Lessons 7–8 · 2 lessons · A. Zikiryayev, A. To‘xtayev, I. Azimov, N. Sonin. Biology. Basics of Cytology and Genetics, Grade 9, revised and expanded 5th edition. “Yangiyul Poligraph Service”, Tashkent, 2019
7
The animal world
Textbook: pp. 25–27
GoalExplain the diversity of the animal world, how animals differ from plants and their importance in nature and human life.
New words
heterotroph · geterotrofinvertebrates · umurtqasizlartaxis · taksiscyst · sista
Explanation
Animals, like plants, have a cellular structure and are similar in chemical composition, metabolism and heredity, which points to a common ancestor. The main difference is in nutrition: most plants are autotrophs while animals are heterotrophs, and an animal cell usually has no cellulose wall or large central vacuole. By number of cells animals are unicellular (amoeba, Paramecium) or multicellular; by skeleton they are invertebrates or vertebrates (phylum Chordata). Unicellular animals move with false feet, flagella or cilia, respond to external influences by movement (taxis) and form a cyst in unfavourable conditions. Animals take part in pollination, seed dispersal, food chains, soil formation (earthworms) and water purification; some spread diseases such as malaria.
Worked examples
An amoeba moves by extending false feet and engulfs food particles; Paramecium swims with its cilia.
Earthworms burrow, improving air and water movement in the soil, and mix plant remains into it, increasing fertility.
Class activity
“Animal or plant?” For a list of 8 organisms (amoeba, cotton, bee, Chlamydomonas, earthworm, moss, frog, Euglena) fill in a table by way of feeding and movement.
Practice
1
State the most important feature that separates animals from plants.
Heterotrophic nutrition (they feed on ready-made organic matter).
2
List the organelles of movement of unicellular animals.
False feet, flagella, cilia.
3
If mosquitoes multiply in warm, humid conditions, why does the risk of malaria rise?
Mosquitoes (Anopheles) spread the causative agent of malaria; more mosquitoes means a higher chance of infection.
4
Why are water molluscs such as mussels called “biofilters”?
They filter water through themselves, trapping particles and microorganisms, and so clean the water.