Which organism possesses a three-chambered heart?

a. human
b. amphibian
c. arthropod
d. bird
e. fish


b

Biology & Microbiology

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The branch points on a cladogram represent ____

a. the species' extinction b. derived characters c. related clades d. a common ancestor of two lineages e. mass extinctions

Biology & Microbiology

Transcription starts at a region of DNA called a(n)

a. sequencer. b. promoter. c. activator. d. terminator. e. transcriber.

Biology & Microbiology

A model is used by ecologists to

A) prove how nature works by demonstrating cause-and-effect relationships. B) analyze data that have been collected during an experiment. C) make predictions about how nature works using a set of explicit assumptions. D) observe how nature works in an experimental setting.

Biology & Microbiology

Helper T cells secrete ________ to stimulate the proliferation of B-cells.

A. antigens B. antibodies C. MHC proteins D. cytokines

Biology & Microbiology