Evolution Chapter 15 Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Early Evolutionary Concepts Darwin Microevolution Mutations Outline Early Evolutionary Concepts Darwin Microevolution Mutations Chromosomal Changes Migration and Genetic Drift Rate of Evolution Macroevolution Role of Hybridization Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Early Evolutionary Concepts By end of 18th century, many prominent biologists believed heredity changes in populations over long periods of time occurred as a result of the inheritance of acquired characteristics. Long necks of giraffes. Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Guided by ideas of Malthus. Charles Darwin Accepted position as assistant naturalist on HMS Beagle to voyage around the world and chart coastlines. Read Charles Lyell’s book that theorized the earth was much older than previously believed. Guided by ideas of Malthus. Populations grow geometrically until food supplies and other resources limit growth. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Evidence for Evolution Homologous Characteristics Common Ancestry Convergent Evolution Protein Structure and Relationships Fossil Record Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Microevolution Darwin observed that animal breeders, through artificial selection, changed populations of domestic animals by retaining those with desirable traits. Reasoned that in nature, individuals best adapted to available resources would increase in number in succeeding generations. Natural Selection Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Darwin based natural selection on : Overproduction of Offspring. Microevolution Darwin based natural selection on : Overproduction of Offspring. Struggle for Resources and Thus Survival. Inheritance and Accumulation of Favorable Variations. Differential Survival and Reproduction. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

No permanent change occurs unless there is inheritable variation. Mutations General characteristics of a population will eventually change if the environment, or other factors, favor certain heredity variations, and disfavor others. No permanent change occurs unless there is inheritable variation. Arise via mutations. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Chromosome Translocations Chromosome Inversions Mutations Mutations arise via: Chromosome Deletions Chromosome Translocations Chromosome Inversions Generally, the mutation rate for a specific gene remains relatively constant in the absence of environmental changes. Most mutations are harmful. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Chromosomal Changes A. Deletion B. Translocation C. Inversion Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Migration and Genetic Drift Migration - Gene flow occurs between populations when individuals or gametes move from one population to another. Genetic Drift Changes in the genetic make-up of a population due to random events. May occur as a given gene fluctuates due to meiosis and gamete production. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Darwin believed evolution by natural selection was slow and gradual. Rate of Evolution Darwin believed evolution by natural selection was slow and gradual. Many contemporary biologists believe theory of punctuated equilibrium. Major changes occurred in spurts. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Reproductive Isolation Macroevolution Reproductive Isolation If new genes are produced in a freely interbreeding population, they may gradually be spread throughout the population. If some barrier divides the population, two new populations eventually may become distinct from each other. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Macroevolution Geographic Isolation Geographic, or other, isolation of two populations prevents gene flow between the two populations. Random mutations, which are rarely identical, then spread only throughout the population in which they arise. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Macroevolution Ecological Isolation Ecological factors such as climate or soils may play a role in isolation, as do time and mechanical isolating factors. As a result, related species can be sympatric without genes being exchanged. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Role of Hybridization in Evolution Hybrids may be significant or important in evolutionary change, depending on how the characteristics of the parents were combined. Introgression - Backcrossing between hybrid and parent. Polyploidy - New cell wall fails to develop between two daughter cells. Sterility - Chromosomes do not pair up correctly. Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Sterile Hybrids may reproduce asexually. Apomixis Sterile Hybrids may reproduce asexually. Apomixis includes the development and production of seeds without fertilization. May be highly successful. Dandelions and Wild Blackberries Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Early Evolutionary Concepts Darwin Microevolution Mutations Review Early Evolutionary Concepts Darwin Microevolution Mutations Chromosomal Changes Migration and Genetic Drift Rate of Evolution Macroevolution Role of Hybridization Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies

Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display Stern - Introductory Plant Biology: 9th Ed. - All Rights Reserved - McGraw Hill Companies