IB Biology: Unity and diversity practice questions

Question 1

Which structure is present in a plant cell but NOT in a typical animal cell?

Accepted Answer

cell wall — A cellulose cell wall (plus chloroplasts and a large permanent vacuole) is characteristic of plant cells; the others are common to both.

Question 2

A cell is 50 µm across. In a drawing it measures 50 mm. What is the magnification of the drawing?

Accepted Answer

×1000 — Magnification = image size / actual size = 50 mm / 50 µm = 50 000 µm / 50 µm = ×1000.

Question 3

Which organelle is the site of protein synthesis?

Accepted Answer

ribosome — Ribosomes assemble polypeptides during translation; the Golgi later modifies and packages proteins.

Question 4

A defining property of a stem cell is that it

Accepted Answer

can self-renew and differentiate — Stem cells retain the capacity to divide (self-renew) and to differentiate; potency varies (totipotent, pluripotent, multipotent).

Question 5

Which pair of bases forms three hydrogen bonds in DNA?

Accepted Answer

guanine and cytosine — G–C pairs form three hydrogen bonds; A–T pairs form two. More G–C content therefore raises DNA stability.

Question 6

Which of the following provides evidence for evolution?

Accepted Answer

homologous structures — Homologous structures (same basic plan, different function) suggest common ancestry; other evidence includes fossils and molecular sequences.

Unity and diversity practice questions.

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