In birds, sex determination is:
A) similar to that in humans, in which the father has one copy of each of two different sex chromosomes.
B) opposite of that in humans, because the mother has one copy of each of two different sex chromosomes.
C) based on temperature.
D) based on the males being haploid and the females being diploid.
E) based on the males being diploid and the females being haploid.
B) opposite of that in humans, because the mother has one copy of each of two different sex chromosomes.
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What is the most likely explanation for how a group of crocodiles acquired the trait in which lower incubation temperatures give rise to male crocodiles?
A. Horizontal gene transfer from a related species has introduced changes in this group’s genome. B. Horizontal gene transfer from a related species has introduced changes in this group’s proteome. C. One or more mutations in the genome have been passed through the group by vertical descent. D. One or more mutations in the proteome have been passed through the group by vertical descent.
Leptin is a circulating hormone that is produced by fat cells and plays a role in body metabolism and obesity. It normally binds to receptors in the brain and inhibits appetite. Studies have demonstrated that when obese mice that are leptin deficient are injected with leptin they quickly lose their excess weight. Interestingly, however, many overweight people have high levels of leptin in their
bloodstream. Why do you think that the high levels of leptin in obese individuals are insufficient to curb their appetite? A. Paracrine signaling may be disrupted in obese people with high levels of leptin. B. Obese people who have high levels of leptin may have a leptin receptor with decreased sensitivity. C. The form of leptin released by obese people may lack protein kinase activity. D. In obese people with high levels of leptin, the leptin is a non-functional second messenger.
Identify the correct flow of blood through a one-circuit system.
A. ventricle - gill capillaries - systemic capillaries - sinus venosus - atrium B. ventricle - systemic capillaries - gill capillaries - sinus venosus - atrium C. ventricle - pulmonary capillaries - atrium - aorta - systemic capillaries D. ventricle - gill capillaries - systemic capillaries - atrium - sinus venosus
The mortality rate of variola minor is
a) near 100%. b) approximately 50%. c) approximately 20%. d) less than 1%.