IGCSE Biology – Human Influences on the Environment (Cycle 1)

These question-and-answer flashcards cover the key concepts from the Cycle 1 IGCSE Biology slides on human influences on the environment, including food production, habitat destruction, pollution, climate change, sustainability and conservation.

What is the goal of intensive food production?

To produce food more efficiently using a finite amount of land and resources.

How does agricultural machinery increase food supply?

It replaces human labour and allows much larger areas of land to be farmed more quickly and efficiently.

Why do chemical fertilisers improve crop yields?

They add essential nutrients to the soil so plants grow larger and produce more fruit or grain.

What is the purpose of insecticides in crop production?

To kill insect pests that would otherwise damage plants and reduce yield.

What do herbicides do on a farm?

They kill weeds, reducing competition for resources with crop plants.

What is selective breeding in agriculture?

Breeding plants or animals with desirable high-yield traits to produce offspring that reliably give bigger yields.

Define monoculture farming.

The large-scale cultivation of a single crop species on a given area of land.

Why do monocultures lower biodiversity?

They replace the variety of plant species that naturally support many different animal species.

How can monocultures lead to pest population increases?

A single, abundant food source allows the pest that feeds on that crop to reproduce rapidly.

State two environmental problems caused by heavy insecticide use in monocultures.

1) Killing harmless or beneficial insects; 2) Persistent chemicals pollute ecosystems and accumulate in food chains.

What is biodiversity?

The number of different species living in a particular area.

Why is high biodiversity important for ecosystems?

It helps ecosystems remain stable and resilient to change.

Give three main human reasons for habitat destruction.

Clearing land for farming/housing, extraction of natural resources (e.g., logging, mining), and pollution such as marine oil spills or fertiliser runoff.

What is deforestation?

The large-scale removal of trees, often for alternative land use.

List four negative effects of deforestation.

Extinction/loss of biodiversity, soil erosion, increased flooding & landslides, and higher atmospheric CO₂ levels.

How do tree roots help prevent soil erosion?

They stabilise the soil and absorb water, reducing the amount washed away by rain.

Explain why burning cleared forest increases atmospheric CO₂.

Combustion of the trees releases their stored carbon as carbon dioxide while fewer trees remain to absorb CO₂ by photosynthesis.

What happens when untreated sewage enters waterways?

Bacteria multiply, use up dissolved oxygen while respiring, and can cause aquatic organisms like fish to die.

Define eutrophication.

Nutrient enrichment of water leading to algal bloom, oxygen depletion and death of aquatic life.

Describe the sequence of events in fertiliser-driven eutrophication.

Fertiliser runoff → algal bloom → light blocked, plants & algae die → decomposers respire → oxygen falls → fish and invertebrates die.

What is bioaccumulation?

The build-up of persistent chemicals (e.g., heavy metals, pesticides) in organisms up a food chain, poisoning top carnivores.

Why is plastic considered a serious pollutant?

It is non-biodegradable, entangles or is eaten by wildlife, and releases toxins as it fragments.

Give two ways plastic pollution harms marine animals.

Entanglement causing injuries/drowning and ingestion of plastic pieces that can block or poison the animal.

How does sulfur dioxide from fossil fuels produce acid rain?

SO₂ oxidises to SO₃, which dissolves in cloud water to form sulfuric acid that falls as acid rain.

Name two major greenhouse gases that contribute to the enhanced greenhouse effect.

Carbon dioxide (CO₂) and methane (CH₄).

State two human activities that increase atmospheric methane.

Keeping livestock (e.g., cattle) and cultivating rice paddies or maintaining landfills.

What is a sustainable resource?

A resource produced as fast as it is removed, so it does not run out.

Why are fossil fuels classed as non-renewable?

They take millions of years to form and cannot be replaced on a human timescale once used.

Give two benefits of recycling materials like paper, glass or metal.

Reduces environmental waste and lowers the demand for raw materials and energy to produce new items.

Name two practices that help make forestry sustainable.

Re-planting trees after harvest and monitoring logging through schemes such as the Forestry Stewardship Council.

List three measures used to maintain fish stocks sustainably.

Catch quotas, size limits or mesh sizes, seasonal or area closures, restocking programmes and gear restrictions to cut bycatch.

What is an endangered species?

A species whose population has fallen so low that it is at risk of extinction.

Give four factors that can cause a species to become endangered.

Over-hunting, habitat loss, pollution, climate change, or competition from non-native species.

State three conservation measures used to protect endangered species.

Education programmes, captive-breeding (with later release), and legal protection of species and habitats.

Why is conservation important for humans as well as ecosystems?

It maintains biodiversity, supports ecosystem stability, provides resources such as food, fuel and medicines, and helps regulate climate.

What is artificial insemination (AI) in captive breeding?

Collecting sperm from a male and inserting it into a female to produce offspring without natural mating, boosting breeding success.

How does in-vitro fertilisation (IVF) aid conservation genetics?

Gametes with known alleles are combined in the lab, allowing managers to maximise genetic diversity in offspring.

What genetic risk does a species face when its population size declines?

Reduced genetic variation, making the species less able to adapt to environmental change and more prone to extinction.

Give one example of modern technology used for field monitoring in agriculture.

Drones equipped with cameras or sensors that survey crop health and soil conditions.

What is the purpose of catch quotas in fisheries management?

To limit the total number or mass of fish caught each year, preventing over-exploitation of the stock.