Among air-breathing animals, why do birds have the most effective mechanism of extracting oxygen from air?
a. because their air sacs provide additional respiratory surfaces
b. because birds utilize crosscurrent exchange
c. because bird lungs are the largest among vertebrates
d. because bird lungs have more surface area
Answer: b. because birds utilize crosscurrent exchange
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Which organ system includes the spleen, lymph nodes, and thymus?
a. circulatory system b. endocrine system c. nervous system d. digestive system e. lymphatic system
The chytrids in these micrographs are Batrachochytrium dendrobatidis. What reproductive form do chytrids use that distinguishes them from other fungi?
a. ascospores
b. zygospores
c. zoospores
d. basidiospores
We can accurately determine the age of a rock or fossil by measuring its ____
a. proton concentration b. electron concentration c. neutron concentration d. isotope concentration e. ion concentration
The principle of independent assortment states that
a. one allele is always dominant to another. b. hereditary units from the male and female parents are blended in the offspring. c. the two hereditary units that influence a certain trait segregate during gamete formation. d. each hereditary unit on one chromosome is inherited separately from hereditary units on other chromosomes. e. genes on the same chromosome travel separately.