Question

Please give point form or a short essay for each questions below.

1) Are all bilaterians coelomates? Name ONE notable exception and describe the key morphological features of animal under this phylum in detail.

2) Do all acoelomates possess three germ layers during embryonic development? Name ONE notable exception and describe the key morphological features of animal under this phylum in detail.

3) What key features make us human fundamentally different from sponge in developing from embryo to adult?

4) Name ONE invertebrate animal with no known natural predator and describe its defensive mechanism in detail.

5) Do you agree with the statement that "amphibians are in general more successful than the reptiles"?

Answer 1

1. All bilaterians are not coelomates. One notable example which is a bilaterian yet acoelomate are animals under the phylum platyhelminthes. Animals belonging to this phylum include tapeworm, liverfluke etc. Following are features:

• These are bilaterally symmetrical.
• Coelom is absent in them, hence acoelomates.
• Their body is dorsoventrally flattened.
• They are soft bodied with absence of true segments.
• Suckers and hooks are present so as to assist in their parastic mode of life.

2. No, all acoelomates do not possesses three germ layers during embryonic development. Animals belonging to phylum ctenophore are diploblastic yet acoelomates. Key features include:

• They are biradially symmetrical.
• Tentacles may or may not be present.
• Comb like eight ciliary plates for locomotion are present.
• They exhibit the property of bioluminescence.

3. Features making humans different from sponges in developing from embryo to adult are:

• Sponges have cellular level of organisation whereas humans have organ system level of body organisation.
• Sponges are diploblastic organisms whereas humans are triploblastic organisms.
• Sponges do not have a coelom whereas humans are coelomates.
• Sponges are most primitive multicellular organisms whereas humans are most evolved organisms.
• Sponges retain the ability of totipotency whereas in humans totipotency is exhibited only during early embryonic stage.
• Organ systems like digestive system, nervous system, excretory system are absent in sponges but present in humans.

5. Well to begin with amphibians have an advantage of being able to survive in both terrestrial and aquatic environments however, i do not agree with the statement that amphibians are not successful than reptiles. We can count on some advantages that reptiles enjoy over amphibians:

• Amphibians can survive on land but have to return in water for reproduction.
• Eggs of reptiles are hard shelled and hence protected well. However those of amphibians are soft and vulnerable to drying.

Amphibians however are important in terrestrial adaptation. They have slippery skin which makes the predator difficult to grab it which would to it's advantage. ( Sort according to what you think is right)

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