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25 Evolution (Extension) • 25.1 What is evolution? • 25.2 Evidences for evolution – fossil records • 25.3 Natural selection • Mind Map 25.1 What is evolution? 25.1 What is evolution? Plantae Animalia Fungi Prokaryota Protoctista 25.1 What is evolution? Evolution is the gradual development of living things Plantae Fungi Prokaryota from simple to Animalia complex life forms as time passes Protoctista 25.2 Evidences for evolution – fossil records 25.2 Evidences for evolution – fossil records Formation of fossil Volcanic eruption caused the death of dinosaurs 25.2 Evidences for evolution – fossil records Formation of fossil The skeleton was then covered by sand or mud 25.2 Evidences for evolution – fossil records Formation of fossil As time went by, the mud and sand turned into sedimentary rock 25.2 Evidences for evolution – fossil records Formation of fossil A paleontologist discovered the fossil and dug it out 25.2 Evidences for evolution – fossil records What can fossils show? Fossils can provide information about organisms which lived millions of years ago Geological time scale Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 25.2 Evidences for evolution – fossil records Examining fossil record 60 million years ago 25 million years ago Now Forelimb of horses Body size Horses became bigger & their legs became longer 25.2 Evidences for evolution – fossil records Fossil of Archaeopterynx Characteristics of reptiles full set of teeth long tail Characteristics of birds wings and feathers It shows that reptiles and birds may have evolved from a common ancestor 25.3 Natural selection 25.3 Natural selection My book ‘The Origin of Species ’ proposed the theory of natural selection to explain evolution Charles Darwin (1809-1882) 25.3 Natural selection 1. Variation occurs between individuals of the same species. Light moth Dark moth For example, two types of moths exist, light and dark The Origin of Species Charles Darwin 25.3 Natural selection 2. More individuals are born in each generation. However, there is a struggle for existence. Only the individuals that are more adapted than the others to the environment can survive. This idea is known as survival of the fittest. The Origin of Species Charles Darwin 25.3 Natural selection 3. Individuals that survive can reproduce and pass their characteristics to the next generation before they die. 4. After a very long period of time, a group of individuals that once belonged to the same species may separate into different kinds of species – evolution has taken place. The Origin of Species Charles Darwin 25.3 Natural selection Examples of natural selection 1. Peppered moths in Britain Light moth In the 1840s Dark moth The tree trunks were covered by light-coloured lichens & mosses The moths were well camouflaged from predators Thus light moths are more adapted to the environment Struggle for existence 25.3 Natural selection Examples of natural selection 1. Peppered moths in Britain Light moth In the 1840s Dark moth Thus most moths are light in colour Survival of the fittest 25.3 Natural selection Examples of natural selection 1. Peppered moths in Britain Light moth In the early nineteenth century Dark moth The pollutants killed the lichens and mosses on the tree trunks The dark moths were more adapted to their surroundings & can pass on their genes Soon there were more dark moths than light ones 25.3 Natural selection polluted habitat dark form light form unpolluted habitat light form dark form 25.3 Natural selection Examples of natural selection 2. Darwin’s finches feeds on seeds The seed-eating finches had reached the Galapagos Island from the mainland Africa but there was not enough food for all the birds 25.3 Natural selection Examples of natural selection 2. Darwin’s finches feeds on seeds Finches with slightly different beaks were able to eat other types of food These finches survived to breed and passed on their adaptive characteristics to their offspring 25.3 Natural selection Examples of natural selection 2. Darwin’s finches feeds on seeds feeds on leaves feeds on seeds feeds on insects feeds on buds and fruit feeds on grubs tool using finch Birds with different beaks live on the island now 25.3 Natural selection Significance of variation on evolution Provides chances to make an organism better adapted to their environment & help it win in the struggle for existence Thus, the advantageous variation can be passed on and a new improved kind of organism arises Mind Map Evolution gradual development of living things from one evidence fossil records one of the evolutionary theory natural selection proposed by examples simple to complex life forms Charles Darwin 1. peppered moths 2. Darwin’s finches