What is true of the Cambrian explosion?
A) There are fossils of animals in geological strata that are older than the Cambrian explosion.
B) Only the fossils of microorganisms are found in geological strata older than the Cambrian explosion.
C) The Cambrian explosion is evidence for the instantaneous creation of life on Earth.
D) The Cambrian explosion marks the appearance of filter-feeding animals in the fossil record.
A
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Mutation of the B group gene in Arabidopsis
thaliana affects development in its flower's a. first whorl only. b. second whorl only. c. third whorl only. d. first and second whorls. e. second and third whorls
__________ can be used to estimate the population
density for mobile animals. Fill in the blank(s) with the appropriate word(s).
Regarding the nature of natural selection, which of the following is NOT an accurate statement?
A) Populations evolve traits by natural selection that will be useful for future environmental changes. B) Natural selection acts on the phenotypes of individuals, but evolution occurs with changes in allele frequencies in populations. C) Natural selection can and does produce features that are less than perfect adaptations. D) Natural selection operates as a systematic, nonprogressive mechanism.
Which of the following are incorrectly paired?
a. heroin?premature births and low birth weight b. thalidomide?babies born without toes c. accutane?associated with malformations of the brain d. cocaine?constricts fetal arteries, which leads to retarded development e. cigarette smoking-an addiction to nicotine