Why do we think that the forest communities of eastern North America have changed dramatically over the past 18,000 years?
A) Glacial retreat exposed land for primary succession that long ago.
B) Large fires exposed land for secondary succession that long ago.
C) Successional changes are typically very rapid and all communities change at this speed.
D) Pollen evolved at this time.
A
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A reagent that stains the stored food of a green alga black is
a. India ink. b. I2KI. c. methylene blue. d. both a and b.
What explains the viability of individuals with aneuploidies for the sex chromosomes?
a. Sex chromosomes carry less information than autosomes. b. The lack of crossing-over between the X and the Y chromosomes. c. Sex chromosomes are smaller than most autosomes.
d. The information on sex chromosomes is duplicated on the autosomes. e. Dosage compensation, by which one X chromosome per cell is inactivated
Which of the following best explains why machines can never be 100% efficient?
a. the tendency of energy not to spread out b. the tendency of energy to spread out c. the tendency of energy to be kept d. the tendency of energy to be lost
Nitrogen fixation is an energy-yielding process.
Answer the following statement true (T) or false (F)