Reproduction­ a process that makes new organisms from one or more parent organisms.
1. sexual­ occurs by joining two gametes (sperm or egg). Offspring are genetically unique.
2. asexual­ creation of offspring from a single parent
Offspring are genetically identical to each other and the parent.
*Binary fission­ the asexual reproduction of a single­celled organism, used by most prokaryotes.
http://www.classzone.com/cz/books/bio_
09/resources/htmls/animated_biology/unit2/bio_ch05_0149
_ab_fission.html
Cells communicate and work together in groups that form increasingly larger, more complex structures.
Cells
Tissue
Organs
Organ Systems Organism
Tissue­ groups of cells that work together to perform a similar function.
Organs­ groups of tissues that work together to perform a specific function or related function.
Organ Systems­ organs that carry out similar functions are grouped together to acheive a larger goal.
Organ systems work together to maintain an organisms homeostasis
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How does a complex organism like you...develop?
­Cell differentiation­ process by which unspecialized cells develop into their mature forms and functions.
*Almost every cell in your body has a full set of DNA but only uses the specific genes it needs to carry out its function.
*Think of DNA as a cookbook. A cookbook holds all of the recipes for making different tons of different dishes. DNA holds all of the instructions for all cell types in your body­but it doesn't use all of them at the same time.
*A cell's location within the embryo helps us to determine what type of cell it will be.
Plant cells can not easily migrate because of the cell wall, but they are capable of adapting to changing conditions and continue to develop throughout their lifetime.
In animal cells, the egg undergoes many rapid divisions after its fertilized and the cells quickly begin to differentiate.
­An early human embryo takes a hollow ball shape and soon fills in with three layers of cells.
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Outer layer ­differentiates to form the outer layer of skin and elements of the nervous system.
Middle Layer ­forms bones, muscles, kidneys, and inner layer of skin
Inner layer ­helps form internal organs (pancreas, lungs, and digestive system lining)
Question: Why is regulation of the differentiation process during the early stages of development so critical?
Answer: The early stages of differentiation lead to the development of progressively more specialized tissues and organs. Distribution of cell differentiation in the early stages could cause severe abnormalities in an organism's body structure.
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.
*can be categorized by their ability or potential to develop into the differentiated cell types of different tissues.
*can also be classified by their origin: adult or embryonic
Adult:
*we've known about their existance for decades
*found all over the body
*Major advantage: can be taken from the patient, grown in a culture, and then put back into the patient (no ethical issues)
*Major disadvantages: few in number, difficult to isolate, trickly to grow, contain more DNA abnormalities 3
Embryonic
*Embryos must be donated, then grown in a clinic in vitro fertilization (fertilization outside a woman's body)
­Taken from a cluster of cells in a 3­5 day old embryo
*Advantage­ can form any of the 200+ different cell types, grows indefinately in a culture (will last a long time)
*Disadvantages­ body could reject them, could grow unchecked and form a tumor, unethical because it kills 3­5 day old embryos.
*Currently used to treat patients with leukemia and lymphoma but has the potential to help so many more diseases.
http://www.sd84.k12.id.us/SHS/departments/Science/yost/Biology/6%20­%20DNA%20&%
20The%20Cell%20Cycle/stem_cell_research.htm
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