Zoology 2.1

• The phylum Chordata includes vertebrates, which have a notochord during embryonic development.
• Jellyfish are free-swimming marine coelenterates with a gelatinous bell or saucer-shaped body that has stinging tentacles around the edge

  
• Jellyfish are found in all oceans, from the surface to the depths, and are predators that use their tentacles to capture prey
• Sponges are multicellular animals that live in aquatic environments, with a porous body that allows water to flow through them, carrying food and oxygen to their cells
• Sponges have a variety of cells, including choanocytes that filter food from the water, and amoebocytes that help digest food
• Sponges play a crucial role in the marine ecosystem by filtering water and providing habitat for other animals
• Placozoans are tiny animals that lack specialized tissues
• Placozoans are considered one of the simplest animals, consisting of a few thousand cells organized into upper and lower epithelia, with multi-nucleated fiber cells in between
• Sponges feed by drawing water containing food particles and dissolved organic molecules into their interiors, mostly being sessile and designed for efficient aquatic filter feeding
• Sponges do not have true tissues and have hollow bodies that are either asymmetric or radially symmetric, using flagellated "collar cells" to move water for feeding and oxygen intake
• Sponges have a skeletal structure consisting of fibrous and/or rigid materials like calcareous or siliceous spicules, with the composition and shape of spicules being the basis of classification
• Sponges reproduce through asexual budding or fragmentation, as well as sexual reproduction where sperm are released into the water for fertilization
• Sponges can have different body forms like standing erect, being branched, or encrusting, with growth patterns influenced by factors like substratum shape and water flow direction
• Sponges can host various animals like crabs, nudibranchs, fish, and other species as commensals or parasites, and can grow on other living organisms for camouflage and protection
• Sponges are traditionally grouped into classes based on spicules and chemical composition, such as Calcispongiae, Hexactinellida, Demospongiae, and Homoscleromorpha
• Cnidarians are aquatic animals with radial symmetry and two tissue layers, the epidermis covering the body surface and the gastrodermis lining the internal body cavity specialized for digestion
• Cnidarians transition between a sessile polyp form and a free-swimming medusa form, with the polyp being tubular with tentacles and the medusa having an umbrella-shaped body with tentacles
• Cnidarians are carnivorous with a mouth surrounded by tentacles, have an incomplete digestive tract, and a hydrostatic skeleton for support
• Cnidarians have a nerve net arrangement with ganglia but no central nervous system, and their tentacles are armed with cnidocytes that capture prey and defend against threats
• Cnidarians have a nervous system that includes a nerve net, ganglia, and nerve impulses in one or both directions

  
• Cnidarians have a life cycle that includes alternation of generations, with a medusa phase for sexual reproduction and a polyp phase for asexual reproduction
• Cnidarians have a distribution that includes marine habitats, with most found in shallow water areas and generally in warm tropical regions
• Cnidarians can live symbiotically and commensally with other animals, such as hydroids and sea anemones living on snail shells inhabited by hermit crabs for protection
• Coral-zooxanthellae symbiosis involves photosynthetic dinoflagellates living in a symbiotic relationship with reef corals and other organisms
• Ctenophores have a transparent body with a gelatinous layer, long sticky tentacles to capture prey, and a gastrovascular system for digestion, respiration, and excretion
• Ctenophores have sensory cells in the epidermis to detect stimuli, are mostly monoecious with fertilized eggs discharged into water, and are part of the diploblasts phylogeny along with cnidarians