Cells TECHBOOK UNIT 0 Views Unit Review: Cells MEIOSIS Essential Questions and Answers for Review Sheet What is meiosis? Answer: Meiosis is the process by which specialized cells called gametes form in the sex organs of sexually-reproducing multicellular organisms, including animals, plants, and fungi. What does meiosis do? Answer: Meiosis produces gametes that each contain only half the number of chromosomes as most other body cells in an organism. Meiosis also shuffles the genes around by moving them between chromosomes. How does meiosis occur? Answer: Meiosis begins with a diploid cell that contains pairs of homologous chromosomes. After the DNA replicates, the homologous pairs swap some DNA randomly, a process called crossing over. The homologous chromosomes then separate in the first round of cell division, producing two cells. Each daughter cell contains duplicates of a haploid number of chromosomes. Then the second round of nuclear division takes place in which the chromatids (individual chromosome strands) separate. A second cell division creates four cells, each containing single copies of the haploid number of chromosomes. These four cells are genetically different from each other. In males these are the sperm cells. In females only one cell survives and this becomes the egg cell. Why is meiosis important? Answer: The gametes produced by meiosis are necessary in order for sexual reproduction to take place. Meiosis facilitates the combination of DNA from two individuals. This new combination might express traits or characteristics that were absent in either parent. This is why children are always slightly different from either parent. Through this process and
why children are always slightly different from either parent. Through this process and crossing over, meiosis increases the genetic diversity in a population. Genetic diversity is important because it improves the odds that a population of organisms will be able to adapt to and survive environmental changes. MEIOSIS What is different about the cellular processes taking place during reproduction in singlecelled versus multi-cellular organisms? Answer: Single-celled organisms reproduce using mitosis. Multi-cellular organisms use a different process to produce single-celled gametes. Gametes from two individuals combine to form an embryo. What is the difference between mitosis and meiosis? Answer: Both are processes of cell division; however they are not the same. Mitosis results in the division of one cell to form two cells identical to the parent cell. Meiosis results in the division of one cell to form four cells that each have one-half the number of chromosomes present in the parent cell. When does meiosis occur and what structures are produced as a result? Answer: Meiosis occurs only in multi-cellular organisms and only to produce gametes, the cells involved in sexual reproduction. What is accomplished during Meiosis I and what is accomplished during Meiosis II? Answer: Meiosis I begins with a diploid cell that contains pairs of homologous chromosomes. One chromosome from each pair is maternal in origin; one is paternal in origin. Each chromosome replicates itself. Then, homologous pairs separate. This separation results in two cells, each of which contains duplicates of N (haploid) chromosomes. In Meiosis II, each of the cells just formed split again. This time the duplicate chromosomes separate, which leads to the formation of four cells, each of which contains N chromosomes in single copies. Why is meiosis important to the organisms that use it? Answer: Meiosis produces gametes. Gametes from two parents can fuse to form an embryo with a new mixture of genes. As a result, the embryo has different characteristics than either
with a new mixture of genes. As a result, the embryo has different characteristics than either parent. This provides more opportunities for variation of characteristics. THE STRUCTURE OF LIFE What are cells and why are they important? Answer: Cells are the simplest structures that can carry out all of the characteristic activities of life. They are important because they are the building blocks of life; all living things are made of cells. What structures do most cells have in common? Answer: Most cells have many structures in common. Included among these are cytoplasm, a cell membrane, a nucleus, mitochondria, ribosomes, and vacuoles. How do animal and plant cells differ? Answer: Plant cells usually have additional structures that animal cells do not. These include a cell wall, chloroplasts, and a large, water-filled vacuole. How do cells in unicellular and multicellular organisms differ? Answer: Unicellular organisms are capable of living independently. They often have specialized structures for locomotion, such as cilia, flagella, or pseudopods. The cells in multicellular organisms tend to be highly specialized to perform specific functions, depend on the presence of other cells for their survival, and are usually organized with other similar cells into tissues. Tissues are grouped into organs which, in turn, make up organ systems. CELLULAR RESPIRATION Why is cellular respiration important? Answer: During cellular respiration, a cell obtains energy from glucose and oxygen. The cell then uses this energy to carry out different life processes. Where does cellular respiration take place? Answer: Cellular respiration takes place inside of a cell. Oxygen and nutrients enter the cell
Answer: Cellular respiration takes place inside of a cell. Oxygen and nutrients enter the cell through the cell membrane, and a chemical reaction takes place. Then, the products of the reaction are released from the cell. What are the reactants and products of cellular respiration? Answer: Oxygen enters a cell and reacts with glucose in the cell. These are the reactants of cellular respiration. When glucose is broken down, it releases energy. Carbon dioxide and water are also produced. So, energy, carbon dioxide, and water are the products of cellular respiration. PHOTOSYNTHESIS What is photosynthesis? Photosynthesis is the process of using energy from light to synthesize sugars which then can store this energy. Photosynthesis requires light energy, carbon dioxide, and water to make glucose (sugar), oxygen, and water. Where does photosynthesis occur? Photosynthesis occurs in the chloroplasts of plant cells and other photosynthetic cells. Chloroplasts contain a pigment called chlorophyll that allows photosynthetic cells to carry out photosynthesis. CELL THEORY Why are cells important? Answer: Cells are important because all living things have cells, and they perform all of the functions that an organism needs in order to live. Some organisms have only one cell. Other organisms have more than one cell.
How are new cells formed? Answer: Existing cells divide to form new cells. How do the cells in single-celled and multi-cellular organisms differ? Answer: In single-celled organisms, one cell performs all of the functions of the organism. But in multi-cellular organisms, cells are arranged into larger structures like tissues and organs with specialized functions. What are the main characteristics of cells? Answer: All cells grow, repair and maintain themselves, reproduce, undergo change, move, respond to their surroundings, and eventually grow old and die. GENES AND THE IMPACTS OF MUTATIONS ON ORGANISMS Essential Questions and Answers for Review Sheet What are genes, and how do they affect cell structure and function? Answer: Genes are sequences of DNA found on chromosomes that carry hereditary information for physical traits. Genes contain the codes that control the production of proteins, which are essential for the structure and function of a cell. How do mutations change genes? Answer: Mutations change the sequences of DNA that make up genes. What can happen to organisms when genes change? Answer: When genes change, the effect can be beneficial, harmful, or neutral to organisms.
About this Techbook Unit Labels Student Grade(s) 6-8 Course(s) Grades 6-8 Life Science - for use with NGSS (NEW) Citations MLA Cells Techbook Unit. Discovery Education. Web. 07 January 2018. http://www.discoveryeducation.com APA Cells. [Techbook Unit]. Available from http://www.discoveryeducation.com CHICAGO MANUAL OF STYLE Cells From Discovery Education. Techbook Unit. http://www.discoveryeducation.com (accessed 07 January 2018). Copyright 2017 Discovery Education. All rights reserved. Discovery Education is a subsidiary of Discovery Communications, LLC.