Download Chapter 22: Descent w/ Modification Aristotle (384

Chapter 22: Descent w/ Modification
Aristotle (384-322 BC)
 Greek philosopher
 Viewed species as fixed & unchanging
 Scala Naturae – ladder arrangement; more complex organisms on higher rungs
Carolus Linnaeus (1707-1778)
 Species are matched to their environment = evidence of Divine Creation
 Created taxonomy for classifying organisms (Binomial naming = Genus species…Homo sapiens)
Jean-Baptiste de Lamarck (1744-1829)
 French Biologist, published in 1809
 Species evolve thru use & disuse of body parts & inheritance of acquired characteristics (Giraffe’s neck)
 Mechanisms he proposed are unsupported by evidence
Georges Cuvier (1769-1832)
 French scientist; developed Paleontology (the Study of fossils)
 Old strata had different life forms than present day; species disappeared & new ones appeared
 Catastrophism – Each boundary b/w strata represents a catastrophe
James Hutton (1726-1797)
 Scottish geologist
 Said earth’s geologic features explained by gradual mechanisms still operating today
o e.g. valleys formed by rivers wearing thru rocks
Charles Lyell (1797-1875)
 Believed in Hutton’s gradual changes
 Uniformitarianism
o Mechanisms of change are constant over time, so today’s rate is same as past
Hutton/Lyell to Darwin
 Most believed Earth was a few thousand years old
o If rivers made canyons in slow gradual change, then Earth older
 If slow change works in geology, why not biology
Charles Darwin (1809-1882)
 Studied medicine & then theology at Cambridge University
 After graduation, took unpaid job as naturalist on the Beagle (5 yr voyage)
o Collected specimens of South American plants & animals
o Observed adaptations of species that inhabited diverse environments
 1844 – Darwin wrote essay on origin of species & natural selection; anticipates uproar, doesn’t publish
 1858 – Gets manuscript from Alfred Russell Wallace; proposed similar theory of natural selection
 Darwin quickly finished The Origin of Species & published it the next year
The Origin Of Species
 Developed two main ideas:
o Descent with modification: explains life’s unity & diversity
o Natural selection is a cause of adaptive evolution
 Darwin described 4 observations of nature & drew 2 inferences…
o Observation #1 – members of a population often vary greatly in their traits
o Observation #2 – traits are inherited from parents to offspring
o Observation #3 – all species are capable of producing more offspring than environment can support
(Malthus)
o Observation #4 – owing to lack of food or resources, many of these offspring don’t survive
o Inference #1 – Individuals whose inherited traits give them a higher probability of surviving &
reproducing in an environment tend to leave more offspring than others
 Individuals that are well suited to their environment tend to leave more offspring than other
individuals
o Inference #2 – unequal ability of individuals to survive & reproduce will lead to accumulation of
favorable traits in population over generations
 Over time, favorable traits accumulate in the population
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Steps to Evolution (Unknown to Darwin)
o Mutation – DNA change
 Reproductive cell
 Spontaneous or mutagens
 Genetic Recombination
o Natural Selection
 Adaptation allows organism to leave more offspring
o Time – many generations pass
Evolution Evidence
 Artificial Selection
o Darwin noted that humans have modified other species
o Selectively breeding individuals w/ desired traits
 e.g. dogs, cattle, crops
 Peppered Moth Populations
o England (normally) has light colored trees; light moths dominant
o Industrial revolution causes trees to be soot-covered; dark moths dominant
 HIV (Human Immunodeficiency Virus)
o Retro-virus; genetic material is RNA
o Evolution of Drug-Resistant HIV
 Reverse transcriptase (RT) makes DNA out of HIV’s RNA genome
 Drug ‘3TC’ mimics cytosine (C) nucleotide
 Some RT enzymes pick up 3TC (instead of regular C) & DNA synthesis is blocked
 Problem: not all RTs are fooled by drug 3TC; pick up normal C
 Greater reproductive success = increase in #
 Population of HIV viruses has developed resistance to 3TC
 Fossil Record Evidence
o Evidence of extinctions, new groups, & changes within groups over time
o Darwin ideas predict that evolutionary transitions should leave signs in fossil record
 Homologous Structures
o Same body part on different species that arose from a common ancestor
o Mammal Forearms
 Same bone arrangement – shoulder to fingertips
o Vestigial Structures
 Remnants of features that served functions in organism’s ancestors
 Snakes w/ parts of pelvis & hind limbs & Human’s wisdom teeth
 Comparative Embryology
o Studies anatomical homologies of embryos
 Not visible in adults
o Chordates – notochord, dorsal hollow nerve cord, post-anal tail, pharyngeal gill slits
 Molecular Homology
o Genes shared among organisms inherited from a common ancestor
o All organisms use DNA or RNA
o Humans – Humans = 99.9% genes
o Humans – Chimps = 98%
o Humans – Roundworms = 50%
o Many different organisms use hemoglobin; all same gene
 Convergent Evolution
o Evolution of similar (or analogous) features in distantly related groups
o Analogous Structures
 Similar function as another organism, but different structure


Biogeography
o Geographic distribution of species
o Endemic species – found in only one place on Earth
 Island’s endemic species are closely related to species on nearest mainland or island
Mass Extinctions & Adaptive Radiations
Chapter 26 – Phylogeny & Trees of Life
Building Phylogenetic Trees
 Can use morphological (body form) or molecular (DNA or protein) data
 Characters
o Shared Ancestral Character – originated in ancestor of taxon
o Shared Derived Character – evolutionary novelty unique to a particular clade
o Mammal’s backbone?
o Mammal’s hair?
 Cladistics
o Groups organisms by common descent
o Clade – group of species that includes an ancestral species & all its descendants
 Not all groupings of organisms are clades
o Grouping Types
 Monophyletic (single tribe = clade)
 Ancestral species & all descendents (vertebrae in vertebrates)
 Paraphyletic (beside the tribe)
 Ancestral species & some, but not all, of descendants (ectothermy in vertebrates)
 Polyphyletic (many tribes)
 Group of various species that lack a common ancestor (endothermy in vertebrates)