Survival And Response- Paper 2 Flashcards
Define stimulus
A detectable change in environment. These can either be external or internal
What is an effector
It responds to stimulation by the never cells- a muscle, a gland, an organ and a cell
State the simple reaction pathway
Stimulus—-> receptor—> coordinator—> effector —> response
Why do organisms need to respond to changes in environment: increase survival and reproduction by
Avoiding harmful environments, competition and predators
Keep in favourable environment such as correct temperature and humidity
Grow towards or away from stimuli such as flowering plants
Dispersing to find new mates
Behaviour patterns
Instinctive behaviour is an innate response to stimuli
Innate behaviour is genetically determined and is not learned
Members of a species which inherit alleles for a particular behaviour will produce the same response to a particular stimulus
What is kinesis and give an example using wood lice
A behaviour pattern where an animal responds to a change in stimulus by increasing or decreasing activity. It is a change in the rate of movement and is random
Woodlice move around more when the humidity is low. The rate of movement is related to the intensity of the stimulus. The movement is random and not directional
What experiment can be used to investigate kinesis in an organism
Choice chamber- organism is released into the chamber and after a set amount of time, the position of woodlouse would be recorded. The pattern of movement of the organism can also be recorded and the speed at which it moves
What is taxes and give an example using earthworms
The directional movement of an organism either towards or away from a stimulus
Positive taxis- towards the stimulus
Negative taxis- away from stimulus
Earthworms move away from light which is negative phototaxis, they have more chance of survival as when move into soil they are more likely to find food, more likely to avoid predators and less likely to dehydrate
What is a reflect action and what is its purpose/ what can it allow the organism to do
An example of a behaviour in which a certain stimulus produces a specific short lived response
They may allow the organism to protect against damage to body tissues, help escape from predators,enable homeostatic control, find food, mates or suitable environmental conditions
What is the normal process and what happens instead when a reflex action is happening
Normal: stimulus, coordinator, effector
Reflex: sensory, relay, motor
Describe what is meant by the term taxis
Moves towards or away from directional stimulus
Describe what is meant by the term kinesis
Movement is random/non-directional or animal does not move towards a particular stimulus
Explain the advantages of simple reflex arcs
Rapid
Protect against damage to body tissue
Do not have to be learnt
Help escape from predators
Enable homeostatic control
What is positive trophism and give an example using plant growth
Growth towards a stimulus
Plant shoots grow towards the light as there is an increase chance of light falling on leaves and increase rate of photosynthesis
What is a negative tropism and give an example using plant growth
Growth away from stimulus- plant roots grow away from plants and instead grow into the soil where they are most likely to absorb water and mineral ions
Plant growth factors and examples
Specific growth factors are synthesised in cells located throughout the plant, they then diffuse from growing regions to other tissues, where they regulate growth in response to directional stimuli
Examples:
Fibre lines, auxins, which cause cell elongation as the cell wall gets loose allowing the cell to grow. Uneven distribution of auxins within the growing region causes uneven growth. IAA
Describe IAA
IAA is produced in tips of roots and shoots which are actively growing
Diffuses to growing region
Causes cell elongation in shoots
Inhibits cell elongation in roots
IAA transported to more shaded part of roots and shoots (phototrophism)
IAA moves to underside of roots and shoots (geotrophism)
IAA in the shoots
Promotes cell elongation
IAA synthesised in shoot tips
IAA diffuses into growing/elongating region
Light causes movement of IAA from light to shaded side
Higher concentration of IAA on shaded side
Causes directional growth as there is greater cell elongation on shaded side
Shaded side grows faster and causes roots to bend towards light
IAA in the roots
Inhibits elongation
IAA synthesised in the root tips
IAA diffuses into the growing region
Light causes movement of IAA from light side to shaded side and towards gravity
Higher concentration of IAA on the shaded side
Cell elongation inhibited on the shaded side
Results in directional growth away from light and towards gravity
Halo
Salt
Geo
Gravity
Photo
Light
Hydro
Water
