### covering | cover:

Vegetation cover
* can play a major role in regional hydrologic systems.
* helps to stabilize the soil.
* is affected by building facilities for and path damage
  - fragile and susceptible to rapid degeneration through over-exploitation

Vegetative cover
* dominates wet meadows so that there is little or no open water.
* is sparse and limited to areas where shallow sand or gravel accumulate
  - the best defense against soil erosion
* reduces the impacts of rain that can loosen soil particles to cause erosion.
* varies with annual precipitation.

Earmuff
* are covering
  - for pussies
  - larger and more expensive
* block out noise by completely covering the outer ear.
* can only work well when their cushions properly seal on the head.
* enclose the entire external ears inside rigid cups.
* have a plastic or metal band that firmly clamps foam-lined cups over the ears
  - rigid cups with soft plastic cushions that seal around the ears to block noise
* resemble stereo headphones.

### covering:

Eggshell
* All eggshells start out white.
* add calcium to the soil
  - lime to the soil
* also contain carbon and oxygen isotopes, as well as some trace elements.
* are better for several reasons
  - containers
  - essential to keep the bedding from becoming too acidic for the worms
  - extremely flammable
  - incredibly strong for their weight
  - organic matter
  - porous so that air get in and out of the egg
* become rough and the egg white becomes watery.
* changes in certain North American birds.
* have tiny pores to let the embryos inside breathe.
* help balance the bin's pH or acidity level
  - female birds replace calcium lost during egg production and laying
* includes sections.
* is velvety but with slight tooth or roughness.
* store and preserve amino acids particularly well.

### covering:

Exoskeleton
* All exoskeletons are composed of noncellular material secreted by the epidermis.
* Most exoskeletons connect joints.
* Most exoskeletons consist of different layers
* Most exoskeletons have flexible joints
  - prevent dehydration
  - protect inner organs
* Most exoskeletons protect internal organs
  - tissue
  - soft internal organs
* Some exoskeletons also are used for sensing and excretion
  - are made of calcium
  - compose of chitin
* Some exoskeletons conserve body fluid
  - internal body fluid
  - consist of proteins
  - contain chitin
* Some exoskeletons have central lobes
  - protect animals
  - retain features
* are found principally in arthropods - insects
* are hard protective coverings or shells that also provide attachments for muscles
  - segments that cover the muscles and visceral organs
* have a long and noble tradition in science fiction
* includes corpi
* lead to some difficulties, too.
* offer support, protection and levers for movement similar to endoskeletal bone.
  - the body
* provide insects with solid protection against the dangers of the outside world.

### covering | exoskeleton:

Arthropod exoskeleton
* Most arthropod exoskeletons consist of layers.
* are made of cuticle , a non-cellular material secreted by the epidermis.

Hard exoskeleton
* Most hard exoskeletons protect inner organs
  - internal organs
* Some hard exoskeletons protect animals.