Animal Classification and Characteristics

Comprehensive vocabulary covering animal classification, vertebrate groups, arthropod categories, and physiological traits.

Vertebrates (セキツイ動物)

Animals that possess a backbone or spinal column.

Invertebrates (無セキツイ動物)

Animals that do not possess a backbone or spinal column.

Mammals (哺乳類)

Vertebrates characterized by body hair, breathe through lungs, are viviparous (give birth to live young), and are homeothermic. Examples: humans, lions, dolphins, bats.

Birds (鳥類)

Vertebrates covered in feathers, breathe through lungs, lay eggs with shells on land, and are homeothermic. Examples: sparrows, penguins, ostriches.

Reptiles (爬虫類)

Vertebrates covered in scales, breathe through lungs, lay eggs with shells on land, and are poikilothermic. Examples: crocodiles, snakes, turtles.

Amphibians (両生類)

Vertebrates with moist skin (mucus) that lay shell-less eggs in water; they use gill respiration as larvae and lung/skin respiration as adults. They are poikilothermic. Examples: frogs, newts.

Fish (魚類)

Vertebrates covered in scales that breathe through gills in water, lay shell-less eggs, and are poikilothermic. Examples: tuna, sharks, medaka.

Homeothermic Animals (恒温動物)

Animals that maintain a constant body temperature regardless of the external environment, such as mammals and birds.

Poikilothermic Animals (変温動物)

Animals whose body temperature changes according to the temperature of the external environment, such as reptiles, amphibians, and fish.

Viviparous (胎生)

A mode of reproduction where the mother gives birth to live young or infants.

Oviparous (卵生)

A mode of reproduction where the animal lays eggs.

Mollusks (軟体動物)

A group of invertebrates with soft bodies; representative types include squid, octopus, slugs, and snails, as well as shellfish like clams and scallops.

Commonly Misidentified Invertebrates

Organisms like earthworms and jellyfish that are often mistaken for mollusks but belong to other groups.

Arthropods (節足動物)

Invertebrates with jointed legs and segmented bodies, subdivided into insects, crustaceans, arachnids, and myriapods.

Insects (昆虫類)

Arthropods whose bodies are divided into three parts: head, thorax, and abdomen. They have 3 pairs (6 total) of legs on the thorax. Examples: ants, butterflies.

Crustaceans (甲殻類)

Arthropods with bodies divided into cephalothorax and abdomen, typically possessing 5 pairs of legs. Examples: crayfish, crabs, woodlice.

Arachnids (クモ類)

Arthropods with bodies divided into cephalothorax and abdomen, typically possessing 4 pairs of legs. Examples: spiders, mites, scorpions.

Myriapods (多足類)

Arthropods with bodies divided into head and trunk, with 1 to 2 pairs of legs per body segment. Examples: centipedes, millipedes.

Other Invertebrates

A diverse group including sea urchins, starfish, sea cucumbers, earthworms, leeches, jellyfish, coral, and sea anemones.