Introduction
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What is epigenesis?
When organisms develop through the generation of new structures and forms
What is preformationism?
Organisms develop from miniature versions of themselves
What are the 3 main points of the cell theory?
• All organisms are composed of one or more cells • The cell is the most basic unit of structure, function and organisation in the organism • Cells can only be produced from pre-existing cells
What is Weismanns theory of how cells become different from each other- and who’s experiment backed it up? Who’s experiment opposed it?
Germ plasm determinants theory- the nucleus of the zygote contains many determinants, through cleavage the determinants become unequally distributed to the daughter cells- creating different cells Roux’s experiment supported it Driesch’s experiment on sea urchins opposed it
What is the Spemann-Mangold organiser? How was it proven?
A region in amphibian embryos which determines the the development of neighbouring cells Transplantation of a group of cells from a newt to a host embryo- growth of a partial second embryo on the host
What are the 3 types of cell-cell communication?
• Paracrine • Autocrine • Juxtacrine
What does a instructive signal do?
Initiates a new programme in a cell
What does a permissive signal do?
Provides a favourable environment for a specific programme to occur in a cell
Which germ layer produces neurons, epidermis and pigment cells?
Ectoderm
Which germ layer produces cardiac and skeletal muscle cells, RBCs, smooth muscle or the gut and tubule cells of the kidney?
Mesoderm
Which germ layer produces thyroid cells, pancreatic cells and alveolar cells?
Endoderm
How is tissue homeostasis maintained?
The control of cell division and death through: Negative feedback loops Repair mechanisms- stem cells
What is the point of tissue homeostasis?
Tissue homeostasis maintains the structure and functions of organs in the body