Flashcards · 8461 · Topic 7

Ecology flashcards

23 cards on Topic 7, subtopics 4.7.1 to 4.7.5. Pick a subtopic or study them all.

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Ecosystem, population and community: Ecosystem: the interaction of a community of living organisms with the non-living parts of their environment. Population: all the organisms of one species in a habitat. Community: all the populations of different species in a habitat.
Interdependence: Each species depends on others for food, shelter, pollination, seed dispersal and so on, so removing one species can affect the whole community.
What do plants and animals compete for?: Plants: light, space, water and mineral ions from the soil. Animals: food, mates and territory.
Four biotic factors that affect a community: Availability of food; new predators arriving; new pathogens; one species outcompeting another so its numbers are too low to breed.
Adaptations and extremophiles: Adaptations may be structural, behavioural or functional, and let organisms survive where they live. Extremophiles live in extreme environments: high temperature, high pressure or high salt concentration, for example bacteria in deep-sea vents.

Four 1 m² quadrats hold 3, 5, 0 and 4 plants. Estimate the number in a 200 m² field.: Mean = 12 ÷ 4 = 3.0 per m². 3.0 × 200 = 600 plants. Quadrats are placed at random coordinates.
How is a transect used?: Run a tape across a change in conditions; place a quadrat at regular intervals along it; record the species and measure the abiotic factor at each point. It shows distribution, not abundance.
Predator–prey cycles: Prey increase → more food → predators increase (with a lag) → more prey eaten → prey fall → less food → predators fall.
Factors that increase the rate of decay, and what anaerobic decay produces: Warmth (up to the enzymes' optimum), water and oxygen. Anaerobic decay produces methane, which can be collected as biogas fuel.
Required practical 10: milk falls from pH 6.7 to 5.5 in 40 minutes. Rate of decay?: 1.2 ÷ 40 = 0.03 pH units per minute. The pH falls because microorganisms decaying the milk produce acid.
The three environmental changes that affect the distribution of speciesHigher: Temperature, availability of water, and the composition of atmospheric gases. They may be seasonal, geographic or caused by human interaction.

Why is destroying peat bogs harmful?: Habitat and biodiversity are lost, and the decay or burning of the peat releases carbon dioxide.
Biodiversity, and why it matters: The variety of all the different species of organisms on Earth, or within an ecosystem. High biodiversity makes ecosystems more stable, because species depend less on a single other species for food, shelter and a stable environment.
Effects of global warming on living things: Loss of habitat as sea levels rise, changes in the distribution of species as temperature and rainfall change, and changes to migration patterns, all of which may reduce biodiversity.
Ways to maintain biodiversity: Breeding programmes for endangered species; protecting and regenerating rare habitats; reintroducing field margins and hedgerows; reducing deforestation and carbon dioxide emissions; recycling instead of dumping waste in landfill.

A trophic level holds 2400 g of biomass; the next holds 180 g. Efficiency of transfer?: 180 ÷ 2400 × 100 = 7.5%. Biomass is lost as faeces (egestion), as waste such as urea and CO₂, and as glucose used in respiration.
Trophic levels, from the bottom: Level 1: producers (plants and algae). Level 2: primary consumers (herbivores). Level 3: secondary consumers (carnivores eating herbivores). Level 4: tertiary consumers. Apex predators have no predators. Decomposers break down dead plant and animal matter.
Why is only about 10% of biomass passed to the next trophic level?: Not all the biomass is eaten (such as bones and roots); some eaten material is egested as faeces; much glucose is used in respiration, releasing carbon dioxide and water; and some is lost in waste such as urea in urine.
Pyramid of biomass: A diagram with a bar for each trophic level, drawn to scale to show the mass of living material at that level. Producers are at the bottom.

Food security, and biological factors threatening it: Food security: having enough food to feed a population. Threats: increasing birth rate, changing diets in developed countries, new pests and pathogens, environmental change such as failed rains, the cost of agricultural inputs, and conflicts affecting water or food.
How can farming make food production more efficient?: Restrict energy transfer from food animals to the environment by limiting their movement and controlling the temperature of their surroundings. Some animals are fed high-protein foods to increase growth.
How are fish stocks kept sustainable?: Control of net size (so young fish escape and breed) and fishing quotas, keeping stocks at a level where breeding continues.
Mycoprotein: what it is and how it is made: A protein-rich food suitable for vegetarians, made from the fungus Fusarium grown on glucose syrup in aerobic conditions; the biomass is harvested and purified.