All around the globe every year many animal species become extinct. However some people feel that government should be concerned more with solving problems of human life. Discuss both views and give your opinion.

Any attempt to reduce human-caused

species

extinction

(

i

refers to the speaker or writer

I

.e., to protect endangered

species

) requires an understanding of

extinction

rates over geological time. Fossil records from nearly any geological age reveal two types of

extinction

:

extinction

without replacement ("dead-end") and what might be called "

chronologic

relating to or arranged according to temporal order

chronological

extinction

" or ''taxonomic

extinction

." The

first

type is genuine

extinction

; it is the end of an evolutionary lineage. The

second

type is based on the recognition by

paleontologists

a specialist in paleontology

palaeontologists

palaeontologists'

that one

species

has changed through geological time (

i

refers to the speaker or writer

I

.e., has evolved) to the extent that it is classified as a different

species

from the

next

earliest representative of its lineage. The

species

involved (see Martin and Barnosky, 1993; Nadachowski, 1993; Turner, 1993) represent an evolutionary continuum rather than an evolutionary dead-end. The discussion that follows is concerned only with dead-end

extinction

. The past 20 years have witnessed major advances in our understanding of the earth's physical history (including understanding of

paleoclimate

, changing sea level, volcanism, and plate tectonics), and knowledge of past plant and animal communities is much improved. With refinements in radiometric dating,

stratigraphy

, and the discovery and analysis of varied sources of

paleoenvironmental

data (from cave deposits, ice cores, pollen cores, fossil dung, packrat middens, tree rings, etc.), we now can correlate many biotic and abiotic events in earth history with reasonable accuracy. What we learn from studying the past is important for predicting biotic responses to future changes in climate and other physical phenomena (Burney, 1993). The marine invertebrate fossil record reveals at least five mass-

extinction

events during the past 500 million years, in which from 14% to 84% of the genera or families disappeared from the fossil record (Jablonski, 1991; Raup and Jablonski, 1993; Benton, 1995). Perhaps the two best known of these mass-

extinction

events are the Permian-Triassic (P-T) 245 million years ago and the Cretaceous-Tertiary (K-T) 65 million years ago.

In addition

to marine invertebrates, the P-T event involved

extinction

of terrestrial plants and insects (Retallack, 1995); the K-T event included most reptiles. A much more recent mass

extinction

, that of the Pleistocene-Holocene (PH) only 11,000 years ago, featured

extinction

of more than 100 terrestrial

species

of birds and large mammals in North, Central, and South America.

Although

extinction

is common to the P-T, K-T, and P-H events, they differ from the current

extinction

event in several ways.