Survival and response Flashcards
what is a stimulus?
any change in the internal or external environment eg a change in temperature, light intensity, pressure etc
what happens after a stimulus?
stimulus —> receptor —> coordinator —> effector —> response
what is a tropism?
a directional growth response in which the direction of the response is determined by the direction of the external stimulus
positive tropisms = grow towards the direction of the stimulus
negative tropisms = grow away from the direction of the stimulus
what are the 5 different types of tropism?
1) phototropism - shoots grow towards the light to increase the rate of photosynthesis
2) gravitropism - shoots grow upwards and roots downwards towards pull of gravity
3) chemotropism - pollen tubes grow towards chemicals given off by the ovary in a flower
4) thigmotropism - shoots respond to touch by growing around other plants
5) hydrotropism - roots grow towards water
what are plant growth regulators?
they are plant hormones that coordinate plant growth. They are produced in small quantities and are transported to the target cells by active transport, diffusion and in the phloem and xylem.
they are a specific shape, bind to complementary shaped receptors to target cell plasma membrane
why do shoots grow towards a light stimulus?
because cells in the side of the shoot away from the light elongate more rapidly than cells in the side facing the light
1) cells in the tip of the shoot produce IAA, which diffuses down the stem
2) light on one side of stem causes IAA to move to the shaded side, so a high concentration builds up on shaded side
3) IAA causes cell elongation and there are more IAA on the shaded side so the cells elongate more and the shoot bends towards the light
Positive Phototropism
how does gravitropism occur?
IAA controls the bending of the roots in response to gravity
in shoots = IAA causes cell elongation
in roots = IAA inhibits cell elongation
1) cells in the tip of the root produce IAA, which is then transported along the root.
2) gravity influences the movement of IAA from the upper to lower side of the root
3) a greater concentration of IAA builds up on the lower side of the root
4) IAA inhibits cell elongation so the cells on this side elongate less and the root bends down
what are the two simple responses in animals?
1) taxis
2) kinesis
what is taxis?
taxis is a change in directional movement in response to a stimulus.
Positive taxis = moving towards a stimulus
negative taxis = moving away from a stimulus
what is kinesis?
kinesis is a change in the rate of movement of an animal in response to a stimulus
what does the nervous system consist of?
central nervous system - made up of neurones found in brain and spinal cord
peripheral nervous system - made up of motor and sensory neurones
what are sympathetic neurones?
controls fight or flight response
what are parasympathetic neurones?
calms response
what is a reflex arc?
- it is a rapid, involuntary, short lived response to a stimulus
- they are protective, help organism avoid danger
- present from birth and do not need to be learnt
- can help avoid damage to tissues eg burning
- can help organisms find food as well as escape from predators
what are the three neurones involved in nervous system?
1) relay - transmit nerve impulses between other neurones
2) sensory - transmit nerve impulses from a sensory receptor to the central nervous system
3) motor - transmit nerve impulses from the CNS to an effectors such as a muscle or gland
label the diagram of a reflex arc?
what is the structure of a myelinated motor neurone?
Consists of:
cell body - part of the neurone containign nucleus and organelles
axon - carries nerve impulse away from the cell body
myelin sheath made of schwann cells - speeds up transmission of nerve impulse along a neurone
nodes of ranvier - gaps between schwann cells
