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Biology · OCR Paper 2

Natural Selection and Evolution

How populations change over time: the genetic variation that exists within a species, how mutations make new variants, how natural selection favours the variants best suited to the environment, how evolution can lead to new species, the evidence from fossils and from antibiotic resistance in bacteria, how classification has changed with DNA sequencing, and the work of Darwin and Wallace. Matches OCR GCSE Biology A (Gateway Science) B5.2a to B5.2f. Every lesson is for both Combined Science and separate Biology except Darwin, Wallace and the Theory of Evolution (B5.2f), which is for separate Biology only. There is no Higher tier only content in this chapter.

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Key terms in this chapter

All 57, gathered from every lesson.

Population
A group of individuals of the same species living in the same place.
Genetic variation
Differences in the alleles carried by individuals of the same species.
Mutation
A random change in the base sequence of DNA that may produce a new variant.
Variant
A different version of a gene, also called an allele.
Selection pressure
A factor in the environment, such as predation, disease or competition, that affects the survival and breeding of individuals.
Natural selection
The process in which individuals with the variants best suited to their environment survive and breed more, so their alleles become more common.
Adaptation
A feature that helps an organism to survive and reproduce in its environment.
Camouflage
Colouring or markings that make an organism hard to see against its background.
Predation
One animal, the predator, hunting and eating another, the prey.
Evolution
A change in the inherited characteristics of a population over time, through natural selection.
Species
A group of organisms that can interbreed to produce fertile offspring.
Fertile
Able to reproduce and have offspring.
Hybrid
The offspring of parents from two different species, such as a mule.
Isolation
The separation of two populations of a species so that they cannot interbreed.
Geographical barrier
A physical feature, such as a river, mountain range or the sea, that separates populations.
Interbreed
To mate and produce offspring with another member of the same species.
Adaptation
A feature that helps an organism to survive and reproduce in its environment.
Biodiversity
The variety of living organisms in a habitat or on Earth.
Population
A group of individuals of the same species living in the same place.
Fossil
The remains or traces of an organism from many years ago that are found in rock.
Sediment
Mud, sand or other small particles that settle in layers, usually under water.
Fossil record
All of the fossils that have been found, which shows how life has changed over time.
Extinction
The permanent loss of a species, when no individuals are left alive.
Mass extinction
An event in which a large proportion of the species on Earth die out in a short time.
Transitional fossil
A fossil with features of two groups, such as Archaeopteryx with features of reptiles and birds.
Decay
The breakdown of dead material by microorganisms.
Erosion
The wearing away of rock by wind, water and ice.
Predator
An animal that hunts and eats other animals.
Antibiotic
A medicine that kills bacteria or stops them growing, without harming human cells.
Antibiotic resistance
The ability of a bacterium not to be killed by an antibiotic, because of a variant (allele) that it carries.
MRSA
Methicillin-resistant Staphylococcus aureus, a strain of bacteria that is resistant to many antibiotics.
Pathogen
A microorganism that causes disease.
Selection pressure
A factor in the environment, such as an antibiotic, that affects which individuals survive and breed.
Mutation
A random change in the DNA that may produce a new variant.
Natural selection
The survival and breeding of the individuals with the variants best suited to the environment, so their alleles become more common.
Superbug
A bacterium that is resistant to many antibiotics, so that it is very difficult to treat.
Strain
A genetic variant of a species of bacteria.
Classification
The sorting of living things into groups.
Artificial classification
Grouping organisms by a few easily seen features, which may not show how they are related.
Natural classification
Grouping organisms by many shared features, so that the groups show evolutionary relationships.
Binomial name
A two-part Latin name for a species, made of its genus and species, such as Homo sapiens.
Genus
A group of closely related species.
Domain
The highest rank of classification: Bacteria, Archaea or Eukaryota.
DNA sequencing
Finding the order of the bases along a piece of DNA.
Molecular phylogenetics
Using differences in DNA or protein sequences to work out evolutionary relationships.
Evolutionary tree
A branching diagram that shows how species are related and when they split from common ancestors.
Common ancestor
The species from which two or more other species have evolved.
Theory
An explanation of observations that has been tested many times and is supported by a lot of evidence.
Natural selection
The process in which the individuals with the variants best suited to the environment survive and breed more, so their alleles become more common.
Origin of Species
The book published by Darwin in 1859 that set out the theory of evolution by natural selection.
Wallace Line
A boundary between the animals of Asia and those of Australia, described by Alfred Russel Wallace.
Artificial selection
Humans choosing which individuals to breed from, as pigeon breeders did.
Seedbank
A store of seeds, kept dried and cold, to preserve the genetic variation of plant species.
Biodiversity
The variety of living organisms in a habitat or on Earth.
Genetic variation
Differences in the alleles carried by the individuals of a species.
Peer review
The checking of a scientist's work by other scientists before it is published.
Mechanism of inheritance
An explanation of how features are passed from parents to offspring.