THE INTERACTION FUNCTION

UNIT 3.- THE INTERACTION FUNCTION

1.- WHAT IS THE INTERACTION FUNCTION?

Organisms have to process information to survive, both from inside their body and from their surroundings, and react appropriately to that information.  This is called the interaction function, which consists of three processes:

a)      The perception of information

a.       Living things receive information through stimuli (physical and chemical stimuli)

b.      Living things have receptors (photoreceptors, thermoreceptors, mechanoreceptors, chemoreceptors)

b)      Processing and coordination

a.       Living things process the information and perform a coordinated response

c)       The execution of responses

a.       Living things have effectors to carry out responses

2.- INTERACTION FUNCTION IN PLANTS

Plants react to stimuli:

a)      Tropisms: plant responses which consist of directing their growth towards or away from stimulus.

a.       Phototropism

b.      Geotropism

c.       Hydrotropism

d.      Thigmotropism

b)      Nastic movements: plant responses which consist of rapid movements of some parts (they are usually reversible).

a.       Photonasty

b.      Thigmonasty

c)       Changes in a plant’s vital processes: the most characteristic reactions of this type are the seasonal changes of many plants, like responses to temperature, the light or the length of the day and night.

3.- INTERACTION FUNCTION IN ANIMALS: THE RECEPTORS

The sense organs:

-          They are receptors

-          They contain receptor cells that capture a particular type of stimulus and send a signal to the coordination systems, which interpret them as a sensation.

Types of sense organs:

-          The photoreceptor organs (eyes)

-          The mechanoreceptor organs

o   Hearing organs

o   Balance organs

o   Lateral line of the fish

o   The skin

-          The chemoreceptor organs (smell and taste)

4.- INTERACTION FUNCTION IN ANIMALS: COORDINATION

The nervous system:

-          Capturs the signals from the sense organs, interprets them and gives orders to carry out coordinated responses and to communicate these orders to the effector organs so they can give the responses.

-          The neurons are cells which are specialized in transmitting information through electric signals called nerve impulses.

-          The complexity of nervous systems: the nervous systems of animals differ in complexity depending on the organisation  of the neurons.

The endocrine system:

-          Produces substances called hormones, which travel round the organism and provoke responses, generally slow and lasting, in certain effectors.

-          It is composed of certain organs or groups of cells called endocrine glands, which produce hormones.

5.- INTERACTION FUNCTION IN ANIMALS: THE EFFECTORS

Animals have different effectors to respond to stimuli. The most common responses are:

-          The movements: caused by the muscles. There are some muscles that move internal organs and others, those of the locomotor system which allow the animal to move.

-          The secretions: they are very varied (sweat, digestive juices, the poison of the skin of some amphibians, the milk of mammals…).