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The Leap to Life & Evolution • • • • • Charles Darwin Evidence for Evolution Mechanisms for Evolution Natural Selection Speciation Charles Darwin • Traveled around the world on the Beagle • Most famous stop, the Galapagos Islands • Observed/recorded many species of animals. Wanted to know: “Why do some species survive, while others become extinct?” Adaptations - what are these? Any aspect that enables an organism to respond to a stimuli & SURVIVE!! Adaptations can be: structural behavioral biological (an internal process). • • • Evidence of Evolution Structural Adaptations Structural adaptations include any physical features such as the bill of a bird, the fur on a mammal, teeth, thorns… Evidence of Evolution Structural Adaptations Camouflage enables species to blend in with surroundings Kareius Bicoloratus Evidence of Evolution Structural Adaptations Mimicry one species resembles another Evidence of Evolution Behavioral Adaptations A behavior that allows better evasion of predators and survival. nocturnal herds or large groupings (schools of fish, flock of birds) migration hibernation dormancy • • • • • Evidence of Evolution Physiological Adaptations • • Changes in metabolic processes example: new strains of bacterial infections Evidence of Evolution Physiological Adaptations It begins like this... What other industries would be worried about resistance? Evidence of Evolution Physiological Adaptations Adjustment of the pupil and retina to varying degrees of illumination. ! A camel produces very concentrated urine to reduce water loss. Evidence of Evolution Fossils Evidence of Evolution Anatomy - Homologous Structures structures with common evolutionary origins similar in arrangement, function, or both evidence of evolution from a common ancestor Evidence of Evolution Anatomy - Analogous Structures structures that don’t have a common evolutionary origin, but have a similar function Evidence of Evolution Anatomy - Vestigial Structures Features that serve no function to an organism, but were perhaps useful in ancestral species. Blind fish & Cave dwelling salamanders Snake pelvis & limb bones/buds Whale femur & pelvis Ostrich wings Evidence of Evolution Anatomy - Embryos Similar features during embryological development, although full development not always of the same structure. Mammalian ear bones evolved from reptilian jaw bones. Two bones in reptilian embryos develop into a jaw. The same two bones develop into an ear in a mammalian embryo. Evidence of Evolution Biochemistry Mutation Any change or random error in a DNA sequence. Mechanisms for Evolution Genetic Drift Alteration of allelic frequencies due to chance events. Gene Flow / Migration The transport of genes by migrating individuals. Natural Selection Why those genes “make it” • it’s a mechanism for change in populations • happens when organisms with certain variations survive, reproduce, and pass their variations to the next generation Natural Selection 3 Types - Stabilizing • Favors average individuals • example: small spiders... hard to find food; large spiders... easy prey for birds Small spiders Medium spiders Large spiders Natural Selection 3 Types - Directional • Favors one of the extremes variations of a trait • example: woodpeckers with the longest beaks can feed on insects deeper inside of a tree Short Beaks Medium Beaks Long Beaks Natural Selection 3 Types - Disruptive • Favors both extremes variations of a trait • example: dark & light limpets blend easily with rocks, tan limpets easy to spot for birds of prey Light Limpets Tan Limpets Dark Limpets Speciation • The evolution of a new species. • Species - group of organisms that can interbreed to produce fertile offspring • New Species - when members of similar populations can no longer interbreed to produce fertile offspring Speciation 2 Causes - Geographic Isolation • Physical barrier divides a population • The two populations evolve in different ways, for different reasons until they are no longer populations of the same species Speciation 2 Causes - Reproductive Isolation • Formerly interbreeding organisms can no longer breed and produce fertile offspring Evolution 2 Types - Divergent • species that once were similar to an ancestral species diverge • occurs when populations adapt to difference environmental conditions • can result in new species Evolution Divergent • adaptive radiation • Darwin’s finches Evolution 2 Types - Convergent • evolution in which distantly related organisms evolve similar traits • occurs when species occupy similar environments Evolution Convergent Organ pipe cactus North & South America • unrelated and in similar environments, both developed similar attributes • further evidence for natural selection Euphorbia eritrea Africa