Invertebrates and Vertebrates

Classes of the phylum Annelida

Polychaeta (sandworms), Hirudinea (leeches) , Oligochaeta (earthworms).

Digestive system of the earthworm

Mouth (intakes nutrients) —> pharynx (ingest food and move along to esophagus) —> esophagus (transports food to crop) —> crop (temporary storage for food) —> gizzard (releases food & breaks up organic matter) —> long intestine (absorption of nutrients) —-> anus (exit for waste).

Respiratory system of earthworms

Diffusion of oxygen and carbon dioxide via moist skin. Secretion of mucus to keep moist.

Circulatory system of earthworms

Closed circulatory system, like humans. Ventral (belly side) & dorsal vessels. Aortic arches link ventral and dorsal vessels. They have 5 aortic arches that act like a heart.

Nerve cord

A solid strand of nerve fibers running along the length of the body, usually on the ventral (belly/front) side. It connects the brain to the body's organs and muscles, forming a central nervous system.

Setae

Small, stiff, bristle-like structures, often composed of chitin, that project from the body surface.

Parapodium

Fleshy protrusions on the outside of the body. Not present in earthworms or leeches.

Ventral

The front-side or belly-side of the animal body.

Dorsal

The back-side of an animal body.

Nephridium

excretory tubules in every segment except the first three segments. Removes waste from the body.

Brain

Fused ganglia. Control system of the worm.

Hermaphrodites

Cannot fertilize themselves.

Clitellum

A thick, saddle-like ring found in the epidermis (skin) of the worm, usually with a light-colored pigment. Helps with mating.

Benefits to the ecosystem of earthworms

Decomposers of leaves and organic matter, recycle nutrients, release natural fertilizers (waste), aerates the soil, and are good for fishing.

Vertebrae

Members of the subphylum Vertebrata within the phylum Chordata.

Endoskeleton

An internal skeleton made of bone or cartilage.

Adaptation for buoyancy

Stored gases or liquids help maintain vertical position in water.

Lateral line

A system of canals in the skin that allow fish to sense vibration in the water.

Streamlined body plan

Allows fish to move rapidly in water.

Jawless fishes

Hagfishes (class Myxini) and Lampreys (class Cephalaspidomorphi).

Hagfishes

Bottom-dwellers that feed on dead and dying fish.

Lampreys

Can be free-living or parasitic. Breed in freshwater. Fertilization occurs outside the body.

Parasitic Lamprey

They attach themselves to their host with disc-shaped mouths and feed on the blood and body fluids of other fishes.

Cartilaginous fishes

Sharks, stingrays, skates, ratfishes. They have skin covered with placoid scales.

Placoid scales

Reduce turbulence and increase swimming efficiency.

Chondrichthyes

Sharks, rays, skates, and ratfishes. They have skeletons made of cartilage.

Chordates

Animals with a notochord, dorsal hollow nerve cord, pharyngeal gill slits, post-anal tail.

Ampullae of Lorenzini

Sense organs that can detect weak electric fields.

Cartilage

A flexible lightweight material made of cells surrounded by tough fibers of protein.

Shark body shape

Torpedo shaped bodies.

Rays body shape

Diamond- or disk-shaped bodies.

Skates body shape

Triangular bodies.

Ratfishes

Small group of strange looking fish that have a flap of skin covering their gill slits. They have long tails and feed on crustaceans and mollusks.

Chemoreception

The ability to detect chemicals in the environment, includes the senses of smell and taste.