Ecosystems & Biodiversity (AQA GCSE Combined Science: Synergy: Life & Environmental Sciences): Flashcards

Competition occurs when organisms require the same limited resource to survive and reproduce. It can be between the same species (intraspecific) or different species (interspecific).

Plants compete for light, space and water and nutrients from the soil, while animals compete for food, mates and territory.

True.

In a stable community, all species and environmental factors are in balance, so population sizes remain fairly constant rather than rising or crashing.

Intraspecific competition is between members of the same species competing for the same resource. Interspecific competition is between members of different species competing for the same resource.

The frog population would decrease because earthworms are their only food source. With fewer earthworms available, frogs cannot get enough food to survive and reproduce successfully.

False.

Due to interdependence, removing one species creates knock-on effects throughout the community, affecting many other species — not just those that directly feed on it.

Examples of interdependence beyond food include:

1. Plants depend on insects (e.g. bees) for pollination

2. Plants depend on animals to disperse their seeds

3. Animals may depend on plants or other animals for shelter and protection

An abiotic factor is a non-living component of the environment that can affect the organisms in a community, such as light intensity, temperature, moisture, soil pH and CO₂ levels.

A biotic factor is a living component of the environment that can affect a community, such as food availability, new predators, new diseases, or one species outcompeting another.

Seven abiotic factors that can affect a community include light intensity, temperature, moisture levels, soil pH and mineral content, wind intensity and direction, carbon dioxide levels for plants, and oxygen levels for aquatic animals.

True.

A new predator is a biotic (living) factor. It can reduce prey populations and disrupt the balance of the community through predation and competition.

Biotic factors:

1. Availability of food

2. New disease arriving

Abiotic factors:

1. Light intensity

2. Temperature

Grey and red squirrels compete for the same resources. Grey squirrels are better adapted to use these resources and outcompeted the red squirrels, reducing red squirrel numbers until too few were left to breed successfully.

False.

Higher CO₂ concentration increases plant growth rate because CO₂ is used in photosynthesis to produce glucose, providing energy for growth.

Referencing specific figures from the data supports the conclusion with evidence. For example, stating exact values at two points on the graph shows the trend more convincingly than a general statement alone.

A quadrat is a square frame placed on the ground to record the organisms within it, used to measure the abundance or distribution of plants and slow-moving animals.

Quadrats can record abundance in three ways: the number of individuals of a species, species richness (total number of different species), and percentage cover (percentage of quadrat area covered by a species).

A transect is a line set up through a changing habitat, along which quadrats are placed at regular intervals to investigate how the distribution of a species changes with an abiotic factor.

A transect is used when investigating how species distribution changes across a gradient (e.g. altitude or distance from a river). Random quadrats cannot show how an abiotic factor influences distribution along a continuous change.

False.

Transects can investigate how any abiotic factor affects distribution — including light intensity, moisture levels, or distance from woodland edge — not just altitude.

A square should be counted as covered if more than half of it is covered by the species being recorded.

True.

Random placement using a grid and random number generator prevents students from choosing sampling sites that favour certain results, making the sample unbiased and more representative.

Species richness is the total number of different species present in a quadrat. It is measured by recording each different species found — without counting the number of individuals of each species.

Random sampling is a technique where sampling sites are chosen without bias — using a grid and random number generator — so the sample represents the whole population.

The two investigation types are:

1. Using random quadrat sampling to estimate the population size of a plant species

2. Using a transect and quadrat to investigate how a factor affects the distribution of that species

To estimate population size, the number of organisms in several quadrats are counted. The mean count is then used alongside the total area of the survey area to calculate the estimated population.

False.

Sampling the nearest organisms introduces bias — it does not give a representative sample of the whole population. Quadrats must be placed randomly using a grid and random number generator.

A large enough sample reduces the effect of chance and gives results more likely to reflect the true population. An unbiased sample ensures that every part of the habitat has an equal chance of being selected, making the sample representative.

A tape measure is laid through the habitat as the transect line. A quadrat is placed at regular intervals (e.g. every 5 metres) along the line and the species is recorded at each point, showing how distribution changes with the environmental factor.

True.

Percentage cover is used when it is impractical to count individuals of a species. It records the approximate percentage of the quadrat area occupied by the species.

In population sampling, reducing the time spent counting all organisms is achieved through sampling, which allows us to estimate the total population size from a subset of data.

Biodiversity is the variety of different species of organisms on Earth, or within an ecosystem.

True.

A wide range of different habitats provides different conditions and resources, allowing a greater variety of species to survive and supporting larger populations of each.

Small populations have fewer individuals to reproduce and less genetic variation, so they are less able to recover from disruption such as disease, habitat loss or changes in food supply.

High biodiversity provides resources essential for human survival including food, oxygen, clean water and raw materials, as well as economic benefits through agriculture, fishing and forestry.

High biodiversity reduces the dependence of one species on another. If one species declines, other species can provide alternative food sources or roles, preventing the collapse of food chains.

False.

In a food web with sufficient biodiversity, foxes can rely on other food sources such as rabbits and frogs, so the fox population would decrease but would not necessarily be wiped out.

High biodiversity is important because:

1. It provides resources essential for survival — food, oxygen, clean water and raw materials

2. It provides economic benefits by sustaining resources used in agriculture, fishing and forestry

A stable community is one in which all species and environmental factors are in balance, so that population sizes remain fairly constant over time.

Deforestation is the large-scale removal of trees. When unsustainable, it destroys habitats, reduces biodiversity, and releases stored carbon dioxide, contributing to global warming.

Eutrophication is the process by which excess fertiliser run-off causes algal blooms that block light, leading to the death of aquatic plants, increased decomposition and reduced oxygen levels, killing aquatic animals.

Peat bogs are important because they store carbon as peat — a non-renewable resource. Destroying them releases carbon dioxide into the atmosphere and reduces biodiversity.

False.

Destroying peat bogs releases carbon dioxide — especially when peat is burned as fuel. Methane is not released from peat bog destruction.

Human activities that destroy habitats include:

1. Building and quarrying

2. Farming and clearing woodland

3. Dumping waste in natural areas

(Also: deforestation; drainage and destruction of peat bogs)

Global warming is the rise in Earth's average temperature caused by increased greenhouse gases trapping heat. It reduces biodiversity through flooding of coastal habitats, coral bleaching, and more frequent extreme weather events that disrupt food chains.

True.

Carbon dioxide increases from burning fossil fuels. Methane increases from cattle digestion and rice paddy fields. Both contribute to the enhanced greenhouse effect and global warming.

Tropical deforestation removes trees faster than they can regenerate (unsustainable), destroying habitats and reducing biodiversity. It also reduces the number of trees available to absorb CO₂, worsening global warming.

A breeding programme is a conservation measure in which endangered species are bred in captivity to increase their population and prevent extinction.

Programmes to maintain biodiversity include:

1. Breeding programmes for endangered species

2. Protecting and regenerating habitats

3. Reintroducing hedgerows and field margins in monoculture areas

4. Recycling resources rather than dumping in landfill

5. Producing peat-free composts

6. Reducing deforestation and CO₂ emissions

Peat-free composts help biodiversity by reducing the destruction of peat bogs which are important carbon stores and provide habitats for many species.

True.

Hedgerows and field margins create habitats and corridors for wildlife in otherwise species-poor monoculture farmland, increasing the variety of species present.

There are conflicting pressures:

1. Cost — conservation programmes are expensive and subsidies may be needed

2. Food security — protected land could otherwise be used for farming

3. Development — growing human population demands land for housing and agriculture

True.

Recycling reduces the need for landfill sites, which can destroy habitats and pollute surrounding ecosystems, thereby helping to protect biodiversity.

Protecting land reduces the area available for farming. In areas with food shortages, there is pressure to use protected land for agriculture to improve food security, creating conflict with conservation goals.