A chlorophyll molecule has a porphyrin ring containing a single atom of:
a. manganese.
b. magnesium.
c. phosphorus.
d. nitrogen.
e. iron.
b
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Which of the following statements regarding schistosomiasis is incorrect?
A. Once a person has recovered from an infection with Schistosoma mansoni, they are protected with lifelong immunity. B. Schistosomiasis is transmitted by exposing the skin to a water source that has been contaminated with sewage. C. There is only a single drug available to treat Schistosoma infection, praziquantel, and drug-resistant strains are beginning to arise. D. Efficacy of treatment is assess by observing fecal samples placed in water for whether eggs can hatch to release live miracidia.
In mammals, an egg fertilized by one sperm divides repeatedly (1-2-4-8-16-32-64, etc.). At the 64-cell stage, only three cells go on to become the embryo while 61 grow to become the fetal side of the placenta. In plants, fertilization likewise results in the development of an embryo and nourishing endosperm. However, how does this process differ from the mammal embryo and placenta?
What will be an ideal response?
Signal transduction is best described as ________
A) transmission of signals from cancer cells to normal cells B) communication between cells through physical interaction C) transmission of signals external to the cell to the nucleus D) communication between nuclei of two organisms
Classify the following explanation as one of Tinbergen's four levels of explanation: "Lactose intolerance is common in hunter-gatherer societies because these human populations did not traditionally have a diet de-rived from the milk of dairy animals."
a. proximate c. evolutionary b. developmental d. phylogenetic