The sekeleton provides support and protection. Jellyfish and earthworms do not have a bony skeleton. However, jellyfish are supporte686.jpgd by water around them. Earthworms are supported by water inside their bodies: this is called hydrostatic skeleton. Animals with backbones are called vertebrates and have internal skeletons called endoskeletons. Animals like lobsters and insects, wich are invertebrates, do not have backbone.

However, they have a tough outside or external skeleton, wich is called an exoskeleton. Exoskeletons provide good overall protection.

This skeleton is like an armoured overcoat but as the animal grows, it needs to replace it.

It sheds its ough protective outer skeleton, and a new larger skeleton takes place.

However, the new skeleton is soft to start with. During the shedding of

the old skeleton and the hardenning of the new one, the animal is

extremely vulnerable to predators, because it has not protection.

skeleton we would be shapeless blobs. a sakelton has many similarities to the frame of a bicycle.

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- strong and ligh for easy movement.

- they are both structures made up of many parts.

- bones and bicycle frames tend to be tubes, wich carry loads and transfer forces



There are 206 bones in the human skelton. some of the bones are hollow and

contain this makes them extremely light and strong. Bones are

a mixture of living tissue and non-living material.

The living tissues contain cells amd collagen fibres.

The collagen allows bones to be flexible. The non-living part of

bone is made up of minerals and salts such as calcium

phosphate. This makes the bone hard. Without it, the bone

would be flexible like the cartilage found in the ear or in the end of the nose.

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Bone growth occurs in childres and adolescents. Growth takes place at the ends of

the bones. if there is a shortage of calcium during a child's life then the

bones remain soft and can become deformed. this is called rickets. in later life,

aduts whose bones lack calcium can develop brittle bones wich break easily

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more calcium phosphate. Bone can also be

strengthened during exercise.

Extra fibres and calcium salts are added.

The bones of the skeleton have four main


- they provide support, wich allows the body to satnd upright

- they give protection to many organs

- together with muscle they can produce movement

- blood cells are made in the bone marrow


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Different paof the body need tomove in different ways. a joint is a place where 2 bones meet.

There are three types.

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- hinge joint: the bones here move in only one direction.

- ball and shocket joint: the bones can swivel and move in any direction.

- fixed joint: bones meet but there is no movement.


the bones of a skeleton cannot move on their own. the movement of joints is controlled by muscles. these are attached to the bones and can pull the bones into different positions. muscle is tissue that can contract and makes up part of the body.
it is attached to bones by cords called tendons which do not strech. a muscle works by shortening and pulling. when this happens a muscle gets shorter. We can actually see our muscles working. as a muscle works its gets shorter or contracts, it becomes hard, looks fatter and bulges out more. A muscle can relax and stop
bulling, but it cannot strech and push on the bones to get the joint back to its original position. the bone must be pulled by another muscle. muscle always work in pairs. this arrangement is known as an antagonistic pair.

Responses and behaviour

How do living things respond to changes in their enviroment? STIMULLY are changes in the enviroment, which cause a response. A Stimulus can be large or small and may come in different forms. In plant, light is an important stimulus. Animals respond more quikly than plant and their behaviour is coordinate by the nervous system.The main function of the nervous systemis to carry mesages calles IMPULSES to and from parts of the body.

The nervous system
The nervous sytem is made up of two parts :
-The central nervou system (CNS) the brain and the spinal cord form the CNS which interprets and coordinates the information.

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and the peripheral nervous system (PNS).
cience.pngThe PNS has nerves an receptors. Receptors are cells or modified nerve endings that can respond to a stilulus. The receptors detect stimuli and send electrical impulses to the CNS. The five sense organs8eyes, skin, ears, nose and tongue) are important receptors organ of the nervous system.The nervou system contains many nerve cells called neurones.

-Sensory neurones carry impulses from a receptor to the CNS.
-Motor neurones carry impulses from a receptor to the CNS to a muscle or a gland. These cause a response in the body, for example a muscle will contract and move a limb.


Nerve cells are made up of a cell body that contains the nucleus and a long fibre called an axon.The poition of the cell body is different in sensory neurones and motor neuones.The dendrites at the ends of the nerve cell body are very important.These interconnct with other neurones so that nerve impulses can pa from one neurone to anothe ,but only in one direction.
Neurones don't touch each other.Synapses are junctions in-between neurones. The synapses pa informatiopn between neurones. Susbtances are releaed from the end of the neurone. The substances diffuse acrothe gap between the two neurones and then set up an impilse in the next neurone. Substances like alcohol reduce the speed of the substances crossing the gap.This slows down he body's reactions.

-Reflex action.
A rapid automatic response to a stimulus is called a reflex action. Whenyou move your hand away from a hot object you are responding to a heat stimulus.
The impilses are sent from the hand to the spinal cord then o the muscle, wich moves the hand .The impulses take the shortest posible route which is called a reflex arc. There are different types of reflexes.
Plants do not have reflexes but do repond to stimulisuch a light.
Sunflowers trak the sun as he earth moves during the day.

​Our ear help us to balance.
A sound results in the compression of air forming a sound wave. This is a pattern, which travels like ripples on a pond when a stone in thrown in. The air is very sensitive. A change in air preassure, makes the eardrum bulge outwards. When we swallow or yawn the eardrum moves back to the original position. When we move our head the fluid in the semi-circular canals moves. Each canal has a small chamber called ampulla at one end that is lined with sensitive hair cells.

First, the sound waves enter to the ear through the ear canal because the pinna directs the sound waves into it. Then the stirrup hit the eardrum wich vibrates and moves the ossicles ( the 3 ear bones : the hammer, stirrup and anvil).
After this the tiny stirrup bone moves backwards and forwards causing the thin, membrane covering the oval window to move, so this movement sets up waves which travel throug the cochela fluid.
Finally, the waves travel different distances according to the wavelength and stimulate sensitive hairs where they bounce against a memabrane. And the sensitive hair cells snd impulses along the auditory nerve t the brain which interprets them as sound of different frequences.
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- The eye

The structure of the eye is very complex. The image that is formed on the retina is upside-down because light travels in striaght lines. The brain then processes the information so that the image is interpreted as being the correct way up.
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The tounge and nose

The tounge is covered with many bumps called taste buds, they contain sensory cells that are sensitive to certain chemicals: sweet, sour, bitter and salt. The saliva in the mouth acts as a solvent.
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Inside the roof of the nose are sensory cells to detect smells. Smells are chemicals in the air thath dissolve in the moist lining of the nose.
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the skin

The skin is made up of layers with sensory cells called receptors. These receptors are nerve endings.
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Are soluble substances that help us to control our bodies.We have two control system, the nervous system and the hormonal system
The responses that are controlled by hormones are slow but may last for a longer time.
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Hormones are soluble substances made by a number of glands that makes up the endocrine system.
An endocrine gland makes hormones and releases them directly to the bloodstream.Hormones help us to control inside our bodies and carry messages thruought the body.
Most endocrine glands are controlled by the pitutary gland, wich is at the base of the brain.

For the body to work properly it needs to have the correct amount of each hormone. The pitutary gland is known as the master gland because it produces many hormones, wich control and coordinate other hormones.

Some tall people have grown more than usual because tha have too much gowth hormone. Others are small because thay have too litle growth hormone.

The thyroid gland is found inthe neck and releases tha hormone thyroxine. thyroxine controls the body´s metabolism and growth.
Metabolism is the release of energy carried out inside cells.

The pancreas releases tha horomne insulin wich controls the body´s blood sugar levels
Most peolple have the correct blood sugar levels but people who suffer from the disease diabetes can´t control the leval of sugar in their blood because they do not make enough insulin.

Diabetics can control their condition with regular injections of insulin and careful eating.


The adrenal glands secrete the hormone adrenaline. that prepares the body and causes inmediate response in the body.
The adrenal glands only make a very small amount of adrenaline but it has an instant and dramatic affect on the body,

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The testes secrete tha male hormone testosterone, it causes sexual development in males e.g production of sperm and the depeening of the voice and it also causes sexual development in females e.g the development of breasts and the widering of hips.

The female sex hormones are also responsible for controlling the menstrual cycle.