Speciation occurs
a. after populations become reproductively
isolated.
b. when mutations generate observable
differences.
c. when transitional forms develop between
different populations.
d. when natural selection pressures reach their
maximum.
e. with all of these
A
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____ is the process by which the nuclei within a heterokaryotic fungal cell fuse
Fill in the blank with the appropriate word.
Some combinations of recessive alleles cause problems so severe that a fetus may cease to develop. Such lethal allele combinations appear to alter Mendelian ratios because
A) carriers do not constitute a progeny class. B) they do not show a 1:2:1 genotypic ratio. C) homozygotes for the lethal allele do not appear as a progeny class. D) homozygotes for the lethal allele pass it on to half their offspring.
Identical twins
A. are the result of one fertilized egg dividing to become two individuals. B. do not usually have the same DNA. C. result from two eggs being fertilized by one sperm. D. result from one egg being fertilized by two sperms.
Which of the following statements about fats is INCORRECT?
A. Fats are a good source of energy. B. Fats contain approximately 2 hydrogens per carbon in the molecule. C. Most fats do not dissolve in water. D. Fats contain nitrogen, carbon, hydrogen, and oxygen atoms.