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5.4 evolution
 

5.4 evolution

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    5.4 evolution 5.4 evolution Presentation Transcript

    • 5.4 Evolution Topic 5 – Ecology & Evolution
    • 5.4 Evolution 5.4.1 Define Evolution: the process of cumulative change in the heritable characteristics of a population. Macroevolution – the change from one species to another Microevolution – the change from one variation within a species to another. i.e. – a Chihuahua and a Great Dane
    • 5.4 Evolution Evidence for evolution…. • Fossil record • Selective breeding of domesticated animals • Homologous structures
    • The Fossil Record • Darwin first collected convincing evidence for biological evolution • Earlier scholars had recognised that organisms on Earth had changed systematically over long periods of time. • Because bottom layers of rock logically were laid down earlier and thus are older than top layers, the sequence of fossils also could be given a chronology from oldest to youngest. • Today, many thousands of ancient rock deposits have been identified that show corresponding successions of fossil organisms. • Hundreds of thousands of fossil organisms, found in well-dated rock sequences, represent successions of forms through time and manifest many evolutionary transitions.
    • Life Form • • • • • • • • • • • • Microbial (procaryotic cells) Complex (eucaryotic cells) First multicellular animals Shell-bearing animals Vertebrates (simple fishes) Amphibians Reptiles Mammals Nonhuman primates Earliest apes Ancestors of humans Modern humans Millions of Years Since First Known Appearance 3,500 2,000 670 540 490 350 310 200 60 25 4 150,000 years
    • Archaeopteryx
    • Selective breeding
    • Homologous structures • Inferences about common descent are reinforced by comparative anatomy. For example, the skeletons of humans, mice, and bats are strikingly similar, despite the different ways of life of these animals and the diversity of environments in which they flourish. • The correspondence of these animals, bone by bone, can be observed in every part of the body, including the limbs. • Scientists call such structures homologous structures and have concluded that they are best explained by common descent.
    • The pentadactyl limb
    • (b) Outline the evidence for evolution provided by fossils (2). • fossils show changes over time (in organisms); • fossilized organisms are different from existing ones; • (yet) share features with existing organisms / homologous structures; • suggest common ancestry; • show intermediate stages in evolution of groups / missing link fossils;
    • 5.4 Evolution 5.4.3 Populations tend to produce more offspring than the environment can support.
    • 5.4 Evolution 5.4.4 • The consequence of the potential overproduction of offspring is a struggle for survival. • More offspring are produced than can be supported, therefore there is a struggle to survive, where some live and some die.
    • 5.4 Evolution 5.4.5 Members of a species show variation.
    • 5.4 Evolution 5.4 Explain how sexual reproduction promotes variation in a species. • Independent assortment • Crossing over • Random fertilisation • Mate selection
    • Natural selection – the mechanism of evolution • Since organisms’ traits vary, some organisms are more adapted to survival than others. • When there is a struggle to survive those with favorable traits tend to survive long enough to pass them on. • Those that have less favorable traits die before being able to pass the traits on.
    • 5.4 Evolution 5.4.7 Explain how natural selection leads to evolution • The Darwin–Wallace theory is accepted by most as the origin of ideas about evolution by means of natural selection
    • • 1854 - Wallace left Britain on a collecting expedition to the Malay Archipelago (now Malaysia and Indonesia). He spent nearly eight years in the region collecting almost 110,000 insects, 7500 shells, 8050 bird skins, and 410 mammal and reptile specimens, including over a thousand species new to science; some of his specimens can be seen in the Sarawak museum. • His best known discoveries are probably Wallace's Golden Birdwing Butterfly Ornithoptera croesus • The book he wrote describing his work and experiences, The Malay Archipelago, is the most celebrated of all travel writings on this region, and ranks with a few other works as one of the best scientific travel books of the nineteenth century.
    • • In February 1855, whilst staying in Sarawak, Wallace wrote what was to become one of the most important papers on evolution. • Wallace's "Sarawak Law" paper made a big impression on the famous geologist Charles Lyell. • Soon after Darwin had explained his theory of natural selection to Lyell (during a visit he made to Down House in April 1856) Lyell sent a letter to Darwin urging him to publish the theory lest someone beat him to it. • Darwin began to write ‘On the Origin of Species’.
    • • 1858 - the idea of natural selection occurred to Wallace . • He wrote out and sent his ideas to Darwin, who he thought might be interested. • Darwin had already discovered natural selection about 20 years earlier, and was part way through writing his "big book" on the subject. • Darwin appealed to his influential friends Lyell and Hooker for advice. • They presented Wallace's essay, along with two excerpts from Darwin's writings, to a meeting of the Linnean Society of London in July 1858. • These documents were published together in the Society's journal.
    • 5.4 Evolution 5.4.8 Explain two examples of evolution in response to environmental change • One must be multiple antibiotic resistance in bacteria….. • The peppered moth (Biston betularia) is another good example!.....
    • Multi-antibiotic resistance in bacteria • Variation: a bacterium gains a gene producing resistance e.g. through plasmids or mutation • Environment: doctors/vets use the antibiotic to control bacterial infections • Selection: favours the bacteria that are resistant to it and kills the non resistant ones • Reproduction: resistant bacteria reproduce producing more resistant bacteria. Eventually most bacteria are resistant • Evolution: doctors/vets use a different antibiotic to control infections repeating the process so evolving multiply resistant strains.
    • 5.4 Evolution The IBO assessment statements:
    • 5.4 Evolution 5.4.1 Define evolution. •Evolution is the cumulative change in the heritable characteristics of a population. •If we accept not only that species can evolve, but also that new species arise by evolution from preexisting ones, then the whole of life can be seen as unified by its common origins. •Variation within our species is the result of different selection pressures operating in different parts of the world, yet this variation is not so vast to justify a construct such as race having a biological or scientific basis.
    • 5.4 Evolution 5.4.2 Outline the evidence for evolution provided by the fossil record, selective breeding of domesticated animals and homologous structures. 5.4.3 State that populations tend to produce more offspring than the environment can support. 5.4.4 Explain that the consequence of the potential overproduction of offspring is a struggle for survival.
    • 5.4 Evolution 5.4.5 State that the members of a species show variation. 5.4.6 Explain how sexual reproduction promotes variation in a species. 5.4.7 Explain how natural selection leads to evolution. •Greater survival and reproductive success of individuals with favourable heritable variations can lead to change in the characteristics of a population. •Aim 7: Computer simulations can be performed.
    • 5.4 Evolution 5.4.8 Explain two examples of evolution in response to environmental change; •one must be antibiotic resistance in bacteria. •other examples could include: the changes in size and shape of the beaks of Galapagos finches; pesticide resistance, industrial melanism or heavy metal tolerance in plants.