Which characteristic led Whittaker to place fungi in a separate kingdom rather than with plants?
A. Multicellular organization
B. Heterotrophic mode of nutrition and chitinous cell walls
C. Use of spores for reproduction
D. Presence of nucleus
Answer (2)
Whittaker placed fungi in a separate kingdom due to their heterotrophic mode of nutrition and the presence of chitin in their cell walls, which are distinct from plants that are autotrophic and have cellulose in their cell walls. The chosen option is B. Heterotrophic mode of nutrition and chitinous cell walls.
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To determine why fungi were placed in a separate kingdom by Robert Whittaker, it's important to understand the characteristics that distinguish fungi from plants.
Robert Whittaker was an American ecologist who proposed the five-kingdom classification system in 1969. The five kingdoms are Monera, Protista, Fungi, Plantae, and Animalia. Before Whittaker's classification, fungi were often grouped with plants due to certain similarities in lifestyle, such as being immobile and having cell walls.
The characteristic that led Whittaker to place fungi in a separate kingdom, rather than with plants, is (B) Heterotrophic mode of nutrition and chitinous cell walls.
Let's break down why option (B) is the correct choice:
Heterotrophic Nutrition : Fungi are heterotrophs, meaning they obtain their food from external sources. They do not perform photosynthesis like plants, which are autotrophs. Fungi absorb nutrients from organic material, either decomposing dead matter or being parasitic on living organisms.
Chitinous Cell Walls : The cell walls of fungi contain chitin, a strong, flexible polysaccharide also found in the exoskeletons of arthropods. In contrast, plant cell walls are primarily made of cellulose. This fundamental chemical difference in the cell wall composition is a key factor in distinguishing fungi from plants.
The other options:
(A) Multicellular organization : Both fungi and plants can be multicellular.
(C) Use of spores for reproduction : While fungi do reproduce via spores, so do some plants (like ferns and mosses).
(D) Presence of nucleus : Fungi, plants, and many other organisms all have a nucleus, making it not unique to fungi.
Therefore, the specific combination of heterotrophic nutrition and the chitinous nature of their cell walls prompted Whittaker to recognize fungi as a distinct kingdom separate from plants.
