Question

Completely terristial , classes in animal kingdom.?

Answer 1

Dear student,

Terrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, spiders), as compared with aquatic animals, which live predominantly or entirely in the water (e.g., fish, lobsters, octopuses), or amphibians, which rely on a combination of aquatic and terrestrial habitats (e.g., frogs, or newts). Terrestrial invertebrates include ants, flies, crickets, grasshoppers and spiders.


Terrestrial Classes

The term terrestrial is typically applied for species that live primarily on the ground, in contrast to arboreal species, which live primarily in trees.

There are other less common terms that apply to specific groups of terrestrial animals:
Saxicolous are rock dwelling creatures. Saxicolus is derived from the Latin word "Saxum" which means Rocks.
Arenicolous creatures live in the sand.
Trogloxenes (or Troglodytes) predominantly live in caves.

Taxonomy

Terrestrial invasion is one of the most important events in the history of life. Terrestrial lineages evolved in several animal phyla, among which vertebrates, arthropods, and mollusks are representatives of more successful groups of terrestrial animals.

Terrestrial animals do not form a unified clade; rather, they share only the fact that they live on land. The transition from an aquatic to terrestrial life has evolved independently and successfully many times by various groups of animals. Most terrestrial lineages originated under a mild or tropical climate during the Paleozoic and Mesozoic, whereas few animals became fully terrestrial during the Cenozoic.

When excluding internal parasites, free living species in terrestrial environments are represented by the following ten phyla: Flatworms (Planarians), Nemertea (ribbon worms), Nematoda (roundworms), Rotifers, Tardigrada (water bears), Onychophora (velvet worms), Arthropods, mollusks (gastropods: land snails and slugs), Annelida and Chordata(tetrapods).

Roundworms, tardigrades, and rotifers are microscopic animals that require a film of water to live in, and are not considered truly terrestrial. Flatworms, ribbon worms, velvet worms and annelids all depend on more or less moist habitats, as do the Arthropods centipedes and millipedes. The three remaining phyla, Arthropods, Mollusks and Chordates, all contain species that have adapted totally to dry terrestrial environments, and contain species that have no aquatic phase in their life cycles.

Animals do not fall neatly into terrestrial or aquatic classification but lie along a continuum: e.g., penguins spend much of their time under water.

So labeling an animal species "terrestrial" or "aquatic" is often obscure and becomes a matter of judgment. Many animals considered terrestrial have a life-cycle that is partly dependent on being in water. Penguins, seals, and walruses sleep on land and feed in the ocean, yet they are all considered terrestrial. Many insects, e.g. mosquitos, and all terrestrial crabs, as well as other clades, have an aquatic life cycle stage: their eggs need to be laid in and to hatch in water; after hatching, there is an early aquatic form, either a nymph or larva.

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