimate the number of bluebells in a small woodland (5)
1. Use tape measures to create a grid
2. Use random no. generator to generate coordinates
3. Count number of individuals in quadrat
4. Repeat at least 30 times and calculate mean
!". "% &'(&)&(*+, "% + -./0&/-
5. 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 = 1"2+, +3/+
Belt transect (population changes over distance)
1. Place tape measure down shore in a straight line at a right angle
2. Place quadrat next to tape measure every 5m
3. Count frequency of species in quadrat
4. Repeat by placing another 30 transects at each interval
Types of abundance measurements
𝑵𝒐. 𝒐𝒇 𝒔𝒒𝒖𝒂𝒓𝒆𝒔 𝒊𝒏 𝒒𝒖𝒂𝒅𝒓𝒂𝒕 𝒄𝒐𝒏𝒕𝒂𝒊𝒏𝒊𝒏𝒈 𝒔𝒑𝒆𝒄𝒊𝒆𝒔
• 𝑭𝒓𝒆𝒒𝒖𝒆𝒏𝒄𝒚 = × 𝟏𝟎𝟎%
𝑵𝒐. 𝒐𝒇 𝒔𝒒𝒖𝒂𝒓𝒆𝒔
𝑵𝒐. 𝒐𝒇 𝒊𝒏𝒅𝒊𝒗𝒊𝒅𝒖𝒂𝒍 𝒐𝒇 𝒂 𝒔𝒑𝒆𝒄𝒊𝒆𝒔
• 𝑫𝒆𝒏𝒔𝒊𝒕𝒚 = 𝑻𝒐𝒕𝒂𝒍 𝒂𝒓𝒆𝒂
𝑵𝒐. 𝒐𝒇 𝒔𝒒𝒖𝒂𝒓𝒆𝒔 𝒄𝒐𝒗𝒆𝒓𝒆𝒅
• % 𝒄𝒐𝒗𝒆𝒓 = 𝑻𝒐𝒕𝒂𝒍 𝒏𝒐. 𝒐𝒇 𝒔𝒒𝒖𝒂𝒓𝒆𝒔
× 𝟏𝟎𝟎%
3
, AQA GCSE Biology notes Topic 7 – Ecology
7.2.2 How materials are cycled
Carbon cycle
• Returns carbon from organisms via
respiration to the atm as CO2 is used by
plants in photosynthesis
• Burning produces CO2
• Decomposition of dead organisms
o Microbial respiration → CO2
o Anaerobic respiration → mineral
ions in soil / convert to fossil fuels
How microorganisms help to recycle materials?
• Microorganisms decay
• Return carbon to atm as CO2 by microbial respiration and mineral ions to soil by anaerobic respiration
Water cycle
• Evaporation, Condensation, Precipitation
• Interception - precipitation caught by the vegetation
• Transpiration - water from vegetation transferred back to atmosphere
• Overland flow (surface runoff) - water flowing over ground surface
• Throughflow - sideways movement of water through soil towards river
• Groundwater flow - sideways movement of water through permeable rock towards river
• Infiltration - downward movement of water into soil
• Percolation - downward movement of water through permeable rock
7.2.3 Decomposition (biology only)
Factor How factor affects rate of decay
• Low temp - ↓ chemical reactions involving enzymes, ↓rate of decay
Temp • Warm temp - ↑ reactions involving enzymes, ↑rate of decay
• Too high – enzymes denature, ↓rate of decay
4
