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At the end of this unit you should: Be able to describe what evolution means. Know that it was Charles Darwin who proposed the theory of evolution. Be able to describe some of the evidence Darwin put forward for this theory. Be able to describe natural selection in your own words.
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At the end of this unit you should: • Be able to describe what evolution means. • Know that it was Charles Darwin who proposed the theory of evolution. • Be able to describe some of the evidence Darwin put forward for this theory. • Be able to describe natural selection in your own words. • Understand how species have evolved over years and use examples of animals that have evolved. • Know that natural selection explains how evolution has occurred. • Know that evolution is ongoing.
adapt breed camouflaged compete diversity evolution extinction fossil habitat natural selection organism predator prey species theory
LIGHTBULB QUESTION Yes. Some are able to withstand different climates as they can adapt to their new surroundings. Science, medical research and technology have allowed some diseases and disorders to be eradicated and therefore species are living for longer.
(a) What does variation mean in biology? ‘Variation’ means the differences between organisms.
(b) What has brought about the huge variation in plants and animals that we have today? Evolution.
(c) Describe in your own words what evolution means. A slow, ongoing change in an organism over a very long time.
(d) Which scientist published a book called On the Origin of Species? Charles Darwin.
(e) What concept did this book put forward? Natural selection.
(i) Discuss the shapes of the finches’ beaks. Create a table of the different types of beak. Can you think of reasons why the beaks are shaped differently?
(ii) Would a finch with a short beak that ate seeds survive on an island where the only food source was insects? Give an explanation for your answer. This can be a ‘yes’ or ‘no’ answer depending on explanation given. No, it would not survive if the species did not adapt to its new environment. Yes, it would survive if the species adapted itself to eat insects; the short beak would have to become pointed, to kill the insect, or remove the body of the insect from a shell, or find or remove the insect from a small opening or gap.
Evolution: A slow, ongoing change in an organism over a very long time. Characteristic: A distinguishing feature or quality, which allows us to tell organisms apart. Natural Selection: A characteristic that an organism has, giving it a better chance of surviving; passed on genetically from generation to generation.
The evolution of the horse is visually dramatic, even if it has been happening over a period of 60 million years! Fig. 04.03.06 shows the evolution of the horse and the changes in body size, height and the length of the fore feet. If you look closely at the pictures, the fossil evidence highlights how the horse has evolved from a small swamp-dwelling animal to what it is today. (i) Discuss why you think this might have happened. The horse may have had to move from the swamp area to an area where they needed stronger and longer legs to allow them to source their food.
(ii) What do you think might happen next to horses? Their legs might grow even longer and stronger.
(iii) How long do you think it will take to happen? Over another few million years.
Using the information you have just read on natural selection, explain how three of the following evolutionary characteristics could have come about. (i) Owls with large eyes. To see at night and to pick out their prey.
Using the information you have just read on natural selection, explain how three of the following evolutionary characteristics could have come about. (ii) A cheetah that runs very fast. Having to chase its prey.
Using the information you have just read on natural selection, explain how three of the following evolutionary characteristics could have come about. (iii) Birds with long, pointed or sharp beaks. To find their food in the soil, pointed and sharp so they can break open seeds or take food from shells or from soil.
Using the information you have just read on natural selection, explain how three of the following evolutionary characteristics could have come about. (iv) A giraffe’s long neck. To eat the leaves at the top of trees.
Using the information you have just read on natural selection, explain how three of the following evolutionary characteristics could have come about. (v) Birds that eat berries and worms. Living in an environment where berries and worms are readily available.
Using the information you have just read on natural selection, explain how three of the following evolutionary characteristics could have come about. (vi) A snake’s ability to eat more than one type of animal. Having to find a different source of food to survive.
Copy and Complete In this unit I learned that the world is made up of millions of different organisms. There is also a huge variationbetween plants and animals. Evolutionis a result of this variation. It has occurred over millions of years. There are estimated to be over twomillion different plants and animals alive today. New species are being discovered all the time. Charles Darwinproposed the theory of evolution. He explained that plants and animals are differentand that each organism competeswith others to exist. Therefore they must adapt to survive. This is where we get the phrase ‘survival of the fittest’. If a plant or animal adapts well to its habitat, it will live/surviveand not become extinct. The animals that survive pass on their genes to their young and then their young are able to survive. This is natural selection.
1. Match each keyword in Table 04.03.02 with the correct meaning and write them in your copy. One has been done for you.
2. Name the scientists who thought that evolution happened by natural selection. Charles Darwin, Alfred Russel Wallace and Jean-Baptiste Lamarck.
3. Describe evolution in your own words. Evolution is the process by which plants or animals adapt to the conditions of their environments over time.
4. Construct a mind map of evolution. Have you used all of the keywords in your mind map? Have you mentioned all the key figures in developing the theory of evolution?
5. Write a short note on natural selection, using ‘survival’ as your keyword. When an animal or plant has to or has adapted to a new habitat or surroundings. This is their survival method. They have made this adaptation to survive and avoid death.
6. ‘It is thought that sexual reproduction allows evolution to happen more so than asexual reproduction.’ Can you provide an explanation for this statement? Asexual reproduction produces cells and individuals that are identical to the parent. This does not allow for variation to take place and therefore adaptation may not be able to happen either. Sexual reproduction allows variation to take place, which increases the organism’s chance of being able to adapt and therefore evolve.
7. What must a predator have over its prey to enable it to survive in a habitat? Favourable characteristics that allow the predator to be either the strongest, fastest, tallest, etc. This then allows the predator an advantage over its prey, leading to survival of the fittest.
8. Why do you think a polar bear would not survive for very long in the desert? It is not best adapted to its surroundings.
