Ecosystems

Abiotic: non-living factors (e.g. light intensity and water)

Biotic: living factors (e.g. how populations interact)

Interspecific: interactions between different populations

Intraspecific: interactions between one population

Ecosystem: community living in habitat and its abiotic and biotic interactions

Community: all populations living in a habitat

Habitat: one part of ecosystem where community lives

Autotrophs: producers

Heterotrophs: consumers

Biomass: mass of inorganic and organic matter in an organisn (drymass)

Abundance: indication of frequency of organisms in a habitat

Distribution: precise location of organisms within habitat

Individual counts: every individual in population is counted

Percentage cover: estimate is made of area covered by members of population

ACFOR scale: subjective estimate of frequency of organisms

Random sample: sample from population without bias

Quadrat frames: used to count number of organisms or estimate percentage cover

Point frames: record what each of ten pins touch

Belt transect: quadrat frame placed continuously along a tape measure

Interrupted belt transect: quadrats placed at regular intervals

Niche: fit of a species living under specific environmental conditions

Primary productivity: measure of light energy fixed by photosynthesis in a given area

GPP: energy that would be released on complete combustion of total biomass produced by plants

NPP: GPP - R

Primary succession: following colonisation of an environment that was originally organism-free e.g. bare rock

Secondary succession: following recolonisation of a previous ecosystem that was destroyed e.g. forest fires

Climax community: stable group of populations after succession

Carrying capacity: represents maximum population size that can survive in environment

Edaphic factors: abiotic factors related to the soil

Primary succession

• Empty inorganic surface
• Opportunists or pioneer species (algae, mosses & fungi) penetrate rock surface, break it down and trap organic material to form soil
• Grasses can establish root systems
• Death and decay adds to soil and more water and nutrients are retained
• Plant biodiversity increases and a climax community is reached

Secondary succession

• Existing soil clear of vegetation
• Soil is already formed and contains seeds, roots and soil
• Happens after disturbances by humans and after fires and floods

Food chain

• Producers
• Primary consumers
• Secondary consumers
• Tertiary consumers
• Decomposers

Pyramids

• Pyramids of numbers: number of organisms decrease at each level, very simple
• Pyramids of biomass: combined mass of all organisms in a particular habitat, more time consuming to produce but more accurate
• Pyramids of energy: takes into account species turnover and biomass

Losses along food chain

• Undigested food, ATP production (exothermic process), urea

Nitrogen cycle

• Nitrogen is unreactive
• Only nitrate is useful to plants
• They absorb nitrate from the soil water and use them to make proteins
• Decomposers break down animal and plant bodies to form ammonium compounds
• Nitrogen-fixing bacteria converts nitrogen from the soil air into ammonia
• Nitrifying bacteria converts ammonia into nitrates
• Legumes are full of nitrogen-fixing bacteria
• Denitrifying bacteria use nitrates as an energy source and break them into nitrogen gas

Carbon cycle

• CO2 is removed from the air by plants by photosynthesis

Carbon sinks

• Reservoir where carbon is removed from the atmosphere and locked up in organic or inorganic compounds
• Limestone, chalk, coal, oil, natural gas & the ocean

Greenhouse effect

• Greenhouse gases reduce heat loss from surface of the earth
• CO2 or methane
• Infrared radiation is absorbed by the surface of the earth and radiated back at a longer wavelength

Frozen isotopes & Dendrochronology

• Oxygen in ice cores indicates temperatures from years ago
• Tree ring growth can also show temperatures

CITES - conserving biodiversity

• International agreement to protect endangered animals and plants to conserve biodiversity
• Regulates trade in both living organisms and products made from them
• Voluntary, 180 nations
• Strict rules about import and export
• Appendix I: threatened by extinction and trade of them/their products is prohibited
• Appendix II: not yet threatened but endangered and could become extinct if not protected
• Appendix III: organisms helped because country has asked other CITES members to protect it
• CITES has limitations: many countries have not signed up, commercial interests override it, no legal obligations