________ transport is required to move a substance across a membrane against a concentration gradient.
Fill in the blank(s) with the appropriate word(s).
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Once fertilization has occurred, the activities of development begin. The first such activity is ________
A) the formation of organ systems B) cellular specialization C) an increase in cell number
Which of the following is NOT a common characteristic of a negative feedback system?
a) regulates conditions in body that remain fairly stable over long periods b) important in maintaining homeostasis c) involves control centers in the nervous or endocrine systems d) stimulates changes that reverse the direction of the stimulus e) usually requires an event outside the feedback system to shut it off
When does oogenesis begin?
A. During pubarche B. During thelarche C. At birth D. During menarche E. During embryonic development
The nervous system employs exclusively electrical means to send messages, whereas the endocrine system communicates by means of chemical messengers.
Answer the following statement true (T) or false (F)