The Invisible Living World: Beyond Our Naked Eye: questions with answers

Hooke was looking at cork, which is dead, and what he saw were the empty compartments left in it. They reminded him of a honeycomb, and he named each small empty space a cell. Living bacteria and blood cells belong to Leeuwenhoek, who saw them for the first time a few years later.

A round-bottom flask filled with water can make letters look larger. Its curved water-filled shape acts like a magnifying glass. The word lens comes from the lentil-seed shape, not from magnifying.

Doing the work and directing it are two different jobs, and the chapter gives one to each part. Most of the life processes take place in the cytoplasm, which also holds the other components of the cell. The nucleus regulates all the activities that occur within the cell and regulates its growth.

Porous is the word that settles it. The membrane separates one cell from another and still lets things across in both directions. What the cell needs comes in, and what it has finished with goes out.

Plant cells have plastids, but only some plastids, such as chloroplasts, contain chlorophyll. Chlorophyll makes a plant part green. In non-green parts, plastids help store substances instead.

A typical plant or animal cell has a cell membrane, cytoplasm and a nucleus. A plant cell has an extra cell wall outside its membrane. Bacteria are different because they do not have a well-defined nucleus.

Smooth muscle cells are spindle-shaped and contract. Nerve cells are long and branched and carry messages. A single body contains cells with different shapes suited to different jobs.

Even the stomach on its own needs more than one kind of cell. Muscle cells in its wall churn the food, while other cells in its lining produce digestive juices and acid. The chapter says all these cells work together to make digestion possible.

Multicellular describes the finished organism, not its start. The life of complex living organisms BEGINS WITH A SINGLE CELL, the egg, whose repeated division builds the many-celled body.

A bacterial cell has a cell membrane and cytoplasm just like the cells of plants and animals. What it does not have is a well-defined nucleus and a nuclear membrane. In their place a bacterium has a NUCLEOID. The chapter says this single feature sets bacteria apart from yeast, protozoa, algae, fungi, plants and animals. So here the answer is: No; a bacterial cell has a nucleoid in its place.

Microorganisms occur in water, soil, air and inside living bodies. Finding some in one place does not restrict them to that habitat.

The chapter contrasts them in a single sentence: instead of producing alcohol like yeast, these bacteria produce LACTIC ACID. The rise of dough is carbon dioxide; the sourness of curd is lactic acid. They are not doing the same thing.

Microalgae live in water, soil, air and even on trees. They make their own food using sunlight.

Rhizobium lives in root nodules of certain crops. The chapter names beans, peas and lentils. The bacteria trap nitrogen from the air and help the plants grow.

Activity 2.7 uses peels and leaves, which is what narrows a reader to plant waste. The chapter goes further in the same section: microorganisms also decompose the bodies of dead animals, and helpful bacteria decompose animal wastes like dung. Time alone does nothing; fungi and bacteria in the soil act on the waste and break it into simpler substances rich in nutrients.