Ecology flashcards

Topic 3: Ecology

How much light energy do plants transfer, and how much biomass passes up each trophic level?

Plants and algae transfer about 1% of the incident light energy. About 10% of the biomass passes up to each trophic level.

Why is about 90% of biomass not passed on?

Waste materials (faeces, urine) carry materials and energy away; respiration supplies energy for life processes such as movement, and much ends up as heat in the surroundings; some parts are not eaten.

Light energy is 3.2 × 10⁶ kJ per m². Energy reaching secondary consumers?

Producers store 1%: 3.2 × 10⁴ kJ. Primary consumers 10%: 3.2 × 10³ kJ. Secondary consumers 10%: 320 kJ.

Why is a short food chain more efficient for food production?

About 90% of the biomass is lost at every extra stage, so eating a crop directly gives more of the producers' biomass to humans than feeding it to livestock (for example 7500 MJ against 750 MJ).

Competition vs interdependence

Competition is for scarce resources (plants: light, space, water, mineral ions; animals: food, mates, territory). Interdependence is reliance on other organisms, such as flowers on pollinators.

Structural, behavioural and functional adaptations: examples

Structural: white fur in snow, a thick waxy cuticle. Behavioural: migration, huddling, burrowing. Functional: concentrated urine, many eggs, hibernation.

Extremophiles

Organisms that live where conditions are very extreme: high salt, high temperature or high pressure. Examples: archaea in salt lakes, Thermus aquaticus in hot springs.

How is a tapeworm adapted to life in the intestine?

Hooks and suckers hold it to the gut wall; a thick covering resists digestive enzymes; it is flat and long to absorb digested food; it produces many eggs.

Conditions for fast decay, and the role of detritus feeders

Warm (enzymes faster, but too hot stops decay), moist and with oxygen. Detritus feeders such as earthworms and woodlice break dead material into small pieces, giving microorganisms a larger surface area.

Processes in the carbon cycle

Photosynthesis removes CO₂ from the air into carbohydrates, fats and proteins; feeding passes carbon along food chains; respiration by plants, algae, animals and microorganisms, decay, and combustion of wood and fossil fuels return CO₂.

Eutrophication in four stages

Mineral ions rise, so algae and plants grow more; dense growth shades others, which die; microorganisms feeding on the dead organisms increase; their respiration depletes the oxygen, so aerobic organisms die.

Effects of deforestation and of global warming

Deforestation: less biodiversity; less CO₂ removed by photosynthesis; burning and decay release CO₂. Global warming (rising CO₂ and methane): climate change, rising sea level, changed migration patterns and species distribution.