52. Molecular-based phylogies place the phylum Platyhelminthes in the Protostomia. How do scientists best explain the morphological differences between flatworms and the other members of the Lophotrochozoa? (A) Modern Platyhelminthes do not have a coelom but did originate from an ancestor that had one. (B) The Platyhelminthes clade separated from other clades before coeloms evolved and consequently Platyhelminthes have never had a coelom. (C) Platyhelminthes originated from ancestors with a coelom and have retained it to the present time. (D) Platyhelminthes evolved from an ancestor without a coelom but developed one during the course of their evolution.

55. Which of the following would NOT be an example of negative feedback control in homeostasis? (A) Blood volume and pressure drop due to minor bleeding. This decreased pressure causes the kidneys to increase water reabsorption to restore blood volume and pressure. (B) Exposure to cold water causes body temperature to drop. Decreased stimulation of heat receptors causes constriction of blood vessels near the skin and better retention of heat. (C) Glucose levels rise following consumption of a big dessert, triggering release of insulin which causes glucose levels to fall. (D) During the birth process, stretch receptors in the uterus stimulate the release of oxytocin from the pituitary gland. This hormone stimulates uterine muscle contraction that increases stimulation of the stretch receptors.

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