Unit 8 Reproduction and Heredity

Transcription

1 stone had replaced its tissues. Sediments continued to build up, and rock continued to form. Organism B died. Sediments built up over the dead organism. Minerals seeped into the bones of the organism, transforming it into fossils. Extended Response 18. Sample answer: The four parts of natural selection are overproduction, variation, selection, and adaptation. Overproduction is the tendency of a species to produce more offspring than will survive to adulthood. Overproduction ensures that enough individuals will survive competition, predation, and accidents to allow a healthy breeding population. Variation is the range of characteristics within a population. Individuals within a population have slightly different characteristics. These differences allow the population to adjust to minor changes in the environment by giving different individuals different advantages. Selection is the process or processes by which organisms are removed from the population. Some selective factors include disease, competition, and predation. Individuals that survive the changes are more likely to reproduce and pass on their traits. When they reproduce, these changes are passed to offspring. As this process is repeated, these changes become more widely distributed in the population. The result is called adaptation. Overproduction is the tendency of a population to produce more offspring than are likely to survive to reproduce. Variation is the range in characteristics that exists within a population. Variation increases the likelihood of success of a population. Selection determines which individual organisms are most likely to survive and reproduce in their environment. Adaptation is the process of becoming adapted to an environment (or the acquisition of traits that improve survival and reproduction). Unit 8 Reproduction and Heredity Unit Pretest 1. B 5. B 9. B 2. A 6. C 10. A 3. D 7. B 4. C 8. D 1. B A is incorrect because the recessive trait of tip flower position would be the only trait seen in self-pollinated recessive plants. B is correct because the recessive tip flower position would be seen in every generation. C is incorrect because the stem flower position is the recessive trait and would be observed in every generation. D is incorrect because the plants that were self-pollinated did not have any dominant alleles. So, subsequent generations could not show the dominant trait. 2. A A is correct because the genes are located on the chromosomes of each cell. B is incorrect because genes are located on chromosomes; chromosomes are not located on genes. C is incorrect because the genes come from both parents and are located on the chromosomes. D is incorrect because chromosomes are not made up of cells, and entire chromosomes are not responsible for earlobe attachment. 3. D A is incorrect because a Punnett square cannot identify other traits for which two individuals have alleles in common. B is incorrect because a Punnett square cannot confirm the alleles of adult individuals. C is incorrect because a Punnett square cannot make predictions about acquired traits. D is correct because a Punnett square can be used to predict the possible combinations of alleles that offspring inherit. 4. C A is incorrect because a cross between these parents would produce offspring in a ratio of 1 DD to 1 Dd. B is incorrect because a cross between these parents would produce offspring in a ratio of 1 DD to 2 Dd to 1 dd. C is correct because a cross between these parents would produce offspring in a ratio of 1 Dd to 1 dd. D is incorrect because a cross between these parents would produce only offspring with Dd. 5. B A is incorrect because sexual reproduction requires two parents and does not produce offspring identical to either parent. B is correct because the production of spores is a form of asexual reproduction. C is incorrect because fertilization takes place during sexual reproduction. D is incorrect because vegetative reproduction takes place when a new plant develops from a stem or root of a parent plant. 6. C A is incorrect because after fertilization, the zygote (cell C) is not genetically identical to the egg (cell A). B is incorrect because after fertilization, the zygote (cell C) is not genetically identical to the sperm (cell B). C is correct because after fertilization, the zygote (cell C) has a full set of chromosomes. Half of these chromosomes are from the sperm (cell B), and the other half are from the egg (cell A). D is incorrect because cell B is the sperm, which contributes genes to cell C (the zygote). 7. B A is incorrect because fertilization is the joining of an egg cell and sperm. 319 Grade 7 Guide Florida

2 B is correct because both male and female sex cells are produced through meiosis. C is incorrect because only body cells are produced through mitosis. D is incorrect because pollination is the process whereby pollen is transferred from a male structure (anther) to a female structure (stigma). 8. D A is incorrect because most tissues are made up of body cells, not sex cells. B is incorrect because sex cells contain autosomal chromosomes as well as sex chromosomes. C is incorrect because sex cells have half the chromosomes of a body cell. D is correct because sex cells carry half of the usual number of chromosomes. 9. B A is incorrect because during cytokinesis, Xander would have observed two cells separating from each other. B is correct because during interphase, genetic material is in the form of chromatin, not chromosomes. C is incorrect because during metaphase, chromosomes are aligned at the middle of the cell. D is incorrect because during prophase, chromosomes have condensed. 10. A A is correct because family history of diabetes is a genetic factor, and diet and exercise are examples of acquired factors that contribute to the risk of diabetes. B is incorrect because there is not enough information given to be able to predict the probability of passing a certain allele to offspring. Additionally, there are environmental factors that contribute to the occurrence of diabetes. C is incorrect because there is not enough information provided to know how many genes are associated with diabetes. D is incorrect because there is not enough information provided to know the pattern of dominance associated with diabetes. Lesson 1 Quiz 1. D 4. B 2. A 5. C 3. A 1. D A is incorrect because cytokinesis should be the last step, and metaphase precedes anaphase. B is incorrect because anaphase and prophase are out of order. C is incorrect because the four phases of mitosis are listed in the opposite order. D is correct because interphase is followed by prophase, metaphase, anaphase, telophase, and then cytokinesis. 2. A A is correct because if the chromatids did not separate properly during anaphase, one cell could get two chromatids and the other cell could get none. B is incorrect because if the DNA had not been duplicated, the resulting cell could not have had two copies of the chromosome. C is incorrect because if the nuclear membrane had not been broken down properly, the effect would likely not be limited to one chromosome. D is incorrect because separation of the cells occurs after the genetic material has been divided up and enclosed in nuclear membranes. 3. A A is correct because single-celled eukaryotes reproduce through mitosis. B is incorrect because ants are multicellular organisms that rely on mitosis for growth and repair but not for reproduction. C is incorrect because bluebirds are multicellular organisms that rely on mitosis for growth and repair but not for reproduction. D is incorrect because jellyfish are multicellular organisms that rely on mitosis for growth and repair but not for reproduction 4. B A is incorrect because cell division for repair occurs in multicellular, not single-celled, organisms. B is correct because single-celled organisms undergo cell division in order to reproduce. C is incorrect because the new cells have the same number of chromosomes as the parent cell. D is incorrect because the new cells have the same number of chromosomes as the parent cell. 5. C A is incorrect because chromosomes would be visible in anaphase, but this is not the first stage of the cell cycle in which they are visible. B is incorrect because chromosomes would be visible during cytokinesis, but this is the last stage in which they are visible. C is correct because during prophase, the first phase of mitosis, the chromatin condenses into chromosomes. D is incorrect because chromosomes are visible during telophase, but this is not the first stage in which they are visible. Lesson 2 Quiz 1. C 4. D 2. B 5. C 1. C A is incorrect because meiosis takes place in reproductive organs, and a bone is not a reproductive organ. B is incorrect because mitosis produces body cells, and not mature sex cells, which are made in the testes. C is correct because meiosis takes place in reproductive organs such as the ovaries. D is incorrect because meiosis takes place in reproductive organs, and the stomach is not a reproductive organ. 2. B A is incorrect because there are four chromatids. Each chromosome consists of two chromatids. B is correct because there are two chromosomes, each consisting of a pair of sister chromatids. C is incorrect because there are only two chromosomes. Each chromosome consists of two sister chromatids. D is incorrect because there are four chromatids. A is incorrect because four sex cells are produced as a result of meiosis. 320 Grade 7 Guide Florida

3 B is incorrect because there are two cell divisions in meiosis. As a result, one cell produces four cells, each with half as many chromosomes as the parent cell has. C is correct because the two cell divisions in meiosis produce four cells that each have half as many chromosomes as the parent cell has. D is incorrect because each of the four cells produced in meiosis has 23 chromosomes. 4. D A is incorrect because the sister chromatids of a chromosome separate during meiosis II. B is incorrect because the homologous chromosomes pair up in meiosis I when the recombination of genetic material between homologous pairs takes place. C is incorrect because two sex cells are produced as a result of meiosis I, and four sex cells are produced as a result of meiosis II. D is correct because each of the two cells at the end of meiosis I has half the chromosome number. The two chromatids of each chromosome separate during meiosis II. 5. C A is incorrect because mitosis involves replication of chromosomes. B is incorrect because meiosis involves replication of chromosomes. C is correct because fertilization does not involve cell division or the replication of chromosomes. D is incorrect because meiosis is the process of forming the sex cells and involves replication of chromosomes. Lesson 3 Quiz 1. A 4. B 2. B 5. D 3. D 1. A A is correct because sexual reproduction requires two parents and results in offspring that have characteristics of each parent. B is incorrect because this statement describes asexual reproduction. C is incorrect because the offspring of sexual reproduction are not genetically identical to either parent. Instead, they have characteristics of both parents. D is incorrect because sexual reproduction requires two parents, and each parent contributes half of the genes. 2. B A is incorrect because fertilization is required for sexual reproduction. B is correct because all three of these modes of reproduction are asexual. C is incorrect because fertilization is required for sexual reproduction. D is incorrect because egg and sperm join in fertilization as part of sexual reproduction. 3. D A is incorrect because constant, favorable conditions favor asexual reproduction. B is incorrect because conditions that promote the growth of many offspring would favor asexual reproduction. C is incorrect because conditions under which the organism can easily obtain nutrients and water would favor asexual reproduction. D is correct because unfavorable conditions tend to favor sexual reproduction among organisms that can reproduce both sexually and asexually. 4. B A is incorrect because an organism produced by sexual reproduction receives chromosomes equally from each of two parents. B is correct because an organism produced by sexual reproduction receives half of its chromosomes from each parent when a sperm cell fertilizes an egg. C is incorrect because an organism produced by sexual reproduction receives half of its chromosomes from each parent. D is incorrect because an organism produced by sexual reproduction receives half of its chromosomes from each parent. 5. D A is incorrect because only statement II refers to sexual reproduction. Sexual reproduction does not enable organisms to increase in number as quickly as asexual reproduction does. B is incorrect because only statement I refers to asexual reproduction. Sexual reproduction does not enable organisms to increase in number as quickly as asexual reproduction does, and asexual reproduction produces offspring that are genetically identical to their parent. C is incorrect because the opposite is true. Statement I refers to asexual reproduction, and statement II refers to sexual reproduction. D is correct because the ability to increase in number very quickly is typical of asexual reproduction, and increasing genetic diversity is typical of sexual reproduction. Lesson 4 Quiz 1. A 4. C 2. D 5. B 1. A A is correct because the genes are located on the chromosomes of each cell. B is incorrect because chromosomes are made up of many genes. C is incorrect because a phenotype is the organism s appearance and not the genes it contains. D is incorrect because the appearance of an organism is its phenotype. 2. D A is incorrect because all of the offspring would have inherited one dominant allele from the parent with purple flowers. B is incorrect because all of the offspring of this cross would inherit a recessive allele for white flowers from one parent and a dominant allele for purple flowers from the other parent. C is incorrect because purple flower color is the dominant trait, so none of the offspring would have white flowers. D is correct because all of the offspring would be heterozygous and have purple flowers. A is incorrect because the phenotype is not determined by a single gene. 321 Grade 7 Guide Florida

4 B is incorrect because most traits are determined by more than one gene. C is correct because some genes determine more than one trait. D is incorrect because each gene can determine more than one trait. 4. C A is incorrect because the alleles are codominant, so both phenotypes are expressed. B is incorrect because both alleles contribute to the phenotype in order to produce blood type AB. C is correct because both alleles contribute to the phenotype in order to produce blood type AB. D is incorrect because individuals with blood type AB produce antigens associated with type A and type B blood. 5. B A is incorrect because a temperature change does not change the alleles that make up the genotype. B is correct because the genotype remains the same, but the phenotype changes depending on environmental conditions. C is incorrect because the cat s alleles do not affect its environment. D is incorrect because the cat s appearance does not change the cat s genetic makeup. Lesson 5 Quiz 1. C 4. D 2. B 5. C 1. C A is incorrect because this choice describes a ratio. B is incorrect because probability does not refer to an actual outcome; it refers to the chances of an outcome. C is correct because probability is the likelihood of a specific outcome in relation to the total number of possible outcomes. D is incorrect because probability gives only the likelihood that something will happen. Probability does not describe what will definitely happen in a given situation. 2. B A is incorrect because in one out of two times, the mouse has the alleles DD and in one out of two times, the mouse has the alleles Dd. B is correct because each of these outcomes has a 50% chance of happening, so they are equally likely to happen. C is incorrect because the mouse is as likely to have DD as it is to have Dd. D is incorrect, These are the only two possible outcomes because their probabilities total 100%. A is incorrect because a pedigree is a diagram of relationships that exist in a family. It does not describe genetic diversity among different species. B is incorrect because a pedigree is a diagram of relationships that exist in a family, but it does not explain dominance. C is correct because a pedigree shows relationships within a family and includes two or more generations. D is incorrect because this choice describes a Punnett square. 4. D A is incorrect because all inherited genetic disorders can be passed from parent to child. B is incorrect because both males and females can be affected by sex-linked disorders. C is incorrect because the inheritance of sex-linked disorders can be traced on a pedigree. D is correct because a sex-linked gene is located on a sex chromosome. 5. C A is incorrect because, as carriers, Alisha and Rob each have an allele for the disease, but they are not immune to the disease. B is incorrect because Alisha and Rob are carriers of the disease, but they will not develop the disease. To be expressed, the disease requires two alleles. C is correct because each parent, as a carrier of the disease, has one allele for the disease. Neither has the disease because, to be expressed, the disease requires two alleles. Each or both parent could pass the allele to a child. D is incorrect because as carriers of the disease, Alisha and Rob do not have the disease. To be expressed, the disease requires two alleles. Lesson 1 Alternative Climb the Ladder: Mitosis Understanding the Cycle: Scrapbooks depict the three stages of the cell cycle, show illustrations of each stages, and describe what occurs during each stage. An Ode to Mitosis: Poems describe the ways that a multicellular organism appreciates mitosis. Tracking Mitosis: Notes and sketches describe the videos. The strengths and weaknesses of the videos are presented. This Just In!: New reports describe a new cell that has just formed, explain how the cell formed (including the three stages of the cell cycle), and identify the cell as a unicellular organism or part of a multicellular organism. To Be DNA: Monologues describe what happens to DNA before and during mitosis. Why, Oh Why?: Videos explain the reasons that unicellular organisms go through cell division and the reasons that multicellular organisms go through cell division. Lesson 2 Alternative Points of View: Meiosis Terms: Terms are defined in students own words, and then by using a dictionary definition. Last, a paragraph uses the terms to describe meiosis. Calculations: Calculations tell how many chromosomes are present in a haploid cell from a squirrel and corn, and how many chromosomes are present in a diploid cell from an alligator. Details: Venn diagrams or other graphic organizers show how meoisis and mitosis are alike and different. Illustrations: Sketches illustrates the differences between the final stages of meiosis I and meiosis II. Analysis: Answers explain why meiosis is important for many living things.. Model: Models show one phase of meiosis, and include cell walls, 322 Grade 7 Guide Florida

5 chromosomes, spindle fibers (if appropriate), and so on. Lesson 3 Alternative Tic-Tac-Toe: Reproduction Plant Detective: Steps explain how to figure out whether the plant reproduces sexually or asexually. Parent Clone: Journal entries describe the advantages of being genetically identical to a parent. Sporific!: Illustrations show the life cycle of a plant that produces spores, and explain in which stage the plant best survives harsh conditions. Diagram It!: Diagram shows how organisms reproduce by mitosis. What re the Advantages?: Charts show the advantages of asexual and sexual reproduction. News Flash!: Reports describe what happens after a giant plant that reproduces by budding is discovered with growing buds. Plan a Garden: Sketches show plants in a garden that reproduce both sexually and asexually, and describe the conditions in which each plant is most likely to succeed. Switching Roles: Explanations tell why the plant may be changing types of reproduction from growing new roots to blooming. Explain It!: Drawings with labels explain fertilization for a person who is learning English. Lesson 4 Alternative Climb the Ladder: It s Hereditary Alien Eyes: Answers explain what color the alien s eyes are, and what alleles the father might have. DNA s Role: Diagrams or sketches explain DNA s role in determining human traits. Diagrams or sketches include labels and descriptions. Dominance Differences: Entries summarize Mendel s findings, and include diagrams or illustrations as needed. Dominance Differences: Charts explain how complete dominance, incomplete dominance, and co-dominance are alike and different. Type Casting: Posters identify the relationship between genotype and phenotype, and include a catchy way to remember what each term means. Genes and Traits: Paragraphs explain how one gene can be responsible for many traits, and how many genes can be responsible for one trait. Lesson 5 Alternative Climb the Pyramid: Make a Flower R = red flower, r = pink flower R r Rr rr r Rr rr L = long stem, l = short stem L r L l Ll Ll l Ll Ll T = thick stem, t = thin stem T T TT Tt t Tt tt O = oval leaf, o = round leaf O t O O OO OO o Oo Oo G = solid green leaf, g = spotted green leaf G g G GG Gg G GG Gg B = big leaf, b = small leaf B B B BB BB b Bb Bb Alleles selected and flowers sketched will vary. Florida Benchmark Review 1. B 5. C 9. C 2. B 6. A 10. C 3. D 7. D 11. C 4. B 8. C 12. D 1. B See Unit 8, Lesson 1 A is incorrect because the order of phases should be prophase, metaphase, anaphase, telophase, and cytokinesis, which would be 2, 4, 5, 1, 3. B is correct because the order of phases should be prophase (card 2), metaphase (card 4), anaphase (card 5), telophase (card 1), and cytokinesis (card 3). C is incorrect because the order of phases should be prophase, metaphase, anaphase, telophase, and cytokinesis, which would be 2, 4, 5, 1, and 3. D is incorrect because the order of phases should be prophase, metaphase, anaphase, telophase, and cytokinesis, which would be 2, 4, 5, 1, and B See Unit 8, Lesson 2 A is incorrect because chromosomes are duplicated during both meiosis and mitosis. B is correct because homologous chromosomes do not pair up during mitosis. C is incorrect because chromosomes line up along the equatorial plate during both types of cell division. D is incorrect because condensation of chromosomes happens before both meiosis and mitosis. 3. D See Unit 8, Lesson 3 A is incorrect because the genetically identical offspring indicate that asexual reproduction rather than sexual reproduction took place. B is incorrect because asexual reproduction requires only one parent. C is incorrect because the genetically identical offspring indicate that asexual reproduction rather than sexual reproduction took place. D is correct. Because the offspring are genetically identical, asexual reproduction took place, and this type of reproduction requires only one parent. 4. B See Unit 8, Lesson 5 A is incorrect because although one parent has the alleles BB, the other is Bb. B is correct because the parental alleles, which are shown at the top and side of the square, are BB and Bb. C is incorrect because although one parent has the alleles Bb, the other is BB. 323 Grade 7 Guide Florida

6 D is incorrect because although one parent has the alleles Bb, the other is BB. 5. C See Unit 8, Lesson 4 A is incorrect because all offspring have the smooth shape, so the smooth shape is a dominant trait. B is incorrect because all offspring have the smooth shape, so the wrinkled shape is a recessive trait. C is correct because only smooth shape shows up in the offspring. Therefore, smooth shape must be the dominant trait. D is incorrect because the offspring do not include any peas with wrinkled seeds. Therefore, wrinkled seeds must be the recessive trait. 6. A See Unit 8, Lesson 4 A is correct because DNA contains the set of instructions that determines traits, such as eye color and hair color. B is incorrect because glucose is a sugar molecule. C is incorrect because cellulose is a starch molecule. D is incorrect because cholesterol is a lipid molecule. 7. D See Unit 8, Lesson 1 A is incorrect because the number of cells produced would be two or less. B is incorrect because the number of chromosomes would be reduced if DNA was not duplicated. C is incorrect because the number of nuclei would likely not be affected by the error. D is correct because if DNA is not duplicated, the chromosome pairs would not separate correctly. The resulting nuclei would have too few chromosomes. 8. C See Unit 8, Lesson 2 A is incorrect because individual 4 is female. B is incorrect because individual 4 is female and is not the offspring of individuals 1 and 2. C is correct because individual 4 is female (the shape representing her is a circle). She is also the mother of individual 3 in generation III because there is a vertical line extending down from the horizontal line connecting individual 4 with individual 3. D is incorrect because individual 4 is not the daughter of individuals 1 and 2. She married the son of individuals 1 and 2 in generation I. 9. C See Unit 8, Lesson 4 A is incorrect because the alleles B and b are two different versions of a gene. B is incorrect because the alleles result in the two different phenotypes: brown fur and white fur. C is correct because each allele is a different version of the same gene. D is incorrect because the alleles both provide different instructions about the same trait. 10. C See Unit 8, Lesson 5 A is incorrect because egg cells are produced by females. B is incorrect because sperm cells are produced by meiosis. C is correct because body cells are produced by mitosis in both males and females. D is incorrect because body cells are not produced by meiosis. 11. C See Unit 8, Lesson 3 A is incorrect because Caryn has a 50% chance of developing Alpha-1 since she will inherit the recessive allele from her mother, and has a 50% chance of inheriting the recessive allele from her father. B is incorrect because Caryn has a 50% chance of becoming a carrier, since she will inherit the recessive allele from her mother but may not inherit the recessive allele from her father. C is correct because Caryn will inherit the recessive allele from her mother, and has a 50% chance of inheriting the allele from her father. So, Caryn has a 50% chance of being a carrier and a 50% chance of developing the disease. D is incorrect because if Caryn does not inherit the recessive allele from her father, she will not develop Alpha-1. She has a 50% chance of becoming a carrier. 12. D See Unit 8, Lesson 3 A is incorrect because budding takes place when a new organism grows from the outside surface of the parent organism, and the resulting offspring are genetically identical. B is incorrect because binary fission takes place when an organism divides into two organisms, and the resulting organisms are genetically identical. C is incorrect because during spore formation, an organism produces a specialized spore that develops into a genetically identical, multicellular organism. D is correct because vegetative reproduction takes place when a new plant develops from a modified stem or root (not a single cell) that is taken from a parent plant. The offspring are genetically identical to the original parent plant. Unit Test A Key Concepts 1. D 6. A 11. C 2. C 7. A 12. B 3. D 8. C 1 4. D 9. B 14. C 5. A 10. D 15. B 1. D A is incorrect because Mendel explained the results by identifying dominant and recessive traits in the plants, not mutations. His studies did not directly address mutations. B is incorrect because Mendel s findings were based on dominant and recessive traits. He did not recognize that the environment could affect the expression of genes. C is incorrect because acquired traits are not inherited, and flower color is an inherited trait. D is correct because Mendel explained the differences in the traits he observed by concluding that plants have both dominant and recessive traits. 2. C A is incorrect because the dominant trait would also be expressed for a codominant trait. B is incorrect because both alleles are expressed in codominance. C is correct because a codominant trait is one in which both alleles are expressed, and the phenotype is a product of the two alleles. D is incorrect because the phenotype is intermediate to both parents in incomplete dominance, but both alleles are expressed in codominance. 324 Grade 7 Guide Florida

7 3. D A is incorrect because eye color is an example of an inherited trait. B is incorrect because wavy, red hair is an inherited trait. C is incorrect because cheek dimples are an inherited trait. D is correct because having long fingernails is a choice, or acquired characteristic. 4. D A is incorrect because this choice describes a pedigree. B is incorrect because a Punnett square does not explain why some genes are recessive; it merely shows how the alleles are passed on. C is incorrect because a Punnett square does not compare inherited and acquired traits; it only shows how alleles are passed on. D is correct because a Punnett square illustrates the probabilities of what alleles offspring will receive from their parents. 5. A A is correct because hemophilia is a sexlinked disorder. B is incorrect because cystic fibrosis is a genetic disease, but it is not sex-linked. C is incorrect because Tay-Sachs disease is a genetic disease, but the gene for this disease is not located on a sex chromosome. D is incorrect because cystic fibrosis is a genetic disease, but it is not sex-linked. The allele for this disease is found on an autosomal chromosome. 6. A A is correct because a ratio compares two quantities and shows the relationship between them. B is incorrect because this choice describes a pedigree diagram. C is incorrect because this choice describes a Punnett square. D is incorrect because this choice describes probability. 7. A A is correct because asexual reproduction is a type of reproduction that requires only one parent and results in genetically identical offspring. B is incorrect because asexual reproduction requires only one parent. C is incorrect because asexual reproduction produces genetically identical offspring. D is incorrect because asexual reproduction produces genetically identical offspring and requires only one parent. 8. C A is incorrect because this statement describes binary fission. B is incorrect because this statement describes spore formation. C is correct because vegetative reproduction takes place when new plants develop from modified stems or roots of the parent plant. D is incorrect because this statement describes sexual reproduction 9. B A is incorrect because sexual reproduction increases genetic diversity, but asexual reproduction does not. B is correct because asexual reproduction requires only one parent, and sexual reproduction requires two parents. C is incorrect because sexual reproduction increases a species chances of surviving unfavorable conditions, but asexual reproduction does not. D is incorrect because the offspring produced by sexual reproduction are not identical to each other, but those of asexual reproduction are identical to each other. 10. D A is incorrect because the cell on the left is a body cell. B is incorrect because the cell on the left is a body cell. C is incorrect because the cell on the right is a sex cell, but it does not function in growth or repair of damaged tissue. D is correct because the cell on the right is the sex cell and it passes on genetic information to offspring during sexual reproduction. 11. C A is incorrect because this pair shows the numbers of cells before and after meiosis I or mitosis. B is incorrect because this pair shows the numbers of cells before and after both meiosis I and meiosis II are complete. C is correct because two cells divide to become four cells in meiosis II. D is incorrect because this pair shows no increase in cell number, which indicates that no cell division has taken place. 12. B A is incorrect because chromosomes are not built by instructions from proteins, and proteins do not provide information for building nucleotides. B is correct because during fertilization, an egg cell and a sperm cell each contribute one half of a pair of homologous chromosomes. C is incorrect because one homologous chromosome is inherited from the female parent, and the other is inherited from the male parent. D is incorrect because chromosomes are found in the nucleus, not in the cytoplasm. 1 A is incorrect because cell division for growth takes place in multicellular organisms, not single-celled organisms. B is incorrect because a multicellular organism can undergo cell division to repair an injury, but single-celled organisms cannot. C is correct because single-celled organisms undergo cell division for reproduction, enabling them to transmit their genetic information to the next generation. D is incorrect because multicellular, not single-celled, organisms undergo cell division for specialization. 14. C A is incorrect because chromatin is the loose form of the material that condenses into chromosomes. It is made up of DNA and proteins. B is incorrect because a chromosome is the condensed form of chromatin, and it is designated by letter W. C is correct because DNA is a doublehelix structure along which the genes reside. This structure is shown at position Z in the diagram. D is incorrect because protein is a part of chromatin fiber along with DNA, but letter Z indicates just the DNA. 325 Grade 7 Guide Florida

8 15. B A is incorrect because new cells do not form until cytokinesis is complete. B is correct because mitosis is the process of cell division that results in the formation of two new nuclei. C is incorrect because DNA is copied once during interphase, but each copy of DNA is separated by mitosis into two nuclei. DNA is not copied two times during mitosis. D is incorrect because, although the chromosomes are copied once, each set of chromosomes is separated by mitosis into the two nuclei. The net number of chromosomes in the new nuclei is the same as in the parent cell. Critical Thinking 16. Sample answer: A genotype is the combination of the alleles that determine a trait, and a phenotype is the trait that is observed. Students answers will vary, but correct definition of genotype. correct definition of phenotype. 17. Sample answer: The allele that causes colorblindness is found on the X chromosome. Because women have two X chromosomes, they can carry the allele but still not be colorblind. Men have only one X chromosome, so they will either have the allele (and be colorblind) or not have the allele (and not be a carrier). Color blindness is a sex-linked trait. Women have two X chromosomes and have two alleles for this trait. Men have only one X chromosome, so they cannot be carriers (which requires having two alleles). 18. Sample answer: Binary fission takes place in single-celled organisms such as an amoeba. In this type of asexual reproduction, an organism divides into two equal halves, producing two identical offspring. Students answers will vary but Identifying binary fission as asexual reproduction A brief description of the process An example of an organism that uses this process 19. Sample answer: Both sexual and asexual reproduction result in the production of new organisms. They are different in that asexual reproduction requires only one parent, but sexual reproduction requires two. They are also different in that sexual reproduction produces offspring with genetic diversity. Students answers may vary, but both types of reproduction produce offspring. one parent is needed for asexual reproduction, and two parents are needed for sexual reproduction. sexual reproduction produces offspring that are genetically different from the parents, and asexual reproduction produces offspring that are genetically identical to the parent. 20. Sample answer: This is a sex cell (an egg), because it has 23 chromosomes. This is half the number that is present in a human body cell. Students answers will vary, but an identification of the cell as a sex cell. an explanation that sex cells have 23 chromosomes in humans. 21. Sample answer: As a result of meiosis, each sex cell has half the number of chromosomes that were present in the original cell. During sexual reproduction, fertilization restores the original number of chromosomes. Students answers will vary, but an understanding of the consequences of meiosis. a recognition of the outcome of fertilization. 22. Sample answer: The salamander s tail was replaced by cell division. Multicellular organisms rely on cell division for growth and repair. Cells divided to replace the cells that were lost. They continued dividing until the tail grew back completely. In the case of the salamander s tail, cell division was part of the growth and repair process. Cells divided many times to replace the tail and continued dividing until the tail grew back. Extended Response 23. Sample answer: In sexual reproduction, organisms have to expend energy to find and attract a member of the opposite sex. Many organisms that reproduce sexually also care for their offspring after they are born. This care requires sexually reproducing organisms to expend even more energy. Sexual reproduction requires the expenditure of energy to find and attract a mate. Sexual reproduction may also require the expenditure of energy to raise offspring. 24. Sample answer: It is most likely that one parent has the alleles GG and the other has the alleles gg. This would mean the parent with GG would pass on a G allele to the offspring 100% of the time. The parent with the gg alleles would pass on a g allele to the offspring 100% of the time. So, all of the offspring would have the alleles Gg. If the parents had other allele combinations, such as Gg and Gg, or GG and Gg, they could possibly have offspring that were Gg, but it is highly unlikely that 1,000 out of 1,000 offspring would be Gg. The parents probably have the alleles GG and gg. The parent who is GG would always pass on a G allele. The parent who is gg would always pass on a g allele. Other combinations are not likely because there is a large sample of 1,000 offspring. 326 Grade 7 Guide Florida