Darwin and the development of the theory The Theory of Evolution

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. There is variation within a population 2. Some variations are good (helpful) 3. 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 wingsBat wingBird 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 Light moths Dark moths Light tree Dark tree Less pollution More pollution

The End