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Life Cycle Summary

Life Cycle Summary. Yes Yes Yes. Yes Yes Yes. Yes Yes Yes. No Yes Yes. Yes No Yes. Yes No Yes. No Yes Yes. Classically: A change in the relative frequencies of heritable traits within a population across generations Relative frequency:

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Life Cycle Summary

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  1. Life Cycle Summary Yes Yes Yes Yes Yes Yes Yes Yes Yes No Yes Yes Yes No Yes Yes No Yes No Yes Yes

  2. Classically: A change in the relative frequencies of heritable traits within a population across generations Relative frequency: 50% Tall plants 50% Short plants 55 generations later 25% Tall plants 75% Short plants Modern: A change in the distribution of relative frequencies of genes (which code for heritable traits) within a population across generations Evolution:

  3. Requirements for Evolution to occur: • Variation in traits [via genes (alleles)] • Heredity

  4. Darwin’s Observations • Biogeography: species are distributed in distinct clumps across the globe

  5. Biogeography: species are distributed in distinct clumps across the globe

  6. Fossils • Evidence of organisms no longer present

  7. Evidence that many living organisms were not present in the past. Loxodonta africana (African savannah elephant) Elephas maximus (Asian elephant) Mammuthus (mammoth) Today Stegodon Mammut (mastodon) 10,000 years ago Deinotherium 2 million years ago Platybelodon 5.5 million years ago 24 million years ago Moeri-therium Bary-therium 34 million years ago

  8. Modern Corn Agriculture: Selective breeding Ancestral Corn (genetically reconstructed)

  9. Agriculture: Selective breeding

  10. Plate tectonics Africa Cenozoic Eurasia North America India Madagascar South America Australia • Plate movements and geological studies indicated the earth was older than the estimated 6,000 years Antarctic • About 250 million years ago Laurasia Millions of years ago Gondwana Mesozoic Pangaea Paleozoic Figure 14.20

  11. Economics: Competition for resources and the effects of overpopulation • Struggle for existence

  12. Evolution by Natural Selection (a mechanism of evolution) • Population level: • If variation exists and • If variation is heritable and • If differential reproduction (differential selection) exists • Then over time, those variations that enhance the ablitiy of the organism to reproduce will increase in any population

  13. Mutation occurs in the trait An example of a spontaneous mutation during the development of plant leaves For evolution to occur via this mechanism, what has to be true of the mutation? The mutation has to be heritable • Mutation directly changes gene frequencies The mutation of fruit flies with four wings is an inherited mutation

  14. The population size is small • Genetic drift – random fluctuations in the allele frequencies Only 5 of 10 plants leave offspring Only 2 of 10 plants leave offspring Generation 3 p = 1.0 q = 0.0 Generation 1 p (frequency of R) = 0.7 q (frequency of r) = 0.3 Generation 2 p = 0.5 q = 0.5

  15. Gene flow • Immigration or emigration occurs based on the trait

  16. Sexual Selection • Mating is non-random in the population with respect to the trait

  17. Which mechanism leads to adaptation to the environment? • Natural selection: Adaptations are traits that increase the probability that an organism will survive and reproduce in the current environmental conditions.

  18. What is an adaptation? • A heritable characteristic of an organism that helps it to survive and reproduce in a particular environment. Mimicry of a poisonous animal will increase the probability of survival and survival until the organism is able to reproduce

  19. Example: Marine IguanaAdaptations do not have to be one trait, they can be a suit of traits • “The guanas are small, and of a sooty black, which, if possible, heightens their native ugliness. Indeed, so disgusting is their appearance, that no one on board could be prevailed on, to take them as food.” Captain James Colnett (1798)

  20. Flattened tail – aids in swimming • Salt gland – Allows drinking of salt water • Long, sharp claws – Aid in clinging to rocks • Diving adaptations. While diving they: • Reduce blood flow to body surface- helps retain heat • Lower metabolic rate – conserves O2

  21. Adaptation refers to traits that are heritable • Acclimation: Changes in the structure or physiology of an individual over its lifetime • Examples: • Increasing muscle mass via weightlifting • High altitude acclimation:

  22. Organizational level evolution occurs? • Living organisms display a natural hierarchy of organization and emergent properties that are more than the simple sum of their parts • Atoms lead to • Molecules, which lead to • Organelles, which are arranged within • Cells, which make up • Tissues, which make • Organs, which form • Organ systems, which together make an • Organism, which is part of a • Population within a • Community in an • Ecosystem, the largest of which is the • Biosphere(=Earth)

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