Question

Identify the characteristic of acoelomates

a. Absence of mesoderm

b. Absence of brain

c. Coelom that is incompletely lined with a mesoderm

d. Solid body without a cavity surrounding internal organs​

Answer 1

Answer:d. Solid body without a cavity surrounding the internal organs

Explanation:

Coelom = body cavity lined by i.e., its bordered by mesoderm

a = absent.

Acoelomate = absence of body cavity

Coelenterata, Cnidaria and Platyhelminthes are the acoelomates.

Porifera (sponges) are just cellular aggregates and so not considered for body plan

They only have a single opening to the external - the mouth. Anus is absent (Platyhelminthes have an excretory pore)

Answer 2

Option(D) is the correct answer.

• Acoelomates have a triploblastic body plan, meaning that their tissues and organs develop from three primary embryonic cell layers. These tissue layers are the endoderm the innermost layer, the mesoderm the middle layer, and the ectoderm the outer layer.
• Acelomates commonly possess a simple nervous system. They possess sense organs for inspecting light and food sources, as well as specialized cells and tubules for eradicating waste.
• The coelom is a body cavity which is completely lined with mesoderm in acoelomates.
• An acoelomate is a creature that doesn't involve a body cavity. Unlike coelomates, creatures with a true body cavity, acoelomates lack a fluid-filled cavity between the body wall and digestive tract.

Hence, option (D) is the correct answer 'a solid body without a cavity surrounding internal organs.