Ecology and the environment flashcards

Topic 4: Ecology and the environment

Population, community and ecosystem

Population: all the organisms of one species in an area. Community: all the populations of different species in an area. Ecosystem: a community and its abiotic environment, interacting.

Estimating a population with quadrats: a mean of 2.5 plants per 1 m² quadrat in a 400 m² field

Place quadrats at random (coordinates from random numbers), at least ten; find the mean per m². Population = 2.5 × 400 = 1000 plants.

Distribution vs biodiversity: how to sample each

Distribution: quadrats at regular intervals along a tape running across a change in conditions. Biodiversity: quadrats at random in each area, recording every species and how many of each. (Paper 2 only)

Abiotic vs biotic factors: examples

Abiotic (non-living): temperature, light intensity, water, pH, soil minerals, oxygen in water, wind. Biotic (living): food supply, predation, competition, disease, parasites.

Pyramids of numbers, biomass and energy: which is always a true pyramid?

The pyramid of energy is always a pyramid. Biomass almost always is. Numbers can be any shape (one tree, many insects).

Primary consumers receive 5000 kJ and pass 450 kJ on. Efficiency, and where the rest goes?

(450 ÷ 5000) × 100 = 9.0%. The rest is lost mainly as heat from respiration, and in parts not eaten, faeces, excretion and movement.

Processes in the carbon cycle that remove and return CO₂

Removed: photosynthesis. Returned: respiration by plants, animals and decomposers; combustion of fossil fuels and wood. Carbon passes along food chains by feeding.

Roles of nitrogen-fixing, nitrifying and denitrifying bacteria

Nitrogen-fixing (soil, legume root nodules): nitrogen gas → nitrogen compounds. Nitrifying (need oxygen): ammonium → nitrite → nitrate. Denitrifying (waterlogged soil): nitrate → nitrogen gas. (Paper 2 only)

Sulfur dioxide and carbon monoxide: source and effect

Sulfur dioxide: burning fossil fuels containing sulfur; acid rain damages leaves, kills trees and acidifies lakes. Carbon monoxide: incomplete combustion; binds to haemoglobin, so less oxygen is carried.

The five greenhouse gases in the specification, and the enhanced greenhouse effect

Water vapour, carbon dioxide, nitrous oxide, methane, CFCs. Extra gases from human activity absorb and re-radiate more infrared back towards the Earth, which may lead to global warming.

Eutrophication: the sequence

Nitrates and phosphates from fertiliser leach into water → algal bloom → plants below die (no light) → decomposing bacteria multiply and respire aerobically → oxygen falls → fish and aerobic invertebrates die.

Effects of deforestation on soil and the atmosphere

Leaching of mineral ions; soil erosion (no roots to hold soil); less evapotranspiration, so less rain; less CO₂ absorbed and more released by burning or decay; less oxygen released. (Paper 2 only)