In spiral and determinate cleavage, the fate of each blastomere is fixed early in development, typical in protostomes like annelids and mollusks.

Hydra reproduces asexually by budding and does not show alternation of generations, unlike Obelia and Aurelia, which have polyp and medusa stages.

Nematodes have a complete tube-like digestive system with a separate mouth and anus, allowing one-way food flow.

Cnidocytes are specialized cells unique to Cnidaria that contain nematocysts for defense and prey capture.

Haemocyanin is a copper-based respiratory pigment in spiders, giving their blood a blue color when oxygenated.

Sponges are filter feeders that primarily consume phytoplankton and small organic particles from water, with phytoplankton being a major component.

In pseudocoelomates, the body cavity (pseudocoelom) is derived from the blastocoel present in the blastula stage.

Some coelenterates, like corals, have exoskeletons made of calcium carbonate for structural support and protection.

Scorpions and some spiders possess book lungs, internal respiratory tissues for gas exchange.

Parazoa is a sub-kingdom including sponges (Phylum Porifera) that lack true tissues and organs.

Sponges (Porifera) are sessile filter feeders and are not parasitic, unlike some species in Nematoda and Platyhelminthes.

Taenia, a tapeworm, has segments called proglottids containing reproductive organs.

Mollusks have haemocyanin, a copper-containing respiratory pigment that binds oxygen, giving blood a blue color.

In deuterostomes, the mesoderm develops from the archenteron wall during gut formation, and the blastopore becomes the anus.

Malpighian tubules are excretory organs in insects like cockroaches for nitrogenous waste removal.

The Cenozoic era is known as the 'Age of Mammals' due to their extensive diversification and dominance.

In acoelomates, the gut is formed from the endoderm, with the space between the gut and body wall filled by mesoderm.

Arthropoda is characterized by a segmented body, jointed appendages, and an exoskeleton made of chitin, including insects, spiders, and crustaceans.

Animals require organic molecules for energy and growth, obtained by feeding on plants or other organisms.

Dugesia, a type of planarian, is a free-living flatworm in the phylum Platyhelminthes, unlike parasitic Fasciola and Taenia.