Osteichthyes Lab

Published: 2021-06-29 06:45:15
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NAME _____________________________

PHYLUM: Chordates
SUBPHYLUM: VERTEBRATA "bone covering nerve cord"

Fishes are the oldest vertebrate group and the most numerous and widespread of all living vertebrates today. 95% of all fish are in the class OSTEICHTHYES meaning "bony fish". All BONY FISH have three characteristics:
1). an endoskeleton made of BONE
2.) lungs or a SWIM BLADDER, and
3.) a body surface covered with SCALES

The skin of the perch is covered with SCALES (thin round discs of bonelike material that grow from pockets in the skin). The scales overlap like roof shingles and point toward the tail to REDUCE FRICTION AS THE FISH SWIMS. Scales grow throughout the fish's life and the resulting growth rings give a good approximation of the fish's age. Scales also PROVIDE PROTECTION.

The fins on a fish are adaptations for swimming and navigation and are supported by RAYS or SPINES which also PROVIDE PROTECTION FROM PREDATORS.

The two DORSAL FINS (one anterior and one posterior) and a ventral ANAL FIN help keep the fish upright and moving in a straight line. The paired PELVIC FINS and PECTORAL FINS are used to stop, move up and down, and even back up. The CAUDAL FIN extends from the tail for propulsion. The ANUS and UROGENITAL OPENING are located near the anal fin.

NERVOUS (Sense organs)
The LATERAL LINE system, which runs along each side of the fish, is a sensory structure which detects water pressure and vibrations in the water. Find the NOSTRILS (dead end pockets) and EYES (with NO EYELIDS).

Fish have a highly developed sense of smell and sight and the parts of the fish's brain that process info from these two areas (OPTIC TECTUM and OLFACTORY LOBES) are the largest parts of a fish's brain.

Pigment cells (CHROMATOPHORES) in the skin give the fish its color and allow it to blend in with its surroundings. Notice the fish has lighter coloration on its ventral surface and is darker on the top so it is less easily seen from above or below.

On each side of the head is the OPERCULUM, a hard plate that covers and protects the GILLS. Water enters through the fish's mouth, passes over the gills, and out through the slits behind the OPERCULUM.

Water moving over the gills flows away from the head, while the blood inside the gills flows toward the head. This arrangement, known as COUNTERCURRENT FLOW, allows more oxygen to diffuse into the gills than would be possible if blood and water both flowed in the same direction.

The GILLS in a fish serve THREE FUNCTIONS:
(oxygen is taken in and carbon dioxide is released),

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