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

36 question-and-answer flashcards covering intensive food production, monocultures, biodiversity, habitat destruction, deforestation, pollution types, eutrophication, plastic and air pollution, greenhouse gases, sustainable resources, forest and fish management, endangered species, and conservation techniques.

What is meant by intensive food production?

Producing food more efficiently on a finite amount of land by using modern technology and practices to maximise yield.

How has agricultural machinery increased food supply?

By replacing human labour and allowing much larger areas of land to be farmed quickly and efficiently.

How 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 role of insecticides in intensive farming?

They kill pest insects, reducing crop damage and loss of yield.

How does selective breeding enhance food production?

High-yield animals or plants are bred together so their offspring reliably produce larger yields.

Define monoculture farming.

The cultivation of a single crop species over a large area of land.

Why do monocultures lead to lower biodiversity?

Only one plant species is present, so fewer niches exist for other plants and animals.

How can monoculture practices increase pest populations?

A continuous food source for a specific pest allows its population to grow rapidly.

What environmental problems can arise from repeated insecticide use?

Killing harmless insects, pollution, bioaccumulation in food chains, and evolution of resistant pests.

Define biodiversity.

The number of different species present in a particular area.

Why is high biodiversity important for ecosystems?

It promotes stability, resilience, and balanced food webs.

List three main human reasons for habitat destruction.

Clearing land for farming/housing, extraction of natural resources (e.g., mining, logging), and pollution (especially marine pollution).

Explain how clearing land for farming reduces biodiversity.

Natural habitats are removed, eliminating many species and disrupting food chains.

What is deforestation?

The large-scale clearing of trees, often permanently, to use the land for other purposes.

Name four undesirable effects of deforestation.

Species extinction, soil erosion/loss, increased flooding/landslides, and higher atmospheric carbon dioxide.

How does deforestation lead to increased atmospheric CO₂?

Fewer trees photosynthesise to remove CO₂, and burning cleared trees releases additional CO₂.

Describe eutrophication and its primary cause.

Nutrient runoff (mainly nitrates/phosphates from fertilisers or sewage) causes algal blooms, oxygen depletion, and death of aquatic life.

How does untreated sewage lead to eutrophication?

Bacteria decompose the organic matter, using up dissolved oxygen and killing aquatic organisms.

What is bioaccumulation?

The build-up of persistent chemicals (e.g., heavy metals, pesticides) along food chains, often poisoning top predators.

Give two negative effects of plastic pollution in marine habitats.

Animals ingest or become entangled in plastic, and toxins released or microplastics enter food chains.

Outline how acid rain forms from sulfur impurities.

Burning fossil fuels releases SO₂, which oxidises to SO₃ and dissolves in cloud water to form sulfuric acid, falling as acid rain.

Why are methane and carbon dioxide called greenhouse gases?

They trap long-wave infrared radiation, warming Earth’s atmosphere.

State two human activities that increase methane levels.

Cattle farming and decomposition in rice fields or landfills.

What is a sustainable resource?

One produced as quickly as it is removed, so it does not run out (e.g., timber from well-managed forests).

Why are fossil fuels considered non-renewable?

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

How does recycling benefit the environment?

It reduces waste, conserves raw materials, and lowers energy use compared with making new products.

Give two strategies for sustaining forests.

Replanting after logging and certification/monitoring schemes like the Forestry Stewardship Council.

List three measures used to manage fish stocks sustainably.

Catch quotas, minimum net mesh sizes to let juveniles escape, and seasonal or area restrictions on fishing.

Define an endangered species.

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

Provide four reasons a species may become endangered.

Over-hunting, habitat loss, pollution, and competition from introduced non-native species.

How do seed banks aid plant conservation?

They store seeds of rare or endangered plants so new individuals can be grown in the future if wild populations decline.

What is artificial insemination used for in conservation?

To produce offspring in captive breeding programmes without needing natural mating, preserving genetic diversity.

Why does reduced population size increase extinction risk?

Genetic variation falls, making the species less able to adapt to environmental change.

Describe the bioaccumulation effect of heavy metals.

Persistent metals build up in organisms and magnify up food chains, leading to toxicity in top carnivores.

What are the consequences of soil erosion following deforestation?

Loss of soil fertility, leaching of nutrients, increased flash flooding, and difficulty for forests to regenerate.

How do greenhouse gases cause the enhanced greenhouse effect?

Higher concentrations absorb more outgoing heat radiation, so less escapes to space, raising global temperatures.