Chordata and Its Classes Overview

Chordata

• Phylum characterized by three embryonic cell layers
• Displays segmented body and bilateral symmetry
• Features a complete digestive system and a closed circulatory system
• Possesses a centralized nervous system
• Key components include notochord, hollow nerve cord, pharyngeal pouches, and endostyle

Mammalia

• Class within Chordata, known as warm-blooded vertebrates
• Endothermic with high metabolic rates
• Distinguished by hair and mammary glands
• Examples include kangaroo, humans, and rabbits

Amphibia

• Class of cold-blooded vertebrates within Chordata
• Four-legged creatures capable of living in both land and water
• Examples include frogs, toads, salamanders, and newts

Reptilia

• Class of cold-blooded vertebrates within Chordata
• Have a multi-cellular structure and can inhabit water or land
• Characterized by scaly skin and a four-chambered heart
• Examples include turtles, crocodiles, rattlesnakes, and iguanas

Aves

• Class of vertebrates within Chordata, covered in waterproof feathers
• Endothermic and known for laying hard-shelled eggs
• Walk on two feet with forelimbs developed into wings
• Examples include ducks, owls, and penguins

Osteichthyes

• Class of cold-blooded vertebrates within Chordata
• Breathe through gills and use fins for swimming
• Composed of a bony skeleton instead of cartilage
• Examples include seahorse, American eel, and trout

Porifera

• Commonly known as sponges, these multicellular organisms are mostly marine
• Body structure is cylindrical, asymmetrical, or exhibits radial symmetry
• Primarily sedentary in nature
• Examples include orange ball sponge and liver sponge

Cnidaria

• Phylum composed of invertebrates with a radially symmetrical body
• Features a sac-like internal cavity and stinging nematocysts
• Reproduction can be asexual or sexual
• Examples include hydras, jellyfish, and corals

Platyhelminthes

• Phylum characterized by spiral cleavage and a complex, incomplete gut
• Hermaphroditic with a lack of skeleton and blood vessels
• Body is flattened on both sides
• Examples include trematodes, cestodes, and turbellarians

Annelida

• Phylum distinguished by segmented bodies
• Lacks lungs and has six major sensory structures
• Possesses ganglia segmented to assist with body control
• Examples include earthworms, leeches, and polychaetes

Mollusca

• Phylum of soft-bodied organisms with a muscular foot
• Often possess a protective shell and exhibit bilateral symmetry
• Have both a mouth and anus with an open circulatory system
• Generally reproduce sexually

Bivalve

• Class within Mollusca featuring laterally compressed bodies enclosed by two hinged shell parts
• Lack eyes and a radula
• Examples include clams, oysters, and mussels

Gastropoda

• Class within Mollusca where most have shells and a well-defined head
• Distinguished by two or more sensory tentacles
• Examples include snails and slugs

Cephalopoda

• Class within Mollusca found in all oceans and only capable of saltwater survival
• Characterized by symmetrical bodies and tentacles
• Known for their ability to squirt ink
• Examples include squid and octopus

Arthropoda

• Phylum with segmented bodies covered by a chitinous exoskeleton
• Exoskeleton provides protection and muscle attachment points
• Features an open circulatory system and a solid ventral nerve cord
• Jointed appendages such as antennae and legs are also present

Insecta

• Class within Arthropoda with a three-segmented body structure: head, thorax, abdomen
• Possesses a pair of antennae, three pairs of legs, and compound eyes
• Examples include cockroaches, beetles, and carpenter ants

Arachnida

• Class within Arthropoda, characterized by cold-blooded creatures with eight legs
• Structure consists of two sections: cephalothorax and abdomen
• Examples include wolf spiders and scorpions

Crustacea

• Class within Arthropoda identified by two or more pairs of antennae
• Features a well-defined head and a shell that may contain calcium carbonate
• Exhibits a segmented body and limbs, with respiration through skin and gills
• Examples include crabs, lobsters, and shrimp