How To Study Living Animals


THE LIVING FISH

Vertebrates adapted to Water Life

Materials.

Living goldfishes or other fishes in small aquaria for individual study and a few fishes in a large aquarium where they have considerable freedom of motion.

Definitions.

Trunk,

the portion of the body between the head and the tail.

Compressed,

a term used to describe the shape of the body when it is narrower from side to side than from dorsal to ventral surface herunterladen. When the opposite is true, the body is said to be flattened.

Median fins,

the unpaired fins situated on the median line, dorsal and ventral, including the tail or caudal fin, the dorsal fin, and the anal fin.

Paired fins,

fins occurring in pairs of which the more anterior are the pectoral fins and the posterior are the pelvic fins herunterladen.

Fin rays,

the framework or skeleton of the fins over which membrane is stretched to form the fins. Fin rays are of two kinds: those composed of bone and those composed of cartilage.

Lateral line,

a sense organ extending along each side of the fish in a line indicated by tubes or perforations in the scales microsoft office kostenlos downloaden vollversion deutsch chip.

Gills,

respiratory organs adapted for taking oxygen from the water.

Operculum,

the flaps covering the gills on each side of the head.

Pigment,

a substance which gives color to an object.

Observations.

Locomotion.

1. Watch the fishes in the large aquarium and determine which fins are most used and how they are used (a) in swimming forward, (b) in swimming upward and downward, (c) in maintaining balance, (d) in remaining at rest, and (e) in guiding the movements of the fish.

2. What advantages are there to the fish (a) in the power to open and close the dorsal and anal fins, (b) in having no neck, and (c) in having a compressed form?

3. Enumerate the various ways by which the body of the fish is adapted to rapid movement through the water.

Feeding.

1. What is the food of the fishes you are studying? Feed them and watch them eat. Why is the upper jaw often called a “lip”? What is the shape and size of the mouth when opened in feeding? Does the fish chew its food? Describe in detail the fishes’ method of feeding.

Respiration.

1. Identify the opercula and the gill openings. Watch the movements of the opercula and mouth, and determine what movements are concerned in breathing and their order. Describe in detail the circulation of water used in breathing and how it is caused.

Sense Organs.

1. Identify the eyes, nostrils, and lateral line. How many nostrils are there and where located? What is the position and extent of the lateral line?

2. Describe the location of the eyes. What is the shape of the outer surface of the eyes? Why this shape? Can the eyes be moved,i.e. can they be rotated, rolled, or retracted? From what direction might an enemy approach without being seen? How would such an enemy be detected?

Protection.

1. With what protective structures is the body covered? Do they hinder the movements of the fish? What are the advantages of the scale covering of fishes over the shell covering of grasshoppers or crayfishes?

2. In what other ways are the fishes you are studying protected against enemies? Since you cannot account for the red color of goldfishes on the basis of use to the fish, then how do you account for this bright color?

The Body.

1. What is the symmetry of the fish? Into what regions is the body divided?

Summary of the study of the living fish.

Enumerate in one column the different adaptations which fit the fish for life in water and in a second column state the special purpose of each adaption.