Explanation

Chondrichthyes (cartilaginous fish, such as sharks and rays) and Osteichthyes (bony fish) differ in several characteristics.

One key difference is the presence of spiracles.

Spiracles are small openings behind the eyes of some cartilaginous fish that allow water to pass over the gills when the mouth is closed.

Bony fish generally do not have spiracles.

Explanation

Luteinizing Hormone (LH) is a glycoprotein hormone.

It is composed of two subunits, alpha and beta, with attached carbohydrate groups.

LH plays a crucial role in regulating the reproductive system, particularly in triggering ovulation in females and stimulating testosterone production in males.

It is not a steroid, peptide, or lipid, but specifically a glycoprotein.

Explanation

Chondrichthyes, which include sharks, rays, and skates, have a high concentration of urea in their blood.

This is due to their method of osmoregulation, which helps them maintain fluid balance in their often saline marine environments.

Explanation

The primary type of lipid present in the plasma membrane is phospholipids.

They form the fundamental structure of the membrane, creating a bilayer that is essential for membrane function and fluidity.

Explanation

Catecholamines are amino acid-derived hormones.

They are synthesized from the amino acid tyrosine and include:

• dopamine
• norepinephrine
• epinephrine hormones.

Explanation

Sea cucumbers belong to the class Holothuroidea within the phylum Echinodermata.

Unlike some other echinoderms like starfish (class Asteroidea), sea cucumbers do not have arms that are sharply set off from a central disc

Explanation

The class Solenogastres (also known as Solengasters) lacks a shell and possesses sclerites, which are small, hard, plate-like structures embedded in the skin.

These organisms are part of the phylum Mollusca, specifically in the class Solenogastres.

Explanation

Ray-finned fishes are present in the class Osteichthyes.

This class is characterized by having a skeleton made of bone and includes the vast majority of fish species.

Explanation

The notochord is a flexible, rod-shaped structure that is present during the embryonic stage of all chordates

It provides support and defines the primitive axis of the body.

This characteristic is a key feature that distinguishes chordates from non-chordates.

Explanation

Kangaroos belong to the infraclass Metatheria, which includes all marsupials.

Metatherians are mammals that give birth to relatively undeveloped young

they are mostly found in Australia and the Americas.