Lessons 1–2 · 2 lessons · O. Mavlonov. Biology (Zoology), Grade 7. Revised and expanded fourth edition. “O‘zbekiston milliy ensiklopediyasi” State Scientific Publishing House, Tashkent, 2017
2
Structure of the animal body; classification of animals
Textbook: pp. 7–10
GoalExplain the animal cell, tissues, organ systems and the units of classification.
New words
tissue · to‘qimaorgan system · organlar sistemasispecies, the smallest unit of classification · turphylum, the largest group in the animal kingdom · tip
Explanation
An animal body, like a plant, is made of cells with a membrane, cytoplasm, organelles and a nucleus. Animal cells have neither green chloroplasts nor the stiff cell wall that plant cells have, so animals cannot photosynthesise and feed on ready-made organic matter. Cells of similar structure and function form a tissue; there are four main tissues: epithelial, connective, muscle and nervous. Several tissues form an organ, and organs with a similar job form an organ system (for example the digestive system). In classification the smallest unit is the species; close species join into a genus, genera into a family, families into an order, orders into a class and classes into a phylum. By body temperature animals are cold-blooded (temperature depends on the surroundings) or warm-blooded (constant temperature; birds and mammals), and a species’ scientific name has two Latin words.
Worked examples
The wall of the intestine has epithelial, connective, muscle and nervous tissue; together they form the intestine, an organ, and the intestine with the mouth, gullet and stomach forms the digestive system.
The domestic cat: species – domestic cat, then genus, family, order (carnivores), class (mammals) and phylum (chordates). The cat is warm-blooded, a fish is cold-blooded.
Class activity
Draw a classification ladder on the board: from bottom to top species – genus – family – order – class – phylum. Write an animal example for each step. Use pictures or posters only, without handling live animals.
Practice
1
Name one similarity and one difference between animal and plant cells.
Similarity: both have a membrane, cytoplasm and a nucleus. Difference: an animal cell has no chloroplasts.
2
List the four main tissues and write the function of nervous tissue.