Theory of Evolution. A. the beginning of life B. the evolution of eukaryotes C. the evolution of archaebacteria D. the beginning of terrestrial life

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1 Theory of Evolution 1. In 1966, American biologist Lynn Margulis proposed the theory of endosymbiosis, or the idea that mitochondria are the descendents of symbiotic, aerobic eubacteria. What does the theory of endosymbiosis help explain? A. the beginning of life B. the evolution of eukaryotes C. the evolution of archaebacteria D. the beginning of terrestrial life 2. Scientists know that organisms that are more closely related will have DNA sequences more similar to each other than organisms that are distantly related. Which two organisms below would most likely have the fewest similar nucleotide sequences in a given gene? A. scorpion and tarantula B. orangutan and howler monkey C. alligator and earthworm D. lion and horse 3. The study of embryological similarities and differences among species is called. A. developmental psychology B. comparative embryology C. investigative neurology D. cooperative anatomy

2 4. The instructions for building proteins necessary for all life functions are coded within an organism's genetic code. The genetic code of an organism consists of codons, or sequences of three nucleotides, that each code for a specific amino acid. Amino acids are the building blocks of proteins. The amino acids coded by specific codons A. differ between members of different species. B. are different for every organism on Earth. C. are almost universal among all living things. D. differ between plants and animals. 5. The front leg of an iguana and the wing of a bird look different, but both limbs likely evolved from the same limb of a shared ancestor. Structures such as these are said to be. A. heterogeneous B. differentiated C. homologous D. vestigial 6. A scientist is doing research on the evolutionary relationship between whales and hippopotamuses. Which of the following is a reasonable hypothesis that the scientist could make about this relationship? Whales are more closely related to dolphins and porpoises than they are to other marine animals. A. Whales are more closely related to hippopotamuses than they are to cartilaginous fish such as sharks. B. Which mammalian species are whales most closely related to in terms of their evolutionary history? C. How did whales evolve to live in the ocean instead of on the land like other mammals? D.

3 7. What does it mean to say that two different species of organisms are closely related? A. They have the same parents. B. They have a common evolutionary ancestor. C. They live in the same habitat. D. They have the same preferences in diet. 8. The theory of endosymbiosis claims that millions of years ago, aerobic bacteria were taken inside of anaerobic cells through endophagocytosis. The aerobic bacteria then fed on the half-digested food molecules in the cell's cytoplasm and gained a great amount of energy, which, in turn, benefited the host cell. Since both organisms benefited, they formed an endosymbiotic relationship, the bacteria evolved into organelles, such as mitochondria and chloroplasts, and the aerobic cells evolved into eukaryotic cells. Which of the following can be cited as evidence for the theory of endosymbiosis? A. B. C. Eukaryotic cells appeared on Earth around 1.5 billion years ago, whereas chloroplasts appeared on Earth only 2.5 million years ago. Mitochondria are typically above 50 microns in size, whereas eukaryotic cells are typically smaller than 10 microns. The ribosomes of chloroplasts are more similar in structure to ribosomes found in prokaryotes than to ribosomes found in eukaryotes. Mitochondria contain multiple linear chromosomes similar to those found in eukaryotic cells. D. 9. Fur seals and sea lions have similar body shapes and features. Based on their anatomy, they seem to have a relatively recent common evolutionary ancestor. What further evidence would best substantiate that the two animals have a recent common ancestor? A. The animals are members of different taxonomic kingdoms. B. Both animals live in the Pacific Ocean. C. Ten million year old fossils are found of both animals. D. The animals have very similar sequences in their DNA.

4 10. Technology Enhanced Questions are not available in Word format. 11. The first organisms evolved on Earth around 4 billion years ago. The fossil record indicates that the first organisms were which of the following? A. plastids B. eukaryotes C. mitochondria D. prokaryotes 12. Nearly all mammals have seven cervical (neck) vertebrae. This fact implies that A. all mammals descended from a common ancestor. B. all mammals have to stretch their necks to obtain food. C. all animals can turn their heads the same amount. D. predators prefer to eat animals with either six or eight cervical vertebrae. 13. Charles Darwin originally published the idea that all species have descended over time from common ancestors. This idea is known as evolution. Evolution is best categorized as A. a scientific theory that is supported by evidence. B. an unproven observation about a small number of organisms. C. a scientific hypothesis that has not been researched. D. a scientific fact that has not been modified since Darwin's time. 14. The study of structural differences and similarities among living things is called. A. neurology B. comparative anatomy C. comparative biochemistry D. embryology 15. The fossil record shows that the forelimbs of humans, cats, dolphins, and bats have the same skeletal elements. These skeletal elements have evolved into different shapes and sizes based on their function. For example, the flipper of a dolphin is adapted for swimming and the wing of a bat is adapted for flying.

5 What do the similarities between the skeletal structures of these four species most likely indicate about their evolutionary history? These four species are not related and do not share a common ancestor. A. These four species are distantly related and share a common ancestor. B. These four species all evolved from a common flying ancestor. C. These four species are all descended from the same parent organism. D.

6 16. Look at the representation of a hillside below. The symbols in each stratus of the cross-section represent fossils of different organisms. Which of the following organisms must have evolved first? A. * B. # C. $ % * ^ ^ * % $ $ $ # # # * * * * * $ * * * $ $ # # # % # * < < < < < = = 17. Which of the following is a direct observation that could be used as evidence to support the theory of evolution? Populations that are separated for thousands of years can evolve into diverse species. A. Humans, cats, whales, and bats all have similar forelimb skeletal structures. B. Species that have similar DNA sequences are probably closely related in terms of evolution. C. Fossils found deeper in the ground are older than fossils found near the surface. D.

7 18. Look at the organisms in the image above. Which of the following organisms are most closely related evolutionarily? A. fish and starfish B. fish and clam C. starfish and sand dollar D. crab and starfish

8 19. Comparison: Percentage Match of Blood Protein Structure Among Four Organisms Organism Organism A B C D A Not Applicable 76% 65% 60% B 76% Not Applicable 85% 51% C 65% 85% Not Applicable 77% D 60% 51% 77% Not Applicable The structure of a certain blood protein was compared among four organisms. Each organism was compared to each of the other organisms. The level that any two protein structures match can be found at intersection of the rows and columns. Based on the data, which of the following organisms are most closely related by evolution? A. B and D B. A and B C. C and B D. D and C 20. The theory of endosymbiosis provides a possible explanation for how eukaryotic cells came into existence. The presence of chloroplasts in photosynthetic organisms is one phenomenon explained by this theory. Based on the theory of endosymbiosis, what was the significance of the development of chloroplasts? A. The development of chloroplasts led to the initial formation of DNA, which allowed organisms to replicate through asexual reproduction. B. The development of chloroplasts caused a large increase in carbon dioxide levels in Earth's atmosphere, which allowed the evolution of organisms that perform cellular respiration. C. The development of chloroplasts led to the oxygenation of Earth's atmosphere, which allowed the evolution of more complex oxygen-breathing organisms. D. The development of chloroplasts caused a large increase in the amount of water on Earth, which led to the existence of living organisms. 21. Technology Enhanced Questions are not available in Word format. 22. Technology Enhanced Questions are not available in Word format. 23. Technology Enhanced Questions are not available in Word format.

9 24. Scientists know that organisms that are more closely related will have DNA sequences more similar to each other than organisms that are distantly related. Which two organisms below would most likely have the fewest similar nucleotide sequences in a given gene? A. alligator and earthworm B. lion and horse C. orangutan and howler monkey D. scorpion and tarantula 25. The following data table summarizes the number of differences in amino acid sequences found for four different species. Amino Acid Dissimilarities for Beta Hemoglobin Protein A B C D A B 0 1 C 5 Based on the data table, which two species are most closely related? A. species B and species D B. species B and species C C. species C and species D D. species A and species B D

10 26. Over the past century, several scientists around the world have made the following observations: New mitochondria and plastids can only be generated by old mitochondria and plastids through a process similar to binary fission. Both mitochondria and plastids contain DNA that is similar in shape and size to that of bacteria. Mitochondria and plastids are surrounded by two or more membranes whose composition is similar to a prokaryotic cell membrane. Mitochondria and plastids are about the same size as bacteria. These observations led scientists to conclude that mitochondria, plastids, and other cellular organelles are the result of ancient bacterial infections. A. B. mitochondria and plastids are vestigial structures, and they do not serve a useful purpose in modern organisms. prokaryotic organisms living inside the cells of other organisms evolved into mitochondria and plastids. C. the cells found within multicellular organisms, such as humans, are actually parasitic bacterial cells. D. 27. The human appendix is a structure that suggests that humans evolved from plant-eating ancestors. A. vestigial B. embryonic C. essential D. behavioral

11 28. The diagram below shows a variety of animals at different stages of development. Which of the following statements is supported by this diagram? Humans undergo more stages of development than other animals, such as salamanders, tortoises, A. chickens, and pigs. The developmental stages of animals are radically different; they do not possess any similarities at all. B. There are similarities in the developmental stages of different organisms in the animal kingdom. C. D. Diverse organisms in the animal kingdom possess more similarities during the fetal stages of development than during their embryonic stages. 29. Which of the following facts implies that humans and fish had a common ancestor? A. Both species have gill slits when they are embryos. B. Both species have the ability to swim. C. Both species must expel waste materials. D. Both species are consumers.

12 30. Comparative biochemistry is the study of similarities and differences in among organisms. A. homologous structures B. DNA sequences C. vestigial structures D. development Answers 1. B 2. C 3. B 4. C 5. C 6. B 7. B 8. C 9. D D 12. A 13. A 14. B 15. B 16. D 17. B 18. C 19. C 20. C A 25. B 26. C 27. A 28. C 29. A 30. B Explanations 1. The theory of endosymbiosis is part of the theory of how eukaryotes, or organisms composed of one or more nucleus-containing cells, first evolved. Endosymbiosis also explains the origins of other eukaryotic organelles, such as chloroplasts. The fact that both mitochondria and chloroplasts contain their own DNA is evidence for endosymbiosis. 2. Organisms classified into the same genus, family, and even order will have DNA sequences that are more similar to each other than organisms outside of that grouping. Scorpions and tarantulas are both invertebrates. Lions and horses are both mammals. Orangutans and howler monkeys are both primates. An alligator is a vertebrate and an earthworm is an invertebrate.

13 3. Comparative embryology is the study of similarities and differences in embryological development among species. By locating similarities in development, scientists can determine if species are related, even if only distantly. For instance, gills are present in all vertebrate embryos at some stage in development. This common feature likely means that all vertebrates descended from a common fish-like organism. 4. Codons are triplet nucleotide sequences that are derived from RNA as opposed to DNA. These sequences code for specific amino acids in addition to start and stop codons. The genetic code is read as a nonoverlapping sequence of codons. The genetic code is almost universal in that the same codons are assigned to the same amino acids in most living things. It is only nearly universal because there are some exceptions where a few of the codons differ from the standard ones. For instance, it has been seen that one or two of the stop codons have been assigned to amino acids instead. The fact that the genetic code is the same in nearly all living organisms is evidence that they all share a common ancestor. That is, it is evidence for biological evolution. 5. Animals with homologous structures evolved from the same distant ancestor. A horse's leg, a bat's wing, and a bird's wing appear different, but they all evolved from the limbs of that same distant ancestor, so they are all homologous. 6. A hypothesis is written in a statement rather than question form. For a hypothesis to be valid, it does not have to be correct, but it must be testable. Statements which are not testable, such as statements about an animal's emotional state, cannot be hypotheses. A reasonable hypothesis that the scientist could make on the evolutionary history of whales and hippopotamuses would be: Whales are more closely related to hippopotamuses than they are to cartilaginous fish such as sharks. The scientist could then gather evidence to prove or disprove the hypothesis. 7. When two different species have similar anatomy and similar DNA, it shows that they have a recent common evolutionary ancestor. Since evolution is a very slow process that happens over thousands or millions of years, a recent common ancestor, in terms of evolution, is still much further back in generations than a parent or grandparent. 8. There is much evidence to support the theory of endosymbiosis. Some of this evidence is cited below. The 70S ribosomes of chloroplasts and mitochondria are more similar to the 70S ribosomes found in prokaryotes than the 80S ribosomes found in eukaryotes. Eukaryotic cells, mitochondria, and chloroplasts all appeared on Earth at around the same time billion years ago. Prokaryotic cells, mitochondria, and chloroplasts are typically smaller than 10 microns, whereas eukaryotic cells are usually larger than 50 microns. Prokaryotic cells, mitochondria, and chloroplasts contain one single, circular chromosome, whereas eukaryotes contain multiple linear chromosomes. 9. Anatomical evidence was the data that originally led Charles Darwin to the idea that different species evolved from common ancestors. Today, genetic testing of DNA can further support this idea. Animals that have more similarities in their DNA are more likely to have a recent common ancestor than those that have fewer similarities.

14 Different species with a recent common ancestor are said to be related to one another The earliest known fossilized organisms are single-celled organisms known as prokaryotes. Prokaryotes are the simplest form of life found on Earth. Most likely, the first prokaryotes were archaebacteria, with eubacteria following closely behind. 12. Structural similarity is one criterion for determining whether organisms share a common ancestor. The fact that most mammals have seven neck vertebrae implies that they descended from a common ancestor and are therefore related. 13. A scientific theory is a widely accepted explanation for a scientific phenomenon that is supported by extensive amounts of data. Scientific theories can be modified over time as new information is discovered, but they are rarely discarded. Therefore, evolution is classified as a scientific theory because it is supported by evidence gathered through extensive experimentation and observation. 14. The study of structural differences and similarities in living things is called comparative anatomy. Much can be learned by comparing the structural similarities and differences of living things. For example, the identification of homologous structures, or structures in different species that may look different but have origins in a common ancestor, implies that the species are related. Also, the identification of vestigial structures, non-functional remnants of structures that were operational in a distant ancestor, can also imply relatedness between two species. 15. Examining the fossil record can offer new insights into the relationship between species and their evolutionary history. The forelimb of humans, cats, dolphins, and bats have the same skeletal elements because these species most likely are distantly related and share a common ancestor. This common ancestor most likely possessed these skeletal structures, and each divergent species inherited this trait from the ancestor. As the new, divergent species moved into different habitats, their forelimbs adapted based on their function. The original skeletal structure, however, remained the same. 16. Often scientists use relative dating to determine when species evolved. They examine consecutive rock layers to do this. Organisms fossilized on the highest rock layers must have died more recently than organisms fossilized on the lowest rock layers. 17. An observation is something that can be measured or directly perceived with the senses. A scientist could examine the skeletons of various species and directly observe that humans, cats, whales, and bats all have similar forelimb skeletal structures. Structures that are similar because species share a distant common ancestor are known as homologous structures. The other answer choices cannot be directly observed; they require making inferences or conclusions based on interpretations of observations. 18. Darwin cited animals with similar body plans as having evolved from a common ancestor. The starfish and the sand dollar both have radial or circular symmetry, while the fish, crab, and clam have a bilateral symmetry. Therefore, of the animals presented, the starfish and sand dollar are most closely related evolutionarily. 19. Organisms that have the highest percentage of matching nucleotide sequence in protein structure are the most closely related by evolution. For this protein, C and B had the highest level of matching: 85%.

15 20. The theory of endosymbiosis claims that millions of years ago, aerobic bacteria were taken inside of anaerobic cells through endophagocytosis. The aerobic bacteria then fed on the half-digested food molecules in the cell's cytoplasm and gained a great amount of energy, which, in turn, benefited the host cell. Since both organisms benefited, they formed an endosymbiotic relationship, and the bacteria evolved into organelles, such as mitochondria and chloroplasts, and the aerobic cells evolved into eukaryotic cells. The theory of endosymbiosis has important significance in terms of the history of life on Earth. For example, the development of chloroplasts through endosymbiosis led to the oxygenation of Earth's atmosphere, which allowed the evolution of more complex oxygen-breathing organisms, such as humans Organisms classified into the same genus, family, and even order will have DNA sequences that are more similar to each other than organisms outside of that grouping. Scorpions and tarantulas are both invertebrates. Lions and horses are both mammals. Orangutans and howler monkeys are both primates. An alligator is a vertebrate and an earthworm is an invertebrate. 25. Species of organisms that are more closely related have fewer differences in their sequences of amino acids. Similarities in amino acids reflect a similarity in DNA because DNA sequences determine which amino acids are produced. Based on the amino acid sequences for beta hemoglobin protein, species B and species C are most closely related because they have the fewest difference in their amino acid sequences. 26. Observations over time have led scientists to conclude that prokaryotic organisms living inside the cells of other organisms evolved into mitochondria and plastids. This theory, known as the endosymbiotic theory, claims that aerobic bacteria were taken inside of anaerobic cells through endophagocytosis. The aerobic bacteria then fed on the half-digested food molecules in the cell's cytoplasm and gained a great amount of energy, which, in turn, benefited the host cell. Since both organisms benefited, they formed an endosymbiotic relationship, and the bacteria evolved into organelles, such as mitochondria and plastids, and the aerobic cells evolved into eukaryotic cells. 27. Vestigial organs or structures are those that no longer function in the modern form of an organism. These structures, however, provide clues to the evolutionary path of the organism, as well as its relationship to other species. 28. Diverse organisms in the animal kingdom possess similarities in their developmental stages. Overall, these similarities are more pronounced during the earlier stages of development (i.e., zygote through embryo) than in the later stages (i.e., fetal). By comparing developmental stages of organisms (and by examining and interpreting fossils), information can be gained about relationships among living organisms and those that inhabited Earth in the past. This information is often used to modify and clarify existing classification systems. By studying embryological development, scientists hope to gain a better understanding of how different animal species have changed over time and how closely they are related to one another. 29. Both species have gill slits when they are embryos. In fish, gill slits are retained after birth. In humans, however, the gill tissue develops into the jaw, tongue,

16 larynx, and middle ear. Scientists use similarities in embryonic development to determine whether species share a common ancestor. In this case, humans and fish seem to be related, even if the relation is distant. 30. One of the ways scientists judge whether two species are related is through comparative biochemistry--the study of organisms' DNA sequences. While each species has its own unique DNA sequence, sequences of related organisms will be more similar than sequences of unrelated organisms.