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Transcript
Evolution and Natural Selection Change over time “The Earth is 4,000 years old” According to some interpretations of the Bible If Earth was only 4,000 years old… How could there have been time for all the extinct species, such as dinosaurs to have lived? “The Earth is very, very old” - Charles Lyell 1797-1875 – Lyell influenced Charles Darwin’s Theory of Natural Selection Radiocarbon dating puts the earth at 4.5 Billion years old Humans have been here less than 1 million years! Thomas Malthus made a contribution to Darwin’s Theory Malthus was an economist He notice that humans produce more offspring than can survive A group will die every generation What happens when the population exceeds the resources? Jean Baptiste Lamarck 1744-1829 Proposed an idea of how organisms change over time “The Theory of Acquired Characteristics” Lamark’s theory Organisms can acquire new traits and pass them on to their offspring If you lift weights your muscles will be bigger Your children will have stronger arm muscles Lamarck suggested that giraffes long necks are the result of individual animals stretching their necks over long periods of time to reach the highest leaves Charles Darwin Born in 1809 Died in 1882 Published a book called “The Origin of Species” Suggested a way that species changed over time The Theory of Natural Selection 1) Variation Exists in all populations Variation comes from random mutation 2) Those individuals that are best suited to their environment survive and pass on their genes to their young 3) Over millions of years species change “Survival of the Fittest” Is not accurate Natural selection is the survival and reproduction of the fittest traits Adaptation: The changing of a species that results in its being better suited for its environment Rough Green snakes Adapted camouflage helps these snakes escape predators Some species change color in the winter Rabbits have a coat change in the winter Turtles adaptation Turtles have Exceptional night Vision. Unlike us, turtles can see in color at night Eagles have extraordinary vision Vision is 4x as sharp as a human They have an extra focal point in the back of their eye They can see even when they blink their eye - eyelids are transparent * can see a rabbit moving a mile away!* Mollusks also have simple eyes Mollusks have many eye features that are similar to vertebrates. Lenses Retina * Their vision is not as good as ours Flatworm has “eyes” Not the kind of eye that can see a picture They can sense light and dark Adaptations can be behavioral Bears hibernate in the winter Snakes and other reptiles sun themselves on rocks to warm up Reproductive Adapations Since Reproduction is necessary for natural selection, species have adapted incredible Reproductive adapations! Likes and Dislikes of Charles Darwin Dislikes Medicine, Blood, Surgery Likes Plants and animals esp. animals Darwin got a job On the H.M.S. Beagle His unofficial title was as a naturalist The Galapagos Islands Before Darwin left for his voyage, People thought species never changed But what Darwin found changed that thought The Galapagos held a vast array of life Many of the species Darwin found closely resembled species Darwin had seen on the mainland Darwins drawings of finches Why would God create so many different finches? 13 islands 13 different finches They had differences in the size of their beaks The food they ate Some ate soft nuts Some ate hard-shelled nuts Some ate insects Some ate berries Darwin had a Hypothesis Finches must have arrived at the galapagos a long time ago, and changed after they arrived! “Descent with Modification” Tortoises 11 different species of tortoises on the 13 Galapagos Islands Different size and shell shape Evidence of Evolution 1) Fossils – found in sedimentary rock, these can be dated and show that many species have changed over time Evolution of Horse foreleg bones found in fossils 2) Vestigial Structures Organs or structures in present day animals that are not used anymore Appendix Did you know whales have leg bones and hips? They are no longer attached to the spine This suggests that whales have an ancestor that walked on land! Evolution of the Whale 3) DNA and Proteins We all share the same DNA code Made with the same 4 nucleotides The more closely related two species are, the more similarities there are in their DNA code Humans and chimps are 98% identical!! All mammals have similar proteins i.e. hemoglobin DNA evidence Most species of mammals are over 90% identical in terms of DNA code Pseudo genes - multiple copies of DNA sequences that no longer function Hox genes These are found within gene families Not transcribed or translated 4) Comparative Anatomy Similar Organisms have similar structures – The forearm in Vertebrates all have the same bone structure 5) Artificial Selection Darwin used this to support his theory, dog breeders select for specific traits in a breed If humans can change an animals traits, why couldn’t this occur in nature? Domestic Pigeons? – these were very popular among aristocratic English in the 1800’s! 6) Evolutionary history is seen in the development of Embryos Each embryo develops a tail, buds that become limbs and pouches which contain gill - like brachial slits Only fish and amphibians retain these and have them develop as gills Amphibians retain gills in their tadpole stages but get rid of them when they become adults 7) Microevolution Change in small groups has been shown to occur Antibiotic resistance is evolution in action!!! Population Genetics Population – A group of genetically similar organisms that live together and interbreed Species – A group of organisms that can and do interbreed and produce fertile offspring Dogs Canis familiaris are all the same species Horses and Donkeys are not Isolation Two populations of the same species cannot breed with each other Gradualism Change occurs very slowly over very long periods of time American scientists beg to differ Successful species remain unchanged for very long times They developed the idea of Punctuated Equilibrium Michigan State Experiment Bacteria reproduce 15,000 times faster than we do Grew thousands of generations of bacteria Showed that changes in e. coli occurred quickly Explains why our fossil histories often lack the “intermediate type” Species remains unchanged until an environmental stimulus changes Peppered Moth London England Use of coal during the Industrial Revolution Moths had adapted to blend in with the trees they lived on Use of coal blackened the trees and moths no longer blended in with their surrounding By the end of the Industrial Revolution, most peppered moths were the darker version So they adapted to blend in with their surroundings… Aren’t the smart?! How did they do that? A mutation occurs randomly, causing the darker versioned moth Industrial melanism The darker version survived better with the blackened trees. 100 years later, trees are back to normal Which moth will survive better? New species are formed through Natural Selection Speciation - appearance of a new species Most evolutionary change is too slow to see Examples of speciation Changes in bacteria 1969 - a new species of salt bush developed from hybrids of a different salt bush and a salt sage Salt bush occurs in south Utah New species of fruit flies have been created using radiation treatment Radiation increases the rate of mutation and therefore increases variation Why is variation important to evolution? Speciation is directly linked with the ability to reproduce As soon as two population become so genetically different that they cannot produce fertile offspring, they are technically different sepecies i.e. Domestic Dog and Wolf The intermediate of a Wolf-dog is infertile In some cases one population will simply out-compete another and extinction of a section will occur Many times the two species are geographically isolated and they evolve separately At one time the Alder flycatcher and the willow fly catcher were considered the same species Ecological isolation Occurs when two species adapt to different habitats. When the habitats are different and no crossbreeding occurs, Sometimes there is a chemical incompatibility between the two gametes This sometimes occurs in plants Sperm and egg may not be chemically compatible Behavioral Isolation Sometimes occurs in animals Ex. Leopard Frogs mate at different times in the year and are in the process of becoming different species When frogs of one sex in the Northern limit of the range are brought together with frogs in the southern limit, they will not mate Founder effect Occurs when one, or a very few individuals from a population move to a new area. The new population will be genetically different from the first because only the genes of the Founders are available Genetic Drift Change in allele frequency in a population Bottleneck Effect When a stress in the environment occurs and only a few individuals survive, the remaining individuals will determine the genetic makeup of the new population Hardy Weinberg Equilibrium We can calculate Allele frequency in a population with the following formula a= dominant allele freqency b= recessive allele frequency a+b=1 a2 + 2ab + b2 = 1 a2 = frequency of homozygous Domanant individuals b2 = frequency of homozygous Recessive individuals 2ab = frequency of heterozygous individuals Hardy Weinberg Equilibrium exits in a population when.. 1) There is NO Genetic Drift occuring 2) There is no Gene Flow in a population Mating is completely RANDOM There is NO Natural Selection There is NO mutation ….. So never, but we still use the formula to estimate allele frequency in populations =) Darwin said in his book, “Origin of Species”, Humans, gorillas and chimpanzees all evolved from a common ancestor NOTE: WE DID NOT EVOLVE FROM APES!!! Many fossils strongly confirm this hypothesis The first primates evolved 5060 million years ago They had two features other mammals lacked 1) Grasping hands and feet - young could hold on to their mothers 2) Eyes facing forward - many other mammals didn’t see strait out = Better depth perception Prosimian is an example of a primate that resembles early Primates Prosimians survive with their adaptations They live in trees They use their tails to help them balance Diurnal v.s Nocturnal Diurnal - active during the day Nocturnal - active at night Cone cells developed for daytime seeing Cone Cells - allow us to see in color! Opposable thumbs Monkeys feed mainly on fruits and leaves rather than insects and they were the first to have opposable thumbs. Take away your thumb and see how hard it is to pick up and move objects! Monkeys appeared in Africa and Asia Old world Monkeys New World Monkeys are monkeys in the Americas Emergence of the apes Apes shared a common ancestor with monkeys Split that occurred with chimps and apes occurred relatively recently Our ancestors descended along the same lines as the great apes These are some actual skulls found.