In balancing selection, two or more alleles are kept in balance, and therefore are maintained in a population over the course of many generations. Which of the following example can support balancing natural selection?

A- Sickle cell allele kept in balance because heterozygotes have greater chance of survival if infected by the malarial parasite, compared with normal homozygotes

B. One morph has selective advantage over another morph

C. One homozygote has greater chance of survival than other genotype results in purity of population

D. many species of invertebrates exist as different colored forms, identical in all respects except color. Visually searching predators often develop a search image for one color form, usually the commoner

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#Question id: 1375

#Unit 4. Cell Communication and Cell Signaling

Four ECM ubiquitous protein components, each of which comprises multiple, distinct, repeating domains, are found in basal laminae. Given below are a list of some extracellular matrix (ECM) proteins in column A and their characteristics in column B.

Column A	Column B
a. Type IV collagen	i. a large multidomain proteoglycan that binds to and cross-links many ECM components and cell-surface molecules.
b. Laminins	ii. a rodlike molecule that cross-links type IV collagen, perlecan, and laminin, which helps incorporate other components into the ECM and also stabilizes basal laminae.
c. Perlecan	iii. a family of multi-adhesive, cross-shaped proteins that form a fibrous two-dimensional network with type IV collagen and that also bind to integrins and other adhesion receptors.
d. Nidogen	iv. trimeric molecules with both rodlike and globular domains that form a two-dimensional network.

Which one of the following is the most appropriate match?

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#Question id: 9239

#Unit 9. Diversity of Life Forms

Why are changes in the global carbon cycle important?

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#Question id: 21240

#Unit 7. System Physiology – Animal

A visual exam in an 80-year-old man shows he has a reduced ability to see objects in the upper and lower quadrants of the left visual fields of both eyes but some vision remains in the central regions of the visual field. The diagnosis is

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#Question id: 12952

#Unit 7. System Physiology – Animal

Which of the following changes would tend to increase Ca2+ reabsorption in the renal tubule?

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#Question id: 12383

#Unit 7. System Physiology – Animal

Which of the following changes tends to increase urinary Ca++ excretion?