SECTION 5.2 ASSESSMENT, p. 183–184 Check Your Understanding Answers Checking Concepts 1. (a) B; (b) A; (c) B; (d) C; (e) E 2. Budding differences: occurs in multicellular organisms, may or may not separate from parents Binary fission differences: occurs in unicellular organisms only, separates from parent Similarities: both are methods of asexual reproduction, new offspring produced are identical to the parent 3. Two multicellular organisms that reproduce by budding are the hydra and the sponge. 4. Ways a plant can reproduce asexually include: fragmentation, vegetative reproduction such as runners and potato eyes, and by grafting, cuttings, and spore formation. 5. Organisms that reproduce asexually often produce large numbers of offspring to outcompete other organisms for nutrients and water. In addition, large colonies may survive when environmental conditions or the number of predators changes. 6. Some spores have a tough outer covering that allows them to survive in harsh conditions, such as drought or extreme temperature, until conditions become favourable. Understanding Key Ideas 7. The number of times a bacterium will be able to divide depends on the amount of nutrients, the availability of moisture, and the temperature (since enzymes that catalyze chemical reactions work at an optimum temperature). 8. Most multicellular organisms are unable to reproduce by budding because there are too many specialized cell types within the organism. Sponges and hydras have only a few different types of cells. 9. In the process of mitosis, the nucleus disappears and the chromosomes assemble themselves at the equator of the cell and move to opposite poles. Bacteria do not undergo mitosis because they do not have a nucleus and they have only one chromosome ring, not the X-shaped chromosomes of eukaryotes. 10. Embryonic stem cells have the potential to become any type of cell. A piece of a plant has the potential to develop into any type of cell of a plant. Plant cells, like embryonic stem cells, are not differentiated. 11. When oyster farmers tried to destroy the sea stars by cutting them into pieces and throwing them back into the ocean, the sea stars multiplied asexually by fragmentation and the population increased even more. 12. If boaters do not clean off their motors, fragments of algae can be carried into another lake where they will multiply. If there are not a lot of competitors, the algae may be successful in taking over the lake. 13. Advantages of asexual reproduction: (a) large numbers of offspring are produced in a short period of time from only one parent when conditions are favourable; (b) large numbers of offspring can out-compete other organisms for nutrients and water; (c) large numbers of offspring mean that species can survive when the conditions or number of predators change; and (d) very little energy is required. Disadvantages of asexual reproduction: (a) offspring are genetic clones and a negative mutation may make the organism susceptible to disease and can destroy large numbers of offspring; (b) some types of asexual reproduction produce offspring that are close together and compete for food and space; (c) unfavourable conditions can wipe out an entire colony. 14. Similarities: types of human-assisted cloning; can use egg cells or stem cells; the nucleus of the cell is removed and replaced with the nucleus of the desired organism. Differences: Reproductive cloning: purpose is to create a genetic clone of an existing animal for some desirable quality; embryo is put into a surrogate mother to complete development. Therapeutic cloning: purpose is to correct health problems; embryonic cells are treated to become a required tissue or organ, not another individual; the tissue or organ is transplanted back into the patient.
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