Evolution Notes PDF

Slide 1 Evolution , Natural Selection The Stories of Charles Darwin and Alfred Russell Wallace Slide 2 A Quick History of Life ⚫ The Earth formed 4.6 BILLION years ago ⚫ Early Earth was very unstable and too hot...

Slide 1 Evolution , Natural Selection The Stories of Charles Darwin and Alfred Russell Wallace Slide 2 A Quick History of Life ⚫ The Earth formed 4.6 BILLION years ago ⚫ Early Earth was very unstable and too hot for life to exist. ⚫ 3.9 Billion years ago Earth cooled enough for water vapor to condense to form rain and seas. ⚫ 3.5 Billion years ago the first living organisms appear. Slide 3 Origin Of Life ⚫ Life began during the first billion years of Earth’s history (which is 4.5 billion years old). ⚫ The ocean received organic matter from the land and the atmosphere, as well as from meteorites and comets. ⚫ Substances such as water, carbon dioxide, methane, and hydrogen cyanide formed key molecules such as sugars, amino acids, and nucleotides - the building blocks of proteins and nucleic acids. Slide 4 The theory of Evolution ⚫ Charles Darwin is credited with the concept of Evolution, but he was not the first person to suggest that organisms change over time. ⚫Several scientists before Darwin alluded to the concept of Evolution. They never explained how it could happen. ⚫Darwin gets the credit for the theory of evolution because he described or explained how evolution could occur. Slide 5 Evolution Defined ⚫ Evolutions was first defined as a change in a species over time. ⚫ This first general definition was too vague and general. It allowed for much debate. ⚫ A current and less arguable definition of Evolution is: ⚫ Evolution is the genetic change in a population over time. Slide 6 Jean Baptiste de Lamarck ⚫ 1. In the early 1800’s, Lamarck, a French biologist, developed a theory of evolution based on his belief in two biological processes. ⚫ 1 The use and disuse of organs. Lamarck believed that organisms respond to changes in the environment by developing new organs or modifying old ones (acquired characteristics). Disuse results in the disappearance of the organ. ⚫ Inheritance of acquired traits. Lamarck believed that these acquired characteristics were then passed on to offspring. Slide 7 Example of Lamarck’s theory ⚫ Lamarck believed that at one time giraffes had short necks and ate grass. Then either grass became scarce or other animals out-competed the giraffes for the grass so they started eating leaves off trees. As lower leaves became scarce, they stretched to reach higher leaves. Their necks gradually got longer and they passed the longer necks to their offspring. Adaptation: Evolutionary modifications that improve the survival and reproductive success of an organism. Slide 8 Darwin ⚫ Was a pigeon breeder and noticed that people could select and breed for specific traits. ⚫ Artificial selection – A technique in which breeders select for a particular trait. ⚫ Darwin applied the idea of artificial selection to the natural environment and termed it Natural Selection. Artificial selection: Eg. Breeds of dogs, such as German Shepherds and Saint Bernards are a result of artificial selection Slide 9 Natural Selection- Definitions ⚫ Population: All of the individuals of the same species that inhabit the same place at the same time. ⚫ Species: a population whose members interbreed in nature. (The Biological Species Concept) ⚫ The Biological Species Concept is the most widely used species definition. According to the concept, it states that a species is a group of organisms can interbreed to produce fertile offspring. Interbreeding: To cause to breed with members of another breed or group. Eg. interbreed wolves with domestic dogs. But, in some cases, organisms of different species mate and produce offspring that are infertile, can’t reproduce. Slide 10 Natural Selection ⚫ Natural selection is the process through which populations of living organisms adapt and change to better survive in their environment. Survival of the fittest Slide 11 Darwin ⚫ 1. As a naturalist, Darwin traveled to South America on the ship the H.M.S. Beagle. While there he found evidence that the Earth was very old by observing an earthquake and discovering marine fossils on mountaintops. He also found evidence of evolution. Slide 12 Darwin ⚫ While on the Galapagos Islands, Darwin noticed that plants and animals were like those on the South American mainland, but not exactly alike. He realized that the species came from the mainland and changed into a new species. He came up with his theory of Evolution by Natural Selection. Galapagos Islands lies off the coast of Ecuador which is in South America Slide 13 Slide 14 ⚫ Darwin observed that: ⚫ Individuals in a population have traits that vary ⚫ Many of these traits are heritable (passed from parents to offspring) ⚫ More offspring are produced than survive ⚫ Competition is inevitable ⚫ Species generally suit their environment Slide 15 ⚫ Darwin inferred that: ⚫ Individuals that are best suited to their environment are more likely to survive and reproduce ⚫ Over time, more individuals in a population will have the advantageous traits ⚫ In other words, the natural environment “selects” for beneficial traits Slide 16 ⚫ Darwin’s theory had 5 main points: ⚫ 1. Variation exists among individuals of a species. ⚫ For example, some gorillas have longer arms than others, some ladybugs have more spots than others, etc. Slide 17 Darwin Evolution by Natural Selection ⚫ 2. All organisms compete for the same limited resources. Such competition would lead to the death of some individuals, while others would survive. 3.Organisms produce more offspring than can survive. The available resources cannot support all these individuals. Slide 18 Darwin Evolution by Natural Selection ⚫ 4. The environment selects organisms with beneficial traits. ⚫ 5. Organisms with traits best suited to the environment will reproduce and pass on these traits at a greater rate than organisms less suited to the environment. This “survival of the fittest” is called Natural Selection. Slide 19 Conditions Necessary for Natural Selection ⚫ Over production of offspring ⚫ Variation of traits ⚫ Individuals with favorable variations survive and pass on variations to the next generation. ⚫ Gradually offspring make-up a larger proportion of the population Slide 20 Origin of Variation ⚫ From where do the “fittest” get their beneficial traits? Variations must be genetic (in the sex cells) to be passed on to offspring. There are two fundamental sources of variation in a species: Mutation - a change in the chemical structure of the gene, so it will be passed on to the offspring. Genetic recombination - mixing of the genes between chromosomes during meiosis. Population genetics is the study of the genetic variability within a population and the forces that change allele frequencies. Slide 21 Selection Pressure ⚫ Selection Pressure is the force exerted by nature which directs an organism’s evolution and causes one trait to be better than another. Slide 22 Processes of Evolution ⚫ 5 main processes that upset the genetic equilibrium of a population: A population in ⚫ A. Natural Selection which the allele and genotype ⚫ B. Migration frequencies do ⚫ C. Genetic Drift not change over ⚫ D. Isolation time is said to be in genetic ⚫ E. Mutation equilibrium. frequencies of alleles in a population don’t change unless there is evolutionary force acting Slide 23 Processes of Evolution ⚫ A. Natural Selection – Disrupts a normal population by allowing fit individuals to survive and reproduce at higher rates than less fit individuals. There are three (3) types of natural selection: Slide 24 Natural Selection ⚫ 1. Directional Selection – Natural selection that proceeds in a given direction. ⚫ Ex.) Necks of giraffes – evolution has proceeded in the direction of longer necks. Slide 25 Natural Selection ⚫ 2. Stabilizing Selection – Selection that eliminates the extremes of a trait causing a reduction in variation of a species. ⚫ Ex.) Leg length of rabbits – long legs are eliminated because the rabbits can’t crawl into a hole to escape predators, short legs are eliminated because they cannot run fast enough to escape predators. Slide 26 Natural Selection ⚫ 3. Disruptive Selection – Selects against the average and favors the extremes of a trait. ⚫ Acorns – squirrels do not eat the smallest, not enough food. Squirrels do not eat the largest, to hard to carry. Squirrels eat the average, after many years the average become eliminated. Slide 27 Migration ⚫ B. Migration – The movement of organisms into or out of a population. ⚫ A herd of caribou lives in Canada. A second, genetically different herd migrates to mix with the first herd. The gene pools of the two herds mix, genetically changing the original population. Migration another process that upsets the genetic equilibrium of a population Two types of migration: 1. Immigration – The movement of new individuals into a population. 2. Emigration – The movement of individuals out of a population. Slide 28 Genetic Drift ⚫ C. Genetic Drift – The change in gene frequency of a population due to chance. ⚫ Ex.) In a population of 16 long-horned beetles, 15 are black and 1 is red. If random mating occurs, there is a chance the red won’t mate, thus eliminating that trait from the population. Genetic drift another process that upsets the genetic equilibrium of a population Slide 29 Isolation ⚫ D. Isolation – Isolation occurs when a geographic boundary separates a population into groups that can no longer interact. Boundaries can include rivers, mountains and canyons. Isolation often results in the evolution of a new species. ⚫ Ex.) The camel originated in the U.S. It spread to Asia and South America over land bridges during the Ice Ages. Over time the separated populations evolved and became different species – the camel in Asia and the llama in South America. Isolation another process that upsets the genetic equilibrium of a population Slide 30 Mutation ⚫ E. Mutation – Harmful mutations are eliminated from a population because the organism usually doesn’t live to reproduce. Beneficial mutations are passed on to offspring, thus changing the population. Mutation another process that upsets the genetic equilibrium of a population Slide 31 Patterns of Evolution ⚫ A. Divergent Evolution ⚫ B. Convergent Evolution Slide 32 Patterns of Evolution ⚫ A. Divergent Evolution – The process by which related organisms become less alike. ⚫ Speciation ⚫ Adaptive Radiation Slide 33 Divergent Evolution ⚫ 1. Speciation – Divergent evolution results in the formation of a new species from an ancestral population. ⚫ Ex.) A group of brown bears becomes isolated from another group. The isolated group moves into northern Canada and eventually develops heads and necks suited for swimming and white fur, thus diverged from their ancestors. Slide 34 Adaptive Radiation ⚫ 2. Adaptive Radiation – Process by which individuals of a new species adapt to a variety of habitats. ⚫ Ex.) Darwin’s finches adapt to eating different types of food by changing beak types. Slide 35 Convergent Evolution ⚫ B. Convergent Evolution – The process by which distantly related organisms develop similar characteristics because they share the same environment. ⚫ Ex.) Whales were once land mammals that adapted to an aquatic environment by changing from legs to flippers for swimming. They began to resemble fish, which are not closely related. Slide 36 Convergent Evolution ⚫ Can lead to Mimicry Viceroy – the evolution of one organism so it resembles another. ⚫ Ex. The Viceroy butterfly, a nontoxic Monarch insect, mimics the Monarch butterfly, a toxic insect. Slide 37 ⚫ Evolutionary relationships are often illustrated with tree-like diagrams that show ancestors and their descendants Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Slide 38 Fig. 1-22 Warbler finches Insect-eaters Green warbler finch Certhidea olivacea COMMON Gray warbler finch ANCESTOR Certhidea fusca Seed-eater Sharp-beaked ground finch Bud-eater Geospiza difficilis Vegetarian finch Platyspiza crassirostris Mangrove finch Cactospiza heliobates Insect-eaters Tree finches Woodpecker finch Cactospiza pallida Medium tree finch Camarhynchus pauper Large tree finch Camarhynchus psittacula Small tree finch Camarhynchus parvulus Cactus-flower- Large cactus eaters ground finch Geospiza conirostris Ground finches Cactus ground finch Seed-eaters Geospiza scandens Small ground finch Geospiza fuliginosa Medium ground finch Geospiza fortis Large ground finch Geospiza magnirostris Figure 1.22 Descent with modification: adaptive radiation of finches on the Galápagos Islands Slide 39 Fig. 1-22a Warbler finches Insect-eaters Green warbler finch Certhidea olivacea Gray warbler finch Seed-eater Certhidea fusca Sharp-beaked ground finch Bud-eater Geospiza difficilis Vegetarian finch Platyspiza crassirostris Figure 1.22 Descent with modification: adaptive radiation of finches on the Galápagos Islands Slide 40 Fig. 1-22b Mangrove finch Cactospiza heliobates Insect-eaters Tree finches Woodpecker finch Cactospiza pallida Medium tree finch Camarhynchus pauper Large tree finch Camarhynchus psittacula Small tree finch Camarhynchus parvulus Figure 1.22 Descent with modification: adaptive radiation of finches on the Galápagos Islands Slide 41 Fig. 1-22c Cactus-flower- Large cactus eaters ground finch Geospiza conirostris Cactus ground finch Ground finches Seed-eaters Geospiza scandens Small ground finch Geospiza fuliginosa Medium ground finch Geospiza fortis Large ground finch Geospiza magnirostris Figure 1.22 Descent with modification: adaptive radiation of finches on the Galápagos Islands Slide 42 Anatomical Evidence of Evolution ⚫ 1.Body parts with the same basic structure are called Homologous Structures. ⚫ These are structures in which the size and shape are different, but the number and arrangement of bones are the same. ⚫ Homologous structures found in different organisms suggest that these organisms share a common ancestor. Slide 43 Anatomical Evidence Slide 44 Anatomical Structures (Continued) ⚫ VestigialStructures, structures that have been greatly reduced in size and no longer serve an important function, also provide evidence for evolution. ⚫ An example of this is the small hipbones in whales and snakes suggesting the whale and snake came from an ancestor with hips, and the splint- like bone in horses that indicated an ancestor with a side toe. Slide 45 Slide 46 Human Vestigial Structures: Slide 47 1. Ear muscles help monkey’s move ears to sense danger, but do nothing in humans. Slide 48 2. Appendix - used by ancestors to digest cellulose of plants. Slide 49 3. Coccyx (tail bone) - No longer needed for original function of balance and mobility. Slide 50 4. Plica semilunaris - remnant of the nictitating membrane (the "third eyelid") which is present in other animals. Plica semilunaris: a small, loose, arc-shaped fold of tissue in the conjunctiva of the eye that helps with eye movement and tear drainage Slide 51 5. Wisdom teeth - third molars that human ancestors used to help in grinding down plant tissue. Slide 52 6. Goose bumps - its purpose in human evolutionary ancestors was to raise the body's hair, making the ancestor appear larger and scaring off predators. Raising the hair is also used to trap an extra layer of air, keeping an animal warm.