☰ Contents · Biology (Zoology)

The agile lizard and the scaly order

Lessons 42–43 · 2 lessons · O. Mavlonov. Biology (Zoology), Grade 7. Revised and expanded fourth edition. “O‘zbekiston milliy ensiklopediyasi” State Scientific Publishing House, Tashkent, 2017
43

Diversity of reptiles: order Squamata

Textbook: pp. 132–135
GoalExplain the lizards and snakes of the scaly order, their differences, the venomous snakes of Uzbekistan and safety rules after a snakebite.
New words
gecko · gekkonmonitor lizard · echkemarvenom fangs · zahar tishlariantivenom serum · zardob
Explanation

The scaly order includes lizards and snakes; the body is covered with horny scales. In the deserts of Uzbekistan live the steppe agama, the grey monitor lizard (a large lizard listed in the Red Book) and the legless yellow lizard called sariq ilon, which is a lizard, not a snake. The gecko is active at night in old buildings and hides in cracks by day, eating insects and spiders. Snakes have no legs and move by bending the body in waves and pushing on the ribs. A lizard has movable eyelids, while a snake’s eye is covered by a transparent watch-glass-like layer, so a snake cannot close its eyes. When a snake moults the skin comes off whole like a sock, a lizard’s in pieces. A snake’s jaw bones are joined by stretchy ligaments, so it swallows prey thicker than itself whole. A venomous snake has two venom fangs in the upper jaw and venom glands. The sand boa and water snake are harmless; the boa wraps prey in its coils and squeezes it, and gives birth to live young. The venomous snakes of Uzbekistan are the cobra, the blunt-nosed viper (ko‘lvor), the saw-scaled viper (charx) and the shieldnose (qalqontumshuq). The cobra spreads its neck when threatened, and the saw-scaled viper rubs its scales to rasp. Venomous snakes also help people by eating rodents, and medicines are made from venom. After a snakebite the person lies calmly, the bitten limb is kept still, and 103 is called at once – only a hospital gives antivenom. Never cut the wound, suck it, tie a tight band or pour alcohol on it.

Worked examples
A shed snakeskin is the whole moulted skin: finding it tells you a snake lives nearby, but do not touch it.
The legless yellow lizard has movable eyelids – so it is a lizard. Eyelids tell a lizard from a snake.
Class activity

Poster: “If you meet a snake” – write 5 rules: stop, step back slowly, do not touch, call adults, 103 if bitten. Safety: do not look for snakes, do not put your hand under rocks or bushes, wear shoes and watch where you step; do not kill or catch a snake.

Practice
1
Name 3 features that separate a snake from a lizard.
2
Which four venomous snakes live in Uzbekistan?
3
What should be done after a snakebite?
4
Why can a snake swallow prey thicker than itself?