What is the main advantage of sexual reproduction?

It introduces genetic variation, so some offspring may survive when the environment changes.

Explain why a whole population that reproduces asexually can be wiped out by a new disease.

All the individuals are genetically identical, so if one has no resistance then none of them has.

Compare the number of offspring produced by a bacterium dividing asexually with the number produced by a large mammal.

The bacterium produces very large numbers in a very short time, while the mammal produces only one or a few live offspring per birth and takes far longer.

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

Asexual and sexual reproduction compared

3 things to know
Paper 4

Overview

The advantages and disadvantages of asexual and sexual reproduction, why an asexual population can be wiped out by a new disease, how offspring numbers compare between bacteria and large mammals, when asexual reproduction is an advantage, why many plants reproduce both ways, and why the variation from sexual reproduction helps a population survive a new predator.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Evaluation

Give two advantages of asexual reproduction.

Evaluation

What is the main disadvantage of asexual reproduction?

Evaluation

Give two disadvantages of sexual reproduction.

Questions from this subtopic

Each one with the model answer underneath.

1
Give two advantages of asexual reproduction.
Model answer
Only one parent is needed, and large numbers of offspring can be produced very quickly.
2
What is the main disadvantage of asexual reproduction?
Model answer
The offspring are genetically identical to the parent, so there is no variation to cope with a change in the environment.
3
What is the main advantage of sexual reproduction?
Model answer
It introduces genetic variation, so some offspring may survive when the environment changes.
4
Give two disadvantages of sexual reproduction.
Model answer
Two parents must find each other and mate, and reproduction is slower with fewer offspring produced.
5
Explain why a whole population that reproduces asexually can be wiped out by a new disease.
Model answer
All the individuals are genetically identical, so if one has no resistance then none of them has.
6
Compare the number of offspring produced by a bacterium dividing asexually with the number produced by a large mammal.
Model answer
The bacterium produces very large numbers in a very short time, while the mammal produces only one or a few live offspring per birth and takes far longer.

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Cell Level Systems

Community Level Systems

Genes, Inheritance and Selection

Global Challenges

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Algae and .

phytoplanktonfungianimals

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AThe blood becomes too dilute.

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