______ have a complex placenta during gestation.

a. Eutherian mammals
b. Monotremes
c. Marsupials
d. Echidnas


a. Eutherian mammals

Eutherian mammals have a complex placenta during gestation, but other mammals such as the marsupials and monotremes, do not.

Biology & Microbiology

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A Barr body is a(n) ____

a. activated X chromosome b. inactivated X chromosome c. immature trophoblast d. immature blastocyst e. mature blastocyst

Biology & Microbiology

In their studies of "ant plants," the scientists in Investigating Life 22.5 were testing what hypothesis?

A. The tramp ants were pollinating the trees. B. The tramp ants promote fruit production in trees with the domatia. C. Other species of ants were competing with the tramp ants for nectar. D. The tramp ants were parasites eating nectar from the trees. E. Trees in good locations have enough energy to both produce food and feed ants.

Biology & Microbiology

The ability to mount an efficient secondary antibody response depends on

A. All of the choices are correct B. Memory T and B cells C. Cross-linking of IgM antibodies D. High concentrations of IgA antibody E. Class switching to IgD production

Biology & Microbiology

What is an average concentration of prokaryotic cells along the surface of pelagic water?

A) 104 cells/ml B) 106 cells/ml C) 108 cells/ml D) 1010 cells/ml

Biology & Microbiology