What common problem do taxonomists have in classifying organisms and how do they solve it? Some organisms don’t fit neatly into the defined classifications. They fix this by inserting immediate classification levels.

Scientists classify living things in order to organize and make sense of the incredible diversity of life. Modern scientists base their classifications mainly on molecular similarities. They group together organisms that have similar proteins and DNA. Molecular similarities show that organisms are related.

The current taxonomic system now has eight levels in its hierarchy, from lowest to highest, they are: species, genus, family, order, class, phylum, kingdom, domain.

Marine organisms can be classified into one of three groups, based on habitat and mobility. Plankton are free-floating forms with little power of locomotion, nekton are swimmers, and benthos are bottom dwellers. Only about 13% of all known species inhabit the ocean, and more than 98% of marine organisms are benthic.

Three main groups of ocean life are plankton, nekton, and benthos.

Ocean animals are classified into 2 major categories. These categories include vertebrates and invertebrates. Invertebrates have a backbone, but invertebrates do not have a backbone. There are six major classes of animals which are known as phylum.

A continuous body of water encircling Earth, the World Ocean is divided into a number of principal areas with relatively uninhibited interchange among them. Five oceanic divisions are usually defined: Pacific, Atlantic, Indian, Arctic, and Southern; the last two listed are sometimes consolidated into the first three.

In accordance with the Linnaeus method, scientists classify the animals, as they do the plants, on the basis of shared physical characteristics. They place them in a hierarchy of groupings, beginning with the kingdom animalia and proceeding through phyla, classes, orders, families, genera and species.

Fishes are typically divided into three groups: superclass Agnatha (jawless fishes), class Chondrichthyes (cartilaginous fishes), and superclass Osteichthyes (bony fishes). The latter two groups are included within the infraphylum Gnathostomata, a category containing all jawed vertebrates.

The five kingdoms of classification of animals are:

• Monera.
• Protista.
• Fungi.
• Plantae.
• Animalia.

There are about 28,000 existing species of fish, and they are placed in five classes: hagfish, lampreys, cartilaginous fish, ray-finned bony fish, and lobe-finned bony fish.

As chordates, vertebrates have the same common features: a notochord, a dorsal hollow nerve cord, pharyngeal slits, and a post-anal tail. Vertebrates are further differentiated from chordates by their vertebral column, which forms when their notochord develops into the column of bony vertebrae separated by discs.

*They all have endoskeletons that are formed of bone or cartilage. *They have brains protected by craniums (skulls). *They have closed circulatory systems in which the walls of the heart are continiuous with the blood vessels. Their circulation system contains veins, arteries, and capillaries.

Vertebrates are animals with backbones. They can be classified according to their features, and include bony fish, amphibians, reptiles, birds and mammals.

Humans, birds, mammals, reptiles, amphibians, and fish are all vertebrates. There are seven living classes of vertebrates.

The major groups of vertebrates include fishes, amphibians, reptiles, birds, and mammals.

Animals are divided into two main groups. Animals that have a backbone are called vertebrates. Animals that don’t have a backbone are called invertebrates.

Insects, crustaceans, and many other invertebrates have a hard outer case called an exoskeleton. This protects them against blows and predators, and keeps them from drying out. Slugs, leeches, and jellyfish have soft bodies and no exoskeleton. The pressure of fluids inside their bodies maintains their shape.

five

Terms in this set (8)

• agnatha. -jawless fish. -mouth is modified as a sucker.
• placoderms. -armored fish. -body covered in heavy armor plates.
• chondrichthyes. -cartilage fish. -skeletons made of cartilage.
• osteichthyes. -bony fish.
• amphibians. -smooth skin.
• reptiles. -scaly skin.
• aves. -birds.
• mammals. -have fur or hair.

Sponges, corals, worms, insects, spiders and crabs are all sub-groups of the invertebrate group – they do not have a backbone. Fish, reptiles, birds, amphibians and mammals are different sub-groups of vertebrates – they all have internal skeletons and backbones.

Insects, crustaceans, and many other invertebrates have a hard outer case called an exoskeleton. Slugs, leeches, and jellyfish have soft bodies and no exoskeleton.

Octopuses, jellyfish, sponges, and starfish are a few of the many mollusks that live in or near the water. Some mollusks, such as snails, clams, and oysters, do not have an exoskeleton. Instead, they have a hard outer shell made of calcium that protects them.

The U.S. Marines are about to start receiving real robotic exoskeletons for testing, but these exo-suits aren’t headed into combat any time soon. Despite the TALOS program’s progress in a number of areas, it was ultimately deemed infeasible for combat.

Arthropods