Membrane-bound organelles have been an important component in the evolution of complex, multicellular organisms. Which of the following best summarizes an advantage of eukaryotic cells having internal membranes?
- Eukaryotic cells are able to reproduce faster because of the presence of organelles.
- Some organelles, such as mitochondria and chloroplasts, are similar to prokaryotic cells in structure.
- Organelles isolate specific reactions, increasing metabolic efficiency.
- Compartmentalization leads to a higher mutation rate in DNA, which leads to more new species.
By discharging electric sparks into a laboratory chamber atmosphere that consisted of water vapor, hydrogen gas, methane, and ammonia, Stanley Miller obtained data that showed that a number of organic molecules, including many amino acids, could be synthesized. Miller was attempting to model early Earth conditions as understood in the 1950s. The results of Miller’s experiments best support which of the following hypotheses?
- The molecules essential to life today did not exist at the time Earth was first formed.
- The molecules essential to life today could not have been carried to the primordial Earth by a comet or meteorite.
- The molecules essential to life today could have formed under early Earth conditions.
- The molecules essential to life today were initially self-replicating proteins that were synthesized approximately four billion years ago.
Simple cuboidal epithelial cells line the ducts of certain human exocrine glands. Various materials are transported into or out of the cells by diffusion. (The formula for the surface area of a cube is 6 ¥ S2, and the formula for the volume of
a cube is S3, where S = the length of a side of the cube.)
Which of the following cube-shaped cells would be most efficient in removing waste by diffusion?
The area covered by tropical rain forest is reduced by millions of hectares per year due to agriculture and logging. Which of the following best describes a likely result of tropical rain forest deforestation?
(A) Populations of plants and animals will decrease as more rain forest disappears, leading to a decrease in biodiversity.
(B) An increase of soil moisture will lead to a rapid increase in new vegetation coverage.
(C) An increase in atmospheric carbon dioxide will lead to higher levels of ultraviolet radiation reaching the surface of Earth.
(D) More oxygen will be available to other organisms as plant numbers decrease.