Category Zoology

Are spiders insects?

No. Spiders belong to a group called arachnids, which also includes scorpions, mites and ticks. Spiders all have eight legs, one pair more than insects. They have two body parts – a head and an abdomen – and most have eight simple eyes.

Is it true? Spiders and insects have bones.

No. Instead they all have a hard casing on the outside called an exoskeleton. This protects their soft insides like a suit of armour and gives them their shape. They have to replace this casing with a new one in order to grow.

Amazing! There are creepy-crawlies living just about everywhere in the world, under water, in caves, down deep holes and even on the tops of mountains. Most of the animals in the world are insects. They make up 85% of all known animal species and there are probably millions more waiting to be discovered!

What makes an insect an insect?

Although they may look different from one another, every adult insect has six legs and three parts to its body. The head is at the front, the thorax in the middle and the abdomen at the back. Many insects have wings for flying and long feelers or antennae.

What is a minibeast?

Creepy-crawlies can also be called minibeasts. You will find other kinds of minibeasts, which are related to spiders and insects, such as woodlice, slugs, snails, worms, centipedes and millipedes.

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Why do spiders spin webs?

Sticky webs can be a home and a trap to catch flying insects. But not all spiders make webs, and not all webs are the same. The ogre-eyed spider makes a web like a net. It hangs down holding the web, waiting to throw it over its prey.

Do spiders have teeth?

No, but they have fangs for stabbing prey and injecting it with poison and special juices. The victims turn to liquid inside so that the spider can then suck them up like soup!

Amazing! The water spider makes its home under the surface of the water. It spins a web like a balloon which it fills with air bubbles. It waits inside until it spots its prey, and then darts out to seize it.

Is it true? Some spiders eat their webs.

Yes. Orb web spiders eat the old web before they spin a new one. A web may take an hour to spin. The silk is as strong as steel of the same thickness.

What can see with its tail?

As well as a sting, some scorpions also have light-sensitive cells in their tails. These cells let them know whether it’s day or night, even when their heads are underground. Scorpions hunt at night and spend the day hidden in their burrows.

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What is the function of ribs and chest muscles?

The chest, or thorax, lies between the neck and the abdomen. Inside the thorax lie the heart, lungs, and major blood vessels. The ribcage surrounding them is formed by the backbone, ribs, costal cartilages, and sternum (breastbone).

The ribcage is strong enough to protect the vital organs, but flexible enough to expand and contract for breathing. Attached to the ribcage are the muscles of the chest. Together with the diaphragm, many of these muscles help with breathing.

They move superiorly, inferiorly, anteriorly and posteriorly to facilitate breathing (their flexibility in their movement increases/decreases the size of the thoracic cavity; assisting the lungs in respiration. Control of these movements is via the diaphragm, external intercostals, and the intercartilaginous portion of the internal intercostals). They play a role in erythropoiesis during development (at birth, the erythropoiesis sites change, it recedes in long bones and persists in flat bones, like ribs).

 

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What is the function of chest and back?

The chest houses the two powerhouse organs that keep the body running – the heart and lungs. All the body’s cells are supplied with essential blood and oxygen thanks to these vital organs. The backbone supports the body and protects the spinal column, which carries messages to and from the brain.

The chest wall is comprised of skin, fat, muscles, and the thoracic skeleton. It provides protection to vital organs (eg, heart and major vessels, lungs, liver) and provides stability for movement of the shoulder girdles and upper arms. 

One important organ in the chest is the thymus, a small butterfly-shaped organ located between the heart and the sternum, or breastbone. This organ belongs to the immune system, and its job is to produce T cells, a type of white blood cell. These are formally known as T lymphocytes; the “T” stands for thymus, where the cells originate.

 

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What part of your body helps you keep your balance?

Different body systems work to keep you balanced. Signals from the inner ear combine with visual signals from the eyes, pressure sensors in the skin, and stretch sensors in the muscles to reveal the body’s position. The brain processes this and makes any adjustments to stop the body falling over.

Utricle and saccule

Inside the inner ear are two tiny organs that sense movements of the head in a straight line. The utricle detects forward and backward movement, and the saccule detects up-and-down movement.

Forward and backward movement, such as travelling in a car, is detected by the utricle. Up-and-down motion, such as riding in a lift, is sensed by the saccule.

 

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What are the inner parts of the ear?

Inner ear shows the semicircular canals and the cochlea. The three fluid-filled canals sit at right angles to each other. When you move your head, the fluid swishes around and causes tiny hairs to bend. This sends nerve signals to the brain, which works out the direction in which you are moving. The snail-shaped cochlea converts sounds into nerve impulses.

Inner ear

The semicircular canals and cochlea are part of the inner ear. They sit within a hollow in the temporal bone of the skull.

Inside a semicircular canal

Bulb-shaped areas called ampullae sit at the base of each semicircular canal. In the middle of each ampulla is the cupula, which houses the bundle of movement-sensing hairs. The brain co-ordinates feedback from the ampullae to maintain a constant fix on the body’s position so the body can keep it balanced.

Utricle

The utricle is a small membranous sac (part of the membranous labyrinth) and paired with the saccule lies within the vestibule of the inner ear. It has an important role in orientation and static balance, particularly in horizontal tilt. The utricle is sensitive to forward and backward movements.

Saccule

The saccule is a small membranous sac, paired with the utricle, within the vestibule of the inner ear. It is part of the membranous labyrinth and has an important role in orientation and balance, particularly in vertical tilt. The saccule senses vertical movements of the head.

Oval window

The stapes, or stirrup bone, fits here to pass sound waves to the cochlea. Sound waves cause vibration of the tympanic membrane and the ossicles transmit those vibrations to the oval window, which leads to movement of fluid within the cochlea and activation of receptors for hearing.

Cochlea

The cochlea contains the spiral organ of Corti, which is the receptor organ for hearing. It consists of tiny hair cells that translate the fluid vibration of sounds from its surrounding ducts into electrical impulses that are carried to the brain by sensory nerves. This snail-shaped organ turns vibrations into audible sounds.

Auditory nerve

This nerve carries signals from the ear to the brain.  It is one of the many pieces that make up the auditory system, which enables effective hearing.

Organ of Corti

Running through the middle of the cochlea is the organ of Corti, the main receptor for hearing. Sound waves create vibrations that make wave-like movements in the fluid inside the organ of Corti. These bend the hairs, producing nerve signals, which are sent to the brain to be registered as sounds.

 

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