The Idea of Evolution In the 1830s, Charles Darwinvisited the Galapagos Islandsand noted that groups ofanimals varied on each island Darwin was convinced thatorganisms had changed overtime Proposed the theory ofevolution – development ofnew types of organisms frompreexisting types of organismsover time
Lamarck’s Ideas on Evolution Jean Baptiste Lamarck supported the idea thatpopulations of organisms change over time His idea was the inheritance of acquiredcharacteristics No supporting evidence and has been rejected
Darwin’s Ideas Darwin published a book – On the Origin ofSpecies by Means of Natural Selection in 1859proposing a new theory for the way evolution tookplace Goals of the book: Present the large amount of evidence that evolution occurs Explain the variety and distribution of organisms on Earth interms of natural selection processes that are observableeveryday
Descent with Modification Darwin reviewed evidence that every species –living or extinct – must have descended byreproduction from preexisting species and thatspecies must be able to change over time First to argue that all species had descendedfrom only one or a few original kinds of life
Evidence of Descent withModification Galapagos Islands are hometo 13 different species offinches Each has a beak that is bestadapted for a certain kind offood Darwin suspected that alldescended from one commonancestor The ancestors could haveflown from elsewhere afterthe islands were formed
Natural Selection Darwin proposed natural selection as themechanism for descent with modification
Natural Selection Overproduction More offspring can be produced than can live tomaturity Genetic Variation Within a population, individuals have different traits– some can be inherited. Occasionally, new traitsmay appear in a population.
Natural Selection Struggle to survive Individuals must compete with each other forresources Some variations increase and individual’s chance tosurvive and reproduce Adaptation – a trait that makes an individual successfulin its environment
Natural Selection Differential Reproduction Organisms with the best adaptations are most likelyto survive and reproduce Through inheritance, the adaptations will becomemore frequent in a population Populations may begin to differ as they adapt todifferent environments, even if they descended fromthe same ancestor
The Fossil Record Fossil – the remains or traces of an organismthat died long ago Among the most powerful evidence of evolution
The Age of Fossils Relative age – possible to tell a fossil’s age bycomparing it to that of other fossils
The Distribution of Fossils From the fossil record we can infer: Different organisms lived at different times Today’s organisms are different from those of thepast Fossils found closer together are more like eachother than ones found further away Where and when different organisms existed
Transitional Species The fossil recordshows that specieshave differed in agradual sequence offorms over time
Biogeography Biogeography – the study of the locations oforganisms around the world Darwin and Wallace observed species thatseemed closely related but were adapted todifferent environments in nearby regions They also observed animals that seemedunrelated but had similar adaptations to similarenvironments in regions that were far apart
Anatomy and Embryology Anatomy – the study of the body structure oforganisms Embryology – the study of how organismsdevelop As generations passed, different populations ofdescendants adapted to different environments Homologous structures- structures that occur indifferent species and that originated by heredityfrom a structure in the most recent commonancestor of the species Analogous structures – closely related functionsbut do not derive from the same ancestral
Anatomy and Embryology Vestigial Structures– structures that seemto serve no functionbut that resemblestructures withfunctional roles inrelated organisms Development ofanimal embryos –some stages ofvertebrate embryodevelopment are veryalike
Biological Molecules In all species, DNA and RNA are the molecularbasis for inheritance of traits Scientists can compare the DNA, RNA, andproteins from many different organisms and lookfor similarities and differences The greater number of similarities, the moreclosely the species are related through a commonancestor
Convergent Evolution Convergent Evolution – the process by whichdifferent species evolve similar traits Example: Caribbean Anole Lizards
Convergent Evolution Many different body types on different islands anddifferent species have the same body types Lizards that live on tree trunks have stocky bodiesand long legs Lizards that live on slender twigs have thin bodies,short legs and tails, and large toe pads Lizards that live in the grass are slender and havevery long tails How did all of this happen?
Convergent Evolution Each species evolved independently on eachisland from different ancestor species
Divergent Evolution Divergent evolution – Process in whichdescendants of a single ancestor diversify intospecies that each fit different parts of theenvironment Ex: Lizards with genes for large toe pads and shortlegs ran so slowly on the trunk and ground thatpredators often caught them
Artificial Selection Artificial Selection –process when ahuman breederchooses individualsthat will parent thenext generation
Coevolution Coevolution – when two or more species haveevolved adaptations to each other’s influence Ex: Humans develop and use antibiotics to killbacteria, many populations of bacteria have evolvedto resist the effects of antibiotics
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