The Invisible Living World: Beyond Our Naked Eye

About this chapter

The Invisible Living World is the second chapter of Class 8 Curiosity. It opens with the human eye's limits — tiny living things stayed hidden until lenses and microscopes were invented. Robert Hooke in 1665 named 'cells' after looking at cork; Leeuwenhoek soon described bacteria and is called the Father of Microbiology. The chapter then builds five locked ideas: the cell as the basic unit of life with cell membrane, cytoplasm and nucleus; the extra cell wall and chloroplasts of plant cells; the five levels of organisation — cell, tissue, organ, organ system, organism; the world of microorganisms — bacteria, fungi, algae, protozoa — that are unicellular or multicellular and live everywhere from hot springs to our gut; and helpful microbes — Lactobacillus in curd, yeast in dough, Rhizobium in legume roots, Spirulina, and Ananda Mohan Chakrabarty's oil-eating bacterium (patented 1980). Viruses sit apart — acellular, and reproduce only inside a host. CTET Paper 2 Science tests this chapter through cell-part identification, plant-vs-animal differences, microbe categories, and dough-or-curd application items. Below — Practice 15, Quiz 15, Hard 15, Mastery 30.