The structure of living organisms
The cell is the structural unit of all living organisms. Bacteria, amoeba, paramecium, chlorella and yeast are single-celled; plants and animals are multicellular. Plant, fungus and animal cells consist of a cell envelope, cytoplasm and a nucleus. A plant cell also has a vacuole and chloroplasts (photosynthesis happens in chloroplasts). In a multicellular organism cells of the same structure and function form a tissue; tissues make an organ and organs make an organ system: cell → tissue → organ → organ system → organism. Plant tissues: protective, conducting, mechanical, storage, basic and forming tissue. In humans and animals: epithelial, muscle, connective and nervous tissue. Features of living things: cellular structure, metabolism, nutrition, respiration, growth, development, response to stimuli and reproduction.
Observation: place a thin skin of onion on a slide and view it under a microscope (prepared by the teacher; a drop of diluted iodine solution may be added). Find the cell envelope and the nucleus and draw them. Without a microscope make a cell model from a clear zip-bag and plasticine: bag – envelope, jelly/water – cytoplasm, plasticine ball – nucleus. Safety: handle slides and cover glasses carefully, keep iodine away from mouths, and wash hands afterwards.