Chapter 16-1Developing a Theory
Objectives
•Why is evolutionary theory associated withCharles Darwin?
•How was Darwin influenced by hispersonal experiences?
•How was Darwin influenced by the ideasof others?
Evolution and Darwin
•Evolution
–a collection of facts, observations, andhypotheses about the history of life
–def.- change over a period of time
Charles Darwin
–main contributor to Evolution
–1831-1836, Made discoveries during trip aroundthe world
–Naturalist of the boat- collected plant and animalspecimens
Darwin’s Voyage
•Living diversity
–variety of living things
–5-50 million different species
•Fossils
–bones and other traces
of ancient organisms
–over 99.9% of all once
living species are now extinct
Galapagos Islands
•Where Darwin was the most
influenced by his observations
•Studied giant tortoises, marine
iguanas and birds
•He noticed differences in characteristics/traits betweenanimals/plants of the different islands.
•wondered if animals of different islands were members ofthe same species and changed due to isolation
Galapagos Islands
•For example, he suggested that all of the finch speciesdescended from one ancestral finch species thatmigrated from South America.
•Then, the descendant finches were modified over time asdifferent groups survived by eating different types offood.
•Darwin called such change
descent with modification. This
idea was a key part of his theory.
Breeding and Selection
•Darwin took interest in the practice of breeding,especially the breeding of exotic pigeons.
•He bred pigeons himself and studied the work ofthose who bred other kinds of animals andplants, such as dogs, orchids, and food crops.
•Eventually, Darwin gained a new insight:breeders take advantage of natural variation intraits within a species
Breeding and Selection
•If a trait can be inherited, breeders can producemore individuals that have the trait.
•Breeders simply select individuals that havedesirable traits to be the parents of each newgeneration.
•Darwin called this process artificial selectionbecause the selection is done by humans andnot by natural causes.
Darwin’s Ideas from Others
•Darwin was influenced by ideas from thefields of natural history, economics, andgeology.
•The ideas of Lamarck, Malthus, Cuvier,and Lyell were especially important.
Jean Baptiste Lamarck
•In 1809, the French scientist Jean BaptisteLamarck proposed an explanation for howorganisms may change over generations.
•Lamarck noticed that each organism isusually well adapted to its environment.
•He proposed that organisms change overtime as they adapt to changingenvironments.
Jean Baptiste Lamarck
•However, Lamarck had an incorrect idea aboutinheritance. He proposed that changes due to useor disuse of a character would be passed on tooffspring.
• He believed that offspring inherited these kinds ofchanges.
•This idea was eventually disproved, but not inDarwin’s time. Darwin once accepted this ideabecause it proposed a role for inheritance inevolution.
Thomas Malthus
•English economist
•The problem of reproduction
–observed that human populations were increasing
faster than the food supply
–Growth controlled by war, famine, and disease
Darwin applied this to plants and animals since they produce moreoffspring than will survive
•oyster-millions of eggs
–Animals/plants will die for different reason as a result of the environment
•A population is all of the individuals of the same species thatlive in a specific place.
Geology and an Ancient Earth
•In Darwin’s time, scientists had becomeinterested in the study of rocks andlandforms, and thus began the science ofgeology.
•In particular, scientists such as GeorgesCuvier, James Hutton, and Charles Lyellstudied fossils and rock layers.
Geology and an Ancient Earth
•Cuvier argued that fossils in rock layersshowed differences in species over timeand that many species from the pastdiffered from those of the present.
•But Cuvier did not see species aschanging gradually over time. He thoughtthat changes in the past must haveoccurred suddenly.
Geology and an Ancient Earth
•Hutton and Lyell, on the other hand, thoughtthat geologic processes—such as those thatwear away mountains and form new rocks andfossils—work gradually and constantly.
•Lyell’s ideas fit well with Darwin’s observationsand showed that Earth’s history was longenough for species to have evolved gradually.
Summary
•Modern evolutionary theory began when Darwinpresented evidence that evolution happens andoffered an explanation of how evolutionhappens.
•Darwin’s experiences provided him withevidence of evolution at work.
•Darwin was influenced by ideas from the fieldsof natural history, economics, and geology.