Transcript Evolution
Sunday, April 10, 2016 Evolution & Speciation To understand the theory of evolution, and how new species develop Evolution Darwin’s theory of evolution explains how species of living things have changed over time The theory is supported by evidence from fossils, and by the rapid changes that can be seen to occur in microorganisms such as antibiotic-resistant bacteria Many species have become extinct in the past and the extinction of species continues to happen… Charles Darwin Charles Darwin was an English naturalist who studied variation in plants and animals during a five-year voyage around the world in the 19th century onboard HMS Beagle He explained his ideas about evolution in On the Origin of Species, published in 1859 Darwin’s ideas caused a lot of controversy, and this continues to this day, because the ideas can be seen as conflicting with religious views about the creation of the world and creatures in it Darwin’s Finches Darwin studied the wildlife on the Galápagos Islands - a group of islands on the equator almost 1,000km west of Ecuador He noticed that the finches (songbirds) on the different islands were fundamentally similar to each other, but showed wide variations in their size, beaks and claws from island to island (their beaks were different depending on the local food source) Darwin concluded that, because the islands are so distant from the mainland, the finches that had arrived there in the past had changed over time – proposing his theory of evolution via natural selection… Darwin’s Finches The finches on the different islands were fundamentally similar to each other, but showed wide variations in their size, beaks and claws from island to island (their beaks were different depending on the local food source) Evolution The basic idea behind the theory of evolution is that all the different species have evolved over millions of years from simple life forms These simple life forms first developed more than three billion years ago (Earth is about 4.5 billion years old) Fossils Fossils provide evidence for evolution, showing how today’s species have changed and developed over millions of years There are quite a few ‘missing links’ though, as the fossil record is incomplete as very few dead plants and animals actually turn into fossils (most simply decay away) Isolation & Speciation Isolation is where a population of a species is separated (a physical barrier such as an earthquake / flood) Conditions on either side of the barrier are slightly different (such as climate) and because the environment is different natural selection will drive changes in the population Eventually if the two populations met again they will have changed so much they won’t be able to breed – they are separate species Isolation & Speciation Speciation is the development of a new species (the splitting of an initial species into distinct groups which can no longer breed to produce fertile offspring) Natural selection is the driving force behind speciation… Model Draw you own example of speciation – start with a common population and create an environmental change which separates the population creating two new species, which when they return can no longer breed viable offspring Natural Selection Individuals in a species show a wide range of variation (due to differences in genes (alleles)) Individuals with characteristics most suited to the environment are more likely to survive and reproduce The genes that allowed the individuals to be successful are passed to the offspring in the next generation Individuals that are poorly adapted to their environment are less likely to survive and reproduce, meaning that their genes are less likely to be passed to the next generation Given enough time, a species will gradually evolve…