Following are the statements related to mammalian chaemotaxis:

A. During chaemotaxis, the oocyte and its accompanying cumulus cells secrete molecules that attract only uncapacitated sperm toward the egg during the last stages of sperm migration.

B. These chaemotactic compound are hormone progesterone, which is made by the cumulus cells.

C. Progesterone has been shown to bind to a receptor that activates Ca2+ channels in the cell membrane of the sperm tail, leading to sperm hyperactivity and provides directional cue.

D. Cumulus cells also secrete a substance, CRISP1, that attracts sperm and hyperactivates them through CatSper channels similar as in sea urchins.

Which of  the following statement is incorrect?

TLS Online TPP Program

#Question id: 13171

#Unit 10. Ecological Principles

Imagine some cosmic catastrophe jolts Earth so that its axis is perpendicular to the orbital plane between Earth and the sun. The most obvious effect of this change would be

TLS Online TPP Program

#Question id: 13170

#Unit 10. Ecological Principles

Which of the following events might you predict to occur if the tilt of Earth's axis relative to its plane of orbit was increased 33.5 degrees?

TLS Online TPP Program

#Question id: 13169

#Unit 10. Ecological Principles

Which of the following causes Earth's seasons?

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#Question id: 13168

#Unit 10. Ecological Principles

Use the following diagram from the text showing the spread of the cattle egret, Bulbulcus ibis, since its arrival in the New World, to answer the following question.

How would an ecologist likely explain the expansion of the cattle egret?

TLS Online TPP Program

#Question id: 13022

#Unit 10. Ecological Principles

A certain species of pine tree survives only in scattered locations at elevations above 2,800 m in the western United States. To understand why this tree grows only in these specific places an ecologist should

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#Question id: 13020

#Unit 10. Ecological Principles

Experts in deer ecology generally agree that population sizes of deer that live in temperate climates are limited by winter snow. The deer congregate in ?yarding? areas under evergreen trees because venturing out to feed in winter is energetically too expensive when snowfall depths accumulate to above 40 cm. Deer often stay yarded until the spring thaw. Snow depth over 40 inches for more than 60 days results in high mortality due to starvation.  This observation best illustrates which of the following principles about factors that limit distribution of organisms?