Macroevolution is opportunistic, not goal oriented. Explain what this means.
What will be an ideal response?
Answers may vary. Macroevolution is not directed toward any certain goal, particular end, or point of perfection. Rather, all organisms arose through common descent with adaptations to local environments. Each population (species) adapts to its particular environment through the process of differential reproductive fitness. Those members who fit best into a particular environment are reproductively more successful and have more offspring. Because their "traits" allow them to thrive in a particular environment and thus provide an opportunity for reproductive success, alleles shift in future generations and adaptation occurs. Environments are constantly changing and thus providing the continued opportunity for evolution to occur.
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When the heart becomes weaker and less efficient at pumping blood, the blood may back up in the veins and cause a condition known as ________.
Fill in the blank(s) with the appropriate word(s).
The group that probably gave rise to chloroplasts is the
A. green photosynthetic bacteria. B. purple sulfur bacteria. C. methane bacteria. D. cyanobacteria. E. nonsulfur purple bacteria.
One function performed by astrocytes is to:
a. form myelin sheaths b. induce synapse formation c. circulate cerebral spinal fluid d. phagocytize bacteria e. transmit action potentials
Which neurotransmitter is released from a motor neuron at the neuromuscular junction?
A. Dopamine B. Acetylcholine C. Epinephrine D. GABA E. Serotonin