Answer:
Cell Wall: This is the rigid outermost layer of a plant cell. It makes the cell stiff -providing the cell with mechanical support - and giving it protection. Animal cells do not have cell walls. Cell Membrane: This is a protective layer that surrounds every cell and separates it from its external environment.
Answer:
<h2>Secondary air pollutants are pollutants which form in the atmosphere.</h2>
Explanation:
Examples of a secondary pollutant include ozone, which is formed when hydrocarbons (HC) and nitrogen oxides (NOx) combine in the presence of sunlight; NO2, which is formed as NO combines with oxygen in the air; and acid rain, which is formed when sulfur dioxide or nitrogen oxides react with water.
You've answered it yourself: its called the crust.
According to Darwin's Theory of Natural Selection, each generation produces more individuals than the ecosystem can sustain. However, not all individuals are identical and phenotypical variation exists.
Due to this variation, some antelopes are better at escaping lions, perhaps due to speed and/or stamina. Thus, the individuals that are slower and thus less fit will be killed and eliminated from the herd. The antelopes with heritable traits that makes them better suited to the environment, will escape and thus, survive and reproduce.
In Darwin's Theory predation is an evolutionary force.
