Survival And Response Flashcards
What is a stimulus?
A change in the internal or external environment of an organism that produces a response
What is a receptor?
Cells that detect stimulus energy and convert it into electrical energy used in neurones
Give two methods of communication within the body
Hormones
Nervous system
Give the basic chain of events that gets a stimulus to a response
Stimulus, receptor, coordinator, effector, response
Give the chain of events from stimulus to response in a reflex arc
Stimulus, receptor, sensory neurone to spinal cord relay neurone, motor neurone effector response
How do reflex arcs work to increase survival?
They are much faster so aid protection, also prevent overloading of brain
What is the main plant growth hormone? What does it cause?
IAA, indoleacetic acid, plant elongation
Give the mechanism by which growth occurs in root tips
Shoot tip produces IAA
During transportation it is moved toone side of the stem,
Causes elongation on one side only causing the plant to bend in one direction
What is different about IAA in roots?
Inhibits growth
Describe the acid growth hypothesis
Protons are actively transported from the cytoplasm into the spaces within the cell membrane
Effects the hydrogen bonding within cellulose
Causes the walls to loosen
More water in via osmosis
Pushes on cell wall causes expansion therefore elongation
Describe four varaitations of plant growth that provided evidence for IAA being produced in the root tip
Unaltered root tip, bent towards the light
Removed tip no bending
Light proof cover no bending
See through cover bent towards light
Describe the series of experiments that stopped the debate as to wether the growth factor was a chemical or an electric current
Mica was inserted bellow the tip, mica is a conductor of electric current but not permeable to chemicals. No bending of the plant occured
Gelatin inserted below tip, geltain is permeable but not a conductor hence the plant saw bending. The growth factor was a chemical
What is a taxes?
A directional response undertaken by an organism, in which its whole body moves
Give an example of some potential taxes
Photo
Chemo
Thermo
What is kineses
A non directional response, where in unfavourable conditions an organism increases its speed and rate at which it changes direction. The kineses stops when the organism get back into favourable conditions
