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Biodiversity Balance Between Speciation and extinction What is biodiversity? • Type 1: Total number of species in world • Type 2: Genetic variation within and between species. • Type 3: Ecosystem biodiversity: huge variety of ecosystems and habitats Total number of species • What patterns do you see? • How do you think scientists estimate the ``unnamed species’’? Genetic biodiversity • European sheep breeders protecting genetic diversity of their breeds. These are all one species • These are all different species • Genetic biodiversity • For example, humans are one species, but we have a great variety of variation in many genes, such as blood type • Each species has thousands of genes Ecosystem biodiversity What is an ecosystem?? • A community of organisms, its abiotic environment, and their interactions Levels of ecological organization • Biosphere: all life on Earth and the life-supporting region of Earth • Ecosystem • Community? – Populations of different species in the same area or habitat • Population? – Group of individuals of same species in same area or habitat Origin of biodiversity • EVOLUTION • Simple definition: Descent with modification – Includes microevolution: changes in gene frequency from one generation to the next • Includes macroevolution: descent of different species from a common ancestor Natural Selection • Darwin’s big contribution • Inherently logical: – – – – Organisms produce more offspring than survive Individuals vary in important characteristics Many characteristics are inherited SO: • some individuals will be better suited to the environment • Those individuals will be more likely to survive and reproduce • Their offspring likely to be more suited to the environment Definition of evolution • Descent with modification – KEY: Evolution proceeds by changes in genes • NOT JUST: ``Change over time’’ – Lots of things change over time: • Trees change color • Mountains erode • Continents move – These are NOT evolution Evolution is NOT • Just a process of getting better • Something that organisms TRY to do Geneology: sharing a common ancestor • Evolution: sharing a common ancestor • Natural Selection • Darwin’s big idea • HOW evolution can happen • Follows logically from some simple ideas: Logic of natural selection • Organisms produce more offspring than can survive. – Even elephants—if all survived . . . • Often, these differences are due to differences in the genes and therefore can be inherited Logic of natural selection • Individuals vary in their characteristics Logic of natural selection • Often, these differences are due to differences in the genes and therefore can be inherited Logic of natural selection -2 • As a result of individuals inheriting characteristics from parents: – Some individuals will be better suited to their environment than others – These better-suited individuals produce more offspring that survive • They may survive longer to reproduce • They may produce more offspring • They may produce offspring of higher quality Logic of natural selection - 3 • As a result of some individuals producing more fit offspring: – Future generations will contain more genes, and more characteristics, of the better-suited individuals. – Better suited are called ``more fit’’ Natural selection doesn’t mean: • Only the strong survive NO – Sometimes, other ways of being fit (e.g., hiding) • Only the best-suited individuals survive NO – Many types may survive. Over long periods, the more fit will leave more offspring. Natural Selection • Often MIScharacterized as ``evolution by random chance’’ • What IS random about natural selection? – The production of variation by mutation and genetic recombination Adaptations • Traits that are successful in their environment • An adaptation to one environment may be NEUTRAL or UNFAVORABLE in another environment • May be simple—heavier coat in colder climate—or complex—the mammalian eye Again: • Adaptations are specific to the environment. – A zebra’s coat pattern is camouflage in the African savannah. It would not be advantageous in a North American grassland. – Running speed is advantageous for a cheetah on the savannah. But cats in the rainforest (e.g., jaguar) are not fast. Strength and stealth are more important than speed there. • Adaptation examples: mimicry • Some orchids have evolved to mimic wasps, fooling other wasps to ``mate’’ with them and thus transfer their pollen Adaptation examples: more mimicry • • Katydids have evolved a body form that looks like a leaf. • Why? What is the advantage to the katydid? Adaptation examples: still more mimicry • Non-poisonous king snakes mimic poisonous coral snakes • Many examples of mimicry in nature • Speciation • One species evolves into another OR splits into two. • How can this happen? – Geographic isolationallopatric speciation • • History of life • As previous picture shows: – Complex creatures and structures have evolved – But simple life forms still common and dominate in many habitats ``Earth still belongs to the bacteria’’ – Speciation generates diversity; extinction reduces it Extinction • The disappearance of a species from Earth • Local disappearance is called extirpation • •