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Evolution

Evolution. commons.wikimedia.org/wiki/Image:DNA_double_helix_vertikal.PNG. commons.wikimedia.org/wiki/Image:Charles_Darwin_1881.jpg. The Tree of Life. All living things share a common ancestor. We can draw a Tree of Life to show how every species is related.

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Evolution

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  1. Evolution commons.wikimedia.org/wiki/Image:DNA_double_helix_vertikal.PNG commons.wikimedia.org/wiki/Image:Charles_Darwin_1881.jpg

  2. The Tree of Life • All living things share a common • ancestor. • We can draw a Tree of Life to • show how every species is related. • Evolutionis the process by which • one species gives rise to another • and the Tree of Life grows en.wikipedia.org/wiki/Image:Phylogenetic_tree.svg

  3. …so no… humans were never monkeys

  4. The central idea of evolution is that life has a history. The living things on Earth have changed over time, and that the different species on Earth today share common ancestors.

  5. Over a great period of time evolution can result in SPECIATION Speciation - The formation of a new species

  6. How does speciation occur?

  7. Extinction • Millions of organisms that lived in the past have gone extinct. We know of their existence from fossils or rarely from frozen specimens.

  8. Related Species • There are many organisms that are different species, but are obviously very closely related. It is very apparent that the American cougar and the African lion are related. They both share a common ancestor from the past.

  9. Related Species • All of the many cat species are related. They have very similar anatomy and DNA. Cats share a common ancestor that lived in the past. Not all cat species that evolved are alive today.

  10. Related Species • The saber- toothed cat became extinct about 10,000 years ago It has the same basic skeleton as other cats. The most distinguishing feature of this cat is its long canine teeth.

  11. Evolution as Theory and Fact • Confusion sometimes arises as to • whether Evolution is a theory or a fact. • Actually it is both! • The theory of Evolution deals with how • Evolution happens. Our understanding • of this process is always changing. • Evolution is also a fact as there is a • huge amount of indisputable evidence • for its occurrence. Rodin’s “The Thinker”

  12. Darwin’s Voyage • From 1831-1836, a • young naturalist called • Charles Darwin toured • the world in HMS • Beagle. • He was dazzled by the • amazing diversity of • life and started to • wonder how it might • have originated Voyage of the Beagle en.wikipedia.org/wiki/Image:Charles_Darwin_by_G._Richmond.jpg en.wikipedia.org/wiki/Image:HMS_Beagle_by_Conrad_Martens.jpg

  13. Survival of the Fittest • In his Origin of Species, • published in 1859, Darwin • proposed how one species • might give rise to another. • Where food was limited, • competition meant that only • the fittest would survive. • This would lead to the natural selection • of the best adapted individuals and • eventually the evolution of a new species. Natural Selection explains adaption Darwin in 1860 en.wikipedia.org/wiki/Image:Darwin%27s_finches.jpeg

  14. Evolution is possible because of…. • Genetic Variation

  15. Why Genetic Variation? If a population was 100% the same… the processes that cause evolution would have NO effect because the genetic make-up would never change.

  16. Evolution only occurs when there is a change in gene frequency within a population over time. 1st generation of Beetle population Many generations later of the same population

  17. What causes these changes? There are 5 main mechanisms for evolutionary changes:

  18. 5 Agents of evolutionary change Gene Flow or Migration Mutation Non-random mating Natural Selection Genetic Drift

  19. Mutation • A change in a DNA sequence, usually occurring because of errors in replication or repair. Mutation is the ultimate source of genetic variation. Fruit Fly Example

  20. Mutation • However, occasional • mutations or copying errors • can and do occur when • DNA is replicated. • Mutations may be caused • by radiation, viruses, or • carcinogens. • Mutations are rare and often have • damaging effects. Consequently organisms • have special enzymes whose job it is to • repair faulty DNA. Types of mutation Mutant fruitfly upload.wikimedia.org/wikipedia/commons/7/79/Types-of-mutation.png humansystemstherapeutics.com/bb.htm

  21. Sometimes mutations are beneficial Only if they help the organism survive…

  22. Mutations produce the genetic variation needed for evolution.

  23. Gene Flow or Migration Either by immigration or emigration (individuals move to another population and shares their genes there).

  24. Gene flow moves alleles from one population to another.

  25. The change of allele frequencies in a population over time due to random events forming successive generations. Genetic Drift

  26. Genetic Drift • A random change in allele frequency

  27. Genetic Drift • These individuals may carry alleles in different relative frequencies than did the larger population from which they came • If so, the population that they found will be genetically different from the parent population • This cause is not natural selection, but chance

  28. For example: Green beetles reduce in numbers because an external factor has caused them to produce less offspring causing a more dominant brown population.

  29. Genetic drift changes allele frequencies due to chance alone.

  30. Natural Selection A process of evolution in which traits that result in better fitness of an individual survives to the next generation.

  31. Natural selection selects for traits advantageous for survival.

  32. Non-Random Mating (Sexual Selection) Peahens choose their mates by the size and shape of his tail. This makes sense in evolutionary terms -- the largest tail would indicate a healthy bird and a better chance for healthy offspring.  The process by which organisms choose their mates based on advantageous traits that will be carried to the next generation.

  33. Sexual Reproduction- brings together a new combination of genes. • Introduces new combinations of genes every generation.

  34. Sexual reproduction = Genetic Variation

  35. Population numbers will always be threatened by different factors • Individual organisms will continue to migrate • New genetic mutations occur frequently • Species select mates; random mating rarely occurs • The environment has changed on Earth and continues to change • In nature, populations are expected to evolve because a population can’t maintain equilibrium forever.

  36. Evolution at work Although evolution cannot be seen on the small scale of time, the works of evolution are occurring all the time in populations. These processes are what contribute to the evolutionary changes between all species.

  37. "One obstacle to understanding evolution is the common misconception that individual organisms evolve. It is the population, not its individuals, that evolves, as some heritable variation becomes more common at the expense of others."

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