The most conspicuous part of any abalone is the shell, with its row of respiratory pores. Shells are prized because of their inner, iridescent layer. The muscular foot has a strong suction power permitting the abalone to clamp tightly to rocky surfaces. A column of shell muscle attaches the body to its shell. The mantle circles the foot as does the epipodium, a sensory structure and extension of the foot which bears tentacles. The epipodium projects beyond the shell edge in the living animal. The epipodium surface may be smooth or pebbly in appearance and its edge may be frilly or scalloped. It is the most reliable structure for identifying abalone species.

The internal organs are arranged around the foot and under the shell. The most conspicuous organ, the crescent-shaped gonad, is gray or green in females and cream colored in males. It extends around the sides opposite the pores and to the rear of the abalone. The abalone head has a pair of eyes, a mouth and an enlarged pair of tentacles. Inside the mouth is a long file-like tongue called the radula, which scrapes algal matter to a size that can be ingested.

After the abalone ingests its food, the gastrodermis secretes digestive enzymes into the gastrovascular cavity. The gastrodermal cells engulf small pieces of the partially digested food by phagocytosis and digestion is completed within the cells in food vacuoles. Flagella on the gastrodermal cells keep the contents of the gastrovascular cavity agitated and help distribute nutrients.

The gill chamber is next to the mouth and under the respiratory pores. It obtains oxygen by extracting the dissolved oxygen from the water. The nitrogen and phosphorous come from the food sources they eat. Water is drawn in under the edge of the shell, and then flows over the gills and out the pores. Waste and reproductive products are carried out in this flow of water. This includes carbon dioxide and nitrogenous wastes. It secretes ammonia (NH₄^- ) and the mode of this nitrogen excretion is called ammonotelism.

Since it has no obvious brain structure, the abalone is considered to be a primitive animal. However, it does have a heart on its left side and blood flows through the arteries,sinuses and veins, assisted by the surrounding tissues and muscles.

Lagenorhynchus obscurus

As a mammal, the dolphin is thought to have evolved from a four-legged terrestrial animal. It has adapted to a swimming, diving way of life. Some of their adaptations are their perfectly streamlined, torpedo-shaped body for rapid swimming and ease of movement through water. A flatter, muscular tail provides for a powerful means of propulsion. The forelimbs have a skeletal structure similar to that of human arm but they have been modified to form paddle-like flippers which are used for steering. They have totally shed their hind limbs. Their adaptation is so perfect, however, that they still are often mistakenly referred to as "fish", and many people have difficulty believing that the dolphin racing through the waves are descended from four-legged animals that once — more than 200 million years ago — dwelt on land.

Because they are mammals, they breathe air direct, instead of extracting oxygen dissolved in water as fishes do. They must therefore return to the surface at regular intervals to take air and when they dive they must hold their breath. They have a high tolerance to carbon dioxide, to help with lengthy dives, and are two to three times more efficient than land mammals at using the oxygen in inhaled air; their rib cages are collapsible for deep diving. As it returns to the surface, the lungs gradually expand again, its blowhole opens wide and the foul air accumulated during the dive, to include carbon dioxide, is expelled explosively.

Dusky dolphins have about 24-36 pairs of small pointed teeth which they use to grab hold of their prey. They eat a wide variety of fish but they prefer anchovies and squid. A strong sphincter muscle in the throat enables dolphins to swallow their food without ingesting too much seawater. Rather than drink saltwater, they acquire fluids from the fish they eat. The fats and proteins metabolized from their food seem to keep dolphins sufficiently hydrated.

The dolphin has a three-chambered stomach — a forestomach which stores the food, a primary stomach where food is broken down, and a pyloric stomach where food is dissolved into nutrients the body can absorb. Further absorption takes place in the small intestines. Any material that cannot be absorbed as nutrient passes through the large intestine and out through the rectum.

To rid the body of any excess salt, dolphins rely on their relatively large kidneys. These are divided into numerous lobules (reniculi), which considerably increase the surface area needed for elimination. Dolphin urine normally has a high salt content. They eliminate nitrogenous waste by excreting urea and the mode of their nitrogen excretion is called ureotilism.