Classification of Animals in the Animal Kingdom

Animal Kingdom

Classification of Animals

Animals are classified based on:
- Body structure
- Level of organization
- Mode of reproduction
- Habitat

Major Phyla in Animal Kingdom

Porifera
- Simple body structure (sponges)
- Asymmetrical, no true tissues
- Aquatic, mostly marine
Cnidaria
- Radially symmetrical (jellyfish, corals)
- Possess stinging cells (cnidocytes)
- Two body forms: polyp and medusa
Platyhelminthes
- Bilateral symmetry (flatworms)
- Acoelomates (no body cavity)
- Can be free-living or parasitic
Nematoda
- Roundworms, bilateral symmetry
- Pseudocoelomates (body cavity present but not entirely lined by mesoderm)
- Diverse habitats, many are parasitic
Annelida
- Segmented worms (earthworms, leeches)
- True coelomates (body cavity fully lined by mesoderm)
- Have a segmented body plan
Arthropoda
- Largest phylum (insects, arachnids, crustaceans)
- Exoskeleton made of chitin
- Jointed limbs and segmented bodies
Mollusca
- Soft-bodied animals (snails, octopuses)
- Usually have a hard shell
- Body divided into head, foot, and visceral mass
Echinodermata
- Marine animals (starfish, sea urchins)
- Radial symmetry in adults, bilateral in larvae
- Endoskeleton made of calcified plates
Chordata
- Animals with a notochord (vertebrates and some invertebrates)
- Key features: dorsal nerve cord, pharyngeal slits, post-anal tail
- Divided into subphyla: Urochordata, Cephalochordata, Vertebrata

Characteristics of Chordates

Subphyla:
1. Urochordata: Tunicates, marine, filter feeders.
2. Cephalochordata: Lancelets, small, aquatic, filter feeders.
3. Vertebrata: Animals with a backbone, includes fish, amphibians, reptiles, birds, mammals.

Invertebrate vs. Vertebrate

Invertebrates: Animals without a backbone (e.g., sponges, cnidarians, arthropods).
Vertebrates: Animals with a backbone (e.g., fish, birds, mammals).

Key Concepts

Animals are categorized into invertebrates and vertebrates.
The classification reflects evolutionary relationships.
Habitat and mode of reproduction influence animal diversity and adaptation.
The Animal Kingdom exhibits a wide range of structures and functions adapted to various environments.

Classification of Animals

Animals are grouped based on body structure, organization level, reproductive mode, and habitat.

Major Phyla in Animal Kingdom

Porifera
- Comprises sponges; characterized by a simple body structure.
- Lacks true tissues and exhibits asymmetry.
- Predominantly aquatic, mostly in marine environments.
Cnidaria
- Includes jellyfish and corals; exhibits radial symmetry.
- Features specialized stinging cells known as cnidocytes.
- Comes in two forms: polyp (sessile) and medusa (free-floating).
Platyhelminthes
- Known as flatworms; has bilateral symmetry.
- Lacks a body cavity (acoelomate).
- Can be found as free-living organisms or parasites.
Nematoda
- Roundworms featuring bilateral symmetry.
- Classified as pseudocoelomates with a body cavity not completely lined by mesoderm.
- Occupies a variety of habitats, with many species being parasitic.
Annelida
- Comprised of segmented worms like earthworms and leeches.
- True coelomates with a body cavity that is entirely lined by mesoderm.
- Features a distinct segmented body plan.
Arthropoda
- The largest phylum, including insects, arachnids, and crustaceans.
- Possesses an exoskeleton made from chitin.
- Characterized by jointed limbs and segmented bodies.
Mollusca
- Soft-bodied animals such as snails and octopuses; often have a hard shell.
- Body structure is divided into three parts: head, foot, and visceral mass.
Echinodermata
- Marine organisms such as starfish and sea urchins.
- Exhibit radial symmetry as adults and bilateral symmetry as larvae.
- Possess an endoskeleton formed of calcified plates.
Chordata
- Defined by the presence of a notochord; includes vertebrates and some invertebrates.
- Key traits include a dorsal nerve cord, pharyngeal slits, and a post-anal tail.
- Divided into subphyla: Urochordata (tunicates), Cephalochordata (lancelets), and Vertebrata (animals with backbones).

Characteristics of Chordates

Urochordata: Tunicates, marine creatures known for filter feeding.
Cephalochordata: Lancelets, small aquatic organisms also filter feeders.
Vertebrata: Backbone-containing animals, encompassing fish, amphibians, reptiles, birds, and mammals.

Invertebrate vs. Vertebrate

Invertebrates are animals lacking a backbone, including sponges, cnidarians, and arthropods.
Vertebrates possess a backbone, represented by species such as fish, birds, and mammals.

Key Concepts

Animals are categorized into invertebrates and vertebrates, highlighting evolutionary relationships.
Identification and classification are influenced by habitat preference and reproductive strategies.
The Animal Kingdom is diverse in structure and function, with adaptations suited to a range of environments.