Evolution Study Guide for Middle School

 Life Science Evolution Study Guide Naturalist _________________ Natural Selection 1. What is evolution? 1. Evolution is any change in the heritable traits within a population across generations. 2. Was Charles Darwin the first person to talk about evolution? 2. No. 3. Was Charles Darwin a laboratory scientist? 3. No, he was a naturalist. 4. What is a naturalist? 4. A naturalist is a person who studies the natural world, including plants, animals, and rock formations. 5. How long did Darwin spend on the HMS Beagle as a naturalist? 5. Darwin spent five years as a naturalist aboard the HMS Beagle . 6. What was the purpose of the Beagle ’s voyage? 6. The Beagle traveled to South America and its remote islands to make navigational maps. 7. What did Darwin do when he visited South America and the Galápagos Islands? 7. Darwin made observations and detailed notes of the biology and geology of the locations he visited. 8. What does diversity mean? 8. Diversity means “being different from others” or “variety.” 9. What did Darwin compare? 9. Darwin compared the similarities and differences among the animals and fossils of animals from the different islands he visited. 10. What did Darwin reason from his observations of differences among organisms on the South American mainland and the Galápagos Islands? 10. Darwin reasoned that animals and plants on the Galápagos Islands originally came from South America, and, over time, they evolved to become different. 11. How do the two types of tortoises Darwin observed on the Galápagos Islands support the concept of evolution? 11. The tortoises that lived on islands where their food was low­growing plants had short necks and dome­shaped shells. Those living on islands where the food was high­growing cacti had long front legs, long necks, and saddle­shaped shells that made it easier for tortoises to stretch vertically to reach food. Over time, tortoises had evolved so that their neck and shell types best suited their islands’ food sources. 12. What kind of bird and what trait of that bird did Darwin study on the Galápagos Islands? 12. Darwin studied finches and their beak size and shape. 13. What are finch beak size and shape related to? 13. Beak size and shape are related to the food the finch eats and where it must go to get the food. 14. Why are the finch species in the Galápagos Islands different from each other, even though they all descended from a common ancestor? 14. The finches are different, or evolved, because they became suited to the different habitats on the islands. The changes occurred through the process of natural selection as a result of different environments on each island. 15. What is selective breeding? 15. Selective breeding is breeding plants or animals to get offspring with specific desired characteristics. 16. Does selective breeding create new species? 16. No, selective breeding does not create new species. 17. How does a trait that helps organisms survive become more common among members of a species? 17. Organisms with a trait that helps them survive produce more offspring than members of their species that do not have the helpful trait. 18. Why is genetic variation necessary for evolution to occur? 18. Genetic variation results in organism’s traits being different. Those differences result in some organisms being better able to survive and reproduce; their relative numbers within a population of organisms increase. The makeup of the population changes. That is evolution. 19. Who was Thomas Malthus? 19. Thomas Malthus was an economist whose ideas on humans’ “struggle to survive” influenced Darwin. 20. How did Darwin explain which organism would survive when there were enough resources for some – but not all – organisms to survive? 20. Darwin reasoned that an organism that was better prepared to get food and protect its space would be better able to survive. 21. What is selective pressure? 21. Different habitats provide organisms with different challenges, which they must overcome in order to survive and reproduce. These pressures result in some organisms being “selected” to survive and reproduce and others not. 22. What is natural selection? 22. Natural selection is a process by which individuals with traits that better suit the environment are more likely to survive longer and reproduce more successfully than those individuals without these traits. 23. What are adaptations? 23. Adaptations are inherited traits that increase an organism’s chance of surviving and reproducing in a particular environment. 24. What are the four requirements of Darwin’s theory of evolution by natural selection? 24. The four steps that explain evolution by natural selection are: ● Overproduction – many organisms die naturally before they can reproduce offspring ● Variation – offspring’s traits vary ● Inherited Variation – the alleles for various traits can be passed from parents to offspring ● Natural Selection – individuals with inherited variations that are better able to survive and reproduce in a particular environment will have more offspring and thus pass on these favorable traits more often than individuals without those features Adaptation and Extinction 1. What causes adaptations? 1. Adaptations evolve over time by the process of natural selection. 2. How do organisms adapt? 2. Adaptations occur in groups of organisms when a trait is passed from one generation to another. The organisms receiving the trait are better suited to survive and reproduce. 3. Are all traits that are passed from generation to generation adaptations? 3. No, not all traits are adaptations. 4. Why do some undesirable traits continue to be passed from generation to generation? 4. Chromosomes have many genes that code for traits. Undesirable traits can be passed from generation to generation, because the genes that code for them are somehow linked to genes that code for other, beneficial traits. Other undesirable traits do not affect an organism’s ability to survive long enough to reproduce. 5. Are adaptations intentionally chosen? 5. No, adaptations are naturally selected, not intentionally chosen. 6. How might rabbits have evolved to have long ears? 6. Possible answer: There used to be rabbits with long, short, and medium­sized ears. The long­eared rabbits were able to hear better than the other rabbits. They were able to hear approaching predators better, so they were more successful than other rabbits in avoiding becoming other animals’ meals. They survived and reproduced more than short­eared and mid­sized­eared rabbits. The numbers of short and medium­eared bunnies dwindled, and eventually none survived. 7. What are structural adaptations? 7. Structural adaptations are inherited physical traits of a species that make its members better suited to the environment (e.g., the long rabbit ears). 8. Name five structural adaptations of desert rabbits. 8. Desert rabbit structural adaptations include: 2 ● Long ears with numerous blood vessels that help it stay cool ● Long ears that help it hear predators ● Long hind legs for running fast and jumping high ● High­placed eyes that allow it to see 360º ● Mottled appearance that helps it blend with its surroundings 9. What kind of structural adaptations are the rabbit’s mottled appearance and the lava lizard’s blackish color? 9. Both the rabbit and the lizard’s appearances are examples of camouflage, the blending in with the surrounding environment. 10. What is mimicry? 10. Mimicry is a structural adaptation in which one species (the mimic) looks like another species (the model) so that a third species is fooled. 11. How does mimicry help the mimic? 11. Mimicry keeps the fooled third species from messing with (eating or otherwise harming) the mimic, because the fool thinks the mimic is the model. 12. What are the three types of mimicry? 12. The three types of mimicry are: ● Batesian Mimicry – The model organism is dangerous or venomous; the mimic isn’t. The mimic benefits, because predators think it’s the model and stay away. [Snake Eel and Banded Sea Snake] ● Mullerian Mimicry – Two species that are either venomous or distasteful have evolved to look like one another. Both the mimic and the model benefit. [Monarch and Viceroy butterflies] ● Self­Mimicry – A species fools its prey by looking inviting or familiar. [Frogfish] 13. What are behavioral adaptations? 13. Behavioral adaptations are inherited behaviors of a species that make its members better suited to their environment. 14. What else do scientists call behavioral adaptations? 14. Scientists sometimes call behavioral adaptations instinctive or inborn behaviors or simply instincts. 15. What behavior has the Clapper Rail adapted to nesting? 15. The Clapper Rail builds its nest so that it will float up as the tide comes in but won’t float away. 16. How is the male Satin Bowerbird’s use of berries, saliva, and blue scraps adaptive? 16. The male Bower bird decorates his nest with berries, saliva, and blue scraps to attract females for mating. This helps make sure he reproduces passing his genes to the next generation. 17. Explain how the herding instinct is a behavioral adaptation. 17. Many animals instinctively know that a group is less likely to be attacked by a predator than one animal alone. 18. What does it mean that a species is extinct? 18. A species is extinct when all the individuals of that species die off. 19. How could a meteorite have caused the extinction of dinosaurs 65 million years ago? 19. When this meteorite collided with the Earth, it caused so much dust in the atmosphere that plants did not have enough sunlight to grow. The dinosaurs starved to death. 20. Name three causes of extinction. 20. Causes of extinction include habitat destruction, loss of genetic diversity, and the introduction of exotic species. 21. What does clear cutting a forest cause? 21. Clear cutting a forest changes the habitat from forest to grassland. 22. Following clear cutting, what happens to the forest­dependent organisms? 22. If a forest­dependent organism can move, it will compete for resources (food, water, space) with organisms in its new habitat. If it cannot move, it will die. 23. How does loss of genetic diversity lead to extinction? 23. Loss of genetic diversity decreases the likelihood that some individuals will have right gene combinations to survive different environmental conditions and reproduce. [Cheetahs] 24. What is meant by competition with exotic species? 3 24. Humans frequently introduce species from one part of the world to another. Often the newly introduced species faces few (or no) organisms in the new environment that eat it. It grows and uses up natural resources that had previously been used by native species. It “outcompetes” with the native species, driving them to extinction. An example is the brown tree snake that was accidentally introduced to Guam, an island in the western Pacific Ocean, in the late 1940’s or early 1950’s. It is a voracious predator. It has reached densities of up to 40 snakes per acre and has caused extinction of at least 12 bird species on Guam. 25. Given the fact that evolution leads to beneficial adaptations, how is it that sudden environmental changes can lead to extinction? 25. A sudden change – in climate, for example – might kill off a species if no individuals have traits that help them survive the change. Imagine a species of fish that only lives in a freshwater lake near the ocean. No individual has traits allowing it to survive in salt water. A sudden rise in sea level floods the lake with salt water killing all members of the species. Biological Evidence of Evolution 1. What is comparative anatomy ? 1. Comparative anatomy is the study of similarities and differences in the structures of organisms. 2. What are homologous structures ? 2. Homologous structures are parts of organisms that are similar in structure and can indicate how closely two or more species share common ancestors. 3. What are analogous structures ? 3. Analogous structures are parts of organisms that appear similar and have similar functions but have different ancestral origins. They are the result of similar environmental conditions. Think of the wings of insects and birds. 4. What are vestigial structures ? 4. Vestigial structures have no (or very little) function in present­day organisms, but they were needed by ancestors. Examples include the pelvis found in modern toothed whales (that do not have legs) and the vermiform appendix found in humans that may have helped our ancestors digest cellulose. 5. What is embryology ? 5. Embryology is the study of embryos from fertilization to birth. 6. How does embryology help us understand how species evolved? 6. The more features different species share during development, the more closely related those species are. 7. What does molecular biology tell us about different species’ origins? 7. Molecular biology, specifically the study of the sequences of monomers making up proteins and DNA, tell us how closely related different species are. Molecular biology tells us (in relative terms) how recently species shared a common ancestor. Humans and rhesus monkeys, for example, share a more recent common ancestor than humans and dogs. One piece of evidence is that human and rhesus monkey cytochrome c is different by only one amino acid. That of humans and dogs is different by eleven amino acids. Note: Students should be able to explain how the following support the theory of evolution: ● homologous structures (e.g., the humerus, radius, ulna, metacarpals, carpals, and phalanges found in forelimbs of several vertebrates); ● analogous structures (e.g., wings of various insects and birds); ● vestigial structures (e.g., enzymes needed by other species to make vitamin C are found in humans); ● embryonic structures (e.g., pharyngeal pouches found in vertebrate embryos); and ● molecular biology (e.g., cytochrome c in organisms that use cellular respiration). 4 
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