PHYLUM NEMATODA,
ANNELIDA,MOLLUSCA ,
ARTHROPODA
PHYLUM NEMATODA
 Eukaryotic cells,
 Pseudocoelomates, two-opening digestive tract (mouth & anus)
ingest or absorb food
 Outer cuticle which is shed periodically as the animal grows
 Circulation by diffusion
 Respiration by diffusion
 Excretion by diffusion through body walls
PHYLUM NEMATODA
 Response to environment by simple nervous system with ganglia
and several sense organs
 Muscles work with hydrostatic skeleton , move by thrashing
 Sexual reproduction with internal fertilization and parasites may lay
eggs in hosts
 Ecological role: predators, parasites decomposers
PHYLUM ANNELIDA
 Coelomates, protostome, segmentation
 Filter feeders, carnivores and parasites-eat via mouth and
undigested wastes leave the anus
 Closed circulatory system (blood all in vessels) with simple
pumping organ
 Respiration in aquatic with gills-terrestrial through the skin
 Excretion using nephridia, digestive wastes through anus
PHYLUM ANNELIDA
 Nervous system with small brain and several nerve cords
 Some sense organs
 Hydrostatic skeleton –sealed segments with longitudinal and
circular muscles, some have appendages
 Reproduction-sexual in most with external fertilization
 Some are hermaphrodites that exchange sperm
PHYLUM ANNELIDA
 Ecological role: parasites, filter feeders in marine communities,
soil enriching burrowers
 Groups:
 Leeches, Marine worms, Earthworms
PHYLUM MOLLUSCA
 Coelomates, protostomes, bilateral symmetry
 Soft bodies , some with shells secreted by mantle, muscular foot
 Two-opening digestive system
 Can be filter feeders, active predators, parasites, herbivores
 Circulatory system open in most, closed circulatory system in
octopi and squid
PHYLUM MOLLUSCA
 Respiration by gills inside mantle cavity or across moist membrane in
mantle cavity
 Excretion- body cells release ammonia into blood which nephridia
remove and release outside the body
 Response-Diverse nervous systems, very simple in clams but complex
in some octopi
 Movement is diverse also-some do not move as adults while squids
may be fast swimmers
PHYLUM MOLLUSCA
 Sexual reproduction
 Groups:
 Bivalves-clams
 Gastropods-snails and slugs
 Cephalopods-octopus, squid, nautilus, cuttlefish
 Filter feeders, herbivores, carnivores, some venomous
 Slugs can damage garden crops some are intermediate hosts for
parasites
PHYLUM ARTHROPODA
 Share eukaryotic cells with other animals, bilateral symmetry,
coelom
 Presence of an exoskeleton with muscles inside and a segmented
body, protostome development and a coelom
 Heterotrophic, ingest food via mouth, some have specialized
appendages for ripping or tearing food (ex: Crayfish)
 Two-opening digestive system, some have stomach with teeth to
mechanically digest food
PHYLUM ARTHROPODA
 Gastric cecae and digestive glands aid in breakdown of food
 Specialized excretory tubules called Malphighian tubules
and green glands adjust concentrations of fluids
 Waste removed via anus
 Ventral (belly) nerve cord and ganglia in each segment control
movement and response to environment
 Compound eyes see movement in the environment very well
PHYLUM ARTHROPODA
 Also sensory organs like antennae, and others for taste and
balance allow them to escape predators and find prey or plant material
 Crayfish shred detritus and scavenge in rivers, streams
 Reproduce sexually, in some females store sperm and fertilize eggs
 Exoskeleton allows flight, walking and response
 Arthropods occupy many ecological niches and are the single most
numerous and successful group on earth
PHYLUM ARTHROPODA
 Arthropods include ticks which can cause a number of serious
diseases (Lyme disease, Erlichia, Babesia)
 Arthropods are a food source in some parts of the world
 Insects can lower crop yields
 Open circulatory system with a pumping organ with vessels, blood,
called hemolymph, flows into sinuses and movement brings it back to
the heart