Animal Classification: Annelids, Insects, Cephalopods, and More
Animal Classification
Annelids. The segmented worms have bodies divided into repeated segments, aiding movement. They possess a true coelom filled with liquid, located between the body wall and digestive tract. They have a closed circulatory system for distributing gases and nutrients. They have excretory organs called nephridia, functioning like kidneys. They reproduce both asexually and sexually.
Insects are the only flying invertebrates. They have a pair of antennae, three pairs of legs, and a pair of wings. Most have compound eyes with multiple light detectors. Insects undergo metamorphosis, a radical change in form from youth to adult.
Cephalopods include octopuses, nautiluses, cuttlefish, and squids. In these mollusks, the foot has evolved into tentacles used to locate and restrain prey. Their vision rivals that of humans, with a highly developed eye design. They move by jet propulsion and emit purple ink.
Echinoderms have thorns, spines, and ridges that are extensions of an endoskeleton. They exhibit bilateral symmetry only in embryos and larvae, transitioning to radial symmetry as adults. Echinoderms move using tiny tube feet, cylindrical protrusions extending from the underside of the body. They have a water vascular system involved in locomotion, respiration, and food capture.
Animals are multicellular and heterotrophic, obtaining energy by consuming other organisms. Almost all are capable of sexual reproduction. Their cells lack a cell wall. Animals are mobile during some stage of their life.
Reptiles – Their hard, scaly skin prevents water loss and protects the body. They have internal fertilization. They lay amniotic eggs with a shell that can be buried in sand or soil, away from water and predators. The shell prevents the egg from drying out, and the amnion encloses the embryo in an aqueous medium. Reptile lungs are more efficient, reducing the need for skin respiration. The 3-chamber heart has been modified for better separation of oxygenated and deoxygenated blood. The limb skeleton provides better support and increases movement efficiency on land.
Mammals have a 4-chamber heart, increasing oxygen delivery to tissues. Their feet are designed for running, making them fast and agile. Mammals produce milk through mammary glands to nurse their young. The nervous system of mammals has contributed significantly to their successful behavioral adaptation to environmental changes. Their highly developed brain allows for curiosity and ease of learning, enabling them to alter behavior based on experience.