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Natural Selection
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- 1What does the theory of evolution state?It states that all living things that exist today, and many more that are now extinct, evolved from simple life forms, which first developed more than 3.5 billion years ago.
- 2What is evolution?It is the slow, continual change of organism groups over a very long period to become better adapted to their environment.
- 3Within a population of organisms there is a range of variations of individuals. What is this caused by?It is caused by genes. Some differences will be beneficial; some will not.
- 4What do beneficial characteristics mean for an organism? What is this ability called?They make an organism more likely to survive and pass on their genes to the next generation. This is especially true if the environment is changing. This ability is called survival of the fittest.
- 5What happens to species that are not well adapted to their environment?They may become extinct..
- 6What is this process of change summed up as? Who put the theory forward?This process of change is summed up in a theory called natural selection, put forward by Charles Darwin in the 19th century.
- 7Darwin's theory is accepted by most scientists today, why?Because it explains a wide range of observations and has been discussed and tested by many scientists.
- 8At the time when Darwin's theory was put forward, why was it not at first accepted?The reaction to Darwin's theory, particularly from religious authorities, was hostile because they felt he was saying that 'men were descended from monkeys' (although he was not) and that he was denying God's role in the creation of man. This meant his theory was only slowly and reluctantly accepted by many people in spite of his many eminent supporters.
- 9What are the five ideas of Darwin's theory?Variation.
Competition.
Survival of the fittest.
Inheritance.
Extinction. - 10Apply Darwin's idea of variation to the peppered moths.Variation - Most peppered moths are pale and speckled; easily camouflaged amongst the lichens on silver birch tree bark. There are some rare dark coloured varieties (originally arose from genetic mutation), but they are easily seen and eaten by birds.
- 11Apply Darwin's idea of competition to the peppered moths.In areas with high levels of air pollution, lichens dies and the bark becomes discoloured by soot. The lighter versions are now at a competitive disadvantage.
- 12Apply Darwin's idea of Survival of the fittest, inheritance and extinction to the peppered moths.Survival of the fittest - The dark (melanic) moths are now likely to avoid detection by predators.
Inheritance - The genes for darker colour are passed on to offspring and gradually become more common on the general population.
Extinction- If environment remains polluted then the lighter form is more likely to become extinct. - 13What are warfarin-resistant rats?Rats are dealt with by poisoning them. Warfarin is an effective poison that prevents blood clotting so the rats slowly bleed to death. Warfarin has been so widely used that a breed of 'super-rats' has emerged.
- 14Apply Darwin's 5 ideas in his theory to the Warfarin-resistant rats.Variation - Mutant rats , able to resist warfarin, arise in population.
Competition - Mutant rats are not killed by the poison.
Survival of the fittest - Warfarin-resistant rats survive, but the non-resistant breed do not.
Inheritance - Resistant rats pass on their warfarin-resistant genes.
Extinction - Non-resistant rats may eventually become extinct. There are already large populations of warfarin-resistant rats in the UK. - 15What are penicillin-resistant bacteria?The resistance of some bacteria to antibiotics is an increasing problem. MRSA bacteria have become more common in hospital wards and are difficult to eradicate.
- 16Apply Darwin's 5 ideas in his theory to the Penicillin-resistant bacteria.Variation - Bacteria mutate by chance, giving them a resistance to antibiotics.
Competition - The non-resistant bacteria are more likely to be killed by the antibiotics.
Survival of the fittest - The antibiotic-resistant bacteria survive and reproduce more.
Inheritance - Resistant bacteria pass on their genes to a new generation. The gene becomes more common in the general population.
Extinction - Non-resistant bacteria are replaced by the newer, resistant strain. - 17What is geographical isolation?It is when groups of the same species that are separated from each other by physical boundaries like mountains or sea will not be able to breed and share their genes.
- 18What is reproduction isolation?Due to geographical isolation, over long periods of time, the separate groups may specialise so much that they cannot successfully breed any longer and so new species are formed.
- 19Before Darwin developed his theory, Lamarck suggested that evolution happened by the inheritance of acquired characteristics. How did he explain this?Organisms change during their lifetime as they struggle to survive.
These changes are passed on to their offspring.
For example, he said that when giraffes stretch their necks to reach leaves higher up, this extra neck length is passed on to their offspring. - 20Why was Jean-Baptiste Lamarck's theory rejected?Because there was no evidence that the changes that happened in an individual's lifetime could alter their genes and so be passed on to their offspring.
- 21What were the very important four points that Darwin observed?1. Many living things produce far more offspring than actually survive to adulthood.
2. In spite of this, population sizes remain fairly constant due to predation, etc.
3. There is variation between members of the same species.
4. Characteristics can be passed on from one generation to the next. - 22From these observations what did Darwin say?Darwin deduced that all organisms were involved in a struggle for survival in which only the best-adapted organisms would survive, reproduce and pass on their characteristics. This formed the basis for his famous theory.
- 23The theory of natural selection has developed further since Darwin's time as new discoveries have been made. What studies have added significantly to our understanding of this basic process?The study of Inheritance and knowledge about DNA.
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- GCSE (B2) biology Fichas sobre Natural Selection, creado por Rebecca Smith el 26/02/2017.
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- Rebecca Smith
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