Chapter 15 Review - Introduction to Evolution

Chapter 15 Review Introduction to Chapter 15 ● Evolution is the change in the pool of populations from one generation to the next. ● Changes in the gene pool can happen when - Mutations produce new gene variants - Individuals move into or out of a population - Because of external forces such as natural disasters ● Darwin proposed that populations change in response to pressures from the environment - Some individuals are better able to survive and reproduce in a particular environment than others. Thus the environment is the force that determines which individuals contribute offspring to the next generation. - Environmental conditions are widely variable, and this variation provides the template by which natural selection shapes the evolution process. - All life has undergone natural selection in response to the environment; the result is a vast tree of life with many branches, all of which can be traced to a common ancestor of all life on Earth. Key Concepts for Chapter 15 ● Darwin’s theory of natural selection proposes that all life on Earth descends from a common ancestor. ● A scientific theory, such as Darwin’s theory of evolution by natural selection, is supported by abundant evidence. ● Evolution by natural selection comes about from interaction between the organism and its environment. Chapter 15 Section 1 Summary: History of Evolutionary Thought ● Linnaeus, the originator of taxonomy, thought that classification should describe the fixed features of species. ● Count Buffon and Erasmus Darwin suggested that species change overtime ● Georges Cuvier and Jean-Baptiste de Lamarck differed sharply on evolution. - Cuvier proposed that changes in the makeup of fossils in the strata of the Earth could be explained by regional catastrophes, or extinctions, followed by repopulation from other regions. - Lamarck supported the idea that species can change as they become adapted to their environments. However he suggested the inheritance of acquired characteristics as a mechanism for evolutionary change. Example: He proposed that the neck of a giraffe would grow longer as it strived to reach tall leaves, and this long neck could then be passed onto its offspring. We now know that only traits encoded in genes are heritable. ● Charles Lyell, a geologist, made popular James Hutton’s theory of slow uniform, geological change. ● Darwin’s observations of geology led him to support Lyell’s proposal that the Earth’s massive geological changes are the result of extremely slow processes, and that the Earth, therefore, must be very old. ● Thomas Malthus proposed that population growth is limited by the availability of resources. Darwin applied this idea to his theory of evolution. Chapter 15 Section 2 Summary: Darwin’s Theory of Evolution ● Charles Darwin formulated hypotheses concerning evolution after taking a five-year voyage as a naturalist aboard the ship the HMS Beagle. ● His hypothesis were that the descent with modification from a common ancestor does occur, led him to conclude that biological diversity arises from adaptation to the environment. ● Darwin’s study of biodiversity, including the animals of the Galapagos Islands, led him to conclude that biological diversity arises from new adaptation to the environment, which can eventually lead to the formation of new species. ● Natural Selection is the mechanism Darwin proposed for how adaptation comes about. ● Natural Selection: - Organisms exhibit variation that can be passed from one generation to the next - that is, they have heritable variation - Organisms compete for available resources. - Individuals within a population differ in terms of their reproductive success. - Organisms become adapted to conditions as the environment changes. ● Darwin stressed that there was a struggle for existence. ● The most-fit organisms are those possessing characteristics that allow them to acquire more resources and to survive and reproduce more than those less fit. Chapter 15 Section 3 Summary: Evidence for Evolution ● The theory that all organisms share a common ancestor is supported by many lines of evidence: - Fossils - Anatomy - Biochemistry - Development ● Fossil Records provide a snapshot of the history of life that allows us to trace descent of a particular group of organisms. ● Biogeography is the study of the range and distribution of plants and animals in different places throughout the world and how, and when they got distributed as they are today. ● A comparison of the anatomy and the development of organisms suggests that all life on Earth is closely related. ● All organisms have certain biochemical molecules and a body plan encoded in genes shared in common, suggesting relatedness.