Chapter 31, Problem 1TYK

Summary Introduction

Introduction:

Animals are multicellular organisms, that is, their body is made up of more than one cell. They cannot synthesize their own food and most of them are motile. Their body is either radially symmetrical (body parts are arranged regularly around the central axis) or bilaterally symmetrical (their body is divided from head to tail; both the sides are mirror images).

Answer to Problem 1TYK

Correct answer:

Sessile type of character is not typically observed in most animals.

Explanation of Solution

The explanation for the correct answer:

Option (b) is given as: the sessile character is not typically observed in most animals. Motility of an organism is defined as its ability to move from one place to another in search of food, shelter, and to interact with other animals at some stage of their life. Most animals are motile or they are motile at least during some stage of their lives. Though some organisms become sessile adults, they were motile at some stage of their life such as during the larval stage (examples like mollusks and barnacles). The sessile character is not typically observed in most mammals. Hence, option (b) is correct.

The explanation for the incorrect answer:

Option (a) is given as: heterotrophic characteristic is not typically observed in most animals. Heterotroph organisms cannot synthesize their own food and they eat other organisms to acquire nutrients and energy. Therefore, all animals are heterotrophs and it is a typical characteristic of most animals. So, it is incorrect.

Option (c) is given as: bilaterally symmetrical characteristic is not typically observed in most animals. Cutting bilateral symmetrical bodies into half from the middle, from head to tail, the left and the right-side form mirror images. Most of the eumetazoans other than the phyla Cnidaria and Ctenophora are bilaterally symmetrical. So, it is incorrect.

Option (d) is given as: multicellular characteristic is not typically observed in most animals. All animals are multicellular; their bodies are made up of more than one cell. It is a typical characteristic of all mammals. So, it is incorrect.

Option (e) is given as: motile at some stage of their life cycle. All the organisms of kingdom Animalia are motile at some stage of their life cycle and this is a typical characteristic of most animals. So, it is incorrect.

Hence options (a), (c), (d), and (e) are incorrect.

Conclusion

Therefore, it can be concluded that the characteristic features of most animals include that they are heterotrophic, multicellular, motile at some stage of their life but, they are not sessile organisms.