Tuesday, April 29, 2014

FACTS OF PANDAS AND RACCOONS

It is only recently that zoologists have sorted out the relationship between pandas and raccoons. Modern scientific techniques now show that the raccoon family is divided into two subfamilies one including raccoons, coatis and the kinkajou, the other containing the red panda. The giant panda is related to bears. Apart from the red panda all members of the raccoon family live in the Americas. The pandas are found only in Asia.


Pandas
The giant panda and the red panda have a number of similar characteristics, such as a false ‘thumb’ so they were once considered to be closely related. It is now though that the pandas’ shared feature probably developed as they evolved to survive is similar habitats.

Giant panda
About 1.5 m (5 ft) long the giant panda lives only in the mountainous forests of southwestern China. Its main food is bamboo. This woody grass is low in nutrients, so pandas must eat about 38 kg (84 lb) of it every day to survive.


Red panda
An agile animal, the red panda is about 1 m (3.3 ft) long including its tail. It lives on the slopes of the southern Himalayas and in parts of China spending much of the day asleep in a tree. At night it looks for food on the ground. Bamboo is just part of its diet. Other food includes birds’ eggs, chicks and berries.


Young pandas
Giant pandas often give birth to twins but usually only one cub survives. A newborn cub is hairless and weighs only 90 – 100 g (3 – 3.5 oz). The female cardles it constantly for the first three weeks and carries it around for four to five months. Red pandas have up four cubs they can walk at about three days old.

Red panda cub

Panda cubs

Paws
Both giant pandas and red pandas have five toes on each foot. They also have a false ‘thumb’ on their forepaws. This can developed from the wrist bone and the pandas use it to grip bamboo stems.


Raccoons
There are seven species of raccoon. The best – known in the common raccoon with its black mark and ringed tail. This inquisitive animal eats most things including fish, frogs, insects, small mammals and fruit. It has adapted well to living near people will rifle through dustbins, picking out food with its forepaws.


Coatis
This forest animal is at home on the ground and in the trees. Females and young from groups and forage together during the day for such as insects, lizards and tubers. They used their forepaws and long flexible snout to hunt in crevices and on the forest floor.


Kinkajou
The nocturnal kinkajou lives in the forests of tropical Central and South America. It spends almost all its time in the trees and in the only American carnivore to have a prehensile tail, which means it can grasp things with it. The kinkajou uses its tail to cling to branches while it feed – mainly on fruit and nectar. Its back teeth have lost the sharp edges that carnivores have for slicing meat. Instead their teeth are blunt and used for crushing fruit.



GIANT PANDA

  • SCIENTIFIC NAME : Aliuropoda melanoleuca
  • ORDER : Carnivora
  • FAMILY :Ursidae
  • DISTRIBUTION : Southwestern China
  • HABITAT : Forests with bamboo
  • DIET : Bamboo, other plants and meat.
  • SIZE : Length: up to 1.7 m (5.5 ft)
  • LIFESPAN : Over 20 years (in captivity)




Monday, April 28, 2014

IMMUNE AND LYMPHATIC SYSTEMS

Every day the body is invaded by disease – causing micro – organisms called pathogens or germs. The immune and lymphatic systems are the body’s defense against these pathogens. The immune system is a collection of cells that keep detailed records of invading pathogens so; if they reappear they can be destroyed making you immune to that disease. The lymphatic system drains fluid called lymph from tissues, filters out any pathogens and returns the lymph to the bloodstream.

Lymphatic system
The lymphatic system consists of a network of tubes called lymph vessels that reach all parts of the body and several lymphatic organs. Lymph is carried by the vessels to the main lymph ducts which empty into the bloodstream.


Lymph vessels
The smallest lymph vessels are capillaries. Excess fluid drains through the walls of lymph capillaries from the surrounding tissue. Lymph capillaries join to form larger lymph trunks.


Lymph nodes
Lymph constantly leaves the bloodstream and flows through the spaces surrounding cells. It passes through lymph nodes which are small swellings of the lymph vessels that clean and filter the lymph. Inside each lymph node is a network of fibres which supports large numbers of two types of immune system cells, lymphocytes and macrophages.


Lymphocytes
Lymphocytes found in the lymph nodes recognize and destroy specific pathogens using chemicals that are called antibodies. Lymphocytes are also to be found circulating within the bloodstream.


Macrophages
Macrophages are cells with voracious appetites that detect, engulf and destroy viruses, cancer cells and any other foreign material in the lymph that passes through the lymph node. 


Immunization
Immunization gives a person protection against a specific disease. There are two types of immunization. In active immunization a vaccine containing some dead pathogens is injected into the body to stimulate the immune system to make antibodies. Passive immunization involves injecting antibodies and gives short-term protection.
  1. A vaccine containing dead or weakened pathogens is injected into the body.
  2. The immune system produces antibodies’ and keeps a ‘memory’ of the pathogen.
  3. If the real pathogens enter the body large numbers of antibodies are released.

AIDS
Acquired immune Deficiency Syndrome (AIDS) is caused by the Human immunodeficiency Virus (HIV). A person with AIDS becomes infected with diseases that the body would normally fight off. This is because HIV attacks and destroys immune system cells. In time the immune system weakens and the person becomes unable to fight infections and eventually dies.

Quilt for AIDS charity

Lady Mary Wortley Montagu
Lady Mary Wortley Montagu (1689 – 1762) was an English author who introduced an early from of immunization against smallpox to English. In Turkey she had seen people scratching pus from small-pox blisters into the skin of healthy people to protect them from catching smallpox. She had her children ‘vaccinated’ and publicized the method.


Allergies
If you have an allergy it means that your immune system has wrongly identified a harmless substance called an allergen as being harmful. The body’s reaction to these allergens produces symptoms such as sneezes and rashes. Common allergens include pollen, fur, dust, shellfish and strawberries.


A skin patch test is used to identify possible allergens

Monday, April 21, 2014

FACTS ABOUT THE MOON

A grey, dry, airless and lifeless ball of rock – the Moon – is Earth’s closest neighbor in space. The moon is about a quarter of Earth’s size and it’s only natural satellite. It orbits the planet as they travel together round the sun. It is the only celestial body, apart from Earth that humans have stood on.


Lunar surface
Every part of the Moon’s surface is made of rock and dust. It is also covered with craters. Most of these carters were formed about three billion years ago when space rocks bombarded the moon. Material thrown out from these impact craters formed mountain ranges and volcanic lava filled many of the larger craters. The lunar surface has remained virtually unchanged for millions of years.


Moon rock
About 2,000 samples of rock and dust have been brought to Earth from the Moon by American astronauts and Russian robotic spacecraft.


Craters
When a space rock collides with the moon it creates a crater. The bigger the impact, the bigger the crater. A rock 1 km (0.6 mile) across travelling at 100,000 kmh (60,000 mph) would produce a crater about 18 km (11 miles) across. The largest on this picture is 80 km (50 miles) across.


Mare
Early observers thought the lava-filled craters were oceans of water and called them mare, which is the Latin for ‘sea’ (plural maria). The name has stuck even though there is no water on the lunar surface.

Terminator
The moon keeps the same side facing Earth because as it orbits earth it also spins on its axis. From earth it is possible to see light areas which are highland and darker areas of lowland. More detail can be seen along the terminator, the line separating the sunlit and dark sides of the moon.

  
Phases of the Moon
The Moon is lit by the Sun. at any one time; half of the Moon is in daylight and half in darkness. As the Moon orbits Earth, different amounts of the sunlit side are visible. These are known as the phases of the moon and range from a thin crescent to a full face. Each cycle lasts for 29.5 days beginning at the ‘New Moon’ when the sunlit side of the Moon is not visible from Earth at all.


Eclipse of the Moon
As the moon orbits around earth it is at times farther from the sun than earth. Sunlight still reaches it because the earth is not in perfect alignment between the sun and the moon. Two or three times a year, the three are aligned directly and the moon is in earth’s shadow. It is eclipsed; no sunlight reaches the moon and it disappears from earth’s view.





Lunar origins
It is not known for certain where the moon came from. It may have been captured by earth’s gravity or formed from material left over when earth was formed. The most popular theory is that an object the size of mars crashed into the young earth and dislodged material, which came together to from the moon.


Moon landings
Twelve men landed on the moon between 1969 and 1972, spending almost 80 hours on its surface. They explored 90 km (55 miles) of it on foot or by ‘moon-buggy’, collected rock set up experiments and played golf before returning to earth.


Footprints
When the astronauts left the moon, they left behind some equipment and their footprints. There is no water, air or life to erode the footprints so they could stay for millions of years unless an impacting space rock wipes them out.


Neil Armstrong

In July 1969, American astronaut Neil Armstrong (b. 1930) was at the centre of one of the most important events in human history. He was the first person to walk on the moon and became instantly famous. He spent 2 hrs 35 mins on its surface.


HUMAN TEETH AND JAWS

Before food can be swallowed it must be cut up into small pieces so it can travel down the esophagus and into the stomach. The job of cutting and grinding is carried out by the teeth. These are small hard structures embedded in the upper and lower jaw bones that grip, bite, slice and crush food into a paste ready for swallowing. Different types of teeth are adapted to perform particular functions. As a child grows his or her jaw bones increase in size until by the end of adolescence they can accommodate a set of 32 adult teeth.


Growth of teeth and jaws
We have two sets of teeth during our lifetime. The first set is called primary or milk teeth and they gradually appear in babies until a set of 20 is in place. At about the age of six the roots of some milk teeth loosen and they start to be pushed out and replaced by the permanent or adult teeth.



A newborn baby has no visible teeth. Within the upper jaw and lower jaw however the milk teeth are developing. These start to erupt at around the age of six months.







A 5 year old child has a full set of 20 milk teeth consisting of four incisors, two canines and four molars in each jaw. The permanent teeth are developing and will push out.




A 9 year old child has a combination of permanent and milk teeth. While most of the teeth are milk teeth the first permanent molars and incisors have already erupted. By age 12, a child’s teeth are all permanent teeth.






A 20 year old’s jaws are fully grown and contain a full set of adult teeth. Some people’s wisdom teeth (the molars at the back of the jaw) do not erupt until their twenties. If there is not enough room for them the wisdom teeth are extracted.





Types of teeth
Each adult jaw contains 16 teeth: four incisors, two canines, four premolars and six molars. Incisors at the front of each jaw are cutting teeth that slide past each other to slice up food. Canines grip and tear food. Premolars and molars have flattened crowns to crush and grind food.




Structure of a tooth
Every tooth is made up of three basic layers. Enamel forms a hard cap that protects the tooth. Dentine forms the bulk of the tooth and extends into the root along the root canal. The pulp contains blood vessels and nerves, which allow you to detect pressure when chewing.


Tooth decay
Food leaves behind a sticky residue on your teeth called plaque. Bacteria in plaque release acids that eat away at the enamel. This can expose the inner parts of the tooth causing tooth decay.

Brushing your teeth regularly helps get rid of plaque

Chewing and biting
The first stage in digestion is chewing, which breaks food up into small particles ready for swallowing. Chewing is controlled by three pairs of muscles that move the lower jaw. The temporalis and masseter muscles pull the lower jaw upwards to crush food. The pterygoid muscles move the lower jaw from side to side and slide it forwards to grind food.


Dentistry
In the past a decaying tooth would have been extracted but dentists now treat tooth extracted but dentists now treat tooth decay by removing affected parts of a tooth and filling the cavities with hard materials. Artificial crowns can be screwed into a tooth to replace the real thing. Dentists are also concerned with the prevention of tooth and gum disease.



Sunday, April 20, 2014

SMELL AND TASTE


The air that we breathe in and the food that we eat contain chemicals that can be detected by our senses of smell and taste. Both senses depend on chemoreceptors which are sensors that react to the presence of certain chemicals by sending nerve impulses to the brain. Chemoreceptors in the nose detect smells or odours while those on the tongue detect tastes. Smell and taste work together. Your sense of smell is about 20,000 times more sensitive than your sense of taste.

Smell
Your sense of smell operates when you breathe in through your nose. Chemicals carried by the air dissolve in the layer of mucus covering the olfactory membrane. The dissolved chemicals cause the olfactory cells to send nerve impulses to the olfactory lobes. From here the nerve impulses are carried to the brain where they are interpreted as smells.

Olfactory membrane
The moist olfactory membrane covers an area the size of a postage stamp in the upper part of each nasal cavity. The membrane contains chemoreceptors called olfactory cells which detect odours.


Nose and mouth
The smelling part of the nose is the nasal cavity which is divided into two halves each served by one nostril. Smell receptors are found in the upper part of each nasal cavity. Taste receptors are found inside the mouth, on the surface of the tongue and in the lining of the mouth cavity.


Smell receptors
Smells are detected by tiny hair-like projections called cilia located at the end of the olfactory cells. There are about 20 million olfactory cells in the nose and about 20 cilia project from each cell. Smell receptors on the cilia react to specific chemicals. This mechanism enables you to distinguish between thousands of different odours.


Sense of smell
Our sense of smell is poor compared to that of some other animals. Dogs for example have an olfactory membrane ten times more extensive than a human’s. this enables them to detect much weaker smells and a wider range of odours than humans can. Dogs can be trained to sniff out drugs or explosives.


Taste
Your tongue can detect only four basic tastes: sweet, salt, sour and bitter. The tongue is divided into different taste areas, each containing taste buds that are sensitive to one of these tastes. There are over 10,000 microscopic taste buds on the tongue and these are located on or between tiny projections called papillae.


Tongue papillae
Your tongue is not smooth. Its upper surface is covered by papillae which makes the tongue rough so it can grip and move food during chewing. Papillae also allow you to lick food such as ice cream. Taste buds are found in pores on and between some of the papillae.


Taste buds
Each taste bud contains a cluster of chemoreceptors (taste cells). When food is chewed chemicals dissolve in saliva and pass into the taste bud through the taste pore. The chemicals stimulate taste hairs on the chemoreceptor cells. These send impulses along nerve fibres to the brain’s taste area where the impulses are interpreted as salt, sour, sweet or bitter tastes.

Inside a taste bud

Detecting flavors

Your senses of smell and taste work together to enable you to detect many flavors. For example when you eat food, information from the chemoreceptors in your nose and mouth is processed by your brain so that you can sense the flavor of the food. Some people use their very good senses of smell and taste to make a living as for example wine tasters and perfume blenders.

the durian is a very unusual fruit. It has a revolting smell but a delicious taste