AQA GCSE Combined Science Biology - Evolution, Extinction, Genetic Engineering & Selective Breeding

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What is evolution?

The gradual change in a species over time through natural selection.

Who proposed the theory of evolution by natural selection?

Charles Darwin.

What are the key steps in natural selection?

Variation → competition → survival of the fittest → reproduction → inheritance of beneficial traits.

Why was Darwin’s theory controversial at the time?

It challenged religious beliefs and there was limited evidence.

What is extinction?

When no individuals of a species remain alive.

Name one cause of extinction.

Changes in environment, new predators, new diseases, competition, or catastrophic events.

What is selective breeding?

Humans choosing specific animals/plants to breed for desirable traits.

Give two examples of selective breeding.

Cows that produce more milk, crops resistant to disease.

What is a disadvantage of selective breeding?

Reduced gene pool can lead to inherited defects and less resistance to disease.

What is genetic engineering?

Modifying the genome of an organism by introducing a gene from another organism.

What is a genetically modified (GM) crop?

A plant with genes from another species to improve yield, resistance, or shelf life.

What are the advantages of GM crops?

Higher yield, resistant to pests/disease, longer shelf life.

What are the concerns about GM crops?

Effects on wild flowers/insects, long-term health risks, ethical concerns.

What is tissue culture?

Growing new plants from small sections of a parent plant under sterile conditions.

What is cloning?

Producing genetically identical organisms.

What is adult cell cloning?

A process where the nucleus from an adult body cell is placed into an empty egg cell and stimulated to divide.

What are the advantages of cloning?

Can save endangered species, reproduce desirable traits.

What are the disadvantages of cloning?

Reduced gene pool, ethical issues, possible health problems.

What is a fossil?

The remains or traces of ancient organisms preserved in rock.

How are fossils formed?

From parts of organisms that do not decay, replacement by minerals, or preserved traces.

Why is the fossil record incomplete?

Many early organisms were soft-bodied, and many fossils have been destroyed.

What is speciation?

The formation of new species through evolution.

What can cause speciation?

Isolation + natural selection → reproductive isolation.

Who was Mendel and what did he discover?

A monk who discovered inheritance patterns using pea plants, showing traits are determined by "units" (now called genes).

Why was Mendel’s work not recognised immediately?

Why was Mendel’s work not recognised immediately?