responses in plants and animals pt.2 Flashcards
what do simple responses do
Simple Responses Keep Simple Organisms in a Favourable Environment
what are the two simple responses
tactic responses and kinetic responses
what happens in tactic responses
the organisms move towards or away from a directional stimulus, e.g. light
what happens in kinetic responses
the organisms’ movement is affected by a non-directional stimulus, e.g. humidity.
what is an example of tactic responses
For example, woodlice show a tactic response to light (phototaxis) — they move away from a light
source. This helps them survive as it keeps them concealed under stones during the day (where
they’re safe from predators) and keeps them in damp conditions (which reduces water loss)
what is an example of kinetic responses
For example, woodlice show a kinetic response to humidity. In high humidity they move
slowly and turn less often, so that they stay where they are. As the air gets drier, they move
faster and turn more often, so that they move into a new area. This response increases the
chance that a woodlouse will move to an area with higher humidity. This improves the survival
chances of the organism — it reduces their water loss and it helps to keep them concealed.
what is a choice chamber and what does it do
A choice chamber is a container with different
compartments, in which you can create different
environmental conditions. It can be used to investigate
how animals, such as woodlice , respond to conditions
like light intensity or humidity in the laboratory
what is step 1 of using a choice chamber
construct a choice chamber using : petri dish, divider, fine mesh, petri dish lid, choice chamber, lid, mesh, base, divider
what is step 2 of using a choice chamber
To investigate the effect of light intensity on woodlouse movement, cover one half of the lid (including the sides)
with black paper. This will make one side of the chamber dark. Put damp filter paper in both sides of the base.
what is step 3 of using a choice chamber
Place 10 woodlice on the mesh in the centre of the chamber and cover the chamber with the lid.
what is step 4 of using a choice chamber
After 10 minutes, take off the lid and record the number of woodlice on each side of the chamber.
Try to minimise the am o u n t o f time the lid is off, so that the environmental conditions created aren’t disturbed.
what is step 5 of using a choice chamber
Repeat the experiment after gently moving the woodlice back to the centre. You should find that
most woodlice end up on the dark side of the choice chamber (a tactic response to light).
Yo u can use a small, soft paintbrush to help with moving the woodlice if necessary. For ethical reasons, you should handle the woodlice
carefully an d return them to their natural habitat as so on as possible. M a k e sure yo u wash your hands after handling the woodlice.
what is step 6 of using a choice chamber
To investigate humidity, place some damp filter paper in one side of the base and a desiccating (drying) agent
in the other side. Don’t cover the lid with paper. Put the lid on and leave the chamber for 10 minutes to
stabilise before carrying out steps 3)-5) above.
what is step 7 of using a choice chamber
You can do a similar experiment using a maze instead of a choice chamber
what equipment is in a petri dish
base is divided into two compartments, petri dish base, fine mesh, divider, petri dish lid
