Interaction and coordination allow living beings to receive stimuli from the environment and respond appropriately. Stimuli are detected by receptors, which send signals to coordination systems like the nervous system. These systems process the information and trigger responses through effectors like muscles. In animals, receptors include sense organs, while plants use receptor cells. Coordination relies on hormones in plants and the nervous system in animals. This enables organisms to interact with their surroundings.

1. INTERACTION
AND
COORDINATIO
N
Autora: Marta García T.

2. What do you remember?
 1. What senses does a predatory animal use when it
hunts?
 2. What body part does the chameleon use to catch its
prey?
 3.What type of living being moves more quickly: a plant
or an animal?
 4. Which of the following are involved in interaction?
heart – roots – runners – brain - kidneys - bones
Autora: Marta García T.

3. What is interaction?
Interaction enables living beings to receive and
respond to a stimulus. It involves different
elements:
1. Stimuli.
2. Receptors.
3. Coordination Systems.
4. Effectors.
Autora: Marta García T.

4.  Stimuli → Detectable changes in the internal or external
environment, which provoke responses. Stimuli can be
Physical, Chemical or Biotic.
 Receptors → Sensory structures which detect external and
internal stimuli.
 In Animals, receptors are the sense organs.
 In Plants, repectors are found in cells.
 Coordination Systems → Organs which process
information received by the receptors and produce a response.
 Effectors → Structures which produce responses, such as
muscles and glands in animals.
Autora: Marta García T.

5. How do receptors work?
SENSE SENSE ORGAN WHAT STIMULI DO THEY
DETECT?
HOW DO THEY WORK?
They detect light.
SIGHT Eyes
SMELL Vertebrates: nose They detect chemical substances
Arthropods: appendage dissolved in air or water.
TASTE Tongue It detects chemical substances
dissolved in water.
HEARING Ears They detect sound, from very loud
noises to soft musical notes.
TOUCH Fish: lateral line They detect pressure, touch, pain and
Arthropods: appendage temperature changes
Most animals: skin
Autora: Marta García T.

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7. Coordination System: The Nervous
System
The nervous system receives information, interprets it,
and transmits a response to the effectors.
It is different for invertebrates and vertebrates.
Autora: Marta García T.

8.  In vertebrates, the nervous system includes:
 The Central Nervous System (CNS ) → The Brain
and the Spinal Cord.
 The Peripheral Nervous System (PNS )→ Nerves
originated in the brain and in the spinal cord. Nerves
can be:
 Sensory: go from the receptors
to the CNS, carrying information.
 Motor: go from the CNS to the
effectors, carrying a response.
Autora: Marta García T.

9. Autora: Marta García T.

10.  Invertebrates have simpler nervous systems, for
example:
 Ganglia system (nerve cells are joined by the nerve
cord).
 Nerve Net system (nerve cells form a nerve net
extending throughout the animal).
Autora: Marta García T.

11. Effectors
They are organs which produce a response.
There are two types of responses to stimuli:
 MOTOR RESPONSES →The response is movement.
They are controlled by the motor system
 ENDOCRINE RESPONSES → The response is the
release of hormones into the blood. Hormones control and
coordinate activities throughout the body. They are
controlled by glands.
Autora: Marta García T.

12. Autora: Marta García T.

13. Coordination In Plants
 Plants do not have a nervous or an endocrine system.
Responses to stimuli in plants are coordinated by
HORMONES , which act as chemical messengers to
respond to factors such as light, gravity, water and
temperature.
 Cells inside the organism detect stimuli
Autora: Marta García T.

14.  There are two types of responses to external
stimuli:
1) Tropism → Permanent responses which produce
changes in the direction of the plant’s growth.
Types:
 Geotropism: The response
is caused by gravity.
 Phototropism: The response
is caused by light.
Autora: Marta García T.

15.  Hydrotropism: The response is caused by
water.
 Thigmotropism: The response is caused
by contact.
Autora: Marta García T.

16. 2) Nastic Movements: are temporary responses
of particular parts of a plant to external stimuli.
Autora: Marta García T.