Descent with Modification Complete 15-1 in Guided Reading Workbook Quest tomorrow (13-14)

Descent with Modification: A Darwinian View of Life A new era of biology began in 1859 when Charles Darwin published The Origin of Species The Origin of Species focused biologists’ attention on the great diversity of organisms

To understand why Darwin’s ideas were revolutionary, we must examine them in relation to other Western ideas about Earth and its life The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species

natural theology 1700’s studying the adaptations of organisms –“ the Creator has designed each species for a purpose”

Taxonomy Carolus Linnaeus –Swedish botanist 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

Fig Younger stratum with more recent fossils Layers of deposited sediment Older stratum with older fossils Fossils – relics or impressions of organisms from the past –mineralized in sedimentary rocks

Hutton and Lyell Hutton – gradualism –profound change results from slow, continuous processes Lyell – uniformitarianis m –geological processes have not changed throughout Earth’s history

Population Limits Thomas Malthus "...in all societies, even those that are most vicious, the tendency to a virtuous attachment is so strong that there is a constant effort towards an increase of population. This constant effort as constantly tends to subject the lower classes of the society to distress and to prevent any great permanent amelioration of their condition."[13][13]

Jean Baptiste Lamarck Use and disuse of parts Inheritance of acquired characteristics

Fig American RevolutionFrench RevolutionU.S. Civil War – The Origin of Species is published. Wallace sends his hypothesis to Darwin. Darwin begins his notebooks. Darwin writes essay on descent with modification. Darwin travels around the world on HMS Beagle. Malthus publishes “Essay on the Principle of Population.” Lyell publishes Principles of Geology. Lamarck publishes his hypothesis of evolution. Hutton proposes his theory of gradualism. Linnaeus (classification) Cuvier (fossils, extinction) Malthus (population limits) Lamarck (species can change) Hutton (gradual geologic change) Lyell (modern geology) Darwin (evolution, natural selection) Wallace (evolution, natural selection)

Voyage of the Beagle ( ) Darwin’s Voyage - During his travels, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time.

Galapagos Islands During his travels Darwin was amazed how different organisms were so well adapted to many different environments. He saw patterns of diversity Not just in living organisms, but also in fossil records. The Galapagos Islands were a microcosm of Evolution

In 1844, Darwin wrote an essay on the origin of species and natural selection In June 1858, Darwin received a manuscript from Alfred Russell Wallace The Origin of Species

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

Fig. 22-7

Fig Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) Moeritherium Barytherium Deinotherium Mammut Elephas maximus (Asia) Stegodon Mammuthus Loxodonta africana (Africa) Loxodonta cyclotis (Africa) Millions of years ago Years ago Platybelodon

Fig. 22-8a Elephas maximus (Asia) Stegodon Mammuthus Loxodonta africana (Africa) Loxodonta cyclotis (Africa) Millions of years ago Years ago Platybelodon

Artificial Selection, Natural Selection, and Adaptation artificial selection –Super CowSuper Cow Darwin then described four observations of nature and from these drew two inferences

Fig Kale Kohlrabi Brussels sprouts Leaves Stem Wild mustard Flowers and stems Broccoli Cauliflower Flower clusters Cabbage Terminal bud Lateral buds

Observation #1: Members of a population often vary greatly in their traits Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Observation #2: Traits are inherited from parents to offspring Observation #3: All species are capable of producing more offspring than the environment can support Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig Spore cloud

Observation #4: Owing to lack of food or other resources, many of these offspring do not survive Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Inference #2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations 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 Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig (b) A stick mantid in Africa (a) A flower mantid in Malaysia

Examples of Natural Selection Predator: Killifish; preys mainly on juvenile guppies (which do not express the color genes) Guppies: Adult males have brighter colors than those in “pike-cichlid pools” Experimental transplant of guppies Pools with killifish, but no guppies prior to transplant Predator: Pike-cichlid; preys mainly on adult guppies Guppies: Adult males are more drab in color than those in “killifish pools” EXPERIMENT

Patients treated with the drug 3TC –interferes with genome replication in HIV 3TC-resistant strains become 100% of the population of HIV in just a few weeks

Evidence of Evolution The Fossil Record Homologous Structures Vestigial Organs Similarities in Embryonic Development Genetic Code

Evidence of Evolution Evidence of Evolution Fossil Record Physical Remains Composed of Biochemistry Protein, RNA, DNA Biochemical Pathways Which Indicates Common Ancestors Biogeography Common Ancestors Which Indicates Homologous Body Structures Similar Genes Which Implies Early Development Similar Genes Which Implies

The Fossil Record

Biogeography Geographical Dist. of Species Common Descent

Homologous Body Structures vestigial organ - organ that serves no useful function in an organism

Vestigial Organs organ that serves no useful function in an organism

Similarities in early development

Theoretical? The conclusion that life has evolved is well supported by an abundance of historical evidence Natural selection is widely accepted in science –its predictions have withstood thorough, continual testing by experiments and observations arguments exist among evolutionary biologists whether natural selection alone accounts for the history of life as observed in the fossil record