amphibian
An animal capable of living both on land and in water. Examples are frogs, toads, and salamanders. 

This is a picture of a salamander.
salamander



decline
to decrease in number, amount, value, or quality



ecosystem
a system formed by the interaction of a community of organisms with their physical environment

This is a picture of a pond.
Pond is an example of an ecosystem.



emit
to send or give out something



gland
in animals, a cell or group of cells that secretes a specific substance.



indicators
something that shows what conditions are



mucus
slimy secretion



mutation
a change or alteration, as in form or nature



predator
a carnivorous animal that hunts, kills, and eats other animals in order to survive

This is a picture of a shark.
A shark is an example of a predator.



secrete
to produce and discharge a substance



species
basic category of biological classification, composed of related individuals that resemble one another, are able to breed among themselves



tympanum
the ear drum



vertebrates
animals with backbone