darwin

I. Lamarkian Evolution A. Jean-Baptiste Lamarck 1. Early evolutionary biologist who tried to explain how organisms change over time 2. Lamarck incorporated two ideas into his theory of evolution Use and disuse – Individuals lose characteristics they do not require (or use) and develop characteristics that are useful Inheritance of acquired traits – Individuals inherit the traits of their ancestors

3. According to Lamark, the theory of use and disuse proposes how the long neck of giraffes came about

Evolution by Natural Selection and Evolution by Natural Selection and Change Over TimeChange Over Time

Lamark’s theory of use and disuse in giraffes

II. Darwinian Evolution by Natural Selection A. Theory of Evolution by Natural Selection 1. Darwin was greatly influenced by geologist, Charles Lyell -Lyell wrote The Principles of Geology which popularized the idea that the Earth’s geology was shaped by slow-moving forces still in operation today -Lyell believed that the world is older than 300 million years, on the basis of its geological anomalies 2. Darwin adopted the idea that as the Earth’s geology changes over time, and living things adapt to the changing environment

Charles Darwin Charles Lyell Thomas Malthus

3. Darwin was also influenced by Thomas Malthus’ writings- An Essay on

the Principle of Population -Malthus stated that human population would grow so large someday, that eventually the population would outstrip the supply of food 4. Malthus’ essay led Darwin to believe that since organisms produce more offspring than could possibly survive, the overpopulation

would result in a “struggle for existence” in which the fittest would survive

5. Darwin coined the term, “survival of the fittest”

C. Voyage of the HMS Beagle 1. Darwin opted to become ship’s naturalist on the HMS Beagle 2. His role was to study the flora and fauna of as the ship traveled around the world on its 5 year journey 3. When at the Galapagoes archipelago, he studied the life inhabiting the 13 islands 4. The island chain arose out of the ocean by volcanism about a million years ago about 970 kilometers off the coast of Ecuador 5. The islands were never part of mainland South America and each of the 13 islands were separated by water 6. The Galapagoes islands were inhabited by fauna and flora that shared common characteristics related to, but not found on mainland South America 7. Also, the fauna and flora were slightly different from island to island 8. To Darwin, this was the “cradle of evolution”

Voyage of the HMS Beagle

Galapagoes archipelago

D. Darwin’s Finches 1. Darwin studied the 14 species of Galapagos Finches found on the different islands 2. All 14 species of finches had the same drab plumages and nesting habits indicating that they diverged from a common ancestor- divergent evolution 3. The birds varied in size from 10 to 20 cm and weigh between 8 and 38 grams- the smallest is the warbler Finch and the largest is the vegetarian Finch 4. The most important differences between species are in the size and shape of their beaks, being highly modified and highly adapted to the different food sources found on the different islands 5. When the ancestral Finches reached the islands from the mainland, there was no competition- no birds to compete with 6. As they settled on the different islands, they adapted to the different food sources, and with little or no competition 7.This allowed the original finch to flourished into 14 different species

Adaptive radiation of Darwin’s finches on the Galapagos archipelago

E. Galapagos Tortoise 1. They are huge turtles that live on the 13 islands 2. They adapted to the different environments they were exposed to on the islands 3. The shell size and shape vary between populations 4. On islands with humid highlands, the tortoises are larger, with domed shells and short necks 5. On islands with dry lowlands, the tortoises are smaller, with "saddleback" shells and long necks 6. These island-to-island differences of the finches and tortoises played a key role in the development of Charles Darwin's theory of evolution by natural selection

Adaptive radiation of the Galapagos tortoise

F. On the Origin of the Species by Natural Selection 1. As a result of years of work, in 1859, Darwin presented his theory of evolution by natural selection as an explanation for adaptation and speciation 2. He defined natural selection as the principle by which each slight variation, if useful to the organism, is passed on to the next generation 3. Natural selection is one of the cornerstones of modern biology

Comparing Lamarkian evolution with Darwinian evolution

III. Evidence for Change A. Geologic Time Scale

B. Extinction Changes Organisms

C. Transitional Forms of Life 1. The Bird- Transition from Dinosaur to Bird Archaeopteryx

Archaeopteryx Modern Day Hawk

2. The Horse- Transition from a Horse the Size of a Small Dog with Toes to Modern Day Horses with Hooves

3. The Whale- Transition from a Land Mammal to an Aquatic Mammal

3. Hominid Skulls- Transition from a Small-Brain Ape-like Hominid to Modern Humans

D. Vestigial Structures

Ear muscles Coccyx bone Goose pimples

Whale leg bones Snake leg bones

Flightless bird

E. Structural Homology- An Example of Divergent Evolution 1. Provides evidence of descent from a common ancestor: 2. Limbs with different functions:  humerus, radius, ulna, carpal, phalanges in vertebrates

F. Artificial Selection 1. Farmers and breeders allowed only the plants and animals with desirable characteristics to reproduce 2. These common vegetables were cultivated from forms of wild mustard

3. Through artificial selection, the wolf has given rise to the many strains of the domesticated dog

G. Convergent Evolution 1. Independent evolution of similar features in species of different lineages 2. The placental and marsupial mammals have adapted to similar enviornments by developing similar anatomical features

3. The fish, reptile and dolphin have fins and swim all "converged" on swimming in water with fins independently

H. Industrial Melanism A. The Peppered Moth- (Biston betularia)

               1. The peppered moth is an example demonstrating how natural selection can occur over a short period of time. 2. The evolution of the peppered moth over the last two hundred years has been studied in detail 3. Originally, the vast majority of peppered moths had light coloration, which effectively camouflaged them against the light-colored trees upon which they rested 4. During the industrial revolution, due to widespread pollution, in England, the trees which peppered moths rested on became blackened by soot, causing most of the light-colored moths, or typica, to die off due to predation

5. At the same time, the dark-colored moths, carbonaria, began to flourish because of their ability to hide from predators on the darkened trees6. If both typica and carbonaria peppered moths are resting on trees with light colored bark, predatory birds will more easily attack and kill the darker moths 7. Likewise if both typica and carbonaria peppered moths are resting on trees with dark colored bark, predatory birds will more easily attack and kill the lighter moths 8. By the mid-19th century, a shift in population developed as the number of dark-colored moths became the dominant moth due the industrial revolution    

Typica Carbonaria

Typica and Carbonaria on a soot covered tree