Estimates of Current Rates of Extinction

question 44

Multiple Choice

Estimates of current rates of extinction

• A)indicate that rates of speciation equal extinction,so an equilibrium has been reached.
• B)suggest that one-half of all animal and plant species may be gone by the year 2100.
• C)indicate that rates may be greater than extinction rates seen in the fossil records.
• D)indicate that only 1% of all of the species that have ever lived on Earth are still alive.
• E)suggest that rates of extinction have decreased globally but have increased locally.

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Definitions:

PCBs

Polychlorinated biphenyls, a class of highly toxic chemical compounds used in various industrial applications, now banned or restricted due to environmental and health risks.

Fetal Development

The progressive growth and formation of a fetus inside a woman's uterus, starting from conception to birth.

Natural Experiments

Observational study designs where the subjects are exposed to the experimental and control conditions that are determined by nature or by other factors outside the control of the investigators.

Cephalocaudal

A principle of growth and development where development proceeds from the head down through the body.