Chapter 19 Descent with Modification A Darwinian View

Chapter 19 Descent with Modification: A Darwinian View of Life 1

Concept 19. 1: The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species • To understand why Darwin’s ideas were revolutionary, we must examine them in relation to other Western ideas about Earth and its life 2 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Scala Naturae and Classification of Species • The Greek philosopher Aristotle viewed species as fixed and arranged them on a scala naturae (scale of nature) • The Old Testament holds that species were individually designed by God and therefore perfect 3 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Methods of Classification Early Classification: (384319 BC) Aristotle was one of the first people to classify things He noticed that living organisms could be grouped into 2 categories: plants and animals 4

Aristotle He noticed plants were green and didn’t move And Animals weren’t green and did move 5

§ Animals were classified according to the presence or absence of “red blood. ” § Animals were further grouped according to their habitats and morphology. § Plants were classified by average size and structure as trees, shrubs, or herbs. 6

Aristotle Next, he divided all the animals into three groups BASED ON WHERE THEY LIVE Animals that live in water Animals that live on land Animals that live in the air and could fly 7

Aristotle Next, he worked out a system of grouping for plants: He based this on the size of the plant and the pattern of growth Tall plants with one trunk were put in the tree group Medium plants with many trunks were considered shrubs Small plants with soft stems went into an herb group 8

The Beginning of Modern Classification As scientists discovered more living things, Aristotles way of classifying things became less useful So, in 1735, Carolus Linnaeus developed a new classification system 9

• Carolus Linnaeus interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose • Linnaeus was the founder of taxonomy, the branch of biology concerned with classifying organisms 10 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Linnaeus He grouped living things into two main categories He called these groups kingdoms Kingdoms: the largest group of living things 11

Linnaeus Animals were one Kingdom Plants were another He placed organisms with similar traits into the same group and called this group a species. He used very specific traits for his groups. 12

Linnaeus He grouped similar species into a larger group called a genus. 13

Linnaeus Important changes that Linnaeus made to Aristotle’s system 1. He classified plants and animals into more groups 2. he based his system on specific traits 3. he gave organisms names that described their traits 14

Classification Domain (the largest grouping) Kingdom Phylum Class Order Family Genus Species (the smallest group) 15

Scientific Names Come From Classification Scientific Name: the genus and species names together Genus name is always capitalized species name is small print always italicized or underlined (only if handwritten) Homo sapiens 16

Why Scientific Names Are Used 1. 2. 3. No mistake can be made about what you are talking about (two different living things don’t have the same genus AND species names) Scientific names seldom change Written in the same language around the world (Latin) 17

The changes that occur over time in the hereditary features of a species. 18

• Darwin noted that current species are descendants of ancestral species • Evolution can be defined by Darwin’s phrase descent with modification • Evolution can be viewed as both a pattern and a process 19 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 19 -1 20

Fig. 19 -2 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 1800 1900 1750 1850 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. Darwin travels around the world on HMS Beagle. 1831– 1836 1837 Darwin begins his notebooks. 1844 Darwin writes essay on descent with modificat 1858 Wallace sends his hypothesis to Darwin 1859 The Origin of Species is published. 21

Ideas About Change over Time • The study of fossils helped to lay the groundwork for Darwin’s ideas • Fossils are remains or traces of organisms from the past, usually found in sedimentary rock, which appears in layers or strata Video: Grand Canyon 22 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 19 -3 Layers of deposited sediment Younger stratum with more recent fossils Older stratum with older fossils 23

Paleontology, the study of fossils, was largely developed by French scientist Georges Cuvier (1769 -1832) He noticed that the older layers had fossils that were dissimilar to (then) current life forms. Cuvier advocated catastrophism, speculating that each boundary between strata represents a catastrophe 24 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Geologists James Hutton and Charles Lyell perceived that changes in Earth’s surface can result from slow continuous actions still operating today Lyell’s principle of uniformitarianism states that the mechanisms of change are constant over time This view strongly influenced Darwin’s thinking 25 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Lamarck’s Hypothesis of Evolution Lamarck hypothesized that species evolve through use and disuse of body parts and the inheritance of acquired characteristics (acquired characteristics) The mechanisms he proposed are unsupported by evidence 26 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Concept 19. 2: Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life As the 19 th century dawned, it was generally believed that species had remained unchanged since their creation However, a few doubts about the permanence of species were beginning to arise 27 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Darwin’s Research As a boy and into adulthood, Charles Darwin had a consuming interest in nature Darwin first studied medicine (unsuccessfully), and then theology at Cambridge University After graduating, he took an unpaid position as naturalist and companion to Captain Robert Fitz. Roy for a 5 -year around the world voyage on the Beagle 28 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The Voyage of the Beagle During his travels on the Beagle, Darwin collected specimens of South American plants and animals He observed adaptations of plants and animals that inhabited many diverse environments Darwin was influenced by Lyell’s Principles of Geology and thought that the earth was more than 6000 years old 29 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

His interest in geographic distribution of species was kindled by a stop at the Galápagos Islands near the equator west of South America 30 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The Galápagos Islands § Darwin began to collect mockingbirds, finches, and other animals on the four islands. § He noticed that the different islands seemed to have their own, slightly different varieties of animals. 31

The Origin of Species § Darwin published On the Origin of Species by Means of Natural Selection in 1859. § Darwin’s theory of natural selection is not synonymous with evolution. § It is a means of explaining how evolution works. 32

Darwin’s Work Important Ideas about natural selection: Observation #1 members of a population vary greatly in their traits. A variation: is a trait that makes an individual different from others of its species OBSERVATION #2: Traits are inherited from parents to offspring. 33

OBSERVATION #3: All species are capable of producing more offspring than their environment can support OBSERVATION #4: Owing to lack of food or other resources, many of these offspring do not survive There are more living things than resources to support them. The result is competition. Competition is the struggle among living things to get their needs for life. 34

Darwin’s Work 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 35

Darwin’s Focus on Adaptation • In reassessing his observations, Darwin perceived adaptation to the environment and the origin of new species as closely related processes • From studies made years after Darwin’s voyage, biologists have concluded that this is indeed what happened to the Galápagos finches 37 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 19 -6 (a) Cactus-eater (c) Seed-eater (b) Insect-eater 38

• In 1844, Darwin wrote an essay on the origin of species and natural selection but did not introduce his theory publicly, anticipating an uproar • In June 1858, Darwin received a manuscript from Alfred Russell Wallace, who had developed a theory of natural selection similar to Darwin’s • Darwin quickly finished The Origin of Species and published it the next year 39 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The Origin of Species • Darwin developed two main ideas: • Descent with modification explains life’s unity and diversity • Natural selection is a cause of adaptive evolution 40 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Descent with Modification Darwin never used the word evolution in the first edition of The Origin of Species The phrase descent with modification summarized Darwin’s perception of the unity of life The phrase refers to the view that all organisms are related through descent from an ancestor that lived in the remote past 41 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

In the Darwinian view, the history of life is like a tree with branches representing life’s diversity Darwin’s theory meshed well with the hierarchy of Linnaeus 42 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Phylogenic Species Concept § Phylogeny is the evolutionary history of a species. § The phylogenic species concept defines a species as a cluster of organisms that is distinct from other clusters and shows evidence of a pattern of ancestry and descent. 45

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Characters § To classify a species, scientists construct patterns of descent by using characters. § Characters can be morphological or biochemical. 47

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 artificial selection Darwin then described four observations of nature and from these drew two inferences 48 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

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• Darwin was influenced by Thomas Malthus who noted the potential for human population to increase faster than food supplies and other resources • If some heritable traits are advantageous, these will accumulate in the population, and this will increase the frequency of individuals with adaptations • This process explains the match between organisms and their environment 50 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Natural Selection: A Summary Individuals with certain heritable characteristics survive and reproduce at a higher rate than other individuals Natural selection increases the adaptation of organisms to their environment over time If an environment changes over time, natural selection may result in adaptation to these new conditions and may give rise to new species Video: Seahorse Camouflage 51 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 19 -12 (a) A flower mantid in Malaysia (b) A stick mantid in Africa 52

Note that individuals do not evolve; populations evolve over time Natural selection can only increase or decrease heritable traits in a population Adaptations vary with different environments 53 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Co-Evolution The term is used to describe cases where two (or more) species reciprocally affect each other's evolution 54

Coevolution • Yucca moths and yucca plants Yucca flowers are a certain shape so only that tiny moth can pollinate them. The moths lay their eggs in the yucca flowers and the larvae (caterpillars) live in the developing ovary and eat yucca seeds. 55

Let’s Watch Mr. Anderson blog about Plants http: //www. youtube. com/watch? v=X 4 L 3 r_XJW 0 I 56

Concept 19. 3: Evolution is supported by an overwhelming amount of scientific evidence New discoveries continue to fill the gaps identified by Darwin in The Origin of Species 57 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Direct Observations of Evolutionary Change Two examples provide evidence for natural selection: the effect of differential predation on guppy populations and the evolution of drugresistant HIV Sexual Selection Natural Selection (through predation/environment) 58 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Predation and Coloration in Guppies : Scientific Inquiry John Endler has studied the effects of predators on wild guppy populations Brightly colored males are more attractive to females However, brightly colored males are more vulnerable to predation Guppy populations in pools with fewer predators had more brightly colored males 59 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

• Endler transferred brightly colored guppies (with few predators) to a pool with many predators • As predicted, over time the population became less brightly colored • Endler also transferred drab colored guppies (with many predators) to a pool with few predators • As predicted, over time the population became more brightly colored 60 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The Evolution of Drug-Resistant HIV The use of drugs to combat HIV selects for viruses resistant to these drugs HIV uses the enzyme reverse transcriptase to make a DNA version of its own RNA genome The drug 3 TC is designed to interfere and cause errors in the manufacture of DNA from the virus (it inserts itself where a cytosine should be-thus stopping mitosis) http: //media. hhmi. org/hl/07 Lect 3. html HHMI evolution of drug resistance 61 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Some individual HIV viruses have a variation that allows them to produce DNA without errors These viruses have a greater reproductive success and increase in number relative to the susceptible viruses The population of HIV viruses has therefore developed resistance to 3 TC The ability of bacteria and viruses to evolve rapidly poses a challenge to our society 62 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

• Natural selection does not create new traits, but edits or selects for traits already present in the population • The local environment determines which traits will be selected for or selected against in any specific population 63 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The Fossil Record (more evidence for evolution) The fossil record provides evidence of the extinction of species, the origin of new groups, and changes within groups over time 64 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Evidence of Evolution Support for Evolution § The fossil record § Fossils provide a record of species that lived long ago. § Fossils show that ancient species share similarities with species that now live on Earth. (we can see that changes occur). Glyptodont Armadillo 65

Fossil Evidence Fossils are the remains of onceliving things from ages past. (footprints, bones, skeletons, amber etc) An extinct life-form is one that no longer exists 66

Fossil Evidence Fossils are found in Earth’s crust. They are found in sedimentary rocks. Sedimentary rocks form from layers of mud, sand, and other fine particles. 67

Fossil Evidence Scientist can tell how old fossils are by dating them (with radioactive isotopes). Being able to date fossils gives scientists an idea of the history of life on Earth. 68

• The Darwinian view of life predicts that evolutionary transitions should leave signs in the fossil record • Paleontologists have discovered fossils of many such transitional forms 69 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 19 -16 (a) Pakicetus (terrestrial) (b) Rhodocetus (predominantly aquatic) Pelvis and hind limb (c) Dorudon (fully aquatic) Pelvis and hind limb (d) Balaena (recent whale ancestor) 70

Evolution Evidence of Evolution § Derived traits are newly evolved features, such as feathers, that do not appear in the fossils of common ancestors. § Ancestral traits are more primitive features, such as teeth and tails, that do appear in ancestral forms. 71

Homology is similarity resulting from common ancestry § Homologous structures: Anatomically similar structures inherited from a common ancestor are called homologous structures. 72

Anatomical and Molecular Homologies Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor 73 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Evidence of Evolution § Analogous structures can be used for the same purpose and can be superficially similar in construction, but are not inherited from a common ancestor. § Show that functionally similar features can evolve independently in similar environments 74

Comparative embryology reveals anatomical homologies not visible in adult organisms 75 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Comparative Embryology If you look at different animals during stages of embryonic development you can see common traits. This shows a common ancestry. 76

Fig. 19 -18 Pharyngeal pouches Post-anal tail Chick embryo (LM) Human embryo 77

HOX genes • A group of related genes that are responsible for determining the basic structure and orientation of body structures for different organisms including humans, flies, worms • Highly conserved throughout many organisms 78

Evolution Evidence of Evolution Vestigial Structures § Structures that are the reduced forms of functional structures in other organisms. 79

Evolutionary theory predicts that features of ancestors that no longer have a function for that species will become smaller over time until they are lost. Many animals still have Those parts and still use them. 80

Evolution Evidence of Evolution Comparative Biochemistry § Common ancestry can be seen in the complex metabolic molecules that many different organisms share. 81

§ The similar appearance of chromosomes among chimpanzees, gorillas, and orangutans suggests a shared ancestry. 82

• Examples of homologies at the molecular level are genes shared among organisms inherited from a common ancestor • (like the HOX genes) 83 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Molecular Clocks § Scientists use molecular clocks to compare the DNA sequences or amino acid sequences of genes that are shared by different species. 84

§ The differences between the genes indicate the presence of mutations. § The more mutations that have accumulated, the more time that has passed since divergence. 85

Biochemical Characters § Scientists use biochemical characters, such as amino acids and nucleotides, to help them determine evolutionary relationships among species. § DNA and RNA analyses are powerful tools for reconstructing phylogenies. 86

Evolution Evidence of Evolution § Comparisons of the similarities in these molecules across species reflect evolutionary patterns seen in comparative anatomy and in the fossil record. § Organisms with closely related morphological (body) features have more closely related molecular (like DNA) features. 87

Homologies and “Tree Thinking” The Darwinian concept of an evolutionary tree of life can explain homologies Evolutionary trees are hypotheses about the relationships among different groups Evolutionary trees can be made using different types of data, for example, anatomical and DNA sequence data 88 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 19 -19 Branch point (common ancestor) Lungfishes Amnion Lizards and snakes 3 4 Homologous characteristic Amniotes Tetrapod limbs Mammals 2 Crocodiles Ostriches 6 Feathers Birds 5 Hawks and other birds 89 Tetrapods Amphibians 1

Convergent Evolution • Convergent evolution is the evolution of similar, or analogous, features in distantly related groups • Analogous traits arise when groups independently adapt to similar environments in similar ways • Convergent evolution does not provide information about ancestry 90 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 19 -20 Sugar glider NORTH AMERICA AUSTRALIA Flying squirrel 91

Biogeography Darwin’s observations of biogeography, the geographic distribution of species, formed an important part of his theory of evolution Islands have many endemic species that are often closely related to species on the nearest mainland or island 92 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Earth’s continents were formerly united in a single large continent called Pangaea, but have since separated by continental drift An understanding of continent movement and modern distribution of species allows us to predict when and where different groups evolved 93 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

What Is Theoretical About Darwin’s View of Life? In science, a theory accounts for many observations and data and attempts to explain and integrate a great variety of phenomena Darwin’s theory of evolution by natural selection integrates diverse areas of biological study and stimulates many new research questions Ongoing research adds to our understanding of evolution 94 Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings