Which of the following has been found in

association with the K-T boundary layer?



a. iridium
b. shocked quartz
c. tektites
d. all of these
e. none of these


D

Biology & Microbiology

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An organism maintaining homeostasis with respect to sodium ion concentration in the blood would ______sodium excretion in the kidneys when sodium levels were low and ______ sodium excretion when sodium levels were high

a. maintain constant; maintain constant b. increase; maintain constant c. increase; decrease d. decrease; maintain constant e. decrease; increase

Biology & Microbiology

The first community that forms on bare rock often has organisms such as

A) broad-leaf trees and conifers. B) grasses and weeds. C) lichens and mosses. D) herbs and conifers. E) woody shrubs and conifers.

Biology & Microbiology

Blood samples are taken from the heel of newborn babies to test for a mutation in the PKU gene, which, if left untreated and in severe cases, can lead to mental retardation, reduced skin pigmentation, and seizures. Which concept is being illustrated by

this example? A) incomplete dominance B) polygenic inheritance C) pleiotropy D) codominance

Biology & Microbiology

N-Ras, K-Ras, and H-Ras are best described as

a) Three unrelated oncogenes that each cause sarcomas b) Three different cancer-causing mutations found in the same ras gene c) Different activation states of the Ras protein d) Three closely related genes that likely evolved from a single ras gene

Biology & Microbiology