The calcium ion passes easily through the membrane of one cell but cannot cross the
membrane of a second cell. which part of the plasma membrane allows this substance
to cross?
a.) carbohydrate groups on the membrane allow the ions to cross.
b.) the fatty acid tails of the phospholipids allow the ions to cross.
c.) protein channels in the plasma membrane allow the ions to cross.
d.) phosphate groups of the phospholipid bilayer allow the ions to cross.

What are characteristics of minerals? select 3 choices

Which of the following observation darwin shape his concept of descent with modification? a) species diversity declines farther from the equator. b) fewer species live on islands than on the nearest continents. c) birds live on islands located farther from the mainland than the bird's maximum nonstop flight distance. d) south american temperate plants are more similar to the tropical plants of south america than to the temperate plants of europe. e) earthquakes reshape life by causing mass extinctions.

Which genetic disorders, caused by an extra x chromosome (xxy), is characterized by a lack of testicular development in males, effeminate features, possible mental impairment, and a thin stature?