Question

One of the characteristics unique to animals is

(A) gastrulation.

(B) multicellularity.

(C) sexual reproduction.

(D) flagellated sperm.

Short answer

(A) The option “gastrulation” is true.

(B) The option “multicellularity” is false.

(C) The option “sexual reproduction” is false.

(D) The option “flagellated sperm” is false.

Step-by-step solution

Features of the animal kingdom

Animals are complex eukaryotic organisms that possess millions of cells within their body. These organisms possess specialized tissues that perform designated functions within the body. They cannot produce their own food, and hence they depend on plants or other organisms to obtain energy.

Step 2:Explanation of option ‘(A)’

Gastrulation is unique only to animals because, in this process, the cell moves and change their location through invagination, giving rise to specific structures. However, the process of gastrulation occurs uniquely in every organism; it is generally only observed in animals because the cells in other organisms do not exhibit movement.

Thus, gastrulation is unique to only animals.

Therefore, the given option is true.

Explanation of option ‘(B)’

Most eukaryotic organisms possess multiple cells within their body. This trait is therefore not unique only to animals. Some examples of multicellularity exhibited by some organisms include plants, fungi, and so on.

Thus, multicellularity is not unique to only animals.

Therefore, the given option is false.

Explanation of option ‘(C)’

Sexual reproduction is not unique to animals. This type of reproduction involves the fusion of male and female gametes that results in the formation of a diploid zygote. It is observed in most animals and plants.

Thus, sexual reproduction is not unique to only animals.

Therefore, the given option is false.

Explanation of option ‘(D)’

Sperms are important gametes that are responsible for sexual reproduction. The sperm that the male produces is motile due to the presence of flagella because it has to swim through the reproductive tract to reach the female gamete called the ovum. These functional motile sperms are observed in plants as well as animals.

Thus, flagellated sperm is not unique to only animals.

Therefore, the given option is false.