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Mechanisms of Evolution

Mechanisms of Evolution. Members of the same species : Can reproduce in a natural setting and produce fertile offspring. Background terms. A horse and donkey can mate in the barnyard to produce a mule. The mule is a very strong, hardworking animal (albeit stubborn!), but alas,

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Mechanisms of Evolution

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  1. Mechanisms of Evolution

  2. Members of the same species: Can reproduce in a natural setting and produce fertile offspring Background terms

  3. A horse and donkey can mate in the barnyard to produce a mule. The mule is a very strong, hardworking animal (albeit stubborn!), but alas, mules cannot have babies. Are horses and donkeys members of the same species? No – the mule cannot reproduce, therefore is not fertile. Apply species definition

  4. Are all birds members of the same species? Think of the biggest and smallest birds you can imagine. Certainly hummingbirds cannot mate with ostriches! More species defined

  5. Are all domesticated dogs members of one species? Can all dogs mate (theoretically)? Are all normal puppies fertile? Yes. All dogs are members of one species: Canisdomesticus More species defined

  6. A lion and tiger can be artificially mated together in a zoo. This produces a “liger” Are lions and tigers therefore members of the same species? No, they didn’t mate in a natural setting – and never would – they don’t even live on the same continent! More species defined

  7. Branching diagram (CLADOGRAM) Shows changes in species over time Each new branch represents a newly evolved feature Evolution vocabulary

  8. Which organisms have jaws? Which organisms have claws or nails? Is the salamander more closely related to the perch or pigeon? CLADOGRAMS

  9. MORE CLADOGRAMS Where in the image is now? Left, right, top or bottom?

  10. Cladogram showing fish evolution Where is the common ancestor?

  11. CLADOGRAM OF DINOSAURS • If a line stops before the top, what does that mean?

  12. CLADOGRAM SHOWING EVOLUTION OF BIRDS FROM DINOSAURS What is the common ancestor?

  13. MORE CLADOGRAMS - SIDEWAYS Where is NOW in these diagrams?

  14. Evolution: changes in species over time • Speciation: the formation of new species • Gradualism: the theory that species changed very gradually over time. Fossil evidence shows jumps, but the hypothesis is that we simply haven’t found the in-between fossils (missing links). • Punctuated equilibrium: The theory that species are relatively unchanged for long periods, but then go through sudden rapid changes and new speciation, usually due to geographic isolation or environmental pressures. Mechanisms of Evolution - vocabulary

  15. Gradualism vs. punctuated equilibrium Evolution - vocabulary

  16. Natural selection: (aka Survival of the Fittest) The members of the species that are best adapted to the environment will survive to pass their genes on to the next generation. The less well adapted will be more likely to die before reproducing, reducing the proportion of their particular set of alleles in their population. The “environment selects” which members survive. Mechanisms of Evolution

  17. During an especially cold winter, the birds with the most under-feathers (down) are more likely to survive, while some the others will die off. The “environment selects” the survivors, who then pass on their genes to the next generation. Examples of natural selection

  18. Slower sea turtles may be eaten by gulls before fast ones, when trying The fast ones pass their genes on to produce fast offspring. Examples of natural selection

  19. A strong species is one in which there are many differences, or variations, between individuals in the population. These variations allow individuals to survive changes in the environment, and multiple situations. Mechanisms of Evolution –Genetic Variations

  20. Ex: The faster turtles on land may attract more attention from gulls, and may also be slower swimmers. Slow, better camouflaged ones may swim better and have higher chance of survival from predators once in the water. Mechanisms of Evolution – Variations examples:

  21. Not all members of a population are susceptible to the same illnesses, or they would all die from the same disease. Clones, which have identical genes, are all strong in the same areas and weak in the same areas. One event (drastic environmental change, new germ, loss of particular food source) could kill them all at once. Irish potato famine. Antibiotic resistance Pesticide resistance Mechanisms of Evolution – Variations examples:

  22. Many species purposely produce more offspring than they know will survive This introduces competition, so that only the members with the best adaptations survive and the less well adapted die off. The less adapted may have survived if they didn’t have to compete with so many others Mechanisms - overproduction

  23. Overproduction examples Frog eggs

  24. Overproduction examples Maple seeds

  25. Overproduction examples

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