Lessons 1–2 · 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
2
Levels of organisation of life
Textbook: pp. 8–9
GoalName the levels of organisation of life in order and explain the essence of each.
Modern biology divides life into several levels of organisation: molecule, cell, organism, population–species, biogeocenosis and biosphere. At the molecular level macromolecules such as proteins, nucleic acids, lipids and carbohydrates take part; metabolism and the transfer of hereditary information begin here. The cell is the unit of structure, development and function of a living organism. The unit of the organism level is the individual; a multicellular organism consists of tissues and organs. A population is a group of individuals of one species that lives for a long time in the species’ range, interbreeds freely and gives fertile offspring; the first evolutionary changes occur at this level. A biogeocenosis unites organisms with their living environment, and the sum of all biogeocenoses makes up the biosphere, where the cycling of matter takes place.
Worked examples
The fish, plants, water and mud of one lake together are an example of the biogeocenosis level.
A group of birds of one species in the Khorezm oasis that can interbreed is studied at the population level.
Class activity
“The ladder”. Draw a ladder with 6 steps on the board; students place example cards (DNA, a heart muscle cell, a swallow, a juniper forest in the mountains, all life on Earth) on the matching step.
Practice
1
List the levels of organisation of life from smallest to largest.