How much genetic variation is usually present within a population of one species?

There is usually extensive genetic variation between the individuals.

Do all the members of one species carry the same genes?

They carry the same genes, but they carry different variants of many of them.

Why is extensive genetic variation useful to a population?

It means that if conditions change some individuals are likely to survive and pass on their variants.

Would two individuals of the same species picked at random be expected to be genetically identical?

No, unless they are identical twins or were produced asexually from the same parent.

OCR GCSE Biology A J247

Cell Level Systems

Topic overview Microscopy, and sub-cellular structures DNA structure: polymer, double helix and nucleotides Protein synthesis and the triplet code 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 How genetic variants influence phenotype 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, and evidence for environmental change 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 Detecting plant disease; white blood cells and platelets Non-specific defences and the immune system Monoclonal antibodies and their uses 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 Investigating and treating the brain Hormonal coordination, thyroxine and adrenaline Hormones in reproduction and the menstrual cycle Contraception and treating infertility Plant hormones and their commercial uses Homeostasis, and the skin in temperature control Insulin and glucagon in blood sugar control Type 1 and type 2 diabetes Osmotic changes in body fluids, and the kidneys The kidney tubule and the effect of ADH Responding to temperature and osmotic challenges

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

Variation within a population, and classification

3 things to know
Paper 4

Overview

How much genetic variation a population holds and where it comes from, why individuals carry the same genes in different variants, why variation helps a population and sexual reproduction gives more of it, what classification is, artificial and natural classification with examples, molecular phylogenetics and how DNA sequencing reveals relationships, and why classification changes over time.

What you need to know

Answer each one before you reveal it.

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Key term

What produces the genetic variation found within a population?

Key term

What does it mean to say there is extensive genetic variation within a population of a species?

Key term

What is an artificial classification system based on?

Questions from this subtopic

Each one with the model answer underneath.

1
How much genetic variation is usually present within a population of one species?
Model answer
There is usually extensive genetic variation between the individuals.
2
What produces the genetic variation found within a population?
Model answer
Mutations create new variants, and sexual reproduction mixes them into new combinations.
3
Do all the members of one species carry the same genes?
Model answer
They carry the same genes, but they carry different variants of many of them.
4
Why is extensive genetic variation useful to a population?
Model answer
It means that if conditions change some individuals are likely to survive and pass on their variants.
5
Would two individuals of the same species picked at random be expected to be genetically identical?
Model answer
No, unless they are identical twins or were produced asexually from the same parent.
6
What does it mean to say there is extensive genetic variation within a population of a species?
Model answer
The individuals in it differ from one another in the alleles they carry, so no two are genetically identical apart from clones.

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Genes, Inheritance and Selection

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