Invertebrates and Phylum Cnidaria

Invertebrates

• Animals lack a backbone
• Approximately 95% of known animal species are invertebrates.

Invertebrate Phylogeny

• An ancestral protist is the common ancestor of all animals.
• Parazoa and Eumetazoa are branches of the phylogenetic tree.

Phylum Porifera

• Classified as Parazoa
• Sponges have an asymmetrical body plan.
• Sponges lack true tissues.
• They are suspension feeders.
• Sponges are sessile
• Fresh and marine waters are the habitats
• Water moves in through porocytes and out through the osculum for feeding
• They collect food particles in the water
• Choanocytes are collar cells
• Amoebocytes transport nutrients, make spicules, and can become any type of cell needed.
• Spicules are skeletal fibers.
• Most sponges are capable of hermaphroditism.
• Can reproduce sexually by releasing gametes
• and asexually by budding

Phylum Cnidaria

• Cnidae are stinging cells (nematocysts)
• exhibit radial symmetry
• Have two tissue layers called diploblastic which includes the endoderm and ectoderm
• No true muscles, but contractile fibers are present
• They possess a nerve net but no brain
• Habitats include freshwater and marine environments.
• Includes jellies, anemones, corals, hydras organisms.
• Cnidarians have Medusa and Polyp body plans
• Cnidarians preform both Asexual and Sexual Lifecycle
• All cnidarians have cnidocytes on their tentacles.
• Cnidocytes are unique cells that function in defense and capturing prey.

Lophotrochozoans

• Characterized by bilateral symmetry
• Characterized by a triploblastic.

Phylum Platyhelminthes

• Characterized as flatworms
• Have an acoelomate body plan
• Considered a protostome
• They have muscle and nervous systems present.
• Present are digestive and excretory systems
• protonephridia (flame bulbs) is for osmotic balance
• Have no respiratory or circulatory system.
• Flatworms are divided into two lineages: Catenulida and Rhabditophora.
• Catenulida ("chain worms") reproduce asexually via budding
• Rhabditophora is more diverse, including both free-living and parasitic species.
• Turbellarians are nearly all free-living, mostly marine flatworms.
• Parasitic flatworms are within the rhabditophorans group like trematodes (flukes) and tapeworms.
• Tapeworms includes scolex and proglottids (contain the sex organs)

Phylum Rotifera

• Characterized as pseudocoelomate
• Considered a protostome
• Habitats: freshwater, marine, damp soils, and mosses
• Type of gut is an alimentary canal
• They are smaller than many protists.
• Are multicellular and have specialized organ systems.
• Crown of cilia draws water into the mouth.
• Contain "jaws" that grind food and help eat microorganisms

Phylum Mollusca

• Coelomate and protostome
• Possess an open circulatory system with a hemocoel
• Foot: muscle used for movement
• Visceral Mass: contains internal organs
• Mantle: fold of tissue that secretes shell (if present) and may form a cavity
• Radula: strap-like organ for feeding.
• Has a complete digestive system.
• Habitats: marine, freshwater & terrestrial
• Shell is commonly present as protection
• Most are separate sexes, although some snails are hermaphroditic

Phylum Mollusca - Class Polyplacophora

• Includes Chitons
• Habitat: marine only
• Graze algae using a radula
• Have 8 dorsal plates made of calcium carbonate.

Phylum Mollusca - Class Gastropoda

• Includes snails, slugs, and limpets
• Found in marine, freshwater, and terrestrial habitats.
• Torsion involves the anus being above their head
• Spiraled shell provides center of gravity back to middle of body
• Consists of Concentration of sensory organs at head region

Phylum Mollusca - Class Bivalvia

• Consists of clams, oysters, mussels, and scallops
• Found in marine and freshwater habitats
• They possess two shells with valves.
• Feeding method: suspension feeders
• Bivalvia have no radula or head

Phylum Mollusca - Class Cephalopoda

• Includes squid, octopus, cuttlefish, and nautilus
• Their ancestors were shelled ammonites, which were dominant invertebrate predators for millions of years until mass extinction at the end of the Cretaceous period
• They Method of feeding as predators
• Have beaklike jaws
• their Shell is reduced and internal or entirely missing
• Type of circulatory system: closed
• Blood remains separate from fluid in body cavity
• Possess a Highly developed nervous system with brain allowing them to be Very intelligent

Phylum Annelida

• Known as Segmented Worms ("little rings")
• Consists of Worms, leeches, and marine worms
• Body plan made of repeating segments
• Annelida are Coelomate and protostomes
• Habitats: freshwater, marine, and terrestrial
• Classified as a closed Circulatory system
• Types of organ systems: digestive, nervous, and circulatory
• Have a Ventral nerve cord and capable of being Hermaphroditic but they cross fertilize
• Examples include Class Hirudinea, Class Oligochaeta Class Polychaeta

Ecdysozoans

• Characterized by Bilateral Symmetry and Triploblastic

Phylum Nematoda

• Roundworms
• The body plan is pseudocoelomate and protostome
• Habitats: freshwater, terrestrial (soil), parasites
• Consists of an alimentary canal and no circulatory system, instead using pseudocoel fluids
• Possesses Separate sexes

Phylum Arthropoda

• Body plan of coelomate and protostomes
• Composed of segmented, exoskeleton, and jointed appendages
• Open circulatory system with hemolymph
• Contains well developed sensory systems and Two out of every three known species of animals are arthropods
• Consists of exoskeletons that Provide protection, barrier against desiccation, act as defense mechanism, and provide attachment for muscles BUT, are more difficult to regulate body temperatures and limits size of the organism
• This cuticle has layers of protein and chitin making it thick and hard in some parts, and thin and flexible in others

Phylum Arthropoda - Subphylum Chelicerata

• Contains scorpions, spiders, mites, ticks, and horseshoe crabs
• They have a respiratory system: book lungs
• Consists ofFour pairs of walking legs
• Chelicerae are responsible for feeding (fangs) and pedipalps are responsible for sensing or feeding

Phylum Arthropoda - Subphylum Myriapoda

• They contain 1 pair of antennae and 3 pairs of appendages for modified mouthparts
• millipedes are the body plan has 2 pairs of legs per segment, are herbivorous, distinct head with antennae and chewing mouthparts, and are terrestrial
• centipedes are the body plan has 1 pair of walking legs per segment, distinct head with mouthparts, poison claws on first segment, and are terrestrial and carnivorous

Phylum Arthropoda - Subphylum Hexapoda

• Contains Lice, beetles, flies, termites, butterflies, dragonflies
• Body is divided into the head, thorax, and abdomen
• Antennae are used for sensing and mouthparts are modified for chewing, sucking, or lapping
• They have 1-2 pairs of wings and 3 pairs of legs
• Their respiratory system has tracheal tubes that open to the outside of the body and deliver oxygen to tissues
• Consists of an Excretory system with Malpighian tubules.

Phylum Arthropoda – Reasons for Diversity

• Adaptability via Their (large populations, high reproductive potential, short life spans)
• Flight

Phylum Arthropoda - Subphylum Crustacea

• A group that includes crabs, lobsters, crayfish, shrimp, and crustaceans
• They are characteristically have Branched appendages and Appendages on abdomen, thorax and head
• Possess Chewing mouthparts and Habitats in marine, freshwater, and terrestrial biomes
• Most segments have a pair of appendages modified for movement, reproduction, sexual display, defense, prey capture, chewing, and sensing environment

Deuterostomes

• Consists of Bilateral Symmetry and Triploblastic

Phylum Echinodermata

• The characteristic "spiny skinned" organism
• Include Sea stars, sea urchins, sand dollars, and sea cucumbers
• Habitat – exclusively marine
• Grouped with Chordata primarily for it's characteristics of Coelomates and deuterostomes
• “Radial” symmetry as adults with bilateral larvae
• Exhibit a Type of skeleton as an endoskeleton composed of calcareous plates which makes the water vascular system aid in locomotion, feeding, and gas exchange
• Examples include Sea stars from the class Asteroidea and Brittle stars from the class Ophiuroidea

Phylum Chordata

• Two subphyla of invertebrates include hagfishes and the vertebrates
• Shares many features of embryonic development with echinoderms