Invertebrate Classification PDF

# L02: Invertebrates Classification ## Cell number - **Multicellular:** made up of many cells that specialized to perform specific functions >- Most invertebrates are multicellular (metazoa) >- Mollusks, crustaceans, annelids - **Unicellular:** made up of a single cell with no membrane-bound orga...

# L02: Invertebrates Classification ## Cell number - **Multicellular:** made up of many cells that specialized to perform specific functions >- Most invertebrates are multicellular (metazoa) >- Mollusks, crustaceans, annelids - **Unicellular:** made up of a single cell with no membrane-bound organelles. >- Many taxa invertebrates are unicellular (Choanozoa) >- Protists (Phylum Protista) ## Body Symmetry - **Bilateral:** Right and left sides are mirror images of each other - Example: Crustaceans, Annelids. - **Radial:** Body parts are arranged around a central axis. - Example: Cnidaria (Jellyfish, corals, starfish) - **Asymmetrical:** No symmetry; organism's body does not exhibit any form of symmetry. - Example: Portifera (Sponges) ## General Characteristics 1. **Development pattern:** - Type of germ layer: - No germ layer - Diploblastic: only has two distinct layers (ectoderm and endoderm) - Triploblastic: has three distinct layers (ectoderm, mesoderm, and endoderm) - Development: - Direct development (no larval stage) - Indirect development (larval stage) 2. **Mouth formation:** - **Protostomes:** - Coelom formation occurs by enlargement of split mesoderm (schizocoely) - Examples: Mollusks, Annelids - **Deuterostomes:** - The coelom forms enterocoely - Mesoderm forms as punches that pinch off the archenteron (the early gut), forming a coelomic activity. - Examples: Echinoderms, Cephalochordates. 3. **Body Cavity Type** - **Acoelomate:** Triploblastic lacking an internal body cavity - Example: Flatworms (Phylum Platyhelminthes) - **Pseudocoelomate:** Region between body wall. - Examples: Roundworms (Phylum Nematoda) - **Coelomate:** A true coelom - an internal, fluid-filled body cavity lying between the gut and outer body wall. - Examples: Mollusks, Arthropods 4. **Habitat** - **Terrestrial animals:** On land - **Marine animals:** Ocean - **Intertidal:** (between the high and low tide marks) Exposed to air periodically - Examples: Barnacles, crabs - **Subtidal:** (below the low tide line) - Examples: Lobsters, Sea anemones - **Open ocean:** (vast ocean) - Example: Jellyfish, sharks, whales 5. **Lifestyle:** - **Mobile:** Move - **Sessile:** Stay in one place - **Sedentary:** Move but don't travel far 6. **Evolutionary relationship** - Taxon: Any named group of organisms that is distinct enough to be classified together. - Example: All members of a particular phylum, considered to have evolved from a single ancestral form - Species Gene pool: - Species: A group of organisms that can interbreed and produce offspring. - Share a special ‘gene pool’ - have the same genetic materials. - This gene pool differs from other species’ gene pools ## Binomial Nomenclature - Scientific name of a specie (2 parts) - **Generic name:** Begins with a capital letter - **Specific name:** ## Aquatic Animals - **Planktonic:** Forced to drift/wander - **Benthic:** Live on/in the ocean floor - **Macrobenthic:** larger organisms live on the ocean floor - **Meiobenthic:** smaller organisms live within sediments ## Feeding - **Herbivores:** Eat plants - **Carnivores:** Eat other animals - **Suspension feeders:** Filter small particles from surrounding medium - **Deposit feeders:** Digest organic components as sediments move through the digestive tract ## Symbiotic Relationship - **Ectosymbionts:** Live on the surface of their hosts. - Example: Cleaner fish live with larger fish and eat parasites. - **Endosymbionts:** Live inside their host's body. - Example: Bacteria in the human gut help with digestion - **Mutualism:** Benefit both participants. - Example: Bees and flowers - **Commensalism:** One organism benefits, other not affected. - Example: Barnacles on whales. - **Parasitism:** One benefits, other is harmed. - Example: Ticks on mammals.