Barrons AP Environmental Science

2000, with primates increasing from 13 to 19 different species. Endangered birds
increased from 403 species to 503 species. Endangered freshwater fish more
than doubled from 10 species to 24 species in four years. One-fourth of all
mammals and reptiles, one-fifth of all amphibians, one-eighth of all birds, and
one-sixth of all conifers are in some manner endangered to the point of
extinction.
Arguments for protecting endangered species include:
■ Maintaining genetic diversity ■ Maintaining keystone species
■ Maintaining indicator species ■ Preserving the endangered species’
aesthetic, ecological, educational, historical, recreational, and scientific
value ■ Preserving the endangered species’ yet to be discovered value
(e.g., more than a quarter of all prescriptions written annually in the
United States contain chemicals discovered in plants and animals) The
following table provides examples of some characteristics that have
contributed to the endangerment or extinction of various species of
animals.

Characteristics That    Have    Contributed to  Endangerment    or  Extinction

Characteristic Example

Compete for food    with

humans

African penguins

High    infant  mortality Leatherback   turtles

Highly  sensitive   to  changes

in  environmental

conditions

Cotton-top  tamarinds

Hunting for sport Passenger pigeons,    blue    whale,  Bengal

tiger

Introduction of

nonnative

invasive species

Bandicoots  threatened  by  cats    that    were

introduced  by  Europeans

Limited environmental Frogs whose   eggs    are sensitive   to  water