Natural Selection and the Evidence for Evolution The theory of evolution is the most fundamental concept in biology.

What is the origin of evolution? Fossil records have been important to science since the 18 th century. Fossils have formed concepts & answers questions Several ideas have been proposed but only 1 ideas accepted today by scientists.

Charles Darwin ( ) English scientists-founder of modern evolutionary theory 1831 – naturalists Collect, study & store specimens while on ship Beagle Developed theory to explain how evolution occurs

HMS Beagle

Darwin on HMS Beagle

Snoppy discovers Darwin's "Voyage of the Beagle" is not about his trip to mall, but about biological evolution

Darwin on the HMS Beagle He began in 1831 at age 22 when he took a job as a naturalist on the English ship HMS Beagle, which sailed around the world on a five-year scientific journey. As the ship’s naturalist, Darwin studied and collected biological and fossil specimens at every port along the route For the next 20 years, Darwin’s work refined his explanations for how species change over time.

In the Galapagos On the Galapagos Islands, Darwin studied many species of animals and plants that are unique to the islands but similar to species elsewhere. He realized that individuals struggle to compete in changing environmental conditions.

Section 15.1 Summary – pages How did this help Darwin? He knew that many species produce large numbers of offspring. Darwin continues his studies He also knew that such species had not overrun Earth. Only some individuals survive the competition and produce offspring

Galapagos tortoise are the largest On Earth, different from other Tortoises in body size and shape Galapagos marine iguanas Eat algae from the ocean Large claws help to cling To slippery rocks Galapagos finch Is adapted to feed On cacti.

Artificial Selection artificial selection is the process of intentional or unintentional modification of a species through human actions which encourage the breeding of certain traits over others Darwin hypothesis that there was a force in nature that worked like artificial selection

Natural Selection Natural selection is a mechanism for change in populations. It occurs when organisms with favorable variations survive, reproduce, and pass their variations to the next generation. As a result, each generation consists largely of offspring from parents with these variations that aid survival. In nature, organisms produce more offspring than can survive Darwin proposed this idea of natural selection to explain how species change over time

Section 15.1 Summary – pages Darwin explains natural selection In any population, individuals have variations. Fishes, for example, may differ in color, size, and speed.

Section 15.1 Summary – pages Darwin explains natural selection Individuals with certain useful variations, such as speed, survive in their environment, passing those variations to the next generation.

Section 15.1 Summary – pages Darwin explains natural selection Over time, offspring with certain variations make up most of the population and may look entirely different from their ancestors.

Adaptations for Evolution According to Darwin’s theory, adaptations in species develop over many generations.

Section 15.1 Summary – pages Structural adaptations arise over time The ancestors of today’s common mole-rats probably resembled African rock rats. Learning about adaptations in mole-rats can help you understand how natural selection has affected them.

Section 15.1 Summary – pages Structural adaptations arise over time Some ancestral rats may have avoided predators better than others because of variations such as the size of teeth and claws.

Section 15.1 Summary – pages Structural adaptations arise over time Ancestral rats that survived passed their variations to offspring. After many generations, most of the population’s individuals would have these adaptations.

Section 15.1 Summary – pages Structural adaptations arise over time Over time, natural selection produced modern mole-rats. Their blindness may have evolved because vision had no survival advantage for them.

Other structural adaptations Mimicry is a structural adaptation that enables one species to resemble another species

This fence lizard has adapted to mimic tree trunk color Caterpillar mimics Bird droppings opossum plays possum well

In one form of mimicry, a harmless species has adaptations that result in a physical resemblance to a harmful species. Caterpillar mimics a viper In both looks & movement The tasty Viceroy Butterfly (left), Mimics the bitter tasting Monarch on The Right

Section 15.1 Summary – pages In another form of mimicry, two or more harmful species resemble each other. For example, yellow jacket hornets, honeybees, and many other species of wasps all have harmful stings and similar coloration and behavior. Structural adaptations arise over time

Animals use Camouflage Camouflage allows animals to blend with their surroundings Tartan Hawkfish – blends with Bright gorgonian fans A narrow-headed frog native to Madagascar, blends with the mud & Tree trunks in its environment

Fossil Evidence Fossils are important in Evolution Because they provide a record Of early life and history

Other Evidence Anatomy Analogous Structures: Similar body parts in function w/ no evolutionary origin Homologous Structures: Similar In arrangement, function or in both Vestigial Structure: A body structure in a present day organism That no longer serves its original purpose, but was useful to An ancestor

Section 2

Natural Selection There are three different types of natural selection that act on variation: 1. Stabilizing 2. Directional 3. Disruptive

Section 15.2 Summary– pages Stabilizing selection is a natural selection that favors average individuals in a population. Selection for average size spiders Normal variation

Section 15.2 Summary– pages Natural selection acts on variations Directional selection occurs when natural selection favors one of the extreme variations of a trait. Normal variation Selection for longer beaks

Natural Selection on Variations In disruptive selection, individuals with either extreme of a trait’s variation are selected for

The Effects Of Natural Selection Natural selection can significantly alter the genetic equilibrium of a population’s gene pool over time Significant changes in the gene pool could lead to the evolution of a new species over time

Speciation The evolution of new species, a process called speciation occurs when members of similar populations no longer interbreed to produce fertile offspring within their natural environment.

Geographic Isolation Geographic isolation occurs whenever a physical barrier divides a population Isolated habitat fragments are similar to islands in the way in which the species living there are effected.

Gradualism Gradualism is the idea that species originate through a gradual change of adaptations

Adaptation Radiation Hawaiian honeycreepers When an ancestral species evolves into an array of species to fit a number of diverse habitats, the result is called adaptive radiation

Differences: structures of their beak-adaptation for cactus eaters, seed eaters, insect eaters… 13 Species of Darwins Finches

Darwin’s finches of the Galapagos

Divergent Radiation Adaptive radiation is a type of divergent evolution, the pattern of evolution in which species that were once similar to an ancestral species diverge, or become increasingly distinct

Section 15.2 Summary– pages Possible Ancestral Lasan finch Amakihi Extinct mamo Crested honeycreeper Akialoa Akepa Akiapolaau Liwi Maui parrotbill Apapane Ou Grosbeak finch Palila Akikiki Niihau Kauai Oahu Lanai Molokai Maui Kahoolawe Hawaii Diversity in new environments

Diversity in a New Environment Divergent evolution occurs when populations change as they adapt to different environmental conditions, eventually resulting in new species.

Convergent Evolution A pattern of evolution in which distantly related organisms evolve similar traits is called convergent evolution

Migration Seasonal movements to an area for breeding Birds Fly south for The winter