Some buildings are meeting places. A large number of people can gather at a temple or theater or stadium to worship god or to hear or see what other people say or do. In Christendom they are called churches. Until we began to build skyscrapers, religious buildings were usually the largest, tallest buildings in a town. Fortresses and castles were also big but usually were not in town. Big buildings require much work to make, thus can symbolize power. They impress and they give a focus to cities.
Buildings are made of various materials. Where wood is plentiful, it is much used. Many very old buildings of stone exist. Concrete is used almost everywhere. Starting in the late 19th century, skyscrapers were made of steel, increasingly combined with glass.
Candle
A candle is a stick made of wax with a string (a thin piece of rope) straight in the middle. If someone puts the string on fire, the flame burns slowly but for a long time.
Fire can burn string very fast. But in a candle, the string does not burn fast, because the fire melts the wax instead. The wax sometimes drips down the side of the candle. When the melted wax is far from the flame, it gets hard again, and can be used again in a new candle.
The flame is very hot, since it is a very small, real fire. The light blue part of the flame can be as hot as . It can still burn people and things. If the fire spreads, it can grow into a very big fire and even burn down a house or building.
If the flame is kept on the candle long enough, the candle will slowly get shorter and shorter until it is gone. The fire on a candle can be put out by blowing air on it. There is also a special tool called a "candle snuffer" that covers the fire with a small metal cup and puts it out. Today, candle snuffers are usually only used in churches or in places where candles are up very high. Stopping the fire stops the candle from burning until it is all gone.
Before light bulbs, candles were used so people could see at night. Some people still use candles today when electricity is down, or because they like the little amount of light that candles make. Some people also like candles because they look nice, or because they smell nice. A special kind of candle called "citronella" can help keep bugs away.
Salamander
Salamanders are amphibians. They are the order Caudata (or Urodela). There are about 500 different species.
Salamanders live in water and on land, and look rather like lizards, with four legs and a tail. They hatch as larvae from eggs in the water. At that stage, they have gills that stick out.
Most salamanders live on land when they are adults, after their change of shape (metamorphosis). On land, salamanders live in moist habitats. Their method of respiration varies. Some salamanders stay in the water, but look like adults. These are called newts. Some salamanders retain gills into sexual maturity, such as the Axolotl. This process is called neoteny.
Often, salamanders may have a chemical defence to predators; they are poisonous to eat. In this case, they will have warning colouration. Otherwise, if not poisonous, they will usually have camouflage.
Salamanders are the only tetrapods able to regenerate limbs, as well as other body parts.
Respiration differs between species of salamanders. Species that lack lungs respire through gills. In most cases, these are external gills, visible as tufts on either side of the head, although the amphiumas have internal gills and gill slits. Some salamanders that are terrestrial have lungs that are used in respiration, although these are simple and sac-like, unlike the more complex organs found in mammals. Many species, such as the Olm, have both lungs and gills as adults.
Some terrestrial species lack both lungs and gills and perform gas exchange through their skin, a process known as valerian respiration in which the capillary beds are spread throughout the epidermis, and inside the mouth. Even some species with lungs can also respire through the skin in this manner.
The skin of salamanders secretes mucus. This helps to keep the animal moist when on dry land, and maintains their salt balance while in water, as well as providing a lubricant during swimming. Salamanders also secrete poison from glands in their skin, and some additionally have skin glands for secreting courtship pheromones.
Hunting is yet another unique aspect of salamanders. In the lungless salamanders, muscles surrounding the hyoid bone contract to create pressure and actually "shoot" the hyoid bone out of the mouth along with the tongue. The tip of the tongue is composed of a mucus which creates a sticky end to which the prey is captured. Muscles in the pelvic region are used in order to reel the tongue and the hyoid back to its original position.
Many of the highly aquatic species, however, have no muscles in the tongue, and do not use it for capturing prey, while most other species have a mobile tongue, but without the adaptations to the hyoid bone. Most species of salamander have small teeth in both the upper and lower jaws. Unlike frogs, even the larvae of salamanders possess these teeth.
To find their prey, salamanders use trichromatic color vision in the ultraviolet range. Permanently subterranean salamanders have reduced eyes, which may even be covered by a layer of skin. The larvae, and the adults of some highly aquatic species, also have a lateral line organ, similar to that of fish, which can detect changes in water pressure. Salamanders have no external ear, and only a vestigial middle ear.
Salamanders can drop their tail to escape predators. The tail will drop off and wriggle around for a little while, and the salamanders will either run away or stay still enough to not be noticed while the predator is distracted. Salamanders routinely regenerate complex tissues. Within only a few weeks of losing a piece of limb, a salamander perfectly reforms the missing structure.
There are ten families in the order Urodela, divided into three suborders:
Newt
Newts or "efts" are small amphibia. They are in a subfamily of the salamanders. They are found in North America, Europe, and North Asia.
Females lay eggs and leave them. Tadpoles are born from those eggs.
Newts have three life stages. First as a tiny aquatic larva, which gradually undergoes metamorphosis. Then they leave the water for a year as a juvenile called an "eft". They go back in the water to breed as adults.
In some species the adults stay in water for the rest of their lives. Others are land-based, but return to water each year to breed.
Many newts produce toxins in their skin secretions as a defence against predators. They have bright skin colours as a warning to other animals.
"Taricha" newts of western North America are particularly toxic; the rough-skinned newt "Taricha granulosa" of the Pacific Northwest produces more than enough tetrodotoxin to kill an adult human. Recently, a 29-year-old man in Coos Bay, Oregon, who had been drinking heavily, swallowed a rough-skin newt for a dare; he died later that day despite hospital treatment.
Most newts can be safely handled, provided that the toxins they produce are not ingested or allowed to come in contact with mucous membranes, or breaks in the skin. After handling, proper hand-washing techniques should be followed due to the risk from the toxins they produce and bacteria they carry, such as salmonella. It is illegal to handle or disturb great crested newts in the UK without a licence.
The term "newt" has traditionally been used as a functional term for salamanders living in water, and not a systematic unit. The relationship between the genera has been uncertain, though they may be a natural systematic unit. Newer molecular analysis tend to suggest they actually do form a clade.
Newts only appear in one subfamily of salamanders, the Pleurodelinae (of the family Salamandridae).
Some genera occasionally listed as Pleurodelinae are not newts ("Salamandrina" and "Euproctus").
Poison