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Asexual Reproduction and Multicellular Life
Chapter 5.4 and 5.5
KEY CONCEPTMany organisms reproduce by cell division.
• Asexual reproduction• Creation of offspring from a SINGLE parent that
does not involve the joining of gametes.
Binary fission is similar in function to mitosis.
• Asexual reproduction is the creation of offspring from a single parent.– Binary fission produces two daughter cells genetically identical
to the parent cell.– Binary fission occurs in
prokaryotes.
parent cell
DNA duplicates
cell begins to divide
daughter cells
Question
• How is asexual reproduction an advantage in some conditions?
• Answer: asexual reproduction produces genetically identical offspring that are well suited to their environment.
• Environment determines what form of reproduction is most advantageous.– Asexual reproduction is an
advantage in consistently favorable conditions.
– Sexual reproduction is an advantage in changing conditions.
Some eukaryotes reproduce through mitosis.
• Budding forms a new organism from a small projection growing on the surface of the parent.
bud
Hydra
Yeast
Question
• How might the asexual reproduction of genetically identical plants be useful to humans?
• Answer We could theoretically grow a particular plant in abundance
• How could it prove harmful to our food supply?• Answer: if condition change a significant portion
of our food supply could be adversely affected.
• Fragmentation is the splitting of the parent into pieces that each grow into a new organism.
Vegetative reproduction forms a new plant from the modification of a stem or underground structure on the parent plant.
Stem Cells—multicelluar life
KEY CONCEPT Cells work together to carry out complex functions.
Multicellular organisms depend on interactions among different cell types.
• Tissues are groups of cells that perform a similar function.
• Organs are groups of tissues that perform a specific or related function.
• Organ systems are groups of organs that carry out similar functions.
CELL TISSUE ORGAN
vascular tissue
leaf
stem
lateralroots primary
root
SYSTEMS
root
syst
emsh
oot s
yste
m
Specialized cells perform specific functions.
• Cells develop into their mature forms through the process of cell differentiation.
• Cells differ because different combinations of genes are expressed.
• A cell’s location in an embryo helps determine how it will differentiate.
Outer: skin cells Middle: bone cells Inner: intestines
Question
• Why is regulation of the differentiation process during the early stages of development so critical?
• The early stages 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 are unique body cells.
• Stem cells have the ability to– divide and renew themselves– remain undifferentiated in form– develop into a variety of specialized cell types
• Stem cells are classified into three types.– totipotent, or growing into any other cell type– pluripotent, or growing into any cell type but a totipotent cell– multipotent, or growing into cells of a closely related cell family
First, an egg is fertilized by a sperm cell in a petri dish. The egg divides, forming an inner cell mass. These cells are then removed and grown with nutrients. Scientists try to control how the cells specialize by adding or removing certain molecules.
• Stem cells come from adults and embryos.– Adult stem cells can be hard to isolate and grow.– The use of adult stem cells may prevent transplant rejection.– The use of embryonic
stem cells raisesethical issues
– Embryonic stem cellsare pluripotent andcan be grown indefinitelyin culture.
• The use of stem cells offers many currently realized and potential benefits.– Stem cells are used to treat leukemia and lymphoma.– Stem cells may cure disease or replace damaged organs.– Stem cells may revolutionize the drug development process.
Biology presentation
• Click on stem cell film clip
Blackboard assignment• Discussion Board—October 25You will need to goggle and research to debate your view point on different stem cell-related treatment options for diseases such as diabetes and acute lymphatic leukemia. Should we or should we not continue and provide federal funding for stem cell research?
• When you author your thread remember to discuss the treatment options and your opinion on whether or not stem cell research should be federally funded.
• Remember---scientific research isn’t always as cut-and-dry as is presented in high school textbooks; researchers defend alternative viewpoints on any given issue, and can make very convincing arguments in favor of their opinions.
Value: 50 points.
