Grade 8 Science - Chapter 2: The Invisible Living World

Vocabulary flashcards based on NCERT Probe and Ponder questions covering cell structures, microorganisms, fermentation, leguminous plants, and microbial growth conditions.

Nucleus

Cell structure present in both plant and animal cells (absent in bacteria) that regulates all cell activities.

Cytoplasm

A jelly-like material present in all cells (plant, animal, and bacterial) that fills the cell and holds the organelles.

Chloroplast

An organelle found only in plant cells that carries out photosynthesis.

Cell wall

The outermost protective layer present in both plant and bacterial cells.

Cell membrane

A structure present in every cell; in plants and bacteria it lies beneath the cell wall, while in animals it forms the outer boundary.

Nucleoid

A region found only in bacterial cells that contains DNA because bacteria lack a true nucleus.

Fermentation by Yeast

The process where yeast breaks down sugar in warm conditions to generate carbon dioxide ($CO_2$) gas and a small amount of alcohol.

Lime Water Test for Carbon Dioxide

A chemical test where clear lime water turns milky upon reacting with carbon dioxide ($CO_2$) gas to form calcium carbonate.

Rhizobium

Bacteria living in the root nodules of leguminous pulse crops that convert atmospheric nitrogen into a usable form in the soil.

Carbon-Nitrogen Balance in Composting

The combination of green waste (fruit and vegetable peels) and dry leaves that provides the proper nutrient ratio needed for efficient microbial decomposition.

Lactic Acid Bacteria

Bacteria in curd that multiply and produce lactic acid, making the curd taste increasingly sour over time or at higher temperatures.

Cell Structure Venn Diagram

Diagram showing distribution of cellular structures: 1 = Nucleus (Plant & Animal), 2 & 5 = Cytoplasm & Cell membrane (All cells), 3 = Chloroplast (Plant only), 4 = Cell wall (Plant & Bacterial), 6 = Nucleoid (Bacterial only).

Yeast Fermentation Experimental Set-up

Experimental arrangement demonstrating that yeast added to warm sugar solution in Test Tube B produces gas ($CO_2$) that inflates the attached balloon, unlike control Test Tube A.

Fermentation and Lime Water Set-up

Experimental apparatus where yeast ferments warm sugar solution in Flask A, releasing $CO_2$ gas through a delivery tube into Test Tube B containing lime water, causing it to turn milky.