1 1. WHAT IS INTERACTION?

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1 UNIT 3. INTERACTION

2 1 1. WHAT IS INTERACTION? 1. All WHAT living IS beings INTERACTION? interact with their environment and with living beings to survive. Interaction enables living beings to receive and respond to stimulus. Interaction involves different elements: Stimuli: these are detectable changes in the internal or external environment. They provoke responses. Receptors: these are structures which receive stimuli from the external or internal environment. Coordination systems: these consist of organs which process information received by the receptors and produce a response. Responsive organs (also called effectors): These are structures which produce responses. Responses: Are actions provoke by a stimuli.

3 2. 2. INTERACTION IN ANIMALS Animals can move around in their surrounding: they do this in order to find food, escape from predator, or look for a mate for reproduction. Some animals change their colour to camouflage themselves so that they are not capture and killed by other animals. Others sleep during the cold winter months (hibernate) so that they use very little energy. Animals eat when they feel hungry ANIMALS INTERACT WITH THE ENVIRONMENT TO SURVIVE

4 2. 2. INTERACTION IN ANIMALS STIMULI Stimulus is a change in the environment of an organism that causes the organism to respond. A stimulus can be either internal (comes from inside the organism) or external ( comes from outside the organism) Stimuli can be classified as: - Physical: light, sound, temperature, pressure, etc - Chemical: the presence or absence of chemical substances - Biotic: changes caused by the presence of other living beings

5 2. 2. INTERACTION IN ANIMALS RECEPTORS Are sensory structures which detect external and internal stimuli. Internal receptors: Animals have receptor inside their bodies that detect internal stimuli. They are found throughout the different tissues and organs. For example, receptor in the muscles and joints inform us of the body s position and movements. They also receive signals of tiredness and pain. The sensation of hunger is caused by receptors found in the stomach wall. The sensation of thirst is caused by receptors that detect the loss of water. External receptors: Animals have five sense organs that detect external stimuli: the eyes, ears, nose, tongue and skin. These sense organs contain receptors, which are a special kind of cells that are sensitive to external stimuli. The five sense organs contain mechanical receptors, chemical receptors, light receptors and thermal receptors.

6 COORDINATION SYSTEM Coordination systems work together to process information received from stimuli and to produce appropriate responses. Animals have two coordination systems: The nervous system regulates the body's activities and responses (functions which require rapid responses, such as locomotion). It works by means of specialised cells called neurons which transmit information in the form of nerve impulses. The responses are rapid and brief. The endocrine system regulates and coordinates the body functions (functions which require maintained responses such as growth, development, metabolism...) by means of chemical substances called hormones. The responses are slow and long.

7 NERVOUS SYSTEM (NS) The nervous system is what animals use in situations where they need to react very quickly. How does the nervous system work? The nervous system receives information from the receptor, interprets it and elaborate a responses and transmits a response to the effectors. Types of NS : Nervous systems in invertebrates o o Invertebrates have simpler nervous systems. Examples are the ganglia system and the nerve net system

8 NERVOUS SYSTEM (NS) Nervous system in vertebrates o The nervous system in vertebrates includes: Central nervous system (CNS). This consist of the brain and the spinal cord. The CNS analyses information and decides on a suitable response The peripheral nervous system (PNS). This consist of nerves which originate in the brain and in the spinal cord. The PNS carries information around the body. Nerves can be classified as: Afferent nerves, also called sensory nerves. These nerves go from the receptive organs to the central nervous system. They carry information received from the stimuli. Efferent nerves, also called motor nerves. These nerve go from the central nervous system to the responsive organs. They carry information about the responses.

9 NERVOUS SYSTEM (NS) Nervous system in vertebrates o What are nerves? Nerves are made of groups of neurons. Neurons are special cells that transmit electrical signals containing information. The electrical signals are called nerve impulses. This happens very quickly. Neurons have special characteristic that allow them to do this:

10 EFFECTOR Are the parts of the body that carry out the response. In animals, these are the muscles (which produce movement (motor responses)) and the glands (which produce hormones (endocrine responses)) The motor and endocrine system need to receive an instruction from the nervous system in order to respond MOTOR SYSTEM The motor system includes the skeleton and the muscles. It has several important functions: It makes it possible for the animal to respond to stimuli by moving It supports the animals and give it shape It protect delicate part inside the animal The motor system is different in vertebrates and invertebrates

11 MOTOR SYSTEM IN INVERTEBRATES: Many invertebrates possess an exoskeleton, or hard outer shell which protects them. Insect need a more flexible, articulated exoskeleton because they make rapid movement. IN VERTEBRATES: Have an internal skeleton or endoskeleton. The endoskeleton is made up of bones, which meet at joints (for example, the elbow and the knee). Muscles are contractile organs attached to the bones by tendons. When the muscles contract or relax the bones move.

12 ENDOCRINE SYSTEM The endocrine system consist of glands. These glands produced hormones which are released into the blood and control and coordinate activities throughout the body Both vertebrates and invertebrates have endocrine system. The endocrine system regulates functions which require maintained responses. These include changes during the metamorphosis of some animals, growth, sexual development, regulate the level of substances in the body and the production of milk in mammals.

13 HOW DO ANIMALS RESPOND TO STIMULI?

14 RESPONSES Responses are the actions performed by an individual when it reacts to a stimulus it has received. The responses can be: Voluntary actions: are responses in which the animal has to think about Reflexes: are automatic responses to stimuli. Some situations are so dangerous that there is no time to wait for the brain to decide what to do. The body reacts without waiting for the brain to make a decision. Here s an example: if you touch something touch something very hot, you take your hand away automatically, without thinking about it first. This shops you being injured

15 RESPONSES VOLUNTARY ACTION REFLEX

16 BEHAVIOUR Is what an animal does to respond to a particular situation. An animals s capacity to survive and reproduce depends on how it behaves when it receives stimuli. Behaviour can either be instinctive or learned. INSTINCTIVE OR INNATE BEHAVIOUR: Is something an animal knows how to do as soon as it is born; they do not have to learn them. Are automatic and cannot be changed, like how to get milk from its mother, coughing, crying and yawing in humans and barking in dogs. LEARNED OR ACQUIRED BEHAVIOURS: Are when an animal reproduces what it has learnt. This allows them to respond to new or changing situations. Can be changed and depend on the intelligent of the animal

17 3. INTERACTION IN PLANTS All plant respond to changes that take place in their surroundings. Plant detect stimuli such as light, gravity, water, contact and temperature, etc. in their surroundings and respond to them. In plant, cells inside the organism detect stimuli. Stimuli are processed and analysed slowly. They have different ways of responding: TROPISM Tropisms are permanent movements in response to a specific stimulus. The plant moves by changing the direction it is growing in. The direction of movement depends on the direction of the stimulus. It can be positive ( the plant moves towards the stimulus) or negative ( it moves away from the stimulus) Tropisms are classified according to the source of the stimuli: Geotropism: response to gravity Phototropism: response to light Hydrotropism: response to water Thigmotropism: response to contact

18 3. INTERACTION IN PLANTS NASTIC MOVEMENT Nastic movements are temporary responses of particular parts of a plant to external stimuli. The plant later returns to its original position. PLANT HORMONES Like animals, plant also produce hormones. However, they do not have special gland, all plant cell can produce hormones. Hormones are transported in two different ways: directly from one cell to the next or in the phloem and xylem In plant, hormones do specific jobs. For example, they control the production of flowers, when fruit ripens, when leaves fall from trees, plant growth.