U1AOS2 Biological Systems Flashcards
Levels of structural organisation
Cell, tissue, organ, system, organism
Four basic tissue types
Muscle tissue, nervous tissue, epithelial tissue, connective tissue
Types of muscle tissue
Striated, cardiac, smooth
Striated muscle tissue
Contracts voluntarily
Attached to the skeleton
Cardia muscle tissue
Contracts involuntarily
Found in heart walls
Smooth muscle tissue
Contracts involuntarily
Surrounds organs
4 main types of nervous tissue
Bipolar interneuron
Unipolar sensory neuron
Multipolar motor neuron
Astrocyte (glial cell)
Epithelial tissues
Include all cells that form the interface between the body and external environment
Connective tissues
Fibrous tissues containing cells separated by an extra cellular matrix
The transpiration stream
Water moves from roots to leaves through xylem vessels through 4 main forces: osmosis, adhesion, transpiration and cohesion
Xylem vessels
Composed of dead, hollow cells with cell walls impregnated with lignin that makes the cells walls waterproof, hard and rigid
Adhesion
The attraction between water and some other surfaces. Water moves by adhesion up the xylem
Cohesion
The attraction of water molecules to one another due to their complimentary poles
Stomata
Tiny pores in the epidermis of a lead that allows the exchange of gases between inside and outside. Allows O2 and CO2 to be exchanged between the leaf and the air
Transpiration
As water is lost through the stomata, there is a negative pressure at the top of the xylem vessel. Works like a straw
Regulation of water loss
Each stoma is surrounded by a pair of guard cells that open and close to let water out or stop water from leaving
Translocation of sugars
Sugar moves into the phloem by active transport through membrane proteins or by simple diffusion through plasmodesmata. Moves down the phloem to the roots under pressure from osmosis
Phloem cells
Living cells that have no nucleus and accompanied by smaller companion cells
