Natural Selection and Evolution

A group of individuals of the same species living in the same place.

Extensive: individuals carry different alleles.

From mutations, which are random changes in the DNA.

No. Mutations are random, and not aimed at a useful result.

They have no effect on the phenotype.

Yes. The advantage depends on the environment, such as dark colour on sooty bark.

Predation, disease, competition for food or mates, and a change in climate.

The survival and breeding of the individuals with variants best suited to the environment, so their alleles become more common.

Those with phenotypes best suited to the environment.

The alleles that gave the parent its advantage.

No. The population changes, over many generations.

Predation by birds.

They were easily seen against the dark bark.

They became less common, as the bark became paler again.

It makes an organism hard to see, so predators are less likely to find it.

There are no better-suited variants for natural selection to favour.

Explain which moths are more likely to survive in each wood, and why.

On pale bark the pale moths are camouflaged and the dark moths are eaten by birds. On dark bark the dark moths are camouflaged and the pale moths are eaten. The camouflaged moths survive, breed and pass on their alleles.

Describe what the diagram shows and explain why it happens.

The proportion of dark moths rises from 2 in 10 to 9 in 10. Birds eat more of the pale moths, so more dark moths survive and breed, and the allele for dark colour becomes more common.

A change in the inherited characteristics of a population over time, through natural selection.

A population.

Each generation changes only a little, as selection acts on small differences.

A group of organisms that can interbreed to produce fertile offspring.

The infertile offspring of a horse and a donkey, so horses and donkeys are different species.

It cannot be tested on asexual organisms or fossils.

Two populations of one species being kept apart so they cannot interbreed.

A river, a mountain range, the sea (any two).

The two environments differ, for example in climate, food and predators.

They become more and more different, as different variants are selected and different mutations occur.

When they can no longer interbreed to produce fertile offspring.

The population on an island is cut off from the mainland, so it evolves on its own.

It increases it when new species form, and it explains why all living things are related.

Extinction of species.

No. A stretched neck is not inherited. Variants arise by mutation and are selected.

63, an odd number, so the chromosomes cannot pair in meiosis and it cannot make gametes.

Describe the stages by which one species becomes two in this diagram.

One population interbreeds. A river splits it, and each half faces different selection pressures. After many generations the beetles are so different that they cannot interbreed to produce fertile offspring, so they are two species.

The remains or traces of an organism from many years ago, found in rock.

Hard parts, such as shells, teeth and bones.

Minerals replace the hard part as it decays, making a stone copy of it.

An insect in amber, a mammoth in ice, or a body in a peat bog.

A footprint, a burrow or a rootlet trace.

In the deepest layers.

From four toes in the oldest fossils to a single large hoof.

Features of both reptiles and birds, so it suggests that birds evolved from reptiles.

They decay quickly and leave little behind.

Fossilisation is rare, many fossils are destroyed by movements of the Earth, and many are not yet found.

The permanent loss of a species, with no individuals left alive.

Environmental change, new predators, new diseases, new competitors, hunting or habitat destruction (any three).

Individuals cannot compete and reproduce in the new conditions.

They have little genetic variation, so there may be no variants that can cope with a change.

An asteroid impact changed the climate and food chains, and the non-flying dinosaurs became extinct.

What they looked like, when they lived and how they were related to living species.

Describe the four stages shown in the diagram.

1 The animal dies and is covered by sediment. 2 The soft parts rot and the bones stay. 3 Minerals replace the bone, and the sediment turns to rock. 4 The rock is raised and worn away, which exposes the fossil.

What does this series of fossils show about the evolution of the horse?

The number of toes fell from four in the oldest layer to one in the youngest, and the animal became larger, so the horse evolved gradually over about 55 million years.

It kills bacteria or stops them growing, without harming the person's cells.

No. Viruses are not cells, so antibiotics cannot affect them.

A bacterium not being killed by an antibiotic, because of an allele that it carries.

By a random mutation, before the antibiotic is used.

The antibiotic, which kills non-resistant bacteria.

They are killed by the antibiotic.

They survive, reproduce and pass on the resistance allele.

They reproduce very quickly, they are present in huge numbers and they clone themselves.

About every 20 minutes in good conditions.

Methicillin-resistant Staphylococcus aureus.

It spreads to patients with wounds and weak defences, and few antibiotics will treat it.

So that all of the bacteria are killed and none survive to breed.

A cold is caused by a virus, and the use would only select for resistant bacteria.

It selects for resistant bacteria that may pass to humans.

Washing hands and cleaning equipment, and isolating infected patients.

Natural selection can be seen happening in a short time, in a population of bacteria.

Describe what happens at each of stages 1 to 4 in the diagram.

1 A mutation makes one bacterium resistant. 2 The antibiotic kills the non-resistant bacteria. 3 The resistant survivors reproduce and pass on the allele. 4 The population is now mostly resistant, so the antibiotic no longer works.

The sorting of living things into groups.

Grouping by a few features that are easy to see, which may group unrelated organisms.

Grouping by many shared features, which shows evolutionary relationships.

It shows how organisms are related and lets us predict their features.

Carl Linnaeus.

Kingdom, phylum, class, order, family, genus, species.

It falls, and the members have more in common.

A two-part name of a species: the genus and then the species.

Genus with a capital letter, species with a small letter, in italics or underlined.

They are the same all over the world, so every scientist knows which species is meant.

Bacteria, Archaea and Eukaryota.

Carl Woese, using the sequence of ribosomal RNA genes.

Using differences in DNA to work out how species are related.

That they split from their common ancestor more recently, so they are more closely related.

A common ancestor, where two lineages split.

Unrelated organisms may look alike because they live in a similar way.

Name the seven ranks of the Linnaean system in order, starting with the largest.

Kingdom, phylum, class, order, family, genus, species. For a human these are Animalia, Chordata, Mammalia, Primates, Hominidae, Homo, Homo sapiens.

Which two species are the closest relatives in this tree, and how can you tell?

The chimpanzee and the human, because they share the most recent common ancestor, about 6.5 million years ago. The orangutan split off first, so it is the most distant relative.

HMS Beagle, from 1831 to 1836.

The Galapagos Islands.

The beaks differed from island to island and suited the food available.

That selecting which individuals to breed can change a variety within a few generations.

The individuals best suited to the environment survive and breed more, so their features become more common.

A naturalist who developed the idea of natural selection independently of Darwin.

He sent Darwin an essay setting out natural selection.

On 1 July 1858, at the Linnean Society of London.

1859.

Religious belief, and no known mechanism of inheritance (or too slow to observe).

Genes and mutations were not known.

It showed how features are inherited in units, which are genes.

Fossils such as Archaeopteryx, genetics and DNA, and observed natural selection (any two).

It explains antibiotic resistance, and why new flu vaccines are needed.

A store of seeds, dried and kept cold, to preserve plant biodiversity.

They keep genetic variation as insurance against loss of species and crop varieties.

Explain how these finches show natural selection, and what Darwin inferred from them.

Each beak suits a different food. Finches with beaks best suited to the food on an island survive and breed more, so over generations the populations differ. Darwin inferred that the finches share an ancestor and changed by natural selection.