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Coral reefs are some of the most biodiverse habitats on earth, supporting large numbers of species of corals, fish, molluscs, worms, arthropods, starfish, sea urchins, other invertebrates and algae. Because of the photosynthetic requirements of the corals, they are found in shallow waters, and many of these fringe land masses. [24]
Pacific sea nettles, Chrysaora fuscescens. Cnidaria (/ n ɪ ˈ d ɛər i ə, n aɪ-/ nih-DAIR-ee-ə, NY-) [4] is a phylum under kingdom Animalia containing over 11,000 species [5] of aquatic invertebrates found both in fresh water and marine environments (predominantly the latter), including jellyfish, hydroids, sea anemones, corals and some of the smallest marine parasites.
The mesoglea includes mobile amoeboid cells originating from the epidermis. Scyphozoans have no durable hard parts, including no head, no skeleton, and no specialized organs for respiration or excretion. [6] [7] Marine jellyfish can consist of as much as 98% water, so are rarely found in fossil form.
Neurons differ in invertebrates from mammalian cells. Invertebrates cells fire in response to similar stimuli as mammals, such as tissue trauma, high temperature, or changes in pH. The first invertebrate in which a neuron cell was identified was the medicinal leech, Hirudo medicinalis.
Starfish have sensory cells in the epithelium and have simple eyespots and touch-sensitive tentacle-like tube feet at the tips of their arms. Sea urchins have no particular sense organs but do have statocysts that assist in gravitational orientation, and they too have sensory cells in their epidermis, particularly in the tube feet, spines and ...
Viruses are found wherever there is life and have probably existed since living cells first evolved. [35] The origin of viruses is unclear because they do not form fossils, so molecular techniques have been used to compare the DNA or RNA of viruses and are a useful means of investigating how they arose.
The taxonomic term Bivalvia was first used by Linnaeus in the 10th edition of his Systema Naturae in 1758 to refer to animals having shells composed of two valves. [3] More recently, the class was known as Pelecypoda, meaning "axe-foot" (based on the shape of the foot of the animal when extended).
Agnatha (/ ˈ æ ɡ n ə θ ə, æ ɡ ˈ n eɪ θ ə /; [3] from Ancient Greek ἀ-(a-) 'without' and γνάθος (gnáthos) 'jaws') is a paraphyletic infraphylum [4] of non-gnathostome vertebrates, or jawless fish, in the phylum Chordata, subphylum Vertebrata, consisting of both living (cyclostomes) and extinct (conodonts, anaspids, and ostracoderms, among others).