Variation and Evolution What is Variation In any

Variation and Evolution

What is Variation? • In any population of living things there will be slight differences or variation between individuals in the population. • For example differences in size, colour, behaviour etc.

What do these differences mean? Variation means that some individuals in a population will be better suited to the environment than others. This may mean that these individuals are better camouflaged and therefore less likely to be 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 successful variations 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.

Where did this idea come from? The idea that populations of plants and animals change over time to better suit their environment was first proposed by Charles Darwin in 1850’s.

• From a young age Darwin was passionate about science and nature. He collected lots of different things like stones and beetles and performed experiments with his brother in the garden shed. • From 1831 – 1836 he voyaged around the world as a naturalist on The Beagle, collecting and making detailed observations of many different species of plants and animals. • He published a book On the Origin of Species in 1859 and was ridiculed for his ideas because they opposed the teachings of the church at that time.

• Today Darwin’s idea that species have changed over time to better suit their environment has gained acceptance as a scientific theory. • It is called Natural Selection. • Natural Selection is sometimes called ‘survival of the fittest’. How does it work? http: //www. youtube. com/watch? v=0 SCjh. I 86 gr. U (What is natural selection – stated clearly)

Natural selection Variation Individuals show variation: some variations are more favorable than others Overproduction Populations produce too many offspring, many will die Natural Selection Individuals that are best suited to the environment at the time will survive and reproduce Inheritance Variations are inherited. The best suited individuals will leave more offspring, passing on their successful variations to the next generation.

Darwin’s Theory of Evolution by Natural Selection.

Modelling Natural Selection In your pair you will receive a pile of paper discs which represent different coloured moths. Count out 20 of each phenotype (white, black and speckled). Person 1 scatter them over the sheet of newspaper while the other person is not watching. Person 2 (represents a bird) uses forceps (their beak) to pick up as many moths as they can in 20 seconds (Person 1 times). Swap roles and repeat.

Questions • How many butterflies of each phenotype did you catch? • How many of each phenotype did the whole class catch? • The population contained 20 white, 20 black and 20 speckled butterflies. Which ones were the best at avoiding predation (being eaten by the bird)? Why were they more successful? • What is likely to happen to the proportions of each phenotype in the next generation? Why will this happen?

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 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.

An adaptation is a special change to a species that helps the organism survive in its environment. There are three types of adaptations: Structural: A body part you can see such as wings on a bird to enable it to fly. Functional: The organism’s body is able to perform a function or do something that most organisms can’t. Eg, a snakes ability to produce poison or a deep sea fish’s ability to produce anti-freeze. Behavioural: An instinctive behaviour that the entire species carries out, eg penguins huddling for warmth or bears hibernating for winter.

What is Evolution? • http: //www. youtube. com/watch? v=fa. Rl. F s. Ymke. Y (Simpson’s evolution) • Evolution is the gradual change in species over time. • Evolution happens because the environment is continually changing. • Evolution occurs by Natural Selection. http: //www. youtube. com/watch? v=Gh. HOj. C 4 oxh 8 (What is evolution – stated clearly)

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!

How have some species changed over time?

The ancestral kiwi Tokoeka (Apteryx australis) are thought to be similar to the ancestor of our brown-coloured kiwi. They had short beaks and bigger wings.

Modern day kiwi • Modern day kiwi have long, slender beaks and tiny wings unsuitable for flying.

Ancestral Whales • The early whales had long slender legs and a long tail. They lived near the waters edge.

Modern Whales Now whales have lost the ability to walk and they have only tiny back leg bones. Their front legs are used for swimming

Ancestral Horses The early horses were about the size of a dog.

Ancestral horse • The early ancestors of the modern horse walked on several spread-out toes, because they walked on the soft, moist grounds of primeval forests. They changed from eating leaves to eating grasses so their teeth got larger and stronger. They needed to run faster so their legs go longer and they lifted their toes off the ground. This meant that their weight was carried on their 3 rd toe which was the longest.

Large Southern Land Mass Kiwi are part of a bird family called 'ratites' and are related to African ostriches, the South American rhea and Australian emus. All the ratites probably originated from Gondwanaland, the super-continent that 80 million years ago began splitting into pieces that include Australia and New Zealand.

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/Hidden. Taonga/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 the mass extinction of the dinosaurs, 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.