In-Depth Notes on Animal Phyla

Phylum Overview of Animals

Platyhelminthes

• Body Symmetry: Bilateral

• Body Cavity: Acoelomate

• Tissue Organization: Triploblastic

• Clade:

  1. Bilateria

  2. Protostomia

  3. Lophotrochozoa

• Class: Turbellaria

  • Characteristics:

  • Habitats: Marine, freshwater, and damp terrestrial environments

  • Feeding: Prey on small or dead organisms; free-living (non-parasitic)

  • Digestion: Gastrovascular cavity with one opening (mouth and anus)

  • Example: Planaria (flatworm)

Echinodermata

• Body Symmetry: Bilateral

• Body Cavity: Coelomate

• Tissue Organization: Triploblastic

• Clade:

  1. Bilateria

  2. Deuterostomia

• Class: Echinoidea

  • Characteristics:

  • Habitat: Marine

  • Shape: Roughly spherical or disc-like, lacks arms

  • Movement: Water vascular system with 5 rows of tube feet

  • Structure: Calcium carbonate outer body

  • Examples: Sea urchins and sand dollars

• Class: Asteroidea

  • Characteristics:

  • Shape: Star-shaped with multiple arms

  • Movement: Water vascular system with tube feet; regenerative ability

  • Structure: Calcium carbonate outer body

  • Example: Sea stars

Nematoda

• Body Symmetry: Bilateral

• Body Cavity: Pseudocoelomate

• Tissue Organization: Triploblastic

• Clade:

  1. Bilateria

  2. Protostomia

  3. Ecdysozoa

• Class: Chromadorea

  • Characteristics:

  • Habitat: Free-living in aquatic and soil environments as well as parasitic

  • Structure: Non-segmented body with separate mouth and anus

  • Reproduction: Sexual with distinct genders

  • Digestive System: Complete

  • Example: Ascaris (roundworm)

Cnidaria

• Body Symmetry: Radial

• Body Cavity: None

• Tissue Organization: Diploblastic

• Clade: Eumetazoa

• Class: Scyphozoa

  • Characteristics:

  • Form: Brief sessile polyp stage; prominent free-swimming medusa stage

  • Body Structure: Bell shape body with tentacles containing cnidocytes for capture and defense

  • Example: Jellyfish

• Class: Anthozoa

  • Characteristics:

  • Form: Only polyp stage, either solitary or colonial

  • Defense: Tentacles armed with cnidocytes

  • Structure: Secretes hard skeleton made of calcium carbonate

  • Examples: Coral, sea anemones

Porifera

• Body Symmetry: Asymmetrical

• Body Cavity: None

• Tissue Organization: No distinct tissue organization

• Clade: Metazoa

• Class: Demospongiae

  • Characteristics:

  • Feeding: Suspension feeders

  • Structure: Adults are sessile with skeletal elements called spicules

  • Reproduction: Hermaphroditic

  • Specialized Cells: Contain choanocytes for feeding

  • Example: Sponges

Arthropoda

• Body Symmetry: Bilateral

• Body Cavity: Coelomate

• Tissue Organization: Triploblastic

• Clade:

  1. Bilateria

  2. Protostomia

  3. Ecdysozoa

• Class: Crustacea

  • Characteristics:

  • Habitat: Marine, freshwater, and terrestrial

  • Structure: Segmented body with 2 or 3 parts

  • Features: Hard exoskeleton, 2 pair of antennae and walking legs

  • Examples: Crabs, lobsters

• Class: Insecta

  • Characteristics:

  • Habitat: Mostly terrestrial

  • Structure: Segmented body with 3 parts and hard exoskeleton

  • Features: 3 pairs of legs and usually 2 pairs of wings

  • Examples: Butterflies, grasshoppers

• Class: Arachnida

  • Characteristics:

  • Habitat: Terrestrial

  • Structure: Segmented body with 2 parts; predators or parasites

  • Features: 6 pairs of appendages, lacks antennae

  • Examples: Spiders, ticks

Chordata

• Body Symmetry: Bilateral

• Body Cavity: Coelomate

• Tissue Organization: Triploblastic

• Clade:

  1. Bilateria

  2. Deuterostomia

• Subphylum: Cephalochordata

  • Characteristics:

  • Habitat: Aquatic

  • Structure: Single hollow nerve cord, notochord for skeletal support

  • Features: Pharyngeal slits for feeding and post-anal tail

  • Example: Lancelets

• Subphylum: Vertebrata

  • Characteristics:

  • Habitat: Aquatic or terrestrial

  • Structure: Notochord replaced by vertebral column during development

  • Features: Distinct head region; pharyngeal slits present during development

  • Examples: Mice, frogs, birds

Mollusca

• Body Symmetry: Bilateral

• Body Cavity: Coelomate

• Tissue Organization: Triploblastic

• Clade:

  1. Bilateria

  2. Protostomia

  3. Lophotrochozoa

• Class: Gastropoda

  • Characteristics:

  • Habitat: Marine, freshwater, or terrestrial

  • Features: Developmental torsion; muscular foot for locomotion; radula present

  • Examples: Snails, slugs

• Class: Bivalvia

  • Characteristics:

  • Habitat: Freshwater and marine

  • Structure: Shell divided into 2 halves, no distinct head

  • Feeding: Suspension feeders with siphons

  • Examples: Clams, oysters

Annelida

• Body Symmetry: Bilateral

• Body Cavity: Coelomate

• Tissue Organization: Triploblastic

• Clade:

  1. Bilateria

  2. Protostomia

  3. Lophotrochozoa

• Class: Hirudinea

  • Characteristics:

  • Habitat: Freshwater, marine, terrestrial

  • Diet: Parasitic, predatory, scavenger

  • Body: Segmented with suckers; hermaphroditic

  • Examples: Leeches

• Class: Polychaeta

  • Characteristics:

  • Habitat: Marine

  • Body: Segmented with parapodia used for movement and respiration

  • Examples: Sandworms

• Class: Oligochaeta

  • Characteristics:

  • Habitat: Freshwater, marine, terrestrial

  • Body: Segmented with sparse chaetae (bristles)

  • Reproduction: Hermaphroditic

  • Examples: Earthworms