Extinction is a natural phenomenon. it is estimated that 99% of all species that ever lived are now extinct. why then do we say that we are now in a biodiversity crisis?

The options needed to complete the question:

A) Humans are ethically responsible for protecting endangered species.

B) Scientists have finally identified most of the species on Earth and are thus able to quantify the number of species becoming extinct.

C) The current rate of extinction is high and human activities threaten biodiversity at all levels.

D) Humans have greater medical needs than at any other time in history, and many potential medicinal compounds are being lost as plant species become extinct.

E) Most biodiversity hot spots have been destroyed by recent ecological disasters.

The CORRECT ANSWER is C)

C) The current rate of extinction is high and human activities threaten biodiversity at all levels.

Explanation:

Extinction is used to describe how certain species become extinct due to their lack of adaptability to changes in their habitat. A high rate of human interference in the habitat of certain species as a large effect on its extinction.

Fossils studies reveals that in a century, not less than 2 species from every 10,000 species go into extinction. It also shows an average of 500 species were extinct in the past 100 years due to human interference causing habitat loss and endangering biodiversity as compared to natural evolution.

several tissues working together form an organ, and several organs together make up an organisms.

the group of cell that carries out special jobs are tissue.

answer; both surfaces of the membrane are nonpermeable