Descent with Modification – A Darwinian View of Life Chapter 22 A.P. Biology Liberty Senior High School Rick L. Knowles

Concept 1.4: Evolution accounts for life’s unity and diversity The history of life –Is a saga of a changing Earth billions of years old Figure 1.17

Theodosius Dobzhansky “Nothing in biology makes sense except in the light of evolution.” The American Biology Teacher (1973)

Overview: Darwin Introduces a Revolutionary Theory A new era of biology began on November 24, 1859 –The day Charles Darwin published On the Origin of Species by Means of Natural Selection Charles Darwin, 1831, age 22, starting his voyage on the HMS Beagle

Concept 22.1: The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species In order to understand why Darwin’s ideas were revolutionary –We need to examine his views in the context of other Western ideas about Earth and its life

The historical context of Darwin’s life and ideas Fig. 22.2

The Scale of Nature and Classification of Species The Greek philosopher Aristotle –Viewed species as fixed and unchanging The Old Testament of the Bible –Holds that species were individually designed by God and therefore perfect –“Intelligent Design”

Carolus Linnaeus –Interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose –Was a founder of taxonomy, classifying life’s diversity “for the greater glory of God” –Viewed species similarities not as evolutionary relationship, but as patterns of creation. Carolus Linnaeus,

Fossils, Cuvier, and Catastrophism 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 Figure 22.3

Paleontology, the study of fossils –Was largely developed by French scientist Georges Cuvier –Observed that upper strata were younger and lower strata were older –Noticed that new species would appear in an older strata and then disappear in a newer strata. Cuvier opposed the idea of gradual evolutionary change –And instead advocated catastrophism, speculating that each boundary between strata represents a catastrophe (flood or drought).

Theories of Gradualism Gradualism –Is the idea that profound change can take place through the cumulative effect of slow but continuous processes. –1795, James Hutton proposed that Earth’s geologic features could be explained by gradual mechanisms currently operating (ex. valleys are created by rivers)

Geologists Hutton and Charles Lyell –Perceived that changes in Earth’s surface can result from slow continuous actions still operating today –Lyell proposed uniformitarianism – same geologic processes are operating today as in the past and at the same rate. –Exerted a strong influence on Darwin’s thinking Charles Lyell,

One of the First “Ideas” of Evolution Lamarck compared species today with the fossil record. 1809, hypothesized that species evolve through use and disuse and the inheritance of acquired traits. Organisms have an innate drive to become more complex. But the mechanisms he proposed are unsupported by evidence Jean-Baptiste de Lamarck,

Lamarck’s View of Evolution Plants and animals changed over time through the use and disuse of certain characteristics. These acquired characteristics were inherited by the next generation. No support for this notion.

Darwin and the HMS Beagle During his travels –Darwin observed and collected many specimens of South American plants and animals Darwin observed various adaptations of plants and animals –That inhabited many diverse environments Charles Darwin, 1831, age 22, starting his voyage on the HMS Beagle

Fig The Voyage of the HMS Beagle

Name Two (2) Observations that Darwin Made Leading to His Theory. Name One (1) Observation We’ve Since Made About the Natural World.

Darwin’s Observations about Evolution 1. Fossil Record: noticed that the fossils of South America resembled living species of that continent. Example: Glyptodon related to modern armadillo?

Glyptodon Modern Armadillo, Omaha Zoo, 2009

Darwin’s Observations of Evolution 2. Biogeography – plants and animals in temperate regions of South America resemble tropical species in South America than the temperate species in Europe. The distribution of life across similar climates is not always the same; (climate alone is not causing diversity). Closely related species are found in same geographic region.

Sugar glider AUSTRALIA NORTH AMERICA Flying squirrel Figure Different geographic regions, different mammalian “brands” –Have evolved independently from different ancestors Marsupial Mammal Placental Mammal

Charles Darwin, 1835, Galapagos

What’s so special about a bunch of islands? National Geographic Series Galapagos, Tape #254

Darwin’s Finches

The Galapagos Archipelago

Bartoloma Island

Isabela Island

Darwin proposed that natural selection –Could enable an ancestral species to “split” into two or more descendant species, resulting in a “tree of life” Large ground finch Small ground finch Geospiza magnirostris Seed eater Sharp-beaked ground finch Camarhynchus psitacula Green warbler finch Large tree finch Large cactus ground finch Ground finches Tree finches Insect eaters Bud eater Warbler finches Common ancestor from South American mainland Gray warbler finch Certhidea olivacea Certhidea fusca Geospiza difficilis Cactus flower eater Geospiza scandens Seed eater Geospiza conirostris Geospiza fortis Medium ground finch Geospiza fuliginosa Mangrove finch Cactospiza heliobates Cactospiza pallida Woodpecker finch Medium tree finch Camarhynchus pauper Small tree finch Vegetarian finch Camarhynchus parvulus Platyspiza crassirostris Cactus ground finch Figure 1.23

Large ground finch Small ground finch Geospiza magnirostris Seed eater Sharp-beaked ground finch Camarhynchus psitacula Green warbler finch Large tree finch Large cactus ground finch Ground finches Tree finches Insect eaters Bud eater Warbler finches Common ancestor from South American mainland Gray warbler finch Certhidea olivacea Certhidea fusca Geospiza difficilis Cactus flower eater Geospiza scandens Seed eater Geospiza conirostris Geospiza fortis Medium ground finch Geospiza fuliginosa Mangrove finch Cactospiza heliobates Cactospiza pallida Woodpecker finch Medium tree finch Camarhynchus pauper Small tree finch Vegetarian finch Camarhynchus parvulus Platyspiza crassirostris Cactus ground finch Figure 1.23

Seen one tortoise, you’ve seen them all? Dome-shaped Carapace Saddle-shaped Carapace

Galapagos Tortoise Distribution Galapagos tortoise distribution, Galapagos Islands. Redrawn from Iverson (1992).

Galapagos Tortoise-Env. Club 2008, Omaha Zoo

Darwin’s Focus on Adaptation Years later, Darwin reassessed all that he had observed during the voyage of the Beagle He began to perceive adaptation to the environment and the origin of new species as closely related processes Fig. 22.6

Alfred Russel Wallace, Explored Indonesia and southeast Asia, from , Observed Tigers, Orangs, and Rhinos, Oh My!

Sumatran Rhino Indian Rhino Javan Rhino

Other Observations about Evolution 3. Artificial Selection - humans have modified other species over many generations by selecting and breeding individuals that possess desired traits Fig

The Origin of Species articulated two main points… –Descent with modification –Natural selection Figure 1.19

Natural Selection Darwin proposed natural selection –As the mechanism for evolutionary adaptation of populations to their environments Population of organisms Hereditary variations Differences in reproductive success Evolution of adaptations in the population Overproduction and struggle for existence Figure 1.20

Natural selection is the evolutionary process that occurs… –When a population’s heritable variations are exposed to environmental factors that favor the reproductive success of some individuals over others. 1 Populations with varied inherited traits 2 Elimination of individuals with certain traits. 3 Reproduction of survivors. 4 Increasing frequency of traits that enhance survival and reproductive success. Figure 1.21

The Origin of Species Darwin developed two main ideas –Evolution explains life’s unity and diversity –Natural selection is a cause of adaptive evolution The phrase descent with modification –Summarized Darwin’s perception of the unity of life –States that all organisms are related through descent from an ancestor that lived in the remote past

Elephant Phylogeny Fig. 22.7

Summary of Natural Selection Natural selection is differential success in reproduction –That results from the interaction between individuals that vary in heritable traits and their environment If an environment changes over time –Natural selection may result in adaptation to these new conditions

Over time natural selection can produce an increase –In the adaptation of organisms to their environment Fig

Concept 22.3: Darwin’s theory explains a wide range of observations Darwin’s theory of evolution –Continues to be tested by how effectively it can account for additional observations and experimental outcomes –Natural Selection in Action – Evolution continues today! Guppies HIV Humans

Differential Predation in Guppy Populations Researchers have observed natural selection –Leading to adaptive evolution in guppy populations Reznick and Endler transplanted guppies from pike-cichlid pools to killifish pools and measured the average age and size of guppies at maturity over an 11-year period (30 to 60 generations). EXPERIMENT Pools with killifish, but not guppies prior to transplant Experimental transplant of guppies Predator: Killifish; preys mainly on small guppies Guppies: Larger at sexual maturity than those in “pike-cichlid pools” Predator: Pike-cichlid; preys mainly on large guppies Guppies: Smaller at sexual maturity than those in “killifish pools” Figure 22.12

RESULTS After 11 years, the average size and age at maturity of guppies in the transplanted populations increased compared to those of guppies in control populations Weight of guppies at maturity (mg) Age of guppies at maturity (days) Control Population: Guppies from pools with pike-cichlids as predators Experimental Population: Guppies transplanted to pools with killifish as predators 76.1 Males Females Males Females CONCLUSION Reznick and Endler concluded that the change in predator resulted in different variations in the population (larger size and faster maturation) being favored. Over a relatively short time, this altered selection pressure resulted in an observable evolutionary change in the experimental population.

The Evolution of Drug-Resistant HIV In humans, the use of drugs –Selects for pathogens that through chance mutations are resistant to the drugs’ effects Natural selection is a cause of adaptive evolution

Anatomy of HIV

Inside HIV

Researchers have developed numerous drugs to combat HIV –But using these medications selects for viruses resistant to the drugs Figure 22.13

New Evidence that Darwin Did Not Have How old did most 19 th Century people believe the Earth was? About 6,000 years old (Cuvier’s young Earth) 1. Age of the Earth- 4.5 billion year old. Better dating techniques than in Darwin’s time; more complete fossil record.

2. Transitional Species Have intermediate characteristics of two groups of animals – may represent a link in evolution (missing link?). Changes in structures may be small – difficult to identify in fossils. Species replaced quickly – not common in fossil record.

Archaeopteryx (150 million years ago)

Archaeopteryx

Archaeopteryx at the KU Natural History Museum

Evolution Happens in Small Steps Show me the frogs! Discover- Weird Nature: Marvelous Motion, tape #55

Other Transitional Examples? Rodhocetus balochistanensis Modern Whales

A Walking Whale? Ambulocetus natans

Transitional Skulls

Rodhocetus Foot

Transitional Diatoms in Yellowstone

3. Vestigial Structures Existing structures that have no apparent function, but resemble structures of presumed ancestors. Examples: human appendix; muscle set in humans for moving ears;

The “Pelvis” of a Whale

Evidence of Transitional Species Today! Vestigial Structure- blue whales with femurs? Life of Mammals-Return to the Water video, tape #110

Vestigial Organs in Humans? Structures of little or no use but may represent historical remnants of structures that had important functions in ancestors.

Vermiform Appendix

Goosebumps?

Vomeronasal or Jacobson’s Organ

“Junk”DNA; L-gulonolactone oxidase gene

Extra Ear Muscles – auriculares muscles

Plantaris Muscle – 9% don’t have it

Wisdom Teeth – mandible becoming smaller

Third Eyelid – Plica semilunaris

Darwin’s (Auricular) Tubercle – only 10.4% have it.

Coccyx

Four-Finned Dolphin; Oct, 2006 Divers hold a bottlenose dolphin which has an extra set of human palm-sized fins near its tail in Taiji, Wakayama prefecture in western Japan. -USA Today, Nov. 6, 2006

Four-Finned Dolphin; Oct, 2006 Divers hold a bottlenose dolphin which has an extra set of human palm- sized fins near its tail in Taiji, Wakayama prefecture in western Japan. -USA Today, Nov. 6, 2006

Show me more vestigial structures! Do snakes have “feet”? The story of boas and pythons.

4. Anatomical Homologies Homologous structures between organisms –Are anatomical resemblances that represent variations on a structural theme that was present in a common ancestor Figure HumanCat Whale Bat

Homology Homologous Structures – structures in different species that are similar because of commons ancestry.

Sophie and a Mosasaur

Analogous Structures – similarity in structures due to adaptations from similar evolutionary pressures (convergent evolution) and not a common ancestor. Analogy

The products of natural selection –Are often exquisite adaptations of organisms to the special circumstances of their way of life and their environment Figure 1.22

5. Comparative Embryology –Reveals additional anatomical homologies not visible in adult organisms Figure Pharyngeal pouches Post-anal tail Chick embryo Human embryo

Show me an example of homologous structures! Compare a human hand and bat wing. Life of Mammals- Life in the Trees video, tape #110

6. Molecular Homologies Biologists observe homologies among organisms at the molecular level –Genes and proteins that are shared among organisms inherited from a common ancestor. Fig

Darwin’s Theory of Evolution Natural selection is the driving force of changes within species populations.

Can we see evolution? Weiner, J The Beak of the Finch. Knopf, New York. The video “What Darwin Never Saw”

I want to see evolution in action! Scientific American Frontiers-Voyage to the Galapagos, 2000, VT SCI