Many scientists believe that we are in a global mass extinction caused by human activity. What is conclusive evidence for this assessment?
a. Current estimated extinction rates on islands are 10,000 times greater than background extinc-tion rates.
b. Current estimated extinction rates on continents are 10,000 times greater than background ex-tinction rates.
c. One genus of tropical butterflies lost 90% of its species during the past 30 years.
d. Converting old-growth forest into agricultural fields causes dramatic losses in songbird diver-sity in the converted areas.
B
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When individuals have mitochondrial disorders, why are the skeletal and heart muscles and the brain most often affected?
a. They are the most important organs. b. They have the highest energy needs. c. They are generally very fragile. d. They have fewer mitochondria in the cell. e. They are the most complex organs.
Ferns often have small bumps arranged in rows on their undersides. What are these structures?
A. Seed capsules B. Spore capsules C. Parasites D. Nodules containing symbiotic bacteria
Which bone is part of the axial skeleton?
a. clavicle. b. radius. c. coxal bone. d. sternum.
Information about mean arterial pressure is integrated within what area of the central nervous system?
A) cervical spinal cord B) hypothalamus C) cerebellum D) medulla oblongata E) pons