The Theory of Evolution

The Theory of Evolution Darwin and the development of the theory What is a SPECIES?  Group of similar organisms – Structurally – biochemically  Can interbreed successfully in nature – Offspring are healthy – Offspring are fertile (can reproduce) These organisms are not new species…Why?  Mule  Liger Variation  Variation – differences between individual members of a population Members of a species are very similar, but differences can be observed, or not, make each individual unique.   May be caused by mutations Mutations  Changes in DNA base sequences Most are either neutral or harmful   Those that allow the organism to survive better in a particular environment are good and are more likely to be passed on to future generations. Most variations are not caused by mutations  Sexual reproduction combines genes from different parents  Crossing over during meiosis can produce variations Adaptation An inherited trait that increases the population’s chances of survival and reproduction in a particular environment.  Allows organisms to fit best into a particular niche (habitat and role)  Biodiversity    The variety and abundance of species that makes up a biological community. Pine Barrens forests have little biodiversity – a limited number of species can survive there. Tropical rain forests have great biodiversity – many species in a concentrated area. Organisms have changed over time to produce so many different forms of life Theories accepted before Darwin  1769 – Bonnet – theorized that fossils were from animals/plants that lived before catastrophes that made them extinct. Jean Baptiste Lamarck Use and disuse  Inheritance of acquired characteristics  Darwin and his theory  Charles Darwin lived in early-mid 1800’s.  Went on voyage around the world as the ship’s naturalist – collected specimens of plants and animals during the 5+year-journey. Darwin’s Voyage Galapagos Islands Darwin’s route Darwin Returned Home to Think!  These influenced his development of the theory: – Evidence that the 13 different species of finches found in the Galapagos Islands were the descendents of one species. – HERE ARE JUST A FEW BEAK TYPES: Artificial selection – farm animals and plants – Population control – population limited by resources and nature controls it by killing off some members during natural disasters, illness (epidemics), blights in plants, etc. – Geologic evidence of slow changes Darwin’s Theory of Evolution by Natural Selection 1. 2. 3. There is variation within a population Some variations are good (helpful) Not all young produced in a generation can survive – – – This leads to a struggle for existence. Survival of the fittest. Those that survive and reproduce are those with the good variations. Evidence supporting Evolution  Fossils – remains of plants or animals that lived before – can show structures Homologous Structures – similar in structure, but have different functions Vestigial Structures Inherited  But, reduced in size and often not used.  – Examples  Snake legs (they’re so reduced in size that they are not apparent).  Human appendix –no function, except can cause problems.  Human coccyx – tail bone. Analogous Structures  Similar in function, but very different in structure – indicate organisms are not closely related Insect wings Bat wing Bird wing Embryological Evidence  If organisms have similar embryos, they are more closely related than those with less similar embryos Sea lamprEy pond turtle chicken cat human Origin of Species  Speciation – evolution of one or more species from a single ancestor species. can be from: – isolation – usually because of a geographic barrier such as a canyon, mountain, or island Divergent Evolution  Isolated populations of a species evolve independently of each other. – Ex – polar bears and brown bears Convergent Evolution  Natural Selection produces analagous (similar) adaptations in different organisms in response to similar environments: – African Serval cat & south american maned wolf – See text p 242 – These animals have similar ears, legs, acute hearing, habitat, and Occupy similar niches Coevolution  Species that interact closely often adapt to one another: Adaptive Radiation  Many different species evolve from one ancestral species – each new species has a different niche Evolution Observed: Peppered Moths Less pollution More pollution Light moths Dark moths Light tree Dark tree The End