Question

Which of these has no blood, yet it respires?
A)Earthworm
B)Toad
C)Cockroach
D)Hydra

Answer 1

Blood is a fluid connective tissue which helps in transporting oxygen to various cells and organs in the body. It plays an important role in respiration.

Complete answer:
Before finding the correct answer, first let us understand how blood helps in respiration. So, blood is a red colour fluid that is present all over the body. Blood transports oxygen to various cells and organs and it also removes waste products like carbon dioxide. This is how blood helps in respiration.

Option a: In earthworm blood is present. The blood of earthworms does not have red colour despite the presence of haemoglobin. Therefore, this is the incorrect option.

Option b: In toad blood is present. The colour of blood in toads ranges between yellow to red. Therefore, this is the incorrect option.

Option c: In cockroach, blood is present. The blood of cockroach is white in colour as haemoglobin is absent. Therefore, this is the incorrect option.

Option d: In hydra, there is no blood. Though, there is no blood it respires via diffusion. The oxygen molecules diffuse in and the carbon dioxide diffuse out. Therefore, this is the correct option.

One of the easiest ways of solving this question is by analysing the given options. All the options except for hydra are examples of higher level organisms which means they would definitely have blood. Therefore, leaving us with hydra as the answer.

Hence, the correct answer is option (D)

Note: The characteristics of Hydra are,
1)Their body is a hollow tube and has two layers of cells which is separated by mesoglea
2)They have radially symmetrical body
3)They have stinging tentacles
4)They have a simple gut and have only one opening