Question

Haemocoel is found in
A. Hydra
B. Ascaris
C. Earthworm
D. Cockroach

Answer 1

Hint:
here are two types of circulatory system
A) Open circulatory system
B) Closed circulatory system
Open circulatory system: In an open circulatory system, which is mostly seen in invertebrates, the gases (oxygen and carbon dioxide) reach the various organs directly.
Closed circulatory system: In a closed circulatory system, which mostly found in vertebrates, the gases are supplied to various organs by pipe like structure i.e capillaries.

Complete answer:
So, to answer this question we first need to know about Haemocoel.
Haemocoel- it is defined as an open primary cavity of the body through which haemolymph circulates and bathes the organs and tissues and thus supplies them with oxygen directly.
It is a type of open circulatory system.
The meaning of the word haemocoel can be understood from the word itself.
Haemo-Blood, Coel- Cavity
It is a prominent feature of arthropods and molluscs.

Option A. Hydra- These are freshwater invertebrate animals which are capable of contraction. In this, there is a lack of a specialised circulatory system for flow of gases. It occurs by diffusion through the body.

Option B. Ascaris- This belongs to nematoda. In Ascaris the supply of gases to organs occurs by diffusion only, thus it lacks haemocoel.

Option C. Earthworm- These are terrestrial invertebrates. In earthworms also there are no lungs in a specialised circulatory system, so transport of gases occurs through diffusion.

Option D. Cockroach- These belong to Arthropoda. So it has an open circulatory system. Blood vessels in cockroaches are poorly developed and they open into a hollow cavity known as haemocoel through haemolymph flows and supplies the organs with oxygen.

Hence, the correct answer is

Note:
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