Ecosystems (Cambridge (CIE) IGCSE Environmental Management): Flashcards

An apex predator is a predator with no natural predators, which controls the populations of its prey species.

Producers use energy from sunlight to make their own food.

Primary consumers feed mostly on plants and plant-derived material.

Interdependence is the way the biotic components of an ecosystem depend on each other and on the abiotic components.

Decomposers break down dead organisms into simpler substances, which recycles nutrients (nutrient cycling).

Bioindicator species show the condition of a habitat through their presence or absence.

Waterlogging kills most plants because they become unable to respire.

False.

Greater carbon dioxide concentrations increase plant growth and yields, although CO₂ is an acidic gas and some plants are sensitive to pH changes.

High salinity kills plants and leaves bare soil that erodes easily.

A biotic interaction is a relationship between living organisms in an ecosystem.

An invasive species is a species introduced from elsewhere, often by humans, that spreads quickly and outcompetes native species.

Invasive species spread quickly because they usually have no predators in the new environment.

False.

Native species naturally inhabit an area and fit into its food webs because they evolved there.

Competition between individuals of the same species is called intraspecific competition.

Interspecific competition is competition between individuals of different species, such as grey and red squirrels.

Organisms compete for food, water, mates and territory.

Prey numbers decrease when predator numbers rise, because the predators eat more prey.

Predator numbers fall because less prey is available to eat.

True.

Predators remove weak or sick prey, which leaves a healthier prey population.

Pollination is the transfer of pollen from the anther (male part) to the stigma (female part) of a flower.

Wind-pollinated plants produce tiny, light pollen grains so that the pollen can travel far on the wind.

False.

Wheat and maize are wind-pollinated, which makes wind pollination important for major cereal crops.

Once pollen reaches the stigma, a pollen tube forms so that fertilisation can take place.

A decline in pollinators means fewer seeds and shrinking plant populations, so food becomes scarce for herbivores.

Photosynthesis is the chemical process that green plants and algae use to make glucose, a sugar that stores energy.

The word equation for photosynthesis is carbon dioxide + water → glucose + oxygen.

Chlorophyll is the green pigment in chloroplasts that absorbs light energy for photosynthesis.

Plants convert glucose into starch for storage.

True.

Photosynthesis stores energy from the Sun in plant tissues, so it forms the base of every food chain.

A food chain is a simple model showing how energy passes from one organism to the next.

False.

The arrows show the direction of energy transfer, so they point from the organism eaten to the organism that eats it.

A trophic level is a feeding level in a food chain.

Roughly 10% of energy transfers from one trophic level to the next.

Food chains are usually short because energy is lost at every trophic level, so too little reaches higher levels.

Energy is lost through movement, respiration, digestion, heat loss, excretion and parts that are not eaten.

A food web is a set of combined food chains that shows all the feeding relationships in an ecosystem.

If a predator species disappears, prey populations may increase.

A pyramid of numbers shows how many organisms exist at each trophic level of a food chain.

A pyramid of numbers inverts when a large producer, such as a single oak tree, supports large numbers of consumers.

False.

No trophic level can ever have more energy than the level below it, so pyramids of energy are always pyramid-shaped.

Pyramids of energy always cover a period of time, using units such as kJ per m² per year.

Producers form the widest base because they capture sunlight and bring new energy into the ecosystem.

Aerobic respiration is a chemical process that releases energy from glucose when oxygen is available.

The word equation for aerobic respiration is glucose + oxygen → carbon dioxide + water (+ energy).

False.

Plants respire all the time, 24 hours a day, even while they photosynthesise.

Breathing only brings oxygen into the body, whereas respiration is a chemical reaction that happens inside every living cell.

Respiration releases carbon dioxide into the atmosphere, which plants later use in photosynthesis.

Organisms use the energy for movement, growth, repair and keeping warm.

The carbon cycle is the continuous movement of carbon between the atmosphere, living organisms, oceans and the Earth's crust.

Photosynthesis locks carbon into plant tissues, such as leaves, stems and roots.

When animals eat, the carbon in their food moves into their bodies, which passes carbon along food chains.

Plants, animals and microorganisms release carbon dioxide into the atmosphere when they respire.

False.

Respiration happens day and night, which makes it a major way carbon returns to the air.

Fungi and bacteria break down dead organisms during decomposition.

Decomposition releases carbon back into the soil, the atmosphere and the ocean.

Fossil fuels form over millions of years from buried dead organisms, which traps large amounts of carbon underground.

Combustion releases stored carbon into the atmosphere as carbon dioxide, which speeds up the cycle.

Deforestation reduces the amount of carbon removed from the air by photosynthesis.

False.

Agriculture adds carbon to the atmosphere through soil disturbance and methane release.

Climate change increases carbon release from melting permafrost.

False.

Humans are changing the carbon cycle faster than nature can cope with, which strengthens the enhanced greenhouse effect and contributes to global warming.