Question

Animals possess a nerve network or nervous system to respond to their environment. But the single-cell Amoeba does not possess any nerve cell, so, how it comes to know whether a particle it encounters is a gain or sand and not its dinner
A) By chemotaxis
B) By skin
C) By hormones
D) All of these

Answer 1

Hint: Amoeba is a single-celled organism. Amoeba belongs to the kingdom protista. They are amorphous in shape. Amoeba moves by feet like pseudopodia, these are also used for feeding. These are microscopic organisms but some species are large enough that can be seen with the naked eye. The nervous system in animals coordinates the behavior and transports signals between different parts of the body. Amoeba intakes their food through phagocytosis. By extending their pseudopods they engulf live prey.

Complete answer:
Although the amoeba lacks sense organs.
Amoeba reacts to a chemical stimulus. This determination is made by chemotaxis.
Chemotaxis is a type of chemical sensitivity.
Chemotaxis is the same kind of response mechanism that is used by our white blood cells when they encounter and phagocytize a pathogen.
Chemotaxis involves the movement of cells away or towards a chemical source.
Amoeba lacks a cell wall.
It is the only organism that has no hormones.
Their cellular and cytoplasmic contents are closed within a cell membrane.
Unicellular organisms use skin for respiration.

Hence, the correct answer is option A.

Additional Information: Amoeba can change its shape.
Amoeboid cells not only occur among the protozoa but also in algae, fungi, and animals.
Amoeba moves and feeds with the help of pseudopods.
Amoeba food sources vary, some are predatory and some are detritivores.
Example of chemotaxis, movement of neutrophils, or macrophages towards chemoattractants synthesized at the site of injury or infection(CSF-1).

Note: Amoeba is a single-celled organism. Amoeba belongs to the kingdom protista. They are amorphous in shape. Amoeba moves by feet like pseudopodia, these are also used for feeding. Amoeba intakes their food through phagocytosis. By extending their pseudopods they engulf live prey. Although the amoeba lacks sense organs. Amoeba reacts to a chemical stimulus. This determination is made by chemotaxis. Chemotaxis is a type of chemical sensitivity. Chemotaxis is the same kind of response mechanism that is used by our white blood cells when they encounter and phagocytize a pathogen.