Animal Diversity Notes: Classification, Body Plans, Phyla & Key Terms

Animal Diversity Notes
1. Introduction to Animal Diversity
 Kingdom Animalia includes all multicellular, eukaryotic, heterotrophic organisms
that lack cell walls and depend on others for food.
 Animals show various levels of organization: cellular, tissue, organ, and organ
system level.
 They can reproduce sexually or asexually. Some animals can regenerate lost
parts.
 Many animals are motile (able to move); others are sessile (fixed in one place).
2. Key Terms in Animal Classification
Habitat
 Terrestrial: Live on land
 Freshwater: Live in freshwater bodies like rivers and lakes
 Marine: Live in the ocean
 Extreme Environment: Live in environments with extreme conditions like hot
springs or deep sea vents
Locomotion
 Motile: Capable of movement
 Sessile: Fixed, immobile
 Sedentary: Limited movement or mostly stationary
Location of Structure
 Dorsal: Back side
 Ventral: Belly side
 Anterior: Head or front end
 Posterior: Tail or rear end
Feeding Methods

 Filter Feeding: Filtering out food particles from water
 Deposit Feeding: Eating organic material in sediments
 Predation: Hunting and eating other animals
 Parasitism: Feeding on a host organism causing it harm
 Herbivory: Eating plants
Reproduction
 Sexual: Involving the fusion of male and female gametes
 Asexual: Without fusion of gametes (e.g. budding, regeneration)
 Hermaphroditism: Organism has both male and female reproductive organs
Cephalization
 Concentration of sensory organs and brain in the anterior (head) region.
 Develops along with directional movement (ability to move in a specific direction).
3. Animal Body Plans and Features
Body Symmetry
1. Bilateral Symmetry: Body divided into mirror left and right halves. Most animals
have this.
2. Radial Symmetry: Body parts arranged around a central axis (e.g. jellyfish).
3. Asymmetry: No symmetry (e.g. sponges).
Segmentation
 Division of body into repeated sections, important in annelids and arthropods.
Tissue Layers
 Animals are triploblastic (3 tissue layers): ectoderm, mesoderm, endoderm,
allowing formation of organs.
Number of Gut Openings
 Some animals have one opening (mouth and anus same - incomplete digestive
system).

 Others have two openings (mouth and anus separate - complete digestive
system).
Protostomes vs Deuterostomes
 Protostomes: Blastopore develops into mouth first. Exhibit spiral, determinate
cleavage. Have solid ventral nerve cord. Examples: Annelida, Arthropoda,
Mollusca.
 Deuterostomes: Blastopore develops into anus first. Exhibit radial, indeterminate
cleavage. Have hollow dorsal nerve cord. Examples: Echinodermata,
Hemichordata, Chordata.
Body Cavity (Coelom)
 Animals may have no body cavity, a false cavity (pseudocoelom), or a true
coelom (fluid-filled cavity lined with mesoderm).
Circulatory Systems
 Open circulatory system: Blood is pumped into body cavities (e.g. Arthropods,
Mollusks).
 Closed circulatory system: Blood flows through blood vessels only (e.g. Annelids,
Chordates).
4. Animal Phyla Overview
Phylum
Key Features
Examples
Porifera
Pores on body, porous skeleton, no
true organs, sessile
Sponges (Spongilla,
Sycon)
Cnidaria
Radial symmetry, two tissue layers,
stinging cells
Jellyfish, Hydra
Platyhelminthes
Flat, triploblastic, bilateral
symmetry, no coelom
Flatworms (Planaria,
Tapeworm)

Phylum
Key Features
Examples
Nematoda
Cylindrical, bilateral,
pseudocoelom, many parasitic
Roundworms (Ascaris,
Wuchereria)
Annelida
Segmented body, true coelom,
bilateral symmetry
Earthworms, Leeches
Arthropoda
Segmented, exoskeleton, jointed
limbs, open circulatory
Insects, Spiders,
Crustaceans
Mollusca
Soft-bodied, bilateral, open
circulatory system
Snails, Octopus
Echinodermata
Radial symmetry, spiny skin,
marine, true coelom
Starfish, Sea urchins
Hemichordata
Worm-like, soft body, open
circulation, marine
Acorn worms
Chordata
Bilateral, notochord, dorsal hollow
nerve cord, closed circulation
Vertebrates (fish,
mammals)
5. Additional Concepts
Protozoa
 Unicellular eukaryotes with animal-like behavior: motility and predation. Use
osmotrophy or phagocytosis.
Bryozoans
 Colonial filter feeders with zooids as individual units; mostly aquatic.
6. Tube-within-Tube Body Plan

 Most animals have a digestive tract with two openings: mouth and anus. This
arrangement is called the tube-within-tube body plan.
Summary Tips for Test
 Know phylum names, characteristics, and examples.
 Understand key body plan characteristics (symmetry, segmentation, tissue
layers).
 Be able to differentiate protostomes and deuterostomes based on developmental
features.
 Know open vs closed circulatory systems.
 Be able to define key terms such as cephalization, feeding methods, locomotion
types, and reproduction methods.