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EVOLUTION Taxonomy • Taxonomy— is the science of classifying and naming living things. • How are relationships between living things determined? They are determined by: • 1. Physical Similarities— ex: structure (bones) • 2. Chemical Similarities— ex: DNA • 3. Behavior— ex: mating and survival strategies How are living things classified? Binomial nomenclature- each species is assigned a two-part scientific name. This system includes seven levels or taxa. King Philip Came Over For Good Soup Why is it important for scientists to have a universal classification & naming system? • To avoid confusion caused by the use of different common names, language barriers, & cultural barriers. Species— A group of organisms that can mate • They use scientific names and produce fertile offspring. . • According to Linnaeus’ system, every species has a Latin scientific name composed of the genus and species names. The first letter of the Genus is always capitalized. The first letter of the species is lowercase. The entire scientific name is italicized or underlined 1. Which 2 organisms are the most closely related? Cat & Lion 2. Which organism is least similar to the others? Human Key : A= Human B= Cat C= Lion D= Dog 3. What is the scientific name for a cat? Felis domesticus A dog? Canis familiaris A lion? Panthera leo Explain: • Scientific names of species of organisms consist of two names. • What two taxa (levels) are used to compose the scientific name & why these two? The Genus and species are used; because they are most specific Diversity • Diversity: The number of different species in an ecosystem. • Why is a more diverse ecosystem more stable? • There is more than one type of organism to fill a role (producer, predator, prey, etc.), so if one disappears, there is a “back up”. • Example: An ecosystem with one producer will fall apart, if that species goes extinct. Evaluate • Many species of plants and animals are currently threatened or in danger of extinction. • (1) How does extinction affect biological diversity? Biological diversity decreases • (2) What kind of long-term effects do you think the extinction of other species can have on our lives? Extinction sometimes allows for other organisms to take over an area. Biodiversity will decrease, but new organisms could evolve. Phylogeny • Phylogeny: an organism’s evolutionary history. An organism’s phylogeny can be diagramed using a phylogenetic tree. A phylogenetic tree is a branching diagram that shows evolutionary relationships. Common Ancestor Common Ancestor— A •species Scientists classify organisms based on their from which two similarities in DNA, anatomy, and behavior. or more species are directly descended from. • How is the phylogeny of an organism determined? Apply Examine the phylogenetic tree to answer the following questions: 1. Which organism is most closely related to a flowering plant? Fern 2. Which organism is the most primitive (oldest)? Protista 3. What kingdom is the common ancestor of all these plants? Protista Apply Apply 1. What animal is most closely related to a bird? Crocodile 2. What animal is most closely related to a lizard? Snakes 3. Is a mammal more closely related to a turtle or a shark? Turtle 4. Is a shark more closely related to an amphibian or a turtle? Amphibian 5. Is a crocodile more closely related to a lizard or a turtle? Lizard Explain • (1) How do you determine which organisms on a phylogenetic tree are the most closely related? Their branches are closely traced. • (2) Least related? Their branches are far apart or are separated. • (3) How do you determine which organism on the phylogenetic tree is the common ancestor? The organism where all of the other branches originate. Evolution and Darwin’s Theory • Evolution: change in inherited traits over time. Why Should We Study Evolution? • It helps us understand relationships between species in ecosystems. • It also explains the development of antibiotic resistance in bacteria and insecticide resistance in bugs. Why Should We Study Evolution? • Understanding relationships between organisms can help us make conclusions in medical research. • E.g.: It explains how HIV and influenza can change (mutate). Darwin’s Theory • Darwin’s Theory: In 1859 Darwin combined his observations of living plants, animals, and fossils from around the world, and developed his theory of evolution, which today is the most accepted scientific theory to explain biodiversity. • Species Change through Natural Selection Natural Selection • The most important influence on evolution is natural selection, which occurs when an organism is subject to its environment. • The ‘fittest’ or ‘best’ organisms survive and inherit their genes to their offspring, producing a population that is better adapted to the environment. The genes of less-fit individuals are eventually lost. The important selective force in natural selection is the environment. •RESTATE the above in your own words at the top of page 5. Factor that Affect Natural Selection • I. Genetic variation: All species have natural genetic variation as a result of random mutation. • Variation: Genetic diversity, changes within a species. Variation within a species can be caused by: • a. Mutation: DNA changes during replication • b. Crossing-over: The exchange of genetic material between homologous chromosomes. Factor that Affect Natural Selection • Selective environmental pressures: The environment presents challenges to survival. Organisms sustain their populations by producing more offspring than can survive. • Examples: Predator-prey interactions, resource shortage, changes in environmental conditions. Factor that Affect Natural Selection • Competition: There is a struggle for survival. The fittest individuals (those whose genes give them an advantage) will be able to survive. • Examples: Trees with bitter sap are less appetizing to herbivores than sweeter trees, and therefore survive better than other trees. Factor that Affect Natural Selection • Adaptation: Any variation in the traits that allows an organism to survive and reproduce successfully is inherited to its offspring. Over generations, these traits become more common in the population as the population adapts to its environment. • Examples: Resistance to toxins; camouflage; ability to conserve water; antibiotic resistance. Factor that Affect Natural Selection • Susceptibility: Individuals (and species) that are not able to survive and reproduce will become more susceptible to extinction (die off). • Their traits/genes will become extinct with them. • [Susceptible = Likely to be affected] • Examples of extinction: Javan tiger Organisms who can’t adapt Variation Susceptibility Competition/enviro pressure Adaptation Competition/ adaptation • What do we call a change in the DNA? Mutation • How can natural selection increase diversity? Natural selection provides a way for new species to evolve, which can increase diversity. Are the fittest individuals the same in all environments? No; in different environments, different traits will provide an advantage. Summary (pg. 7) • What were the variations in the ‘organisms’ in the “Quackers” lab? Color = light or dark colored quackers • What was the selective pressure in the “Quackers” lab? Predation • Were you a predator or prey in the “Quackers” lab? Predator • Could little variation in a species cause an organism to die off (become extinct)? Why or why not? Yes, if there is little variation within a species they may not be able to adapt well to any changes in their environment. • In the African savannah there used to be only short-necked giraffes. The environment was green and lush, but a severe drought started. Plants were less available, and there was more competition. After several generations, the giraffe population included long-necked giraffes in addition to short-necked giraffes. Many years later, longnecked giraffes were more prevalent than short-necked giraffes. • • What are the variations in the giraffes? • • What is the selective pressure? Neck length Competition • • Which group of giraffes is the most fit in the new environment? Long Neck • • Which group of giraffes is the most susceptible to extinction? Those with short necks Explain • EXPLAIN: In the ‘Apply’ scenario on the previous page, how did the long- necked giraffes appear in the population? • Why are all current giraffes long-necked? Evidence that Supports Evolution • I. Physiological Adaptations: Changes in organism’s metabolic processes. • Examples: Bacteria developing antibiotic resistance. Evidence that Supports Evolution • II. Biogeography: The study of the distribution of living organisms through space and time on Earth. Biogeography looks at current species of living organisms, as well as at the evidence of past life (fossils), in order to determine how species arose. Evidence that Supports Evolution • III. Fossils: Any evidence of an organism that lived long ago. • Most fossils form in sedimentary rock. This type of rock is formed when sediments (sand, pieces of rock) form layers and is compressed together. • Organic matter trapped between the layers decays slowly and a fossil isleft behind. • Examples: Footprints, pieces of bone…. Evidence that Supports Evolution • How do fossils show evidence of evolution? They can show us what organisms looked like in the past, and we can trace how they change over time. Evidence that Supports Evolution • SUMMARY: The diagram represents different layers of soil. The letters represent fossils of three different species of organisms. • 1. Which species is most likely oldest? C- at the bottom • 2. Which species most likely existed at the same time? A&B, A&C – in the same rock layer Evidence that Supports Evolution • Embryology: The study of the early development of an organism. • How does embryology show evidence of evolution? Organisms who share embryological similarities are probably related (share a common ancestor). Evidence that Supports Evolution • V. Biochemistry: Nearly all organisms share DNA, ATP, and many enzymes among their biochemical molecules. The more closely related organisms are, the more similar their DNA (and therefore, proteins) will be. • Example: The enzyme cytochrome c, occurs in organisms as diverse as bacteria and bison. Biologists compared the differences in the amino acid sequence of cytochrome c that exist among various species. Species that are most closely related to each other have fewer differences in their amino acid sequences. Evidence that Supports Evolution • Example 2:The table shows the results of gel electrophoresis. DNA has been cut into pieces… the smaller pieces move further down the tray. By comparing DNA we can determine who is more closely related. • Which species of deer are most closely related? 1&3 – the most matching bands of DNA Evidence that Supports Evolution • APPLY: Bonobo blood has a protein with the sequence of amino acids shown in the figure. This protein, hemoglobin, carries oxygen in bonobo blood. Hemoglobin is also found in human blood. What does this say about the relatedness between humans and bonobos? That they are related or have a common ancestor. Evidence that Supports Evolution • VI. Homologous Structures: structures found in organisms with a common evolutionary history. Examples: Bat wings, whale fins, and human arms all have similar bone structure and are all mammals . Evidence that Supports Evolution • How do homologous structures show evidence of evolution? If two organisms have homologous structures they are related and have come from a common ancestor. Evidence that Supports Evolution • VII. Vestigial Structures: Structures that have a reduced (or no) use in an organism, but might have had a larger use in an ancestral species. • Examples: Human tail bone, whale pelvis bone, snake leg bones, nictitating membrane in the eye. Evidence that Supports Evolution • How do vestigial organs show evidence of evolution? They indicate a structural history. Vestigial Structure Homologous structure/fossils Biogeography Homologous structure Embryology Biochemistry • Could too little variation cause it to become extinct? • Why or why not? Yes; if there is little variation within a species, the populations may not be able to adapt well to any changes in their environment. Genetics of Natural Selection • Natural selection changes the frequency of certain genes within a population over time as the population adapts to its environment. • Evolution works at the POPULATION level, NOT the individual level. • Gene Pool—The entire collection of genes among a population. Genetics of Natural Selection • Gene Flow (also known as gene migration)- It is the transfer of alleles of genes from one population to another. • Example: When the migrating individuals interbreed with the new population, they contribute their genes to the gene pool of the local population. This establishes gene flow in the population. Gene flow occurs, for example, when wind carries seeds far beyond the bounds of the parent plant population. Genetics of Natural Selection • Genetic Drift- It occurs when a small group of individuals leaves a population and establishes a new one in a geographically isolated region. • For example, when a small population of fish is placed in a lake, the fish population will evolve into one that is different from the original. Fitness of a population is not considered in genetic drift, nor does genetic drift occur in a very large population. Genetics of Natural Selection • Allelic Frequency: The percentage of a particular allele (gene version) within a gene pool; it can increase or decrease. Allelic frequencies can be affected by two types of DNA changes: replication & crossing over. • If an organism survives in their environment they are able to reproduce and pass on their genes to their offspring. This will increase their alleles in the population. • APPLY: In certain cattle, red hair (R) is dominant to white hair (r). Heterozygous (Rr) cattle are ‘roan’ in color and have both red and white hair. What would happen to the allelic frequency of the (r) allele if coyotes noticed the white calves more easily? The percentage of the r allele would decrease in the population. Gradualism vs. Punctuated Equilibrium Darwin's theory included the fact that evolutionary changes take place slowly. In many cases, the fossil record shows that a species changed gradually over time. The theory that evolution occurs gradually is known as gradualism. In contrast to gradualism is the theory of punctuated equilibrium, which is a point of discussion among scientists. According to the theory of punctuated equilibrium, some species have long, stable periods of existence interrupted by relatively brief periods of rapid change. • Both groups of scientists agree that natural selection is the single most important factor in evolutionary changes in species. Whether the change is slow and gradual, or punctuated and rapid, one thing is certain: Organisms have evolved over time. • EVALUATE: After reading the passage above, briefly discuss below (in writing) which of the two theories (gradualism or punctuated equilibrium) you think is best supported by current evidence, and why you think so. Behavior • Behavior: How an organism reacts to changes in its internal and external environment. • What is the effect of natural selection on behavior? Behaviors will be maintained or removed based on their overall contribution to the fitness of an individual. The behavior must be genetic because selection changes the frequency of that gene (alleles) in the gene pool. • Animals display various behaviors for many reasons. Generally, behaviors can be linked to a goal of survival or reproduction. One famous biologist, Niko Tinbergen, noticed that Common Black-headed Gulls would meticulously remove the eggshell fragments from their nests after their offspring hatched. In an attempt to understand this behavior, he painted chicken eggs so that they were camouflaged into the backgrounds where the gulls lived and nested. He then placed some broken eggshells near them. He then noted how many eggs were discovered and eaten by Carrion crows. He observed that crows were able to easily notice the white interiors of the broken shells and consumed many more of the camouflaged eggs near the broken shells than camouflaged eggs with no broken shells near them. • Draw the two nests from the example in the passage • 1. What question was Tinbergen attempting to answer with his experiment? • 2. Why did Tinbergen set up one area with camouflaged eggs and no shell fragments? • 3. In your opinion, why do the gulls behave this way? • 4. Is the behavior learned or inherited? • 5. How is the behavior of the gulls linked to natural selection? Speciation • Speciation: The evolution of a new species from old species. • How can you tell members of two different species apart? • By physical characteristics, DNA, and behavior. • What is a species? • A group of organisms that can mate and produce fertile offspring. Speciation • How can natural selection produce a new species? • 1. Natural selection causes changes in allelic frequency of a population. • 2. Different parts of a population might change in different ways. • 3. Due to these changes, the 2 parts of the population are now unable to mate. • 4. If the two parts can no longer mate this means a new species has evolved. Speciation • Reproductive Barrier: Any factor that prevents fertile offspring from being produced. • Examples of Reproductive Barriers: • Geographical Barriers: Rivers, mountains, canyons, etc. • Temporal (Time) Barriers: Species do not mate at the same time. Different Sides of Explanation • When evaluating the validity of a proposed explanation of a biological phenomenon, one should remain objective and ask oneself questions such as: • − Is the reasoning relevant and sufficient? • − Is the explanation supported by data? • − Has relevant information been omitted? • There is compelling evidence that mitochondria and chloroplasts were once primitive bacterial cells. This evidence is described in the endosymbiotic theory. What does that name mean? Symbiosis occurs when two different species benefit from living and working together. When one organism actually lives inside the other it’s called endosymbiosis. The endosymbiotic theory describes how a large host cell and ingested bacteria easily become dependent on one another for survival, resulting in a permanent relationship. Over millions of years of evolution, mitochondria and chloroplasts have become more specialized and today they cannot live outside the cell. • Mitochondria and chloroplasts have striking similarities to bacterial cells. They have their own DNA, which is separate from the DNA found in the nucleus of the cell. Both organelles use their DNA to produce enzymes and other proteins required for their function. The two organelles also reproduce like bacteria, replicating their DNA and directing their division. • READING COMPREHENSION: After reading the paragraph about the endosymbiotic theory (previous page), and based on what you know about the function of cell organelles, answer the following questions. Mitochondria • ______________ are the result of endocytosis of aerobic bacteria. Chloroplasts • ______________ are the result of endocytosis of photosynthetic bacteria. Support Support Support Not Support Not Support