species
a set of animals or plants in which the members have similar characteristics to each other and can have children with each other
to decrease
to go down in number
habitat
the type of place that a species usually lives in, such as a desert, forest, or lake
generation
a group of people or animals who are born and live around the same time
volunteer
a person who does something without payment, especially helping people or animals
classified as
put information into groups according to different features
conservation
the protection of plants and animals from the damaging effects of human activity
crucial
very important
captivity
when a person or animal is kept somewhere and is not allowed to leave
concern
worry