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Outline An Introduction to Evolution A Brief Overview of the Early Development of Evolutionary Concepts Charles Darwin Evidence for Evolution Microevolution – Evolution within Species Rates of Evolution Macroevolution – How Species Evolve The Role of Hybridization in Evolution

An Introduction to Evolution Natural selection - Tendency of organisms with favorable adaptations to their environment to survive and produce new generations Theory proposed by Charles Darwin, 1859, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. Organic evolution - Accumulation of genetic changes in populations of living organisms through many changes

An Introduction to Evolution The Study of Evolutionary Biology Subdisciplines of evolutionary biology: Behavioral evolution - Study of development of behavioral traits Mating, food gathering, social interactions, predatory- prey relationships Evolutionary developmental biology - Study of effect of genetic variation on traits that effect survival and reproduction Evolutionary ecology - Study of how ecological features, such as life histories and reproductive strategies, effect evolution of species and ecosystems

An Introduction to Evolution The Study of Evolutionary Biology Subdisciplines of evolutionary biology: Evolutionary genetics - Use of molecular and transmission genetics to understand origins of genetic variability Evolutionary paleontology - Use of fossil record to examine large-scale evolutionary change, including origins of lineages and changes in anatomy over time Evolutionary physiology and morphology - Study of adaptation through biochemical, physiological, and anatomical changes

An Introduction to Evolution The Study of Evolutionary Biology Subdisciplines of evolutionary biology: Human evolution - Use of all disciplines of evolution to study genetic variation in both modern and historical human populations Molecular evolution - Study of evolutionary changes in DNA in relation to gene structure, organization, and control of expression Systematics - Naming of species and determination of their evolutionary relationships

An Introduction to Evolution Evolution in Agriculture Humans have used artificial selection, or breeding, to change agricultural and domestic plants and animals. Evolution directed by humans Agricultural systems are agents of change by influencing evolution of native species. Example: insect populations evolving resistance to insecticides Agricultural entomologists study ways to prevent or delay evolution of pesticide resistance.

An Introduction to Evolution Evolutionary Medicine Evolutionary medicine applies evolutionary principles to the way in which we treat illness. Example: evolution of bacteria, obtaining genetic ability to overcome antibiotics Also applies application of evolutionary research involving discovery of natural compounds that may be useful in medicine Can predict where to look for new products in relatives of useful plants Can look for plants that might have undergone selection pressure for those adaptations

An Introduction to Evolution Species Extinctions and Invasions Loss of species undermines health of entire ecosystems. Conservation biology uses evolutionary principles to understand species expansion or contraction in response to changing environments. Kudzu, and invasive plant from Japan Evolutionary biologists study species invasions. Natural selection in introduced plants, where there are no natural pests or herbivores, favors reproduction. Thus, outcompete native vegetation

An Introduction to Evolution Biotechnology and Evolution Evolutionary biologists determine fate of transgenes after genetically engineered crop plants are planted in fields. Transgenes - Foreign genes introduced into plants through genetic engineering Gene exchange between crop plants and their wild relatives? Herbicide resistant weeds

A Brief Overview of the Early Development of Evolutionary Concepts Aristotle (384-322 BC) - Arranged organisms from simplest to most complex, called scale of nature Implied organisms static and do not evolve Leonardo da Vinci (1452-1519) - Observed that fossils part of previously existing organisms that had become extinct Count de Buffon (1707-1788) - Described all known plants and animals Presented evidence that organisms change across generations

A Brief Overview of the Early Development of Evolutionary Concepts By end of 18th century many prominent biologists believed that hereditary changes in populations over long periods of time occurred as a result of inheritance of acquired characteristics. Jean Baptiste Lamarck (1744–1829) - Characters acquired during life were passed on and became cumulative. Major revolutions in evolutionary thought occurred in last 150 years.

A Brief Overview of the Early Development of Evolutionary Concepts First revolution - Charles Darwin, Origin of Species, 1859 Evolution by natural selection Second revolution - 1930’s Theories of Darwinian natural selection, Mendelian genetics and population genetics intersected to provide better understanding of mechanisms of evolution. Third revolution - Now Evolution of development = “Evo-devo” Homeobox genes - Regulatory genes that act as developmental switches. Organisms with nearly identical genomes can look very different because different developmental programs created them.

Charles Darwin (1809–1882) Accepted unpaid position as assistant naturalist on HMS Beagle to voyage around the world and chart coastlines, 1831–1836 Read Charles Lyell’s geology book that theorized the earth was much older than previously believed Collected plants and animals in South America, in Galapagos Islands, in Australia and, in New Zealand Guided by ideas of Malthus, 1798 Populations grow geometrically until food supplies and other factors limit growth. Presented joint paper on natural selection with Alfred Wallace a year prior to publication of Origin of Species

Evidence for Evolution Homology - A characteristic shared by different organisms with common ancestry Cactus and Euphorbia Convergent evolution - Similarities not due to common ancestry. Plants of different ancestry adapted in similar ways to common environmental conditions in different parts of world. Example: cactus and Euphorbia, both adapted to arid habitats.

Evidence for Evolution Structure and relationships of proteins, DNA, and other molecules; and common use of ATP Example: cytochrome c oxidase - universal in all living organisms Suggests early, single origin Fossil Record Fossil fern Geographical distribution of organisms

Microevolution – Evolution Within Species Natural Selection Darwin observed: Artificial selection - Changes in populations of domestic animals by retaining animals with desirable traits Limited supply of food and other resources prevents some individuals from reproducing. Competitive abilities of individuals vary within populations. Comparative anatomy and embryology He reasoned that individuals best adapted to utilize available resources would increase in number in succeeding generations. Natural selection - Descent with modification

Microevolution – Evolution Within Species Natural Selection Darwin based natural selection on: Overproduction of offspring Struggle for existence - Competition for resources Inheritance and accumulation of favorable variations Survival and reproduction of fittest (differential survival and reproduction) Criticism of natural selection in Darwin’s time: natural selection did not explain how hereditary variations originated.

Microevolution – Evolution Within Species Mutation - Change in a gene or chromosome Deletion - Part of a chromosome breaks off. Translocation - Piece of chromosome becomes attached to another. Inversion - Part of chromosome breaks off and then reattaches in an inverted position. One or more nucleotide pairs changes. Most mutations harmful; some silent or some produce characteristic that helps organism survive change. Deletion Translocation Inversion

Microevolution – Evolution Within Species Migration - Gene flow between populations when individuals or gametes migrate from one population to another Depends on size of population and extent of isolation Genetic Drift - Changes in the genetic make- up of a population due to random events

Rates of Evolution Darwin believed evolution by natural selection was slow and gradual. A number of contemporary biologists believe theory of punctuated equilibrium. Major changes occurred in spurts (ca. 100,000 years) followed by millions of years with minor change. Hypothesis based on fossils - Reveal large gaps in fossil record.

Macroevolution – How Species Evolve Geographic isolation Isolation of two populations prevents gene flow. Random mutations spread only throughout the population in which they arise. Genetic changes become so great that gene flow between populations no longer can occur. Ecological isolation Ecological factors such as climate or soils may play role in isolation, as do time and mechanical isolating factors. Results in sympatric species that occupy overlapping ranges of territories, and that do not exchange genes

Macroevolution – How Species Evolve Mechanical isolation Example: pollinia of orchids Other isolating mechanisms: Sperm chemically or mechanically prevented from reaching egg. Postzygotic isolating mechanisms: Failure of embryos to develop Failure of hybrids to survive or breed Chromosomes may not pair normally at meiosis, resulting in sterile hybrids.

The Role of Hybridization in Evolution Hybrids - Offspring produced by parents that differ in one or more characteristics May have gene combinations better suited to new environments Two related species may hybridize. Introgression - Intercrossing between hybrids and parents

The Role of Hybridization in Evolution Polyploidy - Occurrence of double the normal chromosome number Result of failure of meiosis to halve chromosome number in gametes Polyploids produced when these gametes participate in fertilization. Hybrids often sterile because chromosomes do not pair properly at meiosis. If polyploid formed in hybrid, then chromosomes can pair and overcome sterility. Thought that more than half of flowering plant species originated this way

The Role of Hybridization in Evolution Sterile hybrids may reproduce asexually. Apomixis - Production of seeds without fertilization. Combination of apomixis and sexual reproduction may be highly successful. Dandelions Dandelion

Discussion Opinions and convictions about origin of life vary. Scientific creationists - Evolution incompatible with biblical account of creation. Tenets of religion not subject to scientific experimentation. Intelligent design proponents accept much of evidence for evolution, but do not believe it possible that cells arose by chance alone. Propose that complex systems designed by supernatural power Biologists feel evolution is only plausible explanation for unity of life at molecular and cellular level and for great diversity of life. Disagreement of precise pathways of past evolution because fossil record incomplete

Review An Introduction to Evolution A Brief Overview of the Early Development of Evolutionary Concepts Charles Darwin Evidence for Evolution Microevolution – Evolution within Species Rates of Evolution Macroevolution – How Species Evolve The Role of Hybridization in Evolution