Biology 5.5 Multicellular Life

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What are tissues?
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groups of cells that work together to perform a similar function
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What are organs?
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groups of tissues that work together to perform a specific function or related functions
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What are the two types of plant tissues and what do each of them do?
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conductive: transport sugars, water, and minerals to and from other parts of the plant protective: help prevent water loss
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What are organ systems?
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organs that carry out similar functions
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What do organ systems work together to do?
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help an organism maintain homeostasis
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How do plants maintain a certain level of water?
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absorb water through their roots and expel it as water vapor through openings in their leaves called stomata
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What are stomata controlled by, and what do they do?
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special cells called guard cells, which close the stomata when a plant’s water intake cannot keep up with its water loss
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What is cell differentiation?
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process by which unspecialized cells develop into their mature forms and functions
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What helps determine how an embryotic cell will differentiate?
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the cell’s location within the embryo
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What happens during the first division of a fertilized egg in a plant cell?
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it is unequal, or asymmetrical, and produces two cells, the apical and basal cell
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What does the apical cell (in a plant) do?
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forms most of the embryo, including the growth point for the stems and leaves
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What does the basal cell (in a plant) do?
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provides nutrients to the embryo; it also created the growth point for the roots
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Instead of migrating, what do plant cells do to adapt to changing conditions and develop?
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new cells continue to differentiate and change based on their location (may not be the same as the parent cell)
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What happens after the egg is fertilized in animal cells?
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undergoes many rapid divisions, then the cells migrate to a specific area where they begin to differentiate
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What are stem cells?
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unique type of body cell that have the ability to 1. divide and renew themselves for long periods of time 2. remain undifferentiated in form 3. develop into a variety of specialized cell types
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What happens when a stem cell divides?
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forms either two stem cells or one stem cell and one specialized cell
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What are the three different stem cell types?
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totipotent, pluripotent, and multipotent
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What are totipotent stem cells?
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can grow into any other cell type, only a fertilized egg and the cells produced by the first few divisions of an embryo
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What are pluripotent stem cells?
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can grow into any cell type except for totipotent stem cells
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What are multipotent stem cells?
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can grow only into cells of a closely related cell family
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What are adult stem cells and what are they also called?
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partially undifferentiated cells located among the specialized cells of many organs and tissues; also called somatic stem cells
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What are the major advantages of the adult stem cell?
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they can be taken from a patient, grown in culture, and put back in the patient, so the risk of transplant rejection is low, also avoids many ethical issues
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What are the disadvantages of the adult stem cell?
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few in number, difficult to isolate, and sometimes tricky to grow; may contain more DNA abnormalities than embryonic stem cells
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Where do most embryonic stem cells come from?
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donated embryos grown in a clinic, a result of in vitro fertilization
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What is in vitro fertilization?
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a process by which eggs are fertilized outside a woman’s body
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What are the cells in the inner cell mass?
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stem cells taken from a cluster of undifferentiated cells in the three-to-five-day-old embryo
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What is special about the cells in the inner cell mass?
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they do not have the characteristics of any specific cell type, and are pluripotent, so they can form any of the 200 cell types of the body
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What is the disadvantage of embryonic stem cells?
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if the cells are used in treatment, a patient’s body might reject them as foreign material, also may form a tumor if they grow unchecked
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What are stem cells used for?
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treat patients with leukemia and lymphoma, offer hope for treating many other diseases as well

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