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Why are sponges considered unique in the evolution of animals?

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Sponges have no true tissues. All other animals (eumetazoans) have tissues derived from embryonic germ layers. read more

Metazoan animals make up a major portion of the animal kingdom. Not ‘true animals' Sea sponges do not have a gut and nervous system, and are hence not generally considered as ‘true animals.' Yet, scientists are of the opinion that other multicellular metazoan animals evolved from sponge-like ancestors. read more

In some species of sponges, the sexes are separate, but many sponges are hermaphrodites, meaning that the same sponge has both male and female reproductive capabilities. Those sponges tend to produce only sperm or eggs, not both, during a given spawning event. read more

Sponges..animals with many pores, without definite form of symmetry, and do not contain organs or true tissues. They are all sessile. The humble bath sponge, used for centuries particularly in the Mediterranean region were originally thought of as plants but are now considered animals (only in 1765)(even its own subkingdom ..Parazoa) They probably originated from flagellated protozoans or primitive metazoans. read more

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Re: Why are sponges Animals, but colonial ...
Source: madsci.org

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