If a study of several pedigrees demonstrates that two
parents express a characteristic and none of their
children express it, then the trait is controlled by
a. a codominant gene.
b. a simple dominant gene.
c. a recessive gene.
d. a sex-linked gene.
e. No conclusion can be drawn.
Answer: b
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Zach undergoes a sperm analysis and is upset to learn that he has oligospermia. This means that
A) he has cancer of the spermatogonia, and his sperm will never mature. B) he makes too many sperm, and they will crowd and kill each other. C) he makes too few sperm, lowering the probability of one sperm successfully reaching and fertilizing an oocyte. D) his sperm have two heads, each of which contains an entire genome of DNA, making them too heavy to swim to an oocyte.
____ begins in an area where there was a preexisting community and well-formed soil
a. Character displacement b. Species richness c. Primary succession d. Secondary succession e. Competitive exclusion
When some hybrid organisms do not live long, it is an example of
A) temporal isolation. B) hybrid inviability. C) hybrid infertility. D) hybrid vigor. E) gametic incompatibility.
Which of the following statements is true?
A) Gymnosperms have seeds that are not enclosed in a protective casing, while angiosperms have flowers that produce seeds with a protective casing. B) Gymnosperms have flowers that produce seeds with a protective casing, while angiosperms have seeds that are not enclosed in a protective casing. C) Gymnosperms lack true roots and leaves, while angiosperms lack lignin cell walls. D) Gymnosperms lack seeds, while angiosperms have flowers that produce seeds with a protective casing.