Chapter 17Chapter 17Evidence of Evolution
AP Biology Spring 2011
Darwin RevolutionDarwin RevolutionTraditional belief that Earth was
only a few thousand years old and was populated by forms of life that had been created at the beginning and remained unchanged
Darwin RevolutionDarwin RevolutionAristotle: trying to
categorize and organize living things◦Chain of Being: organized life
from lower to higher forms Comparative Morphology: focused on revealing similarities and differences in body plans and structure of organisms
Darwin RevolutionDarwin RevolutionCuvier: suggested that abrupt
changes in the fossil record in different rock strata reflected the concept of catastrophism
Catastrophism: dramatic geological changes unlike what we see today, after each catastrophe fewer species remained
Darwin RevolutionDarwin RevolutionJean-Baptiste de Lamarck:
developed an early theory of evolution, which in part stated that characteristics acquired during an organisms lifetime could be passed on to the next generation◦Modern understanding of genetics
provides no evidence that this is possible!!
◦Giraffe example
Darwin RevolutionDarwin RevolutionLyell: proposed a theory of
uniformity◦The notion of a gradual, lengthy
molding of the earth’s geologic structure
Malthus: suggested that populations are limited in size by the resources available ◦If some resources were scarce there
would be comptetition
Darwin RevolutionDarwin RevolutionAlfred Wallace: studying
geographic distribution of species in the Amazon ◦Sent his work to Darwin for advice
Darwin RevolutionDarwin RevolutionDarwin’s view of life as expressed in The
Origin of Species (1859) contrasted sharply with traditional beliefs
Natural Selection: a population can change over generations if individuals with certain heritable traits produce more viable offspring than other individuals
Evolutionary Adaptation: accumulation of inherited characteristics that enhance organisms’ ability to survive and reproduce in specific environments ◦ Result of natural selection ◦ Natural selection is a mechanism for evolution
Darwin RevolutionDarwin RevolutionTaxonomy: branch of biology
dedicated to the naming and classification of all forms of life
Binomial Nomenclature: two-part naming system that includes the organism’s genus and species ◦Carolus Linnaeus
Darwin RevolutionDarwin RevolutionFossils: found in sedimentary
rock, are remains or traces of organisms from the past◦Provide evidence for the theory of
evolution Paleontology: study of fossils
Darwin RevolutionDarwin RevolutionGradualism: geological theory
that sates that profound changes in Earth’s features over the course of geological time are the result of slow, continuous processes
Uniformetarianism: geological processes that have shaped the planet have not changed over the course of Earth’s history
Natural SelectionNatural SelectionCharles Darwin’s voyage on the
HMS Beagle in 1831 was impetus for the development of his theory of evolution◦Botanist John Henslow arranged for Darwin
to sail around the world as ship’s naturalist Descent with Modification: refers to
Darwin’s idea that all living organisms are related by descent (they evolved) from a remote common ancestor
Remote Common Ancestor
Natural SelectionNatural SelectionTheory of Natural Selection:
◦ Natural Selection is the differential success in reproduction (the unequal ability of individuals to survive and reproduce) that results from the interaction between individuals that vary in heritable traits and their environment
◦ Natural Selection can produce an increase over time in the adaptation of organisms to their environment
◦ If an environment changes over time, or if individuals of a particular species move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species
Natural SelectionNatural SelectionMajor Points:Observations about populations:
◦Populations have the reproductive capacity to increase in numbers over generations
◦As populations expand, resources will dwindle; individuals will run out of food, living spaces, and other resources
◦Individuals will end up competing for dwindling resources
Natural Selection Natural Selection Observations about genetics:
◦Individuals of a certain species share certain traits (gene pool)
◦Individuals of a natural population vary in details of their shared traits (different alleles for a gene)
◦Traits have a heritable basis, in genes. New variations arise from mutations.
Natural SelectionNatural SelectionInferences:
◦Certain forms of a shared trait may make the bearer more competitive for scarce resources
◦Individuals better able to secure scarce resources tend to produce more offspring
◦Alleles associated with an adaptive trait become more frequent in a population
Natural SelectionNatural SelectionHow can we explain the giraffe
through natural selection?
Natural SelectionNatural SelectionArtificial Selection: process by
which species are modified by humans◦Plants and animals are specifically
chosen to breed with the desired goal of producing offspring with specific characteristics
Natural SelectionNatural SelectionPopulation: group of interbreeding
individuals who live in a certain geographic area◦ Smallest unit that can evolve ◦ Individuals cannot evolve
Natural selection can only work on heritable traits (traits passed from organism to offspring)
Darwin’s Theory Explains a Darwin’s Theory Explains a Range of Observations Range of Observations Explains changes in living populations
◦Ongoing evolution of drug-resistant bacteria
Homology: related species share characteristics resulting from common ancestry
Homologous Structures: variations on a structural theme and are anatomical signs of evolution◦Ex. Forelimbs of mammals that are now
used for a variety of purposes◦Can you think of any examples?
Homologous Structures: variations on a structural theme and are anatomical signs of evolution◦Ex. Forelimbs of
mammals that are now used for a variety of purposes
Darwin’s Theory Explains a Darwin’s Theory Explains a Range of Observations Range of Observations Vestigial Organs: structures of
marginal, if any, importance to the organism ◦Remnants of structures that served
important functions in the organisms’ ancestors
◦Ex. Pelvis and leg bones found in some snakes
Darwin’s Theory Explains a Darwin’s Theory Explains a Range of Observations Range of Observations Molecular Homologies: shared
characteristics on the molecular level◦Use of the same genetic code written
in DNA or other molecular similarities◦Because genetic code is shared by
all organisms, it s likely that all species descended from a common ancestor
Darwin’s Theory Explains a Darwin’s Theory Explains a Range of Observations Range of Observations Biogeography: refers to the
geographic distribution of species Species that live closer together
tend to be more closely related than those that do not
Species that are endemic to a certain geographic location are found at that location and nowhere else
Darwin’s Theory Explains a Darwin’s Theory Explains a Range of Observations Range of Observations Darwin’s theory of evolution
through natural selection explains the succession of forms in the fossil record
Transitional fossils have been found that link ancient organisms to modern species, just as Darwin’s theory predicts
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