Chapter 17 Evidence of Evolution AP Biology Spring 2011.

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