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Vocabulary • • • • • • • • • • • Evolution Speciation Fitness Competition Limited resources Adaptation Niche Variation Carrying capacity Biodiversity Natural Selection What is Evolution? • The study of how species change over time • Life began as simple, singlecelled organisms that evolved to become today’s complex, multicellular organisms Evolution • New life forms come into existence over time • New species evolve from pre-existing species via modification (mutations) • All species therefore have descended from a common ancestor The End Result… • Diversity among species, BUT a unity between them (fundamental similarities among life processes) • Therefore, evolution explains the diversity and unity of life Darwin’s Observations: • He studied the geology (rock formations) and observed that the Earth is VERY old • He noticed that some fossils of species found in the rocks are VERY similar to those of today (with some changes) • He noticed that today’s species are related to extinct species Fossil Record • The fossil record shows that organisms have changed over time • Some species that have existed are now extinct • Some current species are not present in the fossil record • Some current species are similar, but not identical, to some previous species •Fossil layers are fossils that formed in sedimentary rock. •Sedimentary rock is rock that is formed in layers by the depositing and pressing of sediments on top of each other Which layer represents the oldest fossils? The top layers are the youngest and the bottom layers are the oldest. •The organisms also tend to become more and more complex. •From this, Darwin concluded that organisms have not remained the same since earth's beginning, that they have changed a lot, gradually becoming more and more complex. He also realized that as new species arise, other ones become extinct. Evidence to Support Theory of Evolution • Scientists use many forms of evidence to support this theory. • Scientists compare similarities among organisms to show how they may have evolved from a common ancestor. Comparative Anatomy • Related organisms share a unity of body plan • Backbone, rib cage, and arrangement of internal organs are similar in fish, amphibians, reptiles, birds and mammals • Among vertebrates, forelimbs have the same set of bones, whether it is used for swimming, walking, flying, hanging or grabbing • Therefore, forelimbs are HOMOLOGOUS structures Homologous Structures • Bones are structurally similar, but have different functions • Ex: forelimbs of birds and mammals • Pelvic bones in whales are homologous to cows Vestigial Structures • Structures which have become reduced in size and are no longer of use, or have diminished in function than they did in the past Comparative Embryology • Related organisms develop similarly • All vertebrate embryos develop gill-like structures even though only fish have gills as an adult Comparative Biochemistry • Basic cell structure is almost universal • All living things use the same basic biological molecules for similar functions • Ex: DNA stores genetic info., proteins serve as enzymes, carbohydrates and fats used for storage, lipids used to build membranes • Metabolic systems such as photosynthesis and respiration are similar among species Comparative DNA • Many organisms have similar DNA sequences So…. If we are all related from a common ancestor then how do we become different??? Lamarck and Darwin had 2 different ideas for how this occurred. Darwin’s Finches • While on the Galapagos Islands, he found 14 different species of finches, all descended from a common ancestor • All 14 species of “Darwin’s finches” have beaks adapted to specific tasks related to a specific environment and ecological niche Define the following terms: 1. Overproduction 2. Variation 3. Competition 4. Natural Selection 5. Adaptation to the environment 6. Fitness Natural Selection • It was once thought that species could evolve based on their needs. • However, today we know that this does not happen • Charles Darwin proposed a mechanism by which organisms evolve (and called it Natural Selection) 1. Overproduction: • More offspring are produced, than can actually survive “Of course, long before you mature, most of you will be eaten” 2. Competition: Since more are produced than survive, there is a competition for resources. Competition •Resources are fixed. (food, shelter) •Many more individuals are produced than can survive •Population grows to a limit •Individuals must compete •There is a struggle for survival Sources of Variation •Sexual Reproduction •Mutations Reproduction • We know that sexual reproduction and random genetic change (mutations) result in variations among individuals • We also know that the genetic instructions for our traits are passed on to new generations in the form of genes (DNA) • The genes that give the organisms an advantage have an adaptive value and are passed on to future generations Sources of Genetic Variation • Meiosis and Sexual Reproduction – Both processes allow for genetic shuffling Sources of Genetic Variation • Mutations – random changes in the DNA base sequences – They can only be passed on to future generations if they occur in the gametes Why are variations good? • Variations lead to biodiversity. • The more variations in organisms, the more stable the ecosystem is because variations increase the likelihood that some organisms will survive and create new future generations Fitness: What does it mean? Some individuals have traits which make them better at surviving. (physical or behavioral) This results in differential reproduction Fitness is linked to a particular environment. The Beaks of Finches State Lab What variations do you see in this population? Why does variation exist in this population? Examine the tools and decide which you think will be the best for picking up small seeds. Give reasons. Choose a tool which will be least successful in picking up small seeds. Explain why. Do you think these differences are important and why? Round 1: No competition Use your beak to pick up the small seeds and place them IN the petri dish. You will have a limited amount of time and you must pick up an average of 20 seeds to survive. Evolution of Giraffes • Darwin’s explanation of evolution as applied to giraffes. • Each generation of short-necked giraffes had slight variations in the lengths of their necks. • Only those with the longer necks survived the process of natural selection and produced the next generation, which started out with slightly longer necks. • The long-necked individuals in the 2nd generation were again favored by natural selection, resulting in even longer necks in the 3rd generation Extra Credit Question for the test • Choose one of the “stories” from the film Voyage to the Galapagos and explain how evolution is occurring in these populations • Use specific examples and include the following terms: – Natural Selection – Fitness – Adaptation How fast does evolution occur? • In organisms that reproduce few offspring and have long life cycles, evolution takes place very slowly. • Ex: Humans How fast do species evolve? • Evolution is much faster in organisms with short life cycles that produce many offspring • Ex: Resistance in bacteria and insects Bacteria Resistance • In bacteria we see evolution taking place with the appearance of antibiotic resistant bacteria. • When a colony of bacteria form, some may have natural variations that make them better adapted. • When antibiotics are taken, the antibiotic resistant bacteria are not killed. • They then can reproduce creating a population dominated by antibiotic resistant bacteria Insecticide Resistance • When insecticides are used, some insects have variations that make them immune to the insecticide. • These insects are not killed. • They survive and reproduce creating a new population of insects that are insecticide resistant Gradualism: • The slow and steady evolution of species over time • Many small changes over millions of years • Eventually, population will evolve into new species • Driven by natural selection Punctuated Equilibrium: • Evolution is rapid and could take place in one generation • Driven by small number of genetic changes (mutations) • Occurs when there is severe environmental change-(asteroid impact) What is Speciation? • The formation of a new species What factors can lead to the evolution of a new species (speciation)? Factors leading to speciation: 1. Geographical Isolation • When two populations are separated by a geographical barrier (such as rivers or mountains) 2. Ecological Competition • Competing for the same resources forces one to either adopt a new food source or become EXTINCT 3. Behavioral Isolation • When two species have differences in courtship rituals Blue-Footed Booby Dance 4. Temporal Isolation(reproductive isolation) • When two different species reproduce at different times • They are fertile at different times of the year Mechanical Incompatibility • Body parts (sex organs) simply do not match up Reproductive isolation Results from Isolating mechanisms Which include Behavioral isoloation Geographical isolation Temporal isolation All can result in the formation of a new species!!! Darwin’s theory of Evolution includes Variety-organisms differ as a result of sexual reproduction and mutations Overproduction causes Favorable adaptations lead to better fitness competition Evolution A C B I G J D E F H Read the following story: You are a bear-eating monster. There are two kinds of bears: happy bears and sad bears. You can tell the difference between them by the way they hold their hands. Happy bears hold their hands high in the air, and sad bears hold their hands down low. Happy bears taste sweet and are easy to catch. Sad bears taste bitter, are sneaky, and are hard to catch. Because of this, you eat only happy bears. New bears are born every 'year' (during hibernation) and the birth rate is one new bear for every old bear left from the last year. These characteristics are controlled by one gene loci and there are two alleles. The allele for paws down (D) is dominant and the allele for paws up (d) is recessive. Essential Questions: What kinds of factors affect the evolution of a species? How do they affect the frequency of alleles in the gene pool? Terms to be familiar with: 1. Genetic Variation 2. Gene pool 3. Natural Selection 4. Selecting Agent 5. Phenotype 6. Genotype What are the 2 different types of bears based on their observable characteristics? Sad, grumpy bears If Happy bear phenotype is the recessive condition what is their genotype? What is the genotype of the Sad bear? Happy Bears Procedure: • Obtain an initial population of 12 bears from your teacher. DO NOT EAT THE BEARS UNTIL INSTRUCTED TO DO SO!!! • Record the number of happy bears, sad bears and the total number of bears in this population in the data table. • Paws Down (Grumpy, bad tasting)Paws Up (d)(happy, sweet • Eat 3 happy bears. (If you do not have three happy bears, then eat the difference in sad bears.) You will receive 3 replacement bears for your new population. Record the number of bears in the new population. • Eat 3 happy bears once more. Again if you do not have 3 happy bears then eat the difference in sad bears. You will receive 3 replacement bears for your third population. Record the number of bears in population #3. Paws Down (Grumpy, bad tasting) Paws Up (d) (happy, sweet tasting) Number of each in population #2 Number of each in Population #3 Total in the class population 5. Graph your results using a histogram. Graph each population separately and note trends evident from the initial population to population #3.