Biology 5.5 Multicellular Life

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