Answer :
To answer the question about which secondary compounds are known to deter herbivores and pests, let's first understand what secondary compounds are.
Secondary compounds, also known as secondary metabolites, are organic compounds that are not directly involved in the normal growth, development, or reproduction of an organism. In plants, these compounds often serve ecological functions such as defense against herbivores and pests.
Now, let's examine each of the options provided:
Sugars: These are primary metabolites that serve as energy sources for plants and animals. They are not typically involved in deterring herbivores or pests.
Flavonoids: These are a group of plant secondary metabolites. While flavonoids can play roles in plant color and UV filtration, they are not primarily known for deterring herbivores and pests.
Alkaloids: These are a class of nitrogen-containing compounds. Alkaloids are well known for their bitter taste and toxic effects, which can deter herbivores and pests. Many plants produce alkaloids as a defense mechanism.
Vitamins: These are organic compounds that are essential for normal growth and nutrition. They are generally involved in metabolic processes rather than defense.
Given this information, the correct answer is 3. Alkaloids. Alkaloids such as nicotine, caffeine, and morphine serve as chemical defenses against herbivory by making plants taste bitter or toxic to predators.
Therefore, among the listed options, alkaloids are the secondary compounds that are known to deter herbivores and pests.