Pikaia gracilens is an extinct invertebrate animal described from the wonderful pre-Cambrian soft-bodied fossils of the Burgess Shale in British Columbia. Examinations by paleontologists have revealed that organisms belonging to this species had a prominent notochord and segmental muscles. From this information, you could conclude that it is closely related to __________.
Fill in the blank(s) with the appropriate word(s).
Answer: lancelets
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Answer the following statements true (T) or false (F)
1. Temperature tends to decline with longitude. 2. Land next to the sea has more variable climate than land farther from the sea. 3. Adaptive explanations for behaviors seek to get at ultimate causes for those behaviors. 4. The monarch butterflies that migrate to Mexico in the winter have not previously flown the route.
What is the purpose of the lac operon, and under what circumstances is it activated? Describe the structure of the lac operon, including the repressor protein, structural genes, and regulatory regions of the operon
What is the role of catabolite repression in the lac operon?
Genes are really just segments of DNA in patterns of As, Ts, Gs, and Cs. How does an RNA polymerase "know" where to start transcribing at the beginning of a particular gene?
A) The polymerase finds the end of the previous gene and copies past that point. B) The polymerase starts transcribing anywhere because the beginning point counts only during translation. C) It looks for a specific promoter region that marks the beginning of a gene. D) RNA polymerase does not know, so it has to rely on the ribosome to help it start at the correct place.
Bacterial production of the enzymes needed for the synthesis of the amino acid tryptophan declines with increasing levels of tryptophan and increases as tryptophan levels decline. This is an example of
A) competitive inhibition. B) noncompetitive inhibition. C) feedback inhibition. D) irreversible inhibition.