Standard 8—Evolution Speciation

Standard 8 Vocabulary Diversity Speciation Gradualism Punctuated Equilibrium Adaptive Radiation Divergent Evolution Polyploidy Geological Time Scale Extinction Convergent Evolution Bottleneck Effect Founder Effect Geographical Isolation Reproductive Isolation Macroevolution Microevolution Fossil

8. Evolution is the result of genetic changes that occur in constantly changing environments.

8a. Know how natural selection determines the differential survival of groups of organisms.

8b. Know a great diversity of species increases the chance that at least some organisms survive major changes in the environment.

Publication of On the Origin of Species Darwin filled notebooks with his ideas about species diversity and the evolution process. Darwin was stunned and disturbed by his discoveries. He shelved his manuscript for years and told his wife to publish it in case he died.

Publication of On the Origin of Species In 1858, Darwin received a short essay from naturalist ___________ _________. The essay summarized Darwin’s thoughts on evolutionary change. Later that year, Wallace’s essay was presented with some of Darwin’s work. In 1859, Darwin published his book, On the Origin of Species.

Publication of On the Origin of Species In his book, Darwin: proposed a mechanism for evolution called natural selection. presented evidence that evolution has been taking place for millions of years—and continues in all living things.

Inherited Variation and Artificial Selection Members of each species vary from one another in important ways. In Darwin’s day, variations were thought to be unimportant, minor defects. Darwin argued that this _____________ mattered.

Inherited Variation and Artificial Selection Darwin noted that plant and animal breeders would breed only the largest hogs, the fastest horses, or the cows that produced the most milk. Darwin termed this process ______________ selection.

Inherited Variation and Artificial Selection –How is natural variation used in artificial selection? –Artificial selection is the selection by _____________ for breeding of useful traits from the natural variation among different organisms.

Inherited Variation and Artificial Selection Brussels Sprouts Kohlrabi Ancestral Species Kale Broccoli Cauliflower

Evolution by Natural Selection Darwin compared processes in nature to artificial selection. By doing so, he developed a scientific hypothesis to explain how evolution occurs.

Evolution by Natural Selection The Struggle for Existence Darwin realized that high birth rates and a shortage of life's basic needs would force organisms to compete for resources. The ___________ ________ ___________ means that members of each species compete regularly to obtain food, living space, and other necessities of life. The struggle for existence was central to Darwin's theory of _______________.

Evolution by Natural Selection –How is natural selection related to a species' fitness? –Survival of the Fittest The ability of an individual to survive and reproduce in its specific environment is _____________. Darwin proposed that fitness is the result of adaptations. An ________________ is any inherited characteristic that increases an organism's chance of survival.

Evolution by Natural Selection Successful adaptations enable organisms to become better suited to their environment and better able to survive and reproduce. Individuals with characteristics that are not well suited to their environment either die or leave few offspring. Individuals that are better suited to their environment survive and reproduce most successfully. Darwin called this process _____________ of the _______________.

Evolution by Natural Selection Because of its similarities to artificial selection, Darwin referred to the survival of the fittest as _________ __________. In natural selection, the traits being selected contribute to an organism's fitness in its environment. –Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species' fitness in its environment.

Summary of Darwin's Theory Individual organisms differ, and some of this ______________ is heritable. Organisms produce more offspring than can survive, and many that do survive do not reproduce. Because more organisms are produced than can survive, they compete for limited resources.

Summary of Darwin's Theory –Individuals best ___________ to their environment survive and reproduce most successfully. –These organisms pass their heritable traits to their offspring. Other individuals die or leave fewer offspring. –This process of natural selection causes ____________________ to change over time.

Summary of Darwin's Theory –Species alive today are descended with ______________ from ancestral species that lived in the distant past. –This process, by which diverse species evolved from common ancestors, unites all organisms on Earth into a single tree of life.

Evolutionary Theory Scientific advances in many fields of biology, geology, and physics have confirmed and expanded most of Darwin’s hypotheses. Evolutionary theory continues to change as new data are gathered and new ways of thinking arise.

Testing Natural Selection in Nature Studies showing natural selection in action involve _______________ of the finches that Darwin observed in the Galápagos Islands. The finches Darwin saw were different, but he hypothesized that they had descended from a ___________ ___________.

Testing Natural Selection in Nature

Peter and Rosemary Grant tested Darwin’s hypothesis, which relied on two testable assumptions: For beak size and shape to evolve, there must be enough heritable variation in those traits to provide raw material for natural selection. Differences in beak size and shape must produce differences in fitness, causing natural selection to occur.

Testing Natural Selection in Nature The Grants tested these hypotheses on the medium ground finch on Daphne Major, one of the Galápagos Islands. During the rainy season, there is plenty of food. –During droughts, food becomes scarce. –Individual birds with different-sized beaks had different chances of survival during a drought.

Testing Natural Selection in Nature When food was scarce, individuals with large beaks were more likely to survive.

Testing Natural Selection in Nature The Grants provided evidence of the process of evolution. Beak size can be changed by natural selection.

Summary Natural Selection _____________ organisms that are well ______________ to their environment. Organisms that are less sated to the environment may die off before passing on their traits. ___________ _____________ can be used to explain adaptation and its effects on the number and types of species that currently exist. When a species is unable to adapt to meet its needs, it may _____ out completely.