Unit 6-Stimulus and Response Flashcards
Give three ways reflex actions are important for an organism
Reduce risk of damage to tissue; Escape predators; Maintain posture; homeostasis
Hydra is a small animal that lives in water. It traps food particles by random movement of its tenticles. The rate of tenticle movement is usually slow but becomes faster as more tenticles touch food. Name the type of behaviour described
Kinesis
Name the neurones involved in a reflex
Motor; Sensory and Relay
Which type of neurone transmits impulses to effectors?
Motor
Why is being able to respond to changes in its environment beneficial to an organism?
Increases an organism’s chance of survival; allows organism to avoid harmful environments; ensure its internal conditions remain optimal.
Give an example of a stimulus that would produce a kinetic response in a simple mobile organism
E.g. Humidity-in a kinetic response, am organism’s movement is affected by a non-directional stimulus.
Roots are positively gravitropic. Which direction do they grow in, and how do auxins cause this?
Roots grow downwards. This happens because the auxin concentration on the lower side of roots increases in response to gravity. A high concentration of auxin inhibits growth in roots so cell elongation occurs at a greater rate on the upper side of the roots causing them to bend downwards.
Identify the structures A, B & E
A-Relay neurone B- sensory neurone E-motor neurone
Describe how the diagram demonstrates that the seedlings show positive phototropism and that the stimulus is detected by the tip.
In the control/J the seedling grow towards the light;
Covering tip/K stops the response, covering the base/L doesn’t so tip is responsible for it.
Explain how positive phototropism helps a plant to grow.
Grows into an area of higher light intensity;
More photosynthesis/more sugar production (so more growth)
Explain the effect of IAA on shoot growth
Increases growth of shoot by increasing elongation of cells when present;
Describe how IAA could cause the results shown in the figures
IAA moves away from the light side of the shoot/to shaded side (Fig 13);
More IAA causes more growth /more cell elongation (Fig 13);
IAA evenly spread so grows straight (Fig 14);
Give a reason why the students put the seedlings on a rotating turn table in figure 14
So all sides are equally exposed to light;
The student concluded that all parts of the plant showed positive phototropism. Give one reason to support then conclusion and one reason against the conclusion
In support:
Plants grow/bend towards light source so positive;
Against:
only one plant/species for 3 days;
don’t know what’s happening to roots or other plant parts;
some plant tissues could be influenced by gravity/water;
no length measurements made (so don’t know if its growing;
Define the term chemotaxis
Movement away or towards a chemical (stimulus)
Mammals can respond to a stimulus with a reflex. Define reflex.
Rapid involuntary/automatic response to a stimulus
Suggest three conclusion you can make from the results shown in the figure.
P & Q roots grow towards source of gravity;
(Q) Mustard roots grow towards water or (S) cucumber roots don’t grow towards water;
Cucumber seeds more sensitive to gravity than direction of water;
or
Mustard seeds more sensitive to direction of water than gravity;
or
Mustard seeds equally sensitive to direction of water or gravity;
The student concluded the flatworms had responded to light. give one alternative explanation for their results and explain your answer
Random chance/small sample size/expt. not repeated;
or
Chemical attraction
or
Temperature; heat from lamp;
or
Tactile; some flat worms in contact
Suggest an advantage of the flatworms behaviour shown in the diagram.
Avoids predators/ avoids damage by light
Name the type of response shown by the body louse in this investigation. give evidence for your answer.
Kinesis;
Random movements/non-directional stimulus/response/ more turning at 35o C/degree of turning depends on strength of stimulus
Suggest and explain one advantage of the behaviour shown to the body louse.
stays longer at warmer/body temperature; so remains longer at food source/host
