Grass

Grass is a type of plant with narrow leaves growing from the base. Their appearance as a common plant was in the mid-Cretaceous period. There are 12,000 species now.

A common kind of grass is used to cover the ground in places such as lawns and parks. Grass is usually the color green. That is because they are wind-pollinated rather than insect-pollinated, so they do not have to attract insects. Green is the best colour for photosynthesis.

Grasslands such as savannah and prairie where grasses are dominant cover 40.5% of the land area of the Earth, except Greenland and Antarctica.

Grasses are monocotyledon herbaceous plants. They include the "grass" of the family Poaceae, which are called grass by ordinary people. This family is also called the Gramineae, and includes some of the sedges (Cyperaceae) and the rushes (Juncaceae). These three families are not very closely related, though all of them belong to clades in the order Poales. They are similar adaptations to a similar life-style.

With about 780 genera and about 12,000 species, the Poaceae is the fifth-largest plant family. Only the Asteraceae, Orchidaceae, Fabaceae and Rubiaceae have more species.

The true grasses include cereals, bamboo and the grasses of lawns (turf) and grassland. Uses for graminoids include food (as grain, shoots or rhizomes), drink (beer, whisky), pasture for livestock,  thatch, paper, fuel, clothing, insulation, construction, sports turf, basket weaving and many others.

Many grasses are short, but some grasses can grow tall, such as  bamboo. Plants from the grass family can grow in many places and make grasslands, including areas which are very arid or cold. There are several other plants that look similar to grass and are referred to as such, but are not members of the grass family. These plants include rushes, reeds, papyrus and water chestnut. Seagrass is a monocot in the order Alismatales.

Grasses are an important food for many animals, such as deer, buffalo, cattle, mice, grasshoppers, caterpillars and many other grazers. Unlike other plants, grasses grow from the bottom, so when animals eat grass they usually do not destroy the part that grows. This is a part of why the plants are successful. Without grass, soil may wash away into rivers (erosion).

Evolution of grass 
Grasses include some of the most versatile plant life-forms. They became widespread toward the end of the Cretaceous. Fossilized dinosaur dung (coprolites) have been found containing  grass phytoliths (silica stones inside grass leaves). Grasses have adapted to conditions in lush rain forests, dry deserts, cold mountains and even intertidal habitats, and are now the most widespread plant type. Grass is a valuable source of food and energy for many animals.

Grass and people 
Lawn grass is often planted on sports fields and in the area around a building. Sometimes chemicals and water is used to help lawns to grow.

People have used grasses for a long time. People eat parts of grasses. Corn, wheat, barley, oats, rice and millet are cereals, common grains whose seeds are used for food and to make alcohol such as beer.

Sugar comes from sugar cane, which is also a plant in the grass family. People have grown grasses as food for farm animals for about 4,000 years. People use bamboo to build houses, fences, furniture and other things. Grass plants can also be used as fuel, to cover rooves, and to weave baskets.

Language 
In English, the word "grass" appears in several phrases. For example:

 "The grass is always greener on the other side" means "people are never happy with what they have and want something else". 
 "Don't let the grass grow under your feet" means "Do something".
 "A snake in the grass" is about a person that will not be honest and will trick others.
 All flesh is grass: Old Testament book of Isaiah, chapter 40, verses 6–8. A very true observation of the present-day ecology. See the Miocene for the ecological relevance.
 Grass is a slang term for cannabis (pot, weed, or marijuana). Cannabis looks like a grass, but it is actually a rosid.

References

Related pages 
Grassland
Cereals
Fertilizer
Bamboo
Thatching

Basic English 850 words
Poales