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Unit 3 Notes
 

Unit 3 Notes

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    Unit 3 Notes Unit 3 Notes Presentation Transcript

    • BIODIVERSITY
    • Biodiversity Unit 2 - Biodiversity Estimates of the number of species that inhabit our planet run as high as 10 million! That means 10 million different kinds of organisms. That number certainly suggests a lot of variety. That is what diversity means--variety. When we say "biodiversity," we refer to the variety of life.
    • Evolution
      • a . The theory that groups of organisms change with passage of time, mainly as a result of natural selection, so that descendants differ morphologically and physiologically from their ancestors. b . The historical development of a related group of organisms; phylogeny.
      Unit 2 - Biodiversity
    • Evolution Unit 2 - Biodiversity
    • The Story of Charles Darwin Unit 2 - Biodiversity
    • The Story of Charles Darwin Unit 2 - Biodiversity
    • Organic Evolution
      • Organic evolution is defined as change in genetics of a population over time (generations)
      • A population refers to all individuals of the same species living in a defined area at the same time.
      Unit 2 - Biodiversity
    • Organic Evolution Unit 2 - Biodiversity
    • Organic Evolution
      • Organic evolution can be studied at two different levels:
        • microevolution, which refers to small-scale genetic changes within populations
        • macroevolution, which refers to the large-scale results of genetic changes in populations, including the formation of new species and the evolution of large scale trends seen across species in what traits they have.
      Unit 2 - Biodiversity
    • MICROEVOLUTION:
      • Microevolution occurs through several mechanisms. The first of these that was discovered, and the form which is best known, is natural selection. It was discovered independently by Charles Darwin and Alfred Russel Wallace.
      • Natural selection is evolution that occurs because individuals with some traits survive and reproduce better than do individuals with other traits. As a result, those traits that result in high survival and reproduction are passed from generation to generation, through reproduction, at a higher rate than are other traits. These traits become increasingly more and more common in populations.
      Unit 2 - Biodiversity
    • MICROEVOLUTION:
      • There are four properties of a population that, together, result in natural selection. These are:
          • Individuals in a population vary in their characteristics. This is also generally observed in species; individuals are not identical to one another.
          • Many of the differences are heritable genetic differences .
      Unit 2 - Biodiversity
    • MICROEVOLUTION:
        • The differences among individuals are based on genetic differences. We know the genetic basis for many traits in natural populations and often have observed that the differences among individuals are present because of genetic differences.
        • Individuals with some characteristics survive and reproduce better (have higher fitness) than do individuals with other characteristics. This has now been observed in hundreds of populations.
      Unit 2 - Biodiversity
    • MICROEVOLUTION:
      • If these four postulates are all true of a population, they result in natural selection; those individuals with higher fitness end up being the ones who survive each generation, and as a result reproduce more (you don't reproduce when you're dead); since the traits are genetic, they get passed on to the next generation, and therefore become more common than they were in the previous generation.
      Unit 2 - Biodiversity
    • Microevolution Unit 2 - Biodiversity
    • MACROEVOLUTION:
      • Speciation refers to the formation of new species; it occurs when one ancestral species evolves into more than one (typically two) descendant species.
      • Species are typically defined as groups of organisms that are so similar to each other that they can reproduce and produce healthy fertile offspring. If organisms belong to different species, they can't reproduce with each other or, if they do, their offspring die or are sterile.
      Unit 2 - Biodiversity
    • MACROEVOLUTION:
      • Since speciation occurs when one species evolves into more than one new species, it increases the number of species that exist. Note that evolution does not necessarily cause speciation -- for example, peppered moths evolved from gray to black but no new species were formed.
      • Phylogeny refers to the evolutionary history of species, or history of speciation; it refers to the family tree of all life, indicating how all living things are related. It is typically diagrammed as a tree.
      Unit 2 - Biodiversity
    • The Hardy-Weinberg Principle
      • The Hardy-Weinberg Principle is a mathematical model that deals with the frequencies of alleles in a gene pool. If the allelic frequency does not change in a population over successive generations, then evolution does not occur and the population is at equilibrium. Several conditions must be met in order to maintain this equilibrium.
      Unit 2 - Biodiversity
    • The Hardy-Weinberg Principle Unit 2 - Biodiversity
    • The Hardy-Weinberg Principle
      • Several conditions must be met in order to maintain this equilibrium. They are:
          • No mutation occurs so that the alleles do not change.
          • All reproduction must be totally random so that one form of the allele is not selected for over another.
          • All forms of the allele must reproduce equally well so that there is no natural selection.
          • Immigration and emigration do not occur as they would alter the gene pool.
          • The population must be large so that changes do not happen by chance alone.
      Unit 2 - Biodiversity
    • The Hardy-Weinberg Principle
      • In real life these conditions are virtually never met.
      • Hardy-Weinberg law gives us a baseline by which to assess whether or not evolution has occurred
      • Any change in allele frequencies indicates evolution.
      Unit 2 - Biodiversity
    • The Hardy-Weinberg Equation
    • Process of Evolution
      • Knowing it is virtually impossible to meet the five conditions of the Hardy Weinberg Principle, what situations or events may alter a gene pool?
      Unit 2 - Biodiversity
    • Process of Evolution
      • Five agents of evolutionary change
        • Natural Selection
        • Gene Flow
        • Non-random Mating
        • Mutations
        • Genetic drift
      Unit 2 - Biodiversity ?
    • Process of Evolution
      • Five agents of evolutionary change
        • Natural Selection
          • Natural selection affects variation in a population as the better adapted (more fit) individuals survive and reproduce, passing on their genes to successive generations.
        • Gene Flow
          • Immigration and emigration of individuals from a population will affect allele frequencies and therefore gene flow.
          • In immigration, new genes are added to the existing gene pool; in emigration, genes are removed.
        • Non-random Mating
          • In animals, non-random mating is more often the case as the choice of mates is often an important part of behaviour (e.g. courtship rituals). Many plants self-pollinate, which is a form of inbreeding or non-random mating.
      Unit 2 - Biodiversity
    • Process of Evolution
      • Five agents of evolutionary change
        • Mutations
          • Mutations, although rare, do constantly occur. They provide the source of new alleles, or variation upon which natural selection can take place
        • Genetic drift
          • The change in the gene pool of a small population due to random chance is genetic drift.
          • 2 main mechanisms
            • Founder effect -a few individuals found a colony and their collective genes represent only a fraction of the original gene pool
            • Bottleneck effect -population is subjected to near extinction by a disaster and so only a few genotypes contribute to next generation
      Unit 2 - Biodiversity
    • Process of Evolution Unit 2 - Biodiversity
    • Process of Evolution
      • In groups of 2 students, find a concrete example for each of the 5 factors that can cause genetic variation.
      • Report and present this example using Prezi.
      Unit 2 - Biodiversity
    • Process of Evolution
      • Population Bottlenecks & Endangered Species Case Study
      Unit 2 - Biodiversity
    • Speciation
      • Overview
        • Species
        • A group of interbreeding subpopulations that share a gene pool and are isolated reproductively from other species
      Unit 2 - Biodiversity
      • Process of speciation
        • Occurs when on species give rise to two species
          • Occurs when reproductive isolation develops
        • Allopatric speciation - geographical barriers separate a population into 2 groups
        • Sympatric speciation - occurs without geographical barriers
      Unit 2 - Biodiversity
    • Speciation (Section 27.4 Page 563) Unit 2 - Biodiversity
    • Allopatric speciation Unit 2 - Biodiversity
      • Allopatric Speciation
        • When a part of a population becomes geographically isolated from the parent population, allopatric speciation can occur. Geographic isolation can occur due to the formation of physical barriers such as mountains, canyons, rising sea levels, glaciers etc.
        • The physical barrier prevents gene flow between the two populations. If the different populations are subjected to different natural selection pressures, allele frequencies for genes will change.
        • The two populations may accumulate substantial genetic differences so that they become reproductively isolated and are unable to interbreed. Two distinct species therefore result.
      Unit 2 - Biodiversity
      • Sympatric Speciation
        • When the gene flow between members of a population is restricted due to ecological isolation (niche differentiation), sympatric speciation can occur.
        • Some members of a population may be better adapted to a slightly different habitat in an ecosystem, and begin to specialize in that habitat. Different selective pressures in the two habitats lead to genetic changes in the organisms.
        • The two populations become reproductively isolated, and two distinct species result, even though there are no physical barriers separating the population.
      Unit 2 - Biodiversity
      • Divergent vs Convergent Evolution
        • Divergent evolution (adaptive radiation) is the process of two or more related species becoming more and more dissimilar.
        • The red fox and the kit fox provide and example of two species that have undergone divergent evolution. The red fox lives in mixed farmlands and forests, where its red color helps it blend in with surrounding trees. The kit fox lives on the plains and in the deserts, where its sandy color helps conceal it from prey and predators. The ears of the kit fox are larger than those of the red fox. The kit fox's large ears are an adaptation to its desert environment. The enlarged surface area of its ears helps the fox get rid of excess body heat. Similarities in structure indicate that the red fox and the kit fox had a common ancestor. As they adapted to different environments, the appearance of the two species diverged.
      Unit 2 - Biodiversity
      • Divergent Evolution Example
        • Galapagos Islands finches- studied by Darwin
          • Example of divergent evolution (adaptive radiation)
          • Mainland finches migrated to one of the islands
            • Reproduced and eventually spread to all the islands
            • Subjected to different environmental selection pressures
          • Gave rise to many species of finches which differ primarily in beak shape
            • Adapted to allow use of different food sources
      Unit 2 - Biodiversity
      • Divergent vs Convergent Evolution
        • Convergent evolution is the process in which different organisms that live in similar habitats become more alike in appearance and behaviour. As they encounter similar environmental pressures, the organisms develop analogous structures.
        • For example, dolphins and sharks live in the water and both use their tails for propulsion. However, their tails are analogous structures with different origins. Sharks move their tails side to side, while dolphins move their tails up and down. Similarly, bat, butterfly and bird wings are analogous structures.
      Unit 2 - Biodiversity
      • The Pace of Speciation - Two Hypotheses
        • Phyletic gradualism-change is slow but steady before and after a divergence
          • Explains why so few transitional fossils are found
          • Reproductive isolation cannot be detected in fossils
        • Punctuated equilibrium-stasis is punctuated by speciation
          • Occurs relatively rapidly
          • Also can explain lack of transitional fossils
            • Rapid development of changes does not result in recognizable transitional links
      Unit 2 - Biodiversity
    • Speciation (Section 27.4 Page 563) Unit 2 - Biodiversity
      • Phyletic Gradualism vs
      • Punctuated Equilibrium
        • Gradualism and punctuated equilibrium are two hypothesis in which the evolution of a species can occur. A species can evolve by only one of these, or by both. Scientists think that species with a shorter evolution evolved mostly by punctuated equilibrium, and those with a longer evolution evolved mostly by gradualism.
      Unit 2 - Biodiversity
      • Phyletic Gradualism vs
      • Punctuated Equilibrium
        • Gradualism is selection and variation that happens more gradually. Over a short period of time it is hard to notice. Small variations that fit an organism slightly better to its environment are selected for: a few more individuals with more of the helpful trait survive, and a few more with less of the helpful trait die. Very gradually, over a long time, the population changes. Change is slow, constant, and consistent.
      Unit 2 - Biodiversity
    • Phyletic Gradualism Unit 2 - Biodiversity
      • Phyletic Gradualism vs
      • Punctuated Equilibrium
        • In punctuated equilibrium, change comes in spurts. There is a period of very little change, and then one or a few huge changes occur, often through mutations in the genes of a few individuals.
      Unit 2 - Biodiversity
      • Phyletic Gradualism vs
      • Punctuated Equilibrium
        • Mutations are random changes in the DNA that are not inherited from the previous generation, but are passed on to generations that follow. Though mutations are often harmful, the mutations that result in punctuated equilibrium are very helpful to the individuals in their environments. Because these mutations are so different and so helpful to the survival of those that have them, the proportion of individuals in the population who have the mutation/trait and those who don't changes a lot over a very short period of time. The species changes very rapidly over a few generations, then settles down again to a period of little change.
      Unit 2 - Biodiversity
    • Punctuated Equilibrium Unit 2 - Biodiversity
    •