The science of biology. Properties and levels of life
Lessons 1–2 · 2 lessons · A. G‘afurov, A. Abdukarimov, J. Tolipova, O. Ishankulov, M. Umaraliyeva, I. Abdurahmonova. Biology, Grade 10, 1st edition. “Sharq” publishing and printing joint-stock company, Tashkent, 2017
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The essence of life and the properties of living things
Textbook: pp. 7–11
GoalList the essence of life, its basic properties and its levels of organisation, and tell them apart from non-living nature.
Living organisms are built mainly of biopolymers – proteins and nucleic acids – and are open, self-regulating systems that exchange matter and energy with their surroundings. The properties of life are: unity of chemical composition (C, O, H and N are the main elements), cellular structure, metabolism and energy exchange, self-renewal, reproduction, growth and development, homeostasis, irritability, and heredity and variation. Individual development is called ontogenesis, and the historical development of species is phylogenesis (evolution). Some features may occur in non-living nature (a crystal grows in a salt solution, a candle burns and releases energy), but there is no homeostasis and no self-reproduction through hereditary information. The levels of organisation of life are: molecule, cell, tissue, organ, organism, population-species, biogeocenosis (ecosystem) and biosphere; each higher level is formed by the combination of the lower one.
Worked examples
A crystal in a salt solution gets bigger, but it does not copy its structure using hereditary information and does not regulate its internal conditions, so it is non-living.
A spruce forest is an example of the biogeocenosis level, one spruce in it belongs to the organism level, and a cell in one of its needles (together with its chloroplasts) belongs to the cell level.
Class activity
“Staircase of levels”. The class forms 8 groups; each takes one level, chooses an example for it and one process occurring at that level, and presents in staircase order.
What is homeostasis? Give one example from the human body.
The ability of an organism to keep its internal conditions and processes constant when external conditions change. Example: keeping body temperature at about 36.6 °C.
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Assign a level: a saxaul thicket near the Aral Sea; a mitochondrion; a heart; one tortoise in the Kyzylkum.
Biogeocenosis (ecosystem); cell level (a mitochondrion is a component of the cell, an organelle); organ; organism.
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Why is a burning fire not alive, even though it releases energy, “grows” and “consumes” oxygen?
Fire has no cell structure, no hereditary information, no homeostasis and no self-renewal; it is only a chemical oxidation reaction. To be called living, something must have all the properties of life together.