The common ancestors of birds and mammals were very early (stem) reptiles, which almost certainly possessed three-chambered hearts (two atria, one ventricle). Birds and mammals, however, are alike in having four-chambered hearts (two atria, two ventricles). The fourchambered hearts of birds and mammals are best described as ________.

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#Question id: 3261

#XL - T Zoology

A parent population (P) is change into daughter populations (Q) which grow in habitats. After 1000 generations, the equilibrium frequency distribution of of the daughter populations is shown in the figure below. For reference, the vertical line represents the mean of the parent population. Which type of natural selection?

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#Question id: 160

#XL - T Zoology

Of the 20 standard amino acids, only ___________ is not optically active.  The reason is that its side chain ___________.

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#Question id: 11304

#XL - Q Biochemistry

In what way do the membranes of a eukaryotic cell vary?

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#Question id: 18534

#XL - R Botany

New world cotton is

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#Question id: 19760

#XL - P Chemistry

Which of the following compound possesses covalent bond ?