Title page from The Origin of Species published 1859 Chapter 22 - Descent With Modification Title page from The Origin of Species published 1859 wrote – Origin of Species by Means of Natural Selection Charles Darwin - - naturalist - sailed on the Beagle, survey ship, 22 years old - collected specimens: plants and animals - he found fossils different from modern species - Darwin was influenced by Lyell’s Principles of Geology and thought that the earth was more than 6000 years old * - He observed adaptations of plants and animals that inhabited many diverse environments

Figure 22.2 The historical context of Darwin’s life and ideas Linnaeus (classification) Hutton (gradual geologic change) Lamarck (species can change) Malthus (population limits) Cuvier (fossils, extinction) Lyell (modern geology) Darwin (evolution, natural selection) Wallace (evolution, natural selection) American Revolution French Revolution U.S. Civil War 1750 1800 1850 1900 1795 Hutton proposes his theory of gradualism. 1798 Malthus publishes “Essay on the Principle of Population.” 1809 Lamarck publishes his hypothesis of evolution. 1830 Lyell publishes Principles of Geology. 1831–1836 Darwin travels around the world on HMS Beagle. 1837 1837 Darwin begins his notebooks. 1844 Darwin writes essay on descent with modification. 1858 Wallace sends his hypothesis to Darwin. 1859 The Origin of Species is published. Figure 22.2 The historical context of Darwin’s life and ideas

acquired characteristics Historical Ideas Taxonomy - Linnaeus: Paleontology – Cuvier: Gradualism - Hutton: Uniformitarianism - Lyell : Evolution - Lamark : Populations - Malthus : Natural Selection - Darwin : Inheritance - Mendel : naming and classifying the diverse forms of life “for the greater glory of God”: kingdom, phylum, class, order, family, genus, species paleontologist, fossils, recognized that extinctions occurred he argued it must have been due to catastrophism geologist: profound change in the Earth’s features, slow and continuous geologist, geologic processes have not changed throughout Earth’s history rates of building and eroding same now as in past Lamarck hypothesized that species evolve through use and disuse of body parts and the inheritance of acquired characteristics The mechanisms he proposed are unsupported by evidence studied populations human suffering was due to populations 2 ideas: 1. descent with modification 2. natural selection through adaptation parents pass traits to offspring

Acquired traits are not inherited Figure 22.4 Acquired traits cannot be inherited

The Voyage of HMS Beagle - discovered that most of the animal species on the Galapagos lived nowhere else in the world but they resemble species on the South American mainland - Darwin studied Finches (birds) adaptation In reassessing his observations, Darwin perceived to the environment and the origin of new species as closely related processes

(a) Cactus-eater (c) Seed-eater (b) Insect-eater Figure 22.6 Beak variation in Galápagos finches (b) Insect-eater

In the Darwinian view, the history of life is like a tree with branches representing life’s diversity Figure 22.7 “I think . . .”

Artificial Selection, Natural Selection, and Adaptation Darwin noted that humans have modified other species by selecting and breeding individuals with desired traits, a process called_________________________ Darwin then described four observations of nature and from these drew two inferences artificial selection Observation #1: Members of a population often vary greatly in their traits Observation #2: Traits are inherited from parents to offspring Observation #3: All species are capable of producing more offspring than the environment can support Observation #4: Owing to lack of food or other resources, many of these offspring do not survive Inference #1: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals Inference #2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations

Observation #1: Members of a population often vary greatly in their traits

individuals populations Adaptations edits selects selected for Note that ______________do not evolve; ______________ evolve over time Natural selection can only increase or decrease heritable traits in a population ________________ vary with different environments Adaptations edits selects Natural selection does not create new traits, but ________ or _________ for traits already present in the population The local environment determines which traits will be __________________ or _________________ in any specific population selected for selected against

(b) A stick mantid in Africa Fig. 22-12b Figure 22.12 Camouflage as an example of evolutionary adaptation (b) A stick mantid in Africa

(a) A flower mantid in Malaysia Fig. 22-12a Observation #2: Traits are inherited from parents to offspring Figure 22.12 Camouflage as an example of evolutionary adaptation (a) A flower mantid in Malaysia

The Evolution of Drug-Resistant HIV The use of drugs to combat HIV _______________ viruses resistant to these drugs HIV uses the enzyme ________________________ to make a DNA version of its own RNA genome The drug 3TC is designed to interfere and cause errors in the manufacture of DNA from the virus selects for reverse transcriptase Some individual HIV viruses have a ______________ that allows them to produce DNA without errors These viruses have a _______________________________ and increase in number relative to the susceptible viruses The population of HIV viruses has therefore _____________________ to 3TC The ability of bacteria and viruses to evolve rapidly poses a challenge to our society variation greater reproductive success developed resistance

The Evolution of Drug-Resistant HIV Fig. 22-14 The Evolution of Drug-Resistant HIV 100 Patient No. 1 Patient No. 2 75 Percent of HIV resistant to 3TC 50 Patient No. 3 Figure 22.14 Evolution of drug resistance in HIV 25 2 4 6 8 10 12 Weeks

The Fossil Record provides evidence transitions The fossil record __________________ of the extinction of species, the origin of new groups, and changes within groups over time transitions The Darwinian view of life predicts that evolutionary __________________ should leave signs in the fossil record Paleontologists have discovered fossils of many such transitional forms

A transitional fossil linking past and present Vestigal structures - historical remnants of structures that had important functions in ancestors ex. snakes – pelvis, leg bones

(a) Pakicetus (terrestrial) Fig. 22-16ab The transition to life in the sea (a) Pakicetus (terrestrial) Figure 22.16 The transition to life in the sea (b) Rhodocetus (predominantly aquatic)

(c) Dorudon (fully aquatic) Fig. 22-16cd Pelvis and hind limb (c) Dorudon (fully aquatic) Figure 22.16 The transition to life in the sea Pelvis and hind limb (d) Balaena (recent whale ancestor)

Homologous structures: anatomical signs of descent with modification new species descend from ancestral species more evidence for evolution anatomical homologies Homologous structures - similarity in characteristics resulting from common ancestors Homologies – ex. forelimb: human, cat, whale, bat - anatomical - embryological – ex. pharyngeal pouches in throat – all vertebrates have - molecular – all use same genetic material (DNA) Analogous structures – body parts resemble one another - evolved independently ex. fins/body shape: sharks, penguins, porpoise all are adaptations for swimming

Pharyngeal pouches Post-anal tail Chick embryo (LM) Human embryo Fig. 22-18 Pharyngeal pouches Post-anal tail Figure 22.18 Anatomical similarities in vertebrate embryos Chick embryo (LM) Human embryo

Homologies and “Tree Thinking” The Darwinian concept of an ___________________ of life can explain homologies Evolutionary trees are hypotheses about the __________________ among different groups Evolutionary trees can be made using different types of data, for example, _______________________________________________ evolutionary tree relationships anatomical and DNA sequence data

Homologous characteristic Fig. 22-19 Branch point (common ancestor) Lungfishes 1 Amphibians Tetrapods 2 Mammals Tetrapod limbs Amniotes 3 Lizards and snakes Amnion 4 Crocodiles Figure 22.19 Tree thinking: information provided in an evolutionary tree Homologous characteristic 5 Ostriches Birds 6 Feathers Hawks and other birds

Convergent Evolution Convergent evolution analogous _________________ is the evolution of similar, or _______________, features in distantly related groups Analogous traits arise when groups ____________________________ to _______________________ in similar ways Convergent evolution does not provide information about _____________ independently adapt similar environments ancestry

NORTH AMERICA Sugar glider AUSTRALIA Flying squirrel Fig. 22-20 Figure 22.20 Convergent evolution Flying squirrel