Question

Which one of the following is a total parasite?
a) Nepenthes
b) Rhizobium
c) Cuscuta
d) Lichens

Answer 1

Hint: Parasitism is a relationship in which one member benefits at the cost of the other member. A total parasite is the one that sucks the sap from its host and cannot prepare its own food.

Complete answer:
Cuscuta (dodder) is a holoparasite. It sucks the sap from the host plant. It does not have chlorophyll so it cannot prepare its own food.

Thus the correct answer is option C- Cuscuta.

Additional information:

Nepenthes is a genus of pitcher plants. Nepenthes are also called tropical pitcher plants or monkey cups. They are perennial herbaceous plants. Pitcher plants are carnivorous plants. They are fed on insects by capturing them with their pitcher-shaped leaves. They usually grow in acidic soil.

Rhizobium is bacteria that live in root nodules of leguminous plants. They show a symbiotic relationship with plants. Rhizobium is of great ecological importance as they help in nitrogen fixation and thus, help in plant growth.

Cuscuta (dodder) is a holoparasite. It is an obligate stem parasite. It sucks the sap from the host plant. It does not have chlorophyll so it cannot prepare its own food.

Dodder attaches itself to the host plant by wrapping itself around it. After the dodder has sensed that the host is beneficial, it produces haustoria which gets inserted in the vascular system of the host to derive nutrition. The original root of the dodder then dies. Dodders can attach to multiple plants for its survival. In tropical areas, it depends on shrubs and trees whereas, in cold temperate regions, it is an annual plant.

Some species of fungi live in a mutually dependent relationship with cyanobacteria. These symbiotic life forms are called lichens. Lichens are seen as large colored patches on the bark of trees. Lichens are indicators of pollution. They cannot grow in areas with air pollution.

Note: Based on the size, characteristics, and relationship with the host, parasitism can be of different types.
Obligate parasites are those that completely depend on the host throughout their life whereas facultative parasites perform parasitic activities only for some time and thus do not depend on the host completely.