Where does the variation that natural selection acts on come from?

From mutations, which produce new variants of genes.

Describe the steps by which natural selection leads to evolution.

Mutation produces variation, the best suited individuals survive and breed, they pass their variants to their offspring, and over many generations those variants become common in the population.

What happens to an individual whose phenotype is poorly suited to its environment?

It is less likely to survive long enough to reproduce, so its variants are passed on less often.

Does an individual organism evolve during its own lifetime?

No, individuals do not evolve; it is the population that changes across generations.

OCR GCSE Biology A J247

Cell Level Systems

Topic overview Microscopy, and sub-cellular structures DNA structure: polymer, double helix and nucleotides Enzyme action, and investigating enzymes Cellular respiration as an exothermic process Aerobic and anaerobic respiration compared Synthesis and breakdown of carbohydrates, proteins and lipids Photosynthesis: producers and the process Photosynthesis as endothermic, and investigating it Limiting factors in photosynthesis

Community Level Systems

Topic overview Cycling materials, and the role of microorganisms The carbon and water cycles, and decomposition Levels of organisation, and abiotic and biotic factors Interdependence, competition and trophic levels Pyramids of biomass and the efficiency of transfer

Genes, Inheritance and Selection

Topic overview Genetic terms, and the genome Genome, environment and mutations Asexual and sexual reproduction compared Haploid, diploid and meiosis Single gene inheritance and Punnett squares Sex determination, multiple genes and Mendel's work Variation within a population, and classification Natural selection and evolution Evidence for evolution, and the work of Darwin and Wallace

Global Challenges

Topic overview Field investigations, and human impact on ecosystems Maintaining biodiversity, monitoring conservation and ecotourism Food security, agricultural and biotechnological solutions Selective breeding and genetic engineering Health, disease, and types of disease Interactions between diseases, and how they spread Reducing the spread of disease, and named examples Physical and chemical plant defences White blood cells, antibodies and platelets Non-specific defences and the immune system Vaccines, medicines and aseptic technique Developing new medicines, and non-communicable disease Treating cardiovascular disease, and lifestyle factors Cancer, and the use of stem cells in medicine Gene technology in medicine, and the human genome

Organism Level Systems

Topic overview The nervous system and coordinated responses The reflex arc The eye and its common defects The structure and function of the brain Hormones and the endocrine glands Hormones in reproduction and the menstrual cycle Methods of contraception Tropisms, auxin and the roles of plant hormones Homeostasis, and the skin in temperature control Insulin and the control of blood glucose Type 1 and type 2 diabetes Osmotic changes in body fluids, and the kidneys Kidney structure and the parts of the tubule

Scaling Up

Topic overview Diffusion, osmosis and active transport Mitosis, the cell cycle and cell differentiation Stem cells in animals and meristems in plants Surface area to volume ratio and exchange surfaces The circulatory system, the heart and blood vessels Red blood cells and plasma Root hair cells, transpiration and translocation Xylem and phloem Factors affecting water uptake, and the potometer

Genes, Inheritance and Selection

Natural selection and evolution

3 things to know
Paper 2

Overview

What natural selection is, where variation comes from, the steps from mutation to a changed population, why individuals do not evolve, what evolution and a species are, and how new species form.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

A population is split in two by a mountain range. Explain how this can lead to two new species.

Key term

What is natural selection?

Key term

Explain why natural selection cannot work without variation.

Questions from this subtopic

Each one with the model answer underneath.

1
What is natural selection?
Model answer
The process by which individuals whose phenotypes are best suited to their environment are the most likely to survive and reproduce.
2
Where does the variation that natural selection acts on come from?
Model answer
From mutations, which produce new variants of genes.
3
Describe the steps by which natural selection leads to evolution.
Model answer
Mutation produces variation, the best suited individuals survive and breed, they pass their variants to their offspring, and over many generations those variants become common in the population.
4
Explain why natural selection cannot work without variation.
Model answer
If every individual were identical none would be better suited than another, so there would be nothing for selection to act on.
5
What happens to an individual whose phenotype is poorly suited to its environment?
Model answer
It is less likely to survive long enough to reproduce, so its variants are passed on less often.
6
Does an individual organism evolve during its own lifetime?
Model answer
No, individuals do not evolve; it is the population that changes across generations.

See the rest and revise

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.

1Closed book

2Open book

3Closed book

The 3-step method, run for you

Answer cold, learn it, then prove it stuck. Levo tracks the jump between your first attempt and your last.

Cell Level Systems

Community Level Systems

Genes, Inheritance and Selection

Global Challenges

Cram a whole paper in one sitting

Sort every topic into what you know and what you do not, then drill only the weak ones.

Algae and .

phytoplanktonfungianimals

Blank Blitz makes facts automatic

Rapid timed gap-fills on the terms and numbers you need to recall without thinking.

AA diet high in sugar and fat leads to obesity.

BBody cells then respond poorly to insulin.

CBlood glucose concentration cannot be controlled.

Build It gets the exam shape right

Assemble a full-mark answer from its marking points, in the order an examiner wants them.

Egestion means passing out of undigested food as faeces.

TrueFalse

Test It catches misconceptions

Spot the fault in a statement. The traps are the mistakes students actually make.

721941163128510

Brain Breaks between sessions

Short focus games to reset attention, so the next set lands better than the last.

Every question in Genes, Inheritance and Selection, on a schedule.

Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.

Start revising, £5 a month See how the method works

Or £46 a year, about £3.83 a month. Cancel anytime.