Aarushhh/wikipedia-simple-splitted huggingface dataset:
In medicine and zoology, toxins and venoms are different from poisons. Toxins are the result of a biological process. Venoms are substances which the organism uses to harm other species. Certain organisms use venoms for hunting, or as a defense. If an organism is poisonous, such as many mushrooms, it is harmful to eat. If it is venomous, like snakes or honeybees, it has a harmful bite or sting. For some very deadly bites, humans have developed effective antivenoms. 

Often it is only the quantity of a substance that makes the difference. Drinking alcoholic drinks may lead to aggressive behavior, problems with speech, and different forms of amnesia. This effect is called intoxication. People who drink even more may go into shock.  At the same time, alcohol can be used as a disinfectant.
Sometimes, poisons have an antidote. The antidote of a poison will slow or reverse its effects. The antidote may itself be a poison. As an example, atropine can be used as an antidote against certain nerve gases, like tabun or sarin, or against certain insecticides. It is also used as a medication.  In high doses, atropine is a poison. Yet, atropine is a core medicine in the World Health Organization's "essential drugs list".

There are other types of dangerous materials. These are:
 Carcinogens (cancer-causing poisons), like acrylamide, asbestos, and benzene
 Mutagens (mutation-causing poisons) such as radiation and benzene
 Teratogens (birth defect-causing poisons), like thalidomide and alcohol

Pollution is also sometimes poisonous, for example toxic waste.

Poison gas 
In wars, some countries use poison gases against their enemies. This is called chemical warfare.
Poison gases such as chlorine gas and mustard gas were used in World War I. In World War II, the Nazis used a form of hydrogen cyanide gas to kill many people in their death camps and concentration camps.

Poison gas has also been used to intentionally kill humans as a method of death penalty.

Being poisoned by gas sometimes happens accidentally. For example, a faulty furnace or heating system can cause carbon monoxide poisoning.

There are many types of poison gases. For example, corrosive poison gases cause serious burns to the skin, eyes, and lungs. Nerve agents are poisons that can kill by damaging the central nervous system. Blister agents cause severe blisters on the inside and the outside of the body. Choking agents make fluid build up in a person's lungs until they drown.

Deaths
Deaths 

In 2010, poisoning resulted in about 180,000 deaths, down from 200,000 in 1990. There were approximately 727,500 emergency department visits in the United States involving poisonings—3.3% of all injury-related encounters.

Related pages
 Exposure to toxins
 Intoxication
 Toxicity (how toxins affect the body)
 Chemical weapons
 NFPA 704 "fire diamond" (system that warns people how poisonous and dangerous a certain chemical is)

References

 
Basic English 850 words
Powder is very small, dry pieces or grains. When we press some dry solids very hard, or when we cut something up into lots of small pieces, we can sometimes make powder.  

For example, people sometimes put face powder on their faces, when they want to look good. Sometimes sports players put powder on their hands, to make them dry. We put curry powder in our food, to make it taste stronger. We put washing powder in the washing machine when we want to have clean clothes. People use gunpowder to make bombs and fireworks.

"Powder" is also a verb - meaning to apply powder.

Materials
Cosmetics
Many animals develop in separate stages. A larva (plural: larvae) develops from the egg in those animals. It is a separate life stage from the adult reproductive stage. A larva does not look like the adult animal, and changes shape (known as metamorphosis) as it grows up. There may be several larval stages before the adult form. Tadpoles, maggots and caterpillars are larvae.

Marine organisms with a larval stage often release large numbers of eggs and sperms into the water column. After fertilisation, the eggs develop into tiny larvae. The larvae develop and grow for some time before metamorphosing into adults. Most marine invertebrates and many fish have a pelagic larval stage or pelagic eggs. These live in the plankton, and may be transported long distances.
Evolutionary theory 
Probably the most widely accepted theory explaining the evolution of larval stages is the need for dispersal. Sessile organisms such as barnacles and tunicates, and sea-floor groups like mussels and crabs, need some way to move their young into new territory, since they cannot move long distances as adults. Many species have relatively long pelagic larval stages (how long a larva is in the water column). During this time, larvae feed and grow, and many species move through several stages of development. For example, most barnacles moult through six nauplius larva stages before moulting to a cipris, when they look to settle. The larvae eat different food from the adults, and disperse.

The other consideration is the small size of the eggs. If animals lay many small eggs (and most do), then the young stages cannot live the life the adults lead. They must live a separate life until they have the size and capability to live as an adult. This is what the larvae do.
Origin of vertebrates 
A long-standing theory is that in transformed larvae of sea-squirts (tunicates) lies the origin of vertebrates. Tunicates are sessile, but their larvae are mobile, and have some features found in early vertebrates. The process of paedomorphosis, where juvenile features are retained in the adult, is the proposed mechanism. Genome analysis does show that the tunicates are the closest living relatives of vertebrates.

References 

Zoology
Developmental biology
Amphibians are members of the class Amphibia. The living ones are frogs (including toads), salamanders (including newts) and caecilians. They are four-legged vertebrates which are cold blooded.

Amphibians lay their eggs in water, usually in a foam nest. After hatching they are tadpoles, which live in the water and have gills. The tadpoles change into adults in a process called metamorphosis.  When they are adult, they have lungs to breathe instead of gills, and legs. Adult amphibians also use their skin to take in oxygen, and some species of salamanders do not have lungs.

The earliest amphibians evolved in the Devonian from lobe-finned fish which had jointed leg-like fins with digits. They could crawl along the sea bottom. Some had developed primitive lungs to help them breathe air when the stagnant pools of the Devonian swamps were low in oxygen. They could also use their strong fins to hoist themselves out of the water and onto dry land if necessary.
For tens of millions of years, during the Carboniferous and early Permian, amphibia were top predators on land, especially in the low-lying tropical river systems.  In drier conditions, they were less effective, and the ancestors of mammals and reptiles (the Synapsids and Sauropsids) gradually took over the land. They laid cleidoic eggs, which had hard shells, and could be laid out of water. Most of the early large amphibians went extinct in the Triassic period; a few survived to the Lower Cretaceous.

The only living amphibiana today are the Lissamphibia. These include the Anura (frogs and toads), Caudata (salamanders and newts) and Gymnophiona (caecilians). They are all rather small, compared with mammals or reptiles. The smallest frog and vertebrate in the world is the New Guinea frog (Paedophryne amauensis). The biggest amphibian is the Chinese giant salamander (Andrias davidianus).
Amphibia are found everywhere in the world, except Antarctica, and there are about 5,565 different species: 88% of them are in the Anura. In number of species, they are more successful than mammals, though they occupy a smaller range of habitats. However, it is said that amphibian populations have been declining all over the world. Conservation is therefore an important concern.

Living amphibia 

Anura: Frogs (including toads)
Caudata: Salamanders (including newts)
Gymnophiona: Legless amphibia, similar to earthworms or snakes

Adaptations

Respiration 
Amphibians like to live near freshwater in warm weather. There have also been species which live in forests, deserts and arctic conditions. Adult amphibians use lungs, and they also get oxygen through their skin, so long as it is moist.

Defences 
Amphibians may be camouflaged in brown and green, and if so they are prey for birds and reptiles. Their colour gives them camouflage, which is their main defence.
Alternatively, many other amphibia have toxic skin, which is harmful to predators. These are poisonous to eat. This is an important defence against predation. Connected to this is the use of warning colouration. They may be in vivid colours of red, black, and yellow. Research into the rough-skinned newt and the garter snake shows this is a typical case of co-evolution. Where they live in the same area, the newts get more poisonous, and the snakes develop more resistance to the poison.

Sight 
Amphibians have colour vision and depth of focus for clear sight. They also have eyelids, glands and ducts which keep the eyes moist. These are adaptations to life on land: amphibia were the first vertebrates to have these features.
Development 
Some amphibia, such as the frog known as the common coquí, lay eggs out of water (in this case, on palm leaves). The eggs develop directly into adult frogs, by-passing the tadpole stage. Others, like mudpuppies and olms, have a different development. In a process called neoteny, they become sexually developed as tadpoles with gills. They continue to live in the water.

Anura 

The order Anura includes the frogs and toads. There is no fundamental difference between frogs and toads. Frogs have a short body, webbed digits (fingers or toes), protruding eyes, forked tongue and no tail. They are exceptional jumpers: many of their features, particularly their long, powerful legs, are adaptations to improve jumping performance. They often live in semi-aquatic or inhabit humid areas.
A popular distinction is often made between frogs and toads on the basis of their appearance. Toads' warty skin is an adaptation for making their toxic slime. Apart from these glands, their skin is dry, and that is an adaptation to drier habitats. These features have evolved a number of times independently: convergent evolution. The distinction has no taxonomic basis. The only family exclusively given the common name "toad" is Bufonidae (the "true toads"), but many species from other families are commonly called "toads".

Caudata 

The order Caudata is the salamanders.

Newts are salamanders which spend their life in the water even though they are adults. They are classified in the subfamily Pleurodelinae of the family Salamandridae.
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. 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. Even some species with lungs 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, keeps their salt balance while in water, and lubricates during swimming. Salamanders also secrete poison from glands in their skin, and some additionally have skin glands for secreting courtship pheromones.
Axolotls, from  the genus Ambystoma (or mole salamanders),  are neotenic amphibians. This means they get to sexual maturity and reproduce while still in a larval form.

Defence mechanisms 
Most salamanders and newts have some defence against predators, usually a poison which makes them uneatable. Their bright colours are warning colouration. If, instead, they are camouflaged, this means they are probably not protected by a toxin.
 
The second line of defence is to shed their tail, which can grow again. The tail wriggles a bit, attracts the predator while the business part of the salamander moves off.
Other characteristics 
There are over 350 lungless salamanders. Most of them are terrestrial and are active in daytime. Lungless salamanders may communicate with their nose.p168 Slender salamanders are found in the Pacific Coast. They are sometimes called "worm salamanders". This is because they have slimmer (skinny) bodies than most salamanders.p182 If touched, slender salamanders will bounce on the ground and then run away.

Gymnophiona 

The order Gymnophiona includes the caecilians. These are long, cylindrical, limbless animals that look like snakes or worms. Their skin has circular folds, increasing their similarity to the segments of earthworms. Some are aquatic, but most live underground in burrows they hollow out. Many caecilians give birth to live young. In species which lay eggs, the eggs may undergo metamorphosis before they hatch. Caecilians are found in tropical Africa, Asia and Central and South America. There are 171 different species.
Their skins make a mucus that makes them slippery enough to slip through the earth.  They can make a toxic material in their skins, as many frogs and toads do.

Reproduction 

Amphibians are the only vertebrates to go through metamorphosis. This means that their young look different from their adult.p8 Amphibians usually reproduce in early spring to late summer, though some reproduce in winter and fall.p156 Most frogs and toads, such as the common frog (Rana temporalis), gather in large groups to ponds, rivers, swamps and lakes to breed.p10 Male frogs and toads may croak to attract a female. When a female frog has chosen a mate, the male frog hops on top of her. They swim together as she lay eggs in the water. Sometimes, males fight to mate with a female.p7 Frogs can lay up to 100 to 60,000 eggs in one clutch. This is called "frogspawn".
It is a fundamental feature of amphibia that their reproduction is, one way or another, tied to water. This is because their eggs, although covered by jelly, cannot survive long in dry conditions.

Eggs 

Most female amphibians lays her eggs in water. Males release sperm to fertilize them. The eggs are laid one by one or in batches. Batches of eggs can look like a long chain or a ball of foam. They may wrap their eggs around plants in the water. They do this so their eggs will not drift away.p8
Tree frogs usually lay their eggs on a leaf in a rainwater pool. Bullfrogs, such as the male American bullfrog and the male African bullfrog, stay with their tadpoles and protect them from predators. They also move their tadpoles by using their nose to dig a channel to another place where there is more water.p9 They do this so their tadpoles do not dry up. Most amphibians leave their eggs to look after themselves. Fish and other animals eat most of their eggs. Male midwife toads carry their eggs on their backs. When they are ready to hatch, the toad goes back to the water and release them.p10

Tadpoles 

Tadpoles do not have lungs when they hatch and instead have gills. Because gills have a large surface area, tadpoles can get more oxygen by using them. Young tadpoles have their gills exposed. When they get older, their gills are covered over by skin.p6  When they hatch, tadpoles eat constantly. The tadpoles eat what is left of their eggs, this is usually their first food.p8
Frog, toad and newt tadpoles eat plants such as algae and pondweed or filter feed. When they get older, they may start to feed on tiny animals in the water. Salamander tadpoles and surinam horned toad tadpoles are carnivorous throughout their tadpole stage.p9 Surinam horned toad tadpoles are very aggressive. They eat other tadpoles if food is nowhere to be found. The eggs of the spadefoot toad hatches in three days. Their tadpoles complete their metamorphosis in six to eight days. This is because spadefoot toads lay their eggs in places where water will dry up soon.p13
Tadpoles of frogs and toads start to grow their back legs first. They then grow front legs a few weeks later. When tadpoles grow their limbs they are called "froglets". This is because they look rather like a smaller version of adult frogs and toads. Tadpoles will also start to grow a backbone after growing their front limbs. After this, their mouths get bigger and their eyes will stick out more. After a tadpole has grown its hands, their tails continue to get shorter until there is nothing left of them.p11

Habitats
Habitats 

Salamanders and newts can be found living in streams. Salamanders can be found in rotten logs, holes or underground places that are wet such as under leaves.p152 Web-toed salamanders live in habitats where there are a lot of rocks. They like to hide under rocks and stones.p195 The tailed frogs, like to live in cold water habitats.p199 In their habitat, amphibians like to live where there are a lot of places to hide. These include nearby small trees, logs and plants. While underwater they like to hide near aquatic plants and rocks. Tree and dart frogs like to live in forests on trees, plants and on the ground under leaves.
Some amphibia can be found living in the desert or the arctic.p12 The desert froglet lives in the desert. They are only active at night, when temperatures are much cooler. It rarely rains in the desert and because of this, desert frogs will burrow to keep cool. They use their mucus to keep them wet. They will spread it all over their bodies. The mucus will harden to keep the water it produces from escaping. Once the desert frog has done this, it will stay in its cocoon and will not move. They will stay like this for several months to years until a rainstorm. Desert frogs and toads lose water more quickly. The spadefoot toad will spit on the ground. Once they have done this, they will lay on it. Their bodies will take in the water. Their bodies are thin and have a lot of blood vessels, this helps them to be able to take water through their skin. The California newt can survive a fire by spreading its mucous over its body.p12
Arctic frogs such as the wood frog, moor frog and the common frog has to live with freezing temperatures for a long time. They will burrow in places where they can get into a cocoon. Like every living organisms, amphibians must have water to survive. Amphibians however, need freshwater. Some frogs such as burrowing frogs can keep water in their bladders. This allows them to stay underground without drying up. The crab-eating frog lives near water that is somewhat salty. They will eat saltwater crabs. Torrent salamanders lives in cold waters. Because of this they have shorter lungs. Short lungs helps them to float easily.

Distribution 
Amphibia are world-wide, though restricted in distribution by their need for moist or watery habitats to reproduce.

Anatomy

Skin
Anatomy

Skin 

Many amphibia have secretions in their skin which makes them toxic. They do not produce toxins themselves. They get toxins from what they eat. They eat insects in their habitat. These insects get the poison from a plant. The toxin has been discovered in beetles. This means that they are likely the cause of poisons found in amphibians. Amphibians do not produce batrachotoxin in captivity, which means that it is not harmful to touch them. The American Indian tribe comechingóns used the toxins of the arrow dart frogs when hunting.

Newts in the genus Taricha has a poison called tetrodotoxin, a neurotoxin. Scientists believe that toxins in newts are caused by bacteria in the genera Pseudoalteromonas, Pseudomonas and Vibrio. Because of this, the newts do not have a lot of predators. However, some species of snakes have develop a resistance. This means that they can eat newts without the toxin hurting them. It is a case of co-evolution.
Senses and skeletal system 
Amphibians' eyes have lids, glands and ducts. They have good colour vision  Caecilian eyes are small and dark. Most of them are blind. Most amphibians have a good sense of smell, even underwater.

The skeletal system of amphibians are similar to other four-legged animals. They have a spine, rib cage, long bones such as the humerus and femur. They also have short bones such as the phalanges, metacarpals, and metatarsals. Most amphibians have four limbs, except for caecilians. The bones in amphibians are hollow and do not weigh much.

Diet
Diet 

Amphibia are predators. They mostly eat live invertebrates and animals that do not move too quickly. These include caterpillars, earthworms, crayfish, water beetles, snails and dragon fly larvae.p667 Many amphibians use their sticky tongues to catch their prey. They swallow the animal whole, but may chew it just a bit for it to go down their throats. The Ranidae family and the Ceratophrys genus eat almost anything they can fit into their mouths.p668 These include rodents, birds, ducklings, small fish and small mammals. Most frogs are cannibalistic, and may eat each other if food is nowhere to be found. Some amphibians may even eat their own tadpoles and eggs if there is no food for them.

Feeding in captivity 
In captivity, pet frogs will be given crickets, worms, small fish, rodents and fruit flies. Adult amphibians can help decrease the mosquito population by eating most of their larvae.
Caecilians eat earthworms, termites and beetle larvae, and also small lizards.p31 Caecilians rely on their smell to find food. They like to eat earthworms and will find them by picking up their chemical signals. Salamanders and newts are fed a lot of different types of worms. These include blood worms and earthworms. They can eat small fish such as goldfish, fathead minnows and guppies. Salamanders also eat crickets and pinkies, which are baby rats.p771

Conservation
Conservation 

The amphibian population have been decreasing from all locations in the world. Scientists have said that the declining of amphibians is one of the most critical threats to global biodiversity. A number of causes are believed to be involved. These include habitat destruction, over-exploitation, pollution, introduced species, climate change, destruction of the ozone layer, and diseases like chytridiomycosis. Ultraviolet radiation damages the skin, eyes and eggs of amphibians. However, the declines of amphibian population are still not understood.
On January 21, 2008, Evolutionarily Distinct and Globally Endangered (EDGE) released a statement to the public. It was created by Helen Meredith, who identified nature's most endangered species. Meredith explains that 85% of the top 100 endangered amphibians list are receiving little or no conservation attention.

Human use

As food
As food 

Bullfrog legs are a source of food for Southern United States and the Midwestern United States. People hunt bullfrogs at night near rivers. The bullfrogs' legs are cooked, while their backs are fried.p9 In China, bullfrogs are sold alive for eating. However, they are later cooked dead with vegetables. In the state of California, people must have a license to catch bullfrogs for food.p256 In schools, bullfrogs are dissected in biology classes. Usually, this is done in grammar school.p85 The dissecting is a method for teaching students the anatomy of a bullfrog.p85 The emperor newt is hunted in China for food. They are also used there for medicine. Burrowing frogs are able to hold water in their bladder, because of this indigenous Australians use them to drink water.p13
As pets 
Amphibians are also kept as pets.p4 They are kept in aquariums or a terrarium. A terrarium is a tank that is decorated with plants and soil on one side. On the other side, there is water. Most amphibians would need one place for land and another for water.p8 Each type of amphibian should have its special needs taken care of. Semi-aquatic amphibians need both land and water divided in the tank. Tropical frogs would need mist and high humidity in their terrariums.p7 Water for amphibia needs dechlorination. The chlorine in tap water can kill amphibia. Some amphibians popular exotic pets, and are found in pet stores that sell reptiles.p22

Related pages
List of amphibians
Frogs as pets

References

Reference books

Other websites
Other websites 

 Amphibian Specialist Group
 AmphibiaWebEcuador 
 Amphibian Ark
 AmphibiaWeb
 EDGE
 Global Amphibian Assessment 
 USGS—Online Guide for the Identification of Amphibians in North America north of Mexico
 General amphibian biology information—Living UnderWorld
 Panama Amphibian Rescue and Conservation Project
 Atlanta Botanical Garden Amphibian Conservation Program
 Froglife (British conservation charity)
 A guide to Amphibians
A father (also called dad or daddy) is a male parent. Most human beings are born from a mother and a father. The father of a person's husband or wife is their father-in-law. Fathers determine the gender of their child through a sperm cell which either contains an X chromosome (female), or Y chromosome (male).

Related pages
God the Father
Patriarchy

Basic English 850 words
Family
Gills are what fish, amphibians, and some other animals use to breathe in water. They have feathery parts which cause water to move across the animal's body, which contains dissolved oxygen, after the animal has swallowed the water. The oxygen is absorbed into the animal's blood, causing carbon dioxide moves out of the animal's blood and into the water through the gills.

Fish and frog gills are hidden on the sides of their heads. Sharks have many gills slits on their necks. Baby salamanders have gills that stick out like leaves from their heads.

In mushrooms, gills are the spore-bearing structure in agarics (gilled mushrooms) while fish and some young amphibians use them to get oxygen others breath.

Some insects that live in water have a plastron, which is a kind of gill. It is a patch of special hairs that keeps the water away from the insect's spiracles. This allows them to continue to take in oxygen and remove carbon dioxide while they are under water.
Animal anatomy
Anatomy of the respiratory system
Frogs are amphibians and vertebrates of the order Anura. There is not much difference between frogs and toads, and they are not classified separately. This is because the toad lifestyle, with its dry, rough, skin, is an adaptation to living in drier habitats. The toad form has evolved a number of times independently, an example of convergent evolution. 

Frogs can live on land and in fresh water. They cannot survive in salt water. Their development is by metamorphosis. They usually hatch as tadpoles  from eggs, which are laid by a female frog. The eggs are called frogspawn. Tadpoles have tails and gills. The next stage, the "froglet," develops lungs to breathe air instead of gills, but still have tails. The fully grown frog has long legs and no tail.
Adult frogs can jump with their legs. They have long tongues that they use to catch bugs. They make a sound called a croak. Some species live in trees, and some types of frog are protected by being poisonous. Frogs live all over the world. If a foreign species of frogs is introduced to another country, the local ecosystem might be affected.

Frog legs are sometimes eaten as food in France, China, and the Midwest of the United States.  The killing of frogs might have an effect on the ecosystem. For example, frogs eat mosquitoes. If frogs are killed, then there are fewer frogs to eat mosquitoes, so more and more mosquitoes are born. Therefore, in these areas, there are more diseases that mosquitoes carry, because there are more mosquitoes. However, for this to apply, frogs would have to be a major predator of mosquitoes. This would only rarely be the case.

Frogs are members of the class Lissamphibia, the only class of amphibia which has survived to the present day.
Characteristics 
Frogs are cold blooded animals. This means that they need heat to keep up their body temperature. If the temperature outside is cold, amphibians will not be active. Amphibians can get heat from the sun, usually indirectly: whereas reptiles can bask in the sun, amphibia usually do not, because it dries their skin. Some frogs aestivate during winter or during droughts. They usually look for underground place to aestivate. These include burrowing in muds and holes. They survive by getting oxygen through their skin. They come out when the weather outside is favourable.

Frogs have skin with no scales or hair. They can take in oxygen from either water or air. Mucus that helps their skin to stay wet and slippery. Many amphibians have toxic skin. They have secretions which makes their skin poisonous.
Many frogs are semi-aquatic. They may live on both land and in water, and in any event prefer damp places. These include ponds, swamps, rivers and lakes. Most adults live where they grew up. Most amphibians lay their eggs in foam nests.

Toads 
A toad is a large type of frog. It is not a scientific term, but a popular one. The reason it is not used in taxonomy is that the toad life-style has evolved a number of separate times in various groups of frogs.

All toads are frogs, but not all frogs are toads. Toads mainly evolved in dry climates, so many toads have rougher, browner skin.  Many toads also burrow, though that depends on the environment that the toad evolved in. Toads lay eggs in strings attached to rocks, unlike true frogs which lay eggs in a jelly-like mass. Also, toads generally have shorter legs and fatter bodies. Toads have paratoid glands behind their eyes which are used to make poison.

Development
Development 

Even though it is true that most frogs develop from tadpoles, and tadpoles develop from eggs laid in water, there are exceptions. Normally the eggs are fertilised after they are laid, that is, outside the body. However, some use internal fertilisation, though how the males do it is not known. When they are fertilised internally, they also lay eggs, but this time the eggs are already fertilised.

However, a new species has been discovered in Sulawasi, Indonesia, which gives birth to live tadpoles. The frog is now known as Limnonectes larvaepartus. The Limnonectes family are known as 'fanged frogs' because of twin projections on their lower jaws that are used in fighting. Sulawesi is an island which is rapidly losing its forests. The tropical forest is where this frog lives.
Distribution and habitats 
Despite these limitations, frogs are widespread, and have adapted to many climates, even deserts. They rely on specific adaptations to survive. Members of the genus Cyclorana live in the Australian central desert. They bury themselves underground where they create a waterproof cocoon in which to aestivate during dry periods. Once it rains, they come out, find a temporary pool, and breed. Egg and tadpole development is very fast in comparison to those of most other frogs, so breeding can be completed before the pond dries up.

Some frog species are adapted to a cold environment. The wood frog (Rana sylvatica), whose habitat extends into the Arctic Circle, buries itself in the ground during winter. Although much of its body freezes during this time, its high concentration of glucose in its vital organs protects them from damage.
There are a number of tiny tree frogs which develop from eggs laid in water pools on tropical leaves many meters above the ground. Most of these species do not come to the ground except to mate. Tree frogs have evolved a number of times, but they all have almost identical adaptations. Many millions of years of convergent evolution have resulted in almost identical morphology and habits.

Overall, frogs are a successful and widespread group. There are about 4,800 recorded species, which is over 85% of living amphibian species. They are one of the five most diverse vertebrate orders.

Largest, smallest 
The largest frog is the African Goliath frog (Conraua goliath). The maximum recorded weight is 3.8 kg (8.4 lb), and a snout-to-vent length of 39 cm (15 in).
Paedophryne amauensis is not just the smallest frog, but the smallest vertebrate, 7.7 millimetres (0.30 in) long.

References
A chemical compound is a chemical formed from atoms of different chemical elements. The different atoms are joined by chemical bonds. Each compound has a fixed ratio between the elements.

The elements stick together so strongly that the compound behaves like it is one substance. The chemical that is made depends upon what atoms it is made of and how they are joined together.

Many compounds are made of separate molecules. Each molecule has the exact same number and types of atoms. For example, every water molecule has one oxygen atom and two hydrogen atoms. Other compounds are made of a large network of atoms. For example, sodium chloride always has equal numbers of sodium and chlorine atoms, but there are no separate molecules.

Chemical compounds can be solids like sodium chloride, liquids like water, or gases like carbon dioxide. We get compounds from natural sources such as plants or make them in laboratories. Compounds can be made from others by scientists and these are called synthetic chemicals.
When different compounds are mixed together they may have a chemical reaction. 
Some chemical compounds can be dangerous but are safe if they are used the right way. Most dangerous chemicals are only used by scientists who have had special training in how to handle and use them. These chemicals might be poisonous, corrosive, explosive, they may catch fire easily, or they may react with other substances.

People who work in factories near chemicals often wear special clothes that stop the chemicals from hurting their body.

References
Wood is the main substance in trees. It is mainly formed by the xylem vessels which carry water up the plant. The two main substances in wood are cellulose and lignin. Wood is used to make buildings and furniture, and also for art. Firewood is a fuel. Paper is made from wood fibres. Wood is a renewable resource although it has become scarcer in recent centuries. Its origin is about 425 million years ago.

Wood is hard to cut, but it is also strong. A lumberjack is a person who cuts down trees. After a tree falls, the wood in it can be cut into long, straight pieces called lumber. Lumber can then be used to make posts, or put together with nails, screws, or even glue to make wooden frames for other shapes.

Wood comes in many different kinds. Oak, maple (hardwood) and pine and redwood (softwood) are widely used types of wood. Woods are usually divided into softwood (from conifers) and hardwood from flowering plants.
Housing 
For a long time and even today, many buildings, mostly houses, have been made of wood. To build a house with wood, lumber is put together into frames that are the shape of each wall, floor, and roof of the house. Then the frames are placed into the shape of a house. Then the frames can be covered to make solid walls. Sometimes the walls are made of more wood.

When the outside of a house or building is covered in wood, the wooden pieces are usually flat and stacked. These pieces are called shingles. Wood is also sometimes used in other parts of the house, like doors and staircases. Wood is also used to make fences.

Carpentry 

Carpenters make houses of mostly soft wood such as pine. For many kinds of furniture they use harder wood such as maple or oak. When someone builds something with wood, they often paint it. Paint protects and beautifies the wood. Some people like the look of wood, so they put clear paint called varnish on it. This helps to protect the wood and gives it a shiny finish.
Some people make art with wood. Sometimes sculptures are built with wood: see Grinling Gibbons.

Regular pencils are made of wood. Inside is the "lead", which is not actually lead. Clay or wax and graphite form the "lead" in a pencil.

Paper 
Wood is turned into paper in large factories called paper mills.  Heat, chemicals and machines separate the cellulose fibers from other parts and press the fibers into paper.

References

Related pages 

 Tree
 Petrified wood
 Plywood
 Firewood

Other websites 
 Wood -Citizendium

Basic English 850 words
Chalk is a type of limestone. It was made by calcareous (CaCO3) skeletons of tiny planktonic algae called coccoliths. They live in the sea in huge numbers. They make chalk (CO2) as a by-product of their photosynthesis. The chalk cliffs of Dover and elsewhere were made when England was below the equator in a tropical sea. It was in the Upper Cretaceous, when the Earth was even warmer than now. There are coccoliths today, but not the same species as formed the white cliffs.

Air and water do not wear chalk away easily, so when chalk is next to the sea, it often makes a large cliff. The "White Cliffs of Dover" in Kent, England are a good example of this. Chalk holds water, so these chalk hills may have a lot of water in them. When the weather is very dry, water comes slowly from the chalk.
Blackboard chalk is not real chalk. It is really gypsum (calcium sulfate), but people call it "chalk". People use it for drawing on hard things, because it is soft. If this chalk is rubbed on something hard or rough, it will leave a mark. People often write with chalk on a chalkboard or blackboard. A chalk eraser or water can be used to clean the chalk marks away so the board is clean again. Shops usually sell blackboard chalk in sticks that are about 5 cm long.

There are also big pieces of soft chalk for children to write on the ground with, for example on concrete (such as a sidewalk) or on asphalt. It is usually okay to write on the ground with this kind of chalk, because the rain will wash the chalk away.

Tailors' chalk is not real chalk either. It is talc (magnesium silicate). Tailors use it to draw on material when they are making clothes.

Basic English 850 words
Carbonate rocks
Writing tools
Cretaceous
Utilitarianism is the view that the right thing to do is whatever is most useful. It is a  about ethics. The word "utilitarianism" comes from the word "utility", which means "usefulness". In most forms of utilitarianism, things that increase human well-being or happiness are called useful. This is not limited to the happiness caused by a single action but also includes the happiness of all people involved and all future consequences.

In general, the theory of utilitarianism is that whatever brings the most happiness to the greatest number of people is the right thing to do.

History 
The theory was made popular by 18th and 19th century British philosophers like Francis Hutcheson, Jeremy Bentham, and John Stuart Mill, but the idea goes all the way back to ancient times.

Bentham wrote about this idea with the words "The greatest good for the greatest number," but did not use the word utilitarianism. It was Mill, a follower of Bentham's ideas, who named the idea.
Utilitarianism in Practice 
Many philosophers argue that utilitarianism has important practical implications for how we should live ethically. For instance, according to utilitarianism we should help the poor, prevent animal suffering, and ensure that future generations have good lives.

Related pages 
Hedonism
Happiness pump

References 

Philosophical movements and positions
Ethics
A village is a place where people live, normally in the countryside. It is usually larger than a hamlet and smaller than a town or city.  In some places, it may be a kind of local government. The dwellings in a village are clustered fairly near one another, not scattered broadly over the landscape.

In the past, villages were where most people lived. Villages were a usual form of community for societies that do subsistence agriculture, and for some non-agricultural societies. After the industrial revolution, when people started making a lot of things in factories, people lived more in towns. Moving to towns is called urbanization. When villages grow a lot they can grow into towns and then cities. This is what happened to Dubai and Chicago.

United Kingdom 
In The U.K. the main difference between a hamlet and a village is that many villages have a church.
Most villages are long-standing. The land has been settled (peopled) since the ice age. The soil is generally very fertile, and the land was once heavily forested. Much of what was forest was cut down to make ships, and farming replaced it. The land is fertile because of the deep loam (soil) in many places. That is partly due to the ice age, since the ice cover moved and ground against the bedrock.

United States

Incorporated villages 
The word "village" is not used in most states. However, in twenty  US states, a "village" is a sort of local government, similar to a city but with less power and for a smaller place. But this is not so in all the United States. In many states, there are villages which are bigger than the smallest cities in the state. The difference is not the population, it is how much power the different sorts of places have, and what they do for people living there.

New York 
In the state of New York, a village is a place which is usually called a town.
Unincorporated villages 
In many states, a "village" is only a place where people live, with no legal power, similar to a hamlet in New York state. The name for these is "unincorporated villages".

References

 
Types of settlements
Chelmsford a city in the county of Essex, England. It is  northeast of London, about halfway to Colchester. It is nearly in the centre of the county and it is the county town of Essex, but it is not the biggest or the oldest town in the county. It is the centre of the borough of Chelmsford, which is a bigger place than the city.

Chelmsford has the smallest cathedral in England. John Dee, who wrote the English version of Euclid, went to the Cathedral school in the sixteenth century. Chelmsford is also home to some of the Anglia Ruskin University campuses.

People
The number of people living in the borough is about 170,000; about 115,000 of those live in the city.

Transport
About 20,000 people from Chelmsford travel to London every weekday. Another 20,000 people work in Chelmsford who live outside the city. This makes Chelmsford the busiest "ordinary" railway station in England (not including junctions and terminuses). (The busiest of all is Clapham Junction railway station).
The A12 road from London, which the Romans first built between London and Colchester, went through the town, but now goes around the east, so the number of cars in the town is smaller.

Industry
Chelmsford has been an important centre for industry since the 19th century. It became home to the UK's first electrical engineering works (in 1878), and its first ball bearing factory (in 1898).

In 1898, Guglielmo Marconi, the "father of radio" opened the World's first radio factory in Hall Street, with about 50 workers. In 1920 the factory was also the home of the first official sound (radio) broadcasts (radio people could listen to from a long way) in the United Kingdom. In 1922 the world's first regular radio broadcasts started at the Marconi Research Centre at Writtle near Chelmsford.

Places of Interest
Places of interest in and near Chelmsford are for example Writtle, where Robert I of Scotland was perhaps born, and Pleshey, where the ruins of a castle in William Shakespeare's play Richard II are.
Hylands House and Park, west of the town, is an old country house. People can visit it, and in the last years it has been the place for a popular yearly music festival, the V Festival.

The old Palace of Beaulieu is also nearby.

Chelmsford is also famous for being the birthplace of radio, Marconi was an Italian man who invented the radio and had his first factory in Chelmsford.

History 
In 1199 the Bishop of London gave a Royal Charter (a special paper) for the town to have a market.  But there have been people living here since pre-historic times. The Romans also lived in Chelmsford. An octagonal temple is under the Odeon roundabout.

In World War II bombs hit Chelmsford a number of times. The worst single loss of life happened on Tuesday December 19, 1944. The 367th V-2 rocket which hit England fell near the Hoffmans' ball bearing factory. 39 people were killed and 138 hurt, 47 of them badly. A lot of buildings were destroyed and hundreds more were damaged.
Geology 
From over 600,000 years ago, the early River Thames went through the place where Chelmsford is now, from Harlow to Colchester. Then it went over  today's North Sea and went into the Rhine.

Twin towns 
Chelmsford is twinned with these:
 Annonay in France
 Backnang in Germany

People from Chelmsford
 Anne Knight (born 1786), anti-slavery campaigner and pioneer of feminism

Nearby places 
 Great Baddow

References

Other websites 
 Chelmsford Borough Council 
 Diocese of Chelmsford
 21st World Scout Jamboree 

 
County towns in England
Do-Aklin or Gangnihessou (Ganye Hessou) or Dogbari was the first of twelve kings of Dahomey in Africa. Gangnihessou might have been the king around the year 1620. One of his symbols was a bird called "gangnihessou" after his name. His other symbols were a drum, and sticks used for throwing or hunting. He had a younger brother called Dakodonou, who was a king. Some historians think Gangnihessou was not actually a king. Instead, Gangnihessou might have led people by giving advice to his brother.

History of Africa
Kings and queens
16th-century births
17th-century deaths
Beninese people
Contract bridge, or just bridge, is a trick-taking card game. It is played by two pairs of players, one pair against the other pair. Partners sit opposite each other at a table.

In face-to-face games, a convenient table size is from 32 to 40 inches (80 to 100 centimeters) square. The table is usually covered by green baize cloth. The point of the cloth is to stop cards skittering (sliding) across the table. In online computer play, players from anywhere in the world sit at a virtual table.

Millions of people play bridge in clubs, tournaments, online and with friends at home. It is one of the world's most popular card games. The World Bridge Federation is the governing body for international competitive bridge.

The game is played in a number of "deals". Each deal goes through four phases: dealing the cards, the auction (also referred to as bidding), playing the cards, and scoring the results.
Duplicate bridge 
Most club and tournament play uses duplicate bridge, where the cards are not re-dealt during a session. The same deals are played by most or all players. This allows comparative scoring. The method has one peculiarity: in competition between pairs, all boards count for an equal number of points. The same number of points are available on each and every board (hand). These points are distributed according to the scores. This is a fundamental difference between duplicate bridge pairs and rubber bridge.

In duplicate play between teams, the original scoring method is
used. This is because teams play the same set of boards at each table, but with the seating of players changed (N/S to E/W and E/W to N/S). Thus both teams play the same set of boards.

History
History

Early history of bridge 
It is played with the standard 52 cards in four suits. The game developed out of whist, which is a relatively old card game. Bridge developed in a series of stages from about 1890 to about 1930. The stages included bridge-whist and auction bridge, and the developments took place mostly in New York and London. The origin of the word "bridge" in this context is not really known. One possibility is that it is taken from an 1886 book, Biritch, or Russian Whist by John Collinson.

Publicity in the 1930s 
Contract bridge became one of the most popular pastimes when it was publicised by Ely Culbertson, a leading American player and organiser. Anglo-American matches got huge publicity in the newspapers, cinema and radio of the 1930s.

Playing method 
Whist is played with the trump suit chosen by chance, whereas in bridge it is chosen by a process called "bidding". A trump is a card which can beat any card from the other three suits.