Chapter 17 Evidence of Evolution AP Biology Spring 2011

Darwin Revolution Traditional 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 Revolution Aristotle: 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 Revolution Cuvier: 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 Revolution Jean-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 Revolution Lyell: 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 Revolution Alfred Wallace: studying geographic distribution of species in the Amazon Sent his work to Darwin for advice

Darwin Revolution Darwin’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 Revolution Taxonomy: 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 Revolution Fossils: 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 Revolution Gradualism: 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 Selection Charles 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 Selection Theory 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 Selection Major 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 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 Selection Inferences: 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 Selection How can we explain the giraffe through natural selection?

Natural Selection Artificial 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 Selection Population: 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 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 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 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 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 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