Biology Chapter 15 Evolution Unit Darwins Theory of

Biology Chapter 15 Evolution Unit: Darwin’s Theory of Evolution

15 -1 The Puzzle of Life’s Diversity I. Background: Evolution and Its Core Principles A. Evolution is a Central theme in biology “Nothing in biology makes sense except in the light of evolution. ”

B. Core principles of evolution: 1. All life is linked through a Common ancestor __________ 2. Populations of living things Change over time (evolve). __________ Environment influences 3. The ____________ this change (natural selection) so that advantageous traits are selected over less advantageous traits become more 4. The advantageous _________________ common in the population __________________ (descent with modification).

II. Voyage of the Beagle A. A sea voyage helped Darwin frame his theory of evolution. __________ 1. Darwin was born in England on February 12, 1809. 2. Set sail on the HMS Beagle from England in 5 year voyage 1831 for a ______ around the world.

Darwin’s Journey

Tortoise Marine Iguana

3. Darwin’s Observations: Patterns of Diversity plants and a. __________: animals seemed remarkably well suited to whatever environment they inhabited.

Living Organisms and Fossils b. ______________: Many of the fossils that Darwin discovered resembled living organisms but were not identical to them. For example, glyptodon, an extinct animal, is an ancient relative of the armadillo of South America. (page 370)

c. The Galapagos Islands: 1. ) Located 1000 km west of South America. 2. ) Islands were close together but had _________ different climates sparse vegetation 3. ) Hood Island had _________. long necks Tortoises on this island had _______ and a curved shell allowing them to reach the sparse vegetation. rich vegetation 4. ) Isabel Island had _________. Tortoises on this island had shorter necks and a dome-shaped shell. _______

Giant Tortoises of the Galápagos Islands Section 15 -1 Pinta Island Tower Marchena Intermediate shell Fernandina James Santa Cruz Isabela Santa Fe Hood Island Floreana Isabela Island Dome-shaped shell Hood Saddle-backed shell

5. ) Galapagos Finches: striking correlation between form of finches and the environment they inhabit; similarities and differences with mainland species

Beak Adaptations

Large Ground Finch Small Tree Finch Woodpecker Finch

15 -2 Ideas That Shaped Darwin’s Thinking I. Evolutionary Thinking before Darwin A. Aristotle ____ believed that species were fixed and did not evolve. B. All species were created in a single act of creation about 6, 000 years ago. C. Buffon (mid-1700’s) suggested that Earth was much older and raised ____________ the possibility that different species arose from common ancestors. _______________

II. An Ancient Changing Earth A. Hutton (1785) 1. ________ Geological processes operate extremely ________ slowly. ________ 2. Earth is much older than a few thousand years.

B. Lyell (1833) 1. Wrote Principles of Geology. 2. Promoted the idea of continual, gradual, consistent geological changes.

C. Lamarck (1809) was the first to support the idea of evolution. 1. Believed organisms acquired or lost certain traits during their lifetime. Example: giraffe 2. Traits could be passed to offspring therefore, this led to a change in a species.

Example: Giraffe

D. Malthus (1798) 1. If human populations increase too fast it ________, would lead to competition for scarce resources, and only some individuals would survive. 2. Limits to population growth.

E. Wallace (1858) 1. Conceived of essentially the same theory as Darwin. 2. Speculates on evolution by natural selection.

15 -3 Darwin Presents His Case I. Publication of On the Origin of Species A. Wallace’s letter outlining basic principles of natural selection spurs Darwin into taking his ideas public.

B. After much fierce debate, Darwin publishes his theory in 1859. 1. Contains a well-constructed argument for natural selection. 2. Backed by considerable evidence. 3. He used the phrase “descent with modification. ” 4. The book is “sold out” in one day.

C. Advances in genetics in the twentieth century yield the mechanism through which natural selection operates, vindicating Darwin’s ideas. DNA Fingerprinting

II. Inherited Variation and Artificial Selection A. Nature provided the variation, and humans selected those variations that they found useful. B. Variation existed both in nature and in farms. This variation was inherited. produced the most milk 1. Cows that _____________ were selected by breeders. the largest and most 2. Plants that produced _____________ flavorful fruit were selected.

Artificial Selection: Dogs

Artificial Selection: Plants

III. Evolution by Natural Selection A. The Struggle for Existence 1. High birth rates and a shortage of life’s basic needs would force organisms to compete. 2. Result: Those prey that are better camouflaged, or better protected, such as a porcupine can avoid being caught. Those predators that are faster or have a better mechanism to catch prey survive.

B. Survival of the Fittest 1. Fitness – ability of an organism to survive and reproduce. 2. Darwin proposed that fitness is a result of adaptation. inherited 3. Adaptation – any _________ characteristic that increases an organism’s chance of survival.

Examples of Adaptations a. Waxy coating on the surface of leaves prevents against water loss b. Ability to climb trees - spider monkey - Tree boa c. Coloration - Octopus

Look closely: It’s an Insect! 4. Those individuals best suited to their environment survive and reproduce most successfully. Darwin called this process “survival of the fittest” or natural selection. Mantids exhibit camouflage.

C. Descent with Modification 1. All living organisms are related to one another. 2. Common descent: all species – living and extinct _________– were derived from common ancestors. 3. A single “tree of life” links all living things.

The “Tree of Life”

The “Tree of Life”

IV. Evidence of Evolution Evidence 1. Fossil Record Example Fossils – the bones, shells, teeth, and other remains of organisms. Fossils of simpler organisms are found in older rocks. Newer strata contain more complex organisms.

Strata of sedimentary rock at the Grand Canyon.

Figure 17 -2 Formation of a Fossil Section 17 -1 Water carries small rock particles to lakes and seas. Go to Section: Dead organisms are buried by layers of sediment, which forms new rock. The preserved remains may later be discovered and studied.

Formation of sedimentary rock and deposition of fossils from different time periods.

Leaf Fossil Ammonites Insect in Amber Dinosaur Fossil

IV. Evidence of Evolution Evidence 2. Geographic Distribution of Animals Example 1. All 13 species of Galapagos finches descended with modification from a common mainland ancestor. 2. Similar ecological conditions cause different animals to end up evolving striking features in common.

Darwin’s Finches

The continent of Australia is home to unique animals, such as these marsupials, that evolved in isolation.

IV. Evidence of Evolution Evidence Example Experimental evidence can demonstrate natural selection 3. Current Evolution at work. Example: Peppered moths, antibiotic resistance of bacteria.

Overuse of Antibiotics has lead to Antibiotic Resistance in bacteria. Evolution of Pesticide Resistance in insect populations.

IV. Evidence of Evolution Evidence Example Humans select from among the naturally occurring genetic 4. Artificial Selection variations in species. Example: Wheat, corn, cows, race horses, domestic breeding of dogs – poodles.

Evidence 5. Comparative Anatomy Example Similarities in form and structure between otherwise differentappearing structures. Homologous structures: Same structure but different function. (organization of bones in fins of whales, wings of bat, paws of cat and gorilla point to their common evolutionary origin) Vestigial Structures: Useless structures. (in humans – appendix, wisdom teeth, muscles that move the ears and nose. )

Evolution Evidence: Comparative Anatomy • Homologous structures (homology) • Descent from a common ancestor • Vestigial organs Ex: whale/snake hindlimbs; wings on flightless birds

Comparative Anatomy: Whale hind limb Fossilized leg bones of Basilosaurus, an ancient whale. A transitional fossil linking past and present.

Whales are mammals that evolved from land dwellers.

Evidence Example Early embryo development in all animals goes through similar 6. Comparative stages, to the extent of producing structures not seen in adults. Embryology Example: The fish, bird, rabbit, and human embryos are similar in appearance and all have a two -chambered heart, pharyngeal slits, and a tail with muscles to move it.

Evolution Evidence: Comparative Embryology

Evolution Evidence: Comparative Embryology • Pharyngeal pouches, ‘tails’ as embryos

IV. Evidence of Evolution Evidence 7. Comparative Biochemistry Example Similarity in genes that control cellular function in very different organisms. Example: Same set of genes controls many early events in the development of the fruit fly and mouse. *All living things contain DNA.

Evolution Evidence: Molecular Biology • Similarities in DNA, proteins, genes, and gene products • Common genetic code

V. Summary of Darwin’s Theory A. Individual organisms differ from one another in a population. B. More organisms are produced than can survive. C. Individual organisms must compete for limited resources.

A few of the color variations in a population of Asian lady beetles. Overproduction of offspring.

D. Individuals best suited to their environment survive and reproduce most successfully. These “best fit” individuals pass their heritable traits to their offspring. E. Natural selection, the environment selecting the best traits (phenotype) under the current conditions, causes species to change over time.

Final words…. . . • “Absence of evidence is not evidence of absence. ”