☰ Contents · Biology (Zoology)

The lancelet, fish external structure and Lab 4

Lessons 31–33 · 3 lessons · O. Mavlonov. Biology (Zoology), Grade 7. Revised and expanded fourth edition. “O‘zbekiston milliy ensiklopediyasi” State Scientific Publishing House, Tashkent, 2017
33

Lab 4. External structure and movement of fishes

Textbook: p. 105
GoalLearn how to observe a fish’s external structure and movement in the lab.
New words
gill cover · jabra qopqog‘iscale · tangachalateral line · yon chiziqaquarium · akvarium
Explanation

This lab is done under supervision with a live fish (in an aquarium) or a fresh fish prepared for study; fixed specimens are prepared by the teacher and children never touch fixing chemicals. First observe body shape and colour and explain why belly and back colours differ. Feel the mucus on the body, find the scales’ arrangement and the lateral line. Look at the mouth, eyes, nostrils and gill covers; in a live fish watch the mouth and gill covers open and close in turn. Find the fins by name and state their functions. Watch a live fish move; do not tap the glass, so as not to alarm it. Record results in a drawing and table.

Worked examples
Table entry: “Carp: streamlined body; dark back, pale belly; 5 kinds of fins; gill cover moves every 1–2 seconds.” This is an observation result.
A live fish in the aquarium pushes forward with its tail fin, stops with paired fins and keeps balance when turning.
Class activity

Work in groups: one observes, one writes, one draws. Safety: wash hands with soap after handling fish; fish bones are sharp – take care; do not touch fixing solutions; do not hurt a live fish and return it to the aquarium afterwards.

Practice
1
Why is a fish’s colour not the same on back and belly?
2
Where do we find the lateral line?
3
Why is a fish hard to hold?
4
Why should you not tap the aquarium glass?