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How Populations Evolve. Chapter 13. 0. Blue-footed Booby. Blue-Footed Booby. Clown? Funny looking or funny acting? Fool? Easily approachable and easily killed by seamen. Well Adapted? Webbed feet Body and bill streamlined
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How Populations Evolve Chapter 13
0 Blue-footed Booby
Blue-Footed Booby • Clown? Funny looking or funny acting? • Fool? Easily approachable and easily killed by seamen. • Well Adapted? • Webbed feet • Body and bill streamlined • Specialized glands in their eye sockets help manage salt intake.
Adaptations • Inherited traits that enhance an organism’s ability to survive and REPRODUCE in a particular environment.
EVOLUTION The Core Theme of Biology Evolution: changes in the allele frequency in the gene pool over time
Darwin’s Theory of Evolution Earth’s many species are descendents of ancestral organisms that were different from living things today.
Modern Theory of Evolution • All life comes from a single ancestor. • All organisms have DNA and make mRNA. • All organism use RNA to make proteins. • All organisms use ATP.
Darwin’s sea voyage on the HMS Beagle (1831-1836)
15 species of Giant Tortoises. Today only 11 species remain.
Marine Iguanas Charles Darwin described them as "hideous-looking" and "most disgusting, clumsy lizards."
Finches Darwin classified them by their types of beaks.
Darwin’s Lasting Contribution • The scientific explanation for the striking ways in which organisms are suited for life in their environment.
Views Prior to Darwin • Aristotle: species were perfect and permanent. • Jean Lamarck: believed that life evolved but ACQUIRED traits could be passed on.
Darwin spent most of time onshore. • He collected thousands of plants, animals, and fossils. • He noted the unique adaptations of these organisms in places as different as the Brazilian jungle, the grasslands of Argentina, and the frigid tip of South America.
Darwin compared the different characteristics of similar species found on different islands.
Survival of the Fittest • After his five-year exploration of the many lands the HMS Beagle took him to, analysis of his collections, and his many readings, Darwin realized: • the Earth was very old • the Earth was constantly changing • organisms that could adapt to the changes would survive and reproduce.
On the Origin of Species by Means of Natural Selection Published by Charles Darwin in 1859
On the Origin of Species by Means of Natural Selection • Presented evidence that present-day species arose from a succession of ancestors. • He called it “descent with modification.” • Descent with modification = Natural Selection
Natural selection v. Artificial selection • Humans have modified other species by selecting and breeding individuals that have desired traits. This is called artificial selection.
Wild Strawberry Domestic Strawberries
Evolution by Natural Selection • Although natural selection occurs through interactions between individual organisms and their environment, INDIVIDUALS DO NOT EVOLVE • Evolution refers to generation-to-generation changes in population.
Evolution by Natural Selection • Natural selection can amplify or diminish only INHERITABLE traits. • ACQUIRED traits are not passed on to offspring because they are not coded for in the individual’s gametes.
Evolution by Natural Selection • Evolution is NOT goal directed; it does not lead to perfectly adapted organisms. • A trait that is favorable in one situation may be useless or detrimental in another situation.
Extinction • Major environmental changes often lead to extinction, a frequent event in Earth’s history resulting in the irrevocable loss of a species. • Extinction can also be man caused.
Extinction • Dodo Bird • Extinct for over 300 years! • Flightless • Became extinct after the introduction of dogs and pigs to its native island.
Biogeography • Geographic distribution of species. • Example: the unique collection of marsupials in Australia such as kangaroos and koalas. • Populations can become geographically isolated and evolve into different species.
Homologous Structures Anatomical similarities between many species give signs of common descent.
Vestigial Organs • Structures that are of marginal or perhaps no importance to the organism. • Remnants of structures that served important functions in the organisms ancestors. • Example: an appendix
Molecular Biology • If two species have homologous genes with sequences that match closely, it is concluded that these seque33nces must have been inherited from a common species.
Gene Pool • Populations are the units of evolution. • A population is a group of the same species living in the same place at the same time. • All of the alleles in all the individuals of population make up the gene pool.
Mutation and Sexual Reproduction • Both mutation and sexual reproduction produce genetic variation, making evolution possible.
Mechanisms of Evolution • Genetic variation • Mutation – results in new alleles • Sexual Reproduction
Natural Selection • Evolution by natural selection is a chance and “sorting”: chance in the random collection of genetic variation packaged in gametes and combined in offspring.
Natural Selection • Natural selection is the only mechanism that consistently leads to adaptive evolution – evolution that results in a better fit between organism and their environment.
Fitness • The contribution an individual makes to the gene pool of the next generation. • The fittest individuals are those that produce the largest number of viable, fertile offspring.
Stabilizing Selection favors intermediate phenotypes. • Directional Selection shifts the population towards one phenotype. • Disruptive Selection favors individuals at both extremes of a phenotypic range.
Sexual Selection • Sexual Dimorphism • Intrasexual Selection • Intersexual Selection
Sexual Dimorphism • Males and females of the same species that have very noticeable differences.
Intrasexual Selection • Competition between the males of a species OR between the females of a species.
