History of Biological Diversity Evolution: Darwin’s travel

Developing the Theory of Evolution The Galápagos Islands Darwin noticed that the different islands all seemed to have their own, slightly different varieties of animals. Somewhat similar species that suited their particular environment. Copyright © McGraw-Hill Education Darwin’s Theory of Evolution by Natural Selection

Origin of Species: Darwin’s Book In 1859 On the Origin of Species presented evidence and proposed a mechanism for evolution that he called natural selection.

Video of Darwin http://www.wfisd.net/Page/13303

Natural Selection is Survival of the fittest Natural selection is a process of elimination ORGANISMS THAT HAVE TRAITS THAT ARE BEST ADAPTED FOR THE CURRENT ENVIRONMENT ARE THE ONES THAT SURVIVE TO BREED AND PASS ON THEIR GENES TO THE NEXT GENERATION, CAUSING A CHANGE IN THE OVERALL POPULATION. Organisms not possessing the beneficial traits either die or don’t have as many offspring. Natural Selection is Survival of the fittest Biological fitness- ability of an organism to survive AND reproduce (pass on its genes)

Main Points of Natural Selection Genetic Variation is present in the population and it is inherited (passed to offspring) -Mutations: Changes in the DNA -Meiosis: crossing over -Random mate selection & fertilization Living Things Overproduce Offspring (not all survive) Competition for Limited Resources Survival of the “Fittest”

Natural Selection Fitness Differential Reproductive Success Genetic Limited Resources Genetic Variation Fitness Competition Organisms produce more offspring than can survive. Environmental Factors Differential Reproductive Success Natural Selection Differential reproduction is the idea that those organisms best adapted to a given environment will be most likely to survive to reproductive age and have offspring of their own Make sure students know the definitions to the following terms: genetic variation, fitness, competition, resources, and environmental factors. Take time to explain how the various components lead to DRS.

Adaptations-a change or the process of change by which an organism or species becomes better suited to its environment. Types of adaptations Camouflage is a suite of morphological adaptations that allow an organism to blend into its environment. Mimicry is a type of morphological adaptation where a species evolves to resemble another species. Antibiotic resistance develops in some bacteria,making them able to survive antibiotic treatments Mimicry Camouflage

Peppered Moth: Natural Selection The light colored form was the predominant form in England prior to the Industrial Revolution. Around the middle of the 19th century the darker form began to appear. It was first reported in 1848. By 1895 98% of the moths in Manchester were the dark variety. In recent years, the burning of cleaner fuels and Clean Air regulations has reduced the pollution there and the lighter colored moths have increased in numbers.

Natural Selection is Survival of the fittest Natural selection is a process of elimination ORGANISMS THAT HAVE TRAITS THAT ARE BEST ADAPTED FOR THE CURRENT ENVIRONMENT ARE THE ONES THAT SURVIVE TO BREED AND PASS ON THEIR GENES TO THE NEXT GENERATION, CAUSING A CHANGE IN THE OVERALL POPULATION. Organisms not possessing the beneficial traits either die or don’t have as many offspring. Natural Selection is Survival of the fittest Biological fitness- ability of an organism to survive AND reproduce (pass on its genes)

Crossing Over Mutations Natural Selection Gene Flow Genetic Drift Recombination Gene Flow Genetic Drift Mutation Selection Gene Flow Genetic Drift

Recombination: Crossing Over Crossing over leads to genetic variation. Crossing over is why siblings can have the same parents but still may look very different (except for identical twins etc.).

Not every mutation has a visible effect. Mutation & Variation Mutation creates variation new mutations are constantly appearing Mutation changes DNA sequence changes amino acid sequence changes protein’s: Structure function changes in protein may change phenotype & therefore change fitness Every individual has hundreds of mutations 1 in 100,000 bases copied 3 billion bases in human genome But most happen in introns, spacers, junk of various kind Not every mutation has a visible effect. Some effects on subtle. May just affect rate of expression of a gene.

Gene Flow Movement of individuals & alleles in & out of populations seed & pollen distribution by wind & insect migration of animals sub-populations may have different allele frequencies causes genetic mixing across regions reduce differences between populations

Genetic drift Effect of chance events founder effect bottleneck small group splinters off & starts a new colony Skews the gene pool of the new population bottleneck some factor (disaster) reduces population to small number & then population recovers & expands again alleles lost from gene pool, narrows the gene pool 1 family has a lot of children & grandchildren therefore has a greater impact on the genes in the population than other families Genghis Khan tracked through Y chromosome.

How Evolution Occurs There are two scientific theories regarding how evolution occurs. Punctuated Equilibrium: This theory proposes that throughout geological time, biological species go through long periods of little change and then have brief periods of rapid change. Gradualism: This theory proposes that throughout geological time, biological species gradually undergo changes that leads to speciation. This will be explored more in the next lesson.