The preserved remains or traces of an organism that lived long ago, usually found in rock.

How do fossils provide evidence for evolution?

They show what organisms were like in the past and how their features changed gradually over very long periods of time.

Explain how a population of bacteria becomes resistant to an antibiotic.

A random mutation makes a few bacteria resistant, the antibiotic kills the rest, and the survivors reproduce until most of the population is resistant.

Why is antibiotic resistance in bacteria such strong evidence for evolution?

It is natural selection happening fast enough to be watched and measured directly.

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

Evidence for evolution, and the work of Darwin and Wallace

3 things to know
Paper 4

Overview

Fossils and antibiotic resistance as evidence for evolution, why the fossil record is incomplete, how bacteria become resistant, Darwin's and Wallace's theory and its slow acceptance, and what seedbanks preserve.

What you need to know

Answer each one before you reveal it.

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Key term

Give two lines of evidence for evolution.

Key term

What is a fossil?

Key term

Why is the fossil record incomplete?

Questions from this subtopic

Each one with the model answer underneath.

1
Give two lines of evidence for evolution.
Model answer
Fossils, and the development of antibiotic resistance in bacteria.
2
What is a fossil?
Model answer
The preserved remains or traces of an organism that lived long ago, usually found in rock.
3
How do fossils provide evidence for evolution?
Model answer
They show what organisms were like in the past and how their features changed gradually over very long periods of time.
4
Why is the fossil record incomplete?
Model answer
Many organisms have soft bodies that decay instead of fossilising, and many fossils that did form have been destroyed or have not yet been found.
5
Explain how a population of bacteria becomes resistant to an antibiotic.
Model answer
A random mutation makes a few bacteria resistant, the antibiotic kills the rest, and the survivors reproduce until most of the population is resistant.
6
Why is antibiotic resistance in bacteria such strong evidence for evolution?
Model answer
It is natural selection happening fast enough to be watched and measured directly.

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Cell Level Systems

Community Level Systems

Genes, Inheritance and Selection

Global Challenges

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Algae and .

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AThe blood becomes too dilute.

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