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Variation and Evolution Charles Darwin • Charles Darwin was a brilliant naturalist who changed the way people think about life on earth. One reason why he was able to do this was because he was always passionate about science and nature! • From a young age Darwin collected lots of different things like stones and beetles and performed experiments with his brother in the garden shed. It was this early interest that helped him become a great man! • Read more about Darwins Life: http://www.christs.cam.ac.uk/darwin200/pages/index.php?p age_id=j1 What is Evolution? • Evolution is the slow process that changes animals and plants and it’s a great piece of science! It describes loads of things in nature like fossils, peacocks' tails, lions’ teeth, birds’ wings and human brains, just to name a few. It is also supported by lots and lots of evidence that has been collected by scientists for more than 150 years! How do species evolve (change over time) This links clearly explains how species evolve. Scroll down to the question ‘How do species evolve’ http://www.christs.cam.ac.uk/darwin200/pages /index.php?page_id=j2 So this is Natural Selection! Our planet is in a state of change. • All the pollution that we produce with our cars, power plants and aeroplanes is changing our climate. At the same time, we’re cutting down lots of forests and moving animals and plants from one part of the world to another. This is causing chaos in the natural world! Climate change is a big issue; Temperatures are predicted to rise rapidly over the next hundred years. This might sound quite nice but it will have lots of bad effects. Sea levels will rise and all the different weather systems will change. Lots of animals and plants are now found where they weren’t before. Their presence is causing lots of problems for local wildlife – they’re messing up all the food webs! The UK has lots of new species which have either been accidently introduced or are taking advantage of the warming weather: cannibalistic ladybirds, rampant crayfish and exotic spiders to name a few! And • The changing weather has also confused many birds which migrate. They rely on clues from the weather to time their migrations. Because the temperature is changing so quickly they’re starting to get it wrong and they can leave too early and arrive at their destination when there’s no food, or leave too late and face the same problem! Rainforests • In many tropical regions people are cutting down the rainforests to use the trees as timber, or to make the land good for farming. Unfortunately half the world's species live in the rainforest! Their habitats are being destroyed or cut up into chunks, isolating small groups from each other and making them more vulnerable Forests in Brazil have been cut down to make way for crops such as soya So We have to tackle these problems otherwise we’ll get ourselves into lots of trouble! But how? Part of the way we can do this is to understand how these changes will affect animals and plants. To do that we need to understand evolution! We can use our modern knowledge to help us conserve species, and cope with invasive species and climate change. So, Darwin and evolution are proving very useful right now! Why is knowing about Evolution important? Take a look at this: http://www.christs.cam.ac.uk/darwin200/docs/ content/why_evolution.pdf Variation • For evolution by natural selection to occur there must be slight differences between members of a population. For example differences in size, colour, behaviour etc . What do these differences mean? Some individuals will be better suited to the environment than others. This may mean that some individuals are better camouflaged and therefore not eaten by predators. So… The individuals that are better suited to the environment will survive longer and therefore be able to mate and pass their genes on to the next generation. For example, after a long period of time there would be larger numbers of the dark moth. We would then say… That the population has evolved which means that it has changed over time. Natural selection Variation Individuals show variation: some variations are more favorable than others Lots of babies Population produces too many offspring, many will die Natural Selection Natural selection favors the best suited at the time Inheritance Variations are inherited. The best suited variants leave more offspring. Modelling Natural Selection • Scattered around the room are different coloured butterflies. You are an insectivorous bird and you have 20 seconds to catch as many butterflies as you can with your ‘beak’ (between thumb and forefinger). • • • • How many different phenotypes did you find? How many butterflies of each phenotype did you catch? How many of each phenotype did the whole class catch? The population contained 80 red, 80 black and 80 clear butterflies. Which ones were the best at avoiding predation? Why were they more successful? • What is likely to happen to the proportions of each phenotype in the next generation? Why will this happen? • What was the ‘selection pressure’ operating in this model? Darwin’s Theory of Evolution by Natural Selection. Darwin’s 5 points 1. 2. 3. 4. 5. Population has variations. Some variations are favorable. More offspring are produced than survive Those that have favourable traits survive. A population will change over time as the individuals with the more favourable characteristics survive and pass their genes on to the future generation. But what about us? • When Darwin told the world about his discovery in his book On the Origin of Species he didn’t really say anything about humans other than to hint his ideas would reveal the secrets of human history. But the message was clear; natural selection is the process which has shaped all species, including us! • Other scientists wrote books about human evolution, often comparing our bones to those of apes and monkeys. Eventually Darwin decided to write a book about it too to set the record straight about what the thought about humans. He wrote a book called The Descent of Man. He presented lots of evidence to support the theory that humans evolved from apes. He also argued that all the different human races were one species, which was a keenly debated subject in Victorian times. Ostrich, rhea, cassowary and kiwi The ostrich, rhea, cassowary and kiwi are all related birds that had a common ancestor in Gondwana. (the large southern supercontinent we were once part of) They are now distributed across New Zealand, South America, South Africa and Australia. (Top left to right clockwise: Ostrich, rhea, kiwi and cassowary.) New Zealand’s Unique Ecology New Zealand has a rich and unique range of plants, animals and fungi. The level of distinctive biodiversity is as high as such world-renowned ecosystems as the Galapagos Islands. So how have our unique ecosystems developed? Visit the Science Learning Hub to find out http://www.sciencelearn.org.nz/Contexts/HiddenTaonga/Looking-Closer/New-Zealand-s-uniqueecology Our very own! • Approximately 65 million years ago when the last land bridge to Gondwana was lost, the flora, fauna and fungi of New Zealand began to evolve in isolation. As a consequence, many of our native species – like the kauri, kahikatea, tōtara, rimu, tuatara, kiwi, kauri snail and wētā – have become uniquely adapted to life on our islands and now only exist in this country. Travelled over the sea to get here Some species were able to reach New Zealand after the separation from Gondwana by floating on currents or being blown by the wind, a process that continues today. Plants such as mānuka, rātā, flax and pōhutukawa, and Birds such as the saddleback, kōkako and huia (now extinct), and our native bats all originated in other lands and travelled across the sea. Once here, these species have evolved separately from their relatives in Australia or South America and, over time, have developed as specialised inhabitants of the New Zealand islands. Then something happened.. • Around the time that New Zealand was losing the last of its land connections to other land masses, a dramatic event occurred that resulted in one of the most devastating loss of species that has ever been recorded. There are different explanations for this loss – some scientists think a meteor hit the earth, others suggest a series of volcanic eruptions blanketed the atmosphere with smoke. Whatever the cause, the result was the mass extinction of the dinosaurs and other species. • Before this, the reptiles had dominated, but within a very short period of time, close to 85% of all species were wiped out, and the mammals began to occupy the vacant ecological niches – everywhere, that is, except New Zealand. But few mammals • For reasons that are not apparent, New Zealand was not inhabited by many mammals. Instead, our fauna became dominated by birds and insects. Birds became the predators, the scavengers, the herbivores and the insectivores. They lived everywhere from the highest mountains to the sea. With few predators, many lost the ability to fly and became ground dwellers. Insects evolved to extremes of big and small and occupied a range of habitats. We are unique.. • This process has made New Zealand unique – nowhere else on the planet has such a range of bird life and insect life, with only two species of bat representing the mammals.