Exam practice

The food factory of a plant is the leaf.

The water absorbed by the roots is carried to the leaves by the stem.

Salts are absorbed from the soil by the root.

The corolla is a part of the flower.

• i.A leaf makes food for the plant by photosynthesis.
• ii.Gases and water vapor pass in and out of the plant through the stomata of the leaf.

(Others: storing water and food, as in aloe; protecting the plant, as spines in cactus; growing new plants, as in Bryophyllum.)

Potato (tuber), ginger (rhizome), taro or pindalu (corm), onion and garlic (bulbs), the tendrils of a grapevine, and the green stem of a cactus.

• i.Roots hold the plant firmly in the soil.
• ii.They absorb water and mineral salts from the soil.
• iii.Some roots store food, as in carrot and radish; some hold the plant up, as the stilt roots of maize and the prop roots of banyan; and new plants grow from some, as from sweet potato.

• i.It holds up the leaves, flowers and fruits.
• ii.It carries water and salts from the roots up to the leaves.
• iii.It carries the food made in the leaves to every part of the plant.
• iv.Some stems store food (potato, ginger, taro).
• v.Green stems make food where there are no proper leaves (cactus).
• vi.New plants grow from the stems of some plants (sugarcane, rose).

• i.A spine has a very small surface and few or no stomata, so the plant loses very little water by transpiration. This helps it survive where water is scarce.
• ii.The sharp spines keep animals from eating the plant.

(The plant’s thick green stem makes its food and stores water instead.)

• i.Reshma bought roots. A sweet potato is a root swollen with stored food; it has no nodes or buds.
• ii.Naresh bought stems. A potato is an underground stem (a tuber): its eyes are nodes with buds.

• i.A, the plumule, grows into the shoot, and B, the radicle, grows into the root. Together they are the embryo.
• ii.B, the radicle. It comes out first and grows down into the soil.
• iii.B (radicle) grows into the root of the new plant. C (the seed coat) covers and protects the inside of the seed.
• iv.A bean is a dicot: it has two cotyledons (F), and its food is stored in them, with little or no endosperm. A wheat grain is a monocot: it has one cotyledon and a large endosperm that holds its food.

Animals with a cylindrical, segmented body are put in the phylum Annelida.

Flat animals are bisexual (hermaphrodite).

Sponges are put in the phylum Porifera.

All single-celled animals are grouped in the phylum Protozoa.

Because it has the features of arthropods: jointed legs (three pairs), a hard exoskeleton covering its body, and compound eyes. Its body is in segments, and the sexes are separate.

• i.The body is made of a single cell.
• ii.They move with pseudopodia, a flagellum or cilia.
• iii.All life processes, such as digestion and reproduction, happen in the one cell; they reproduce asexually.

(Also: most live in water, and some are parasites, such as Plasmodium.)

Animals whose body is full of tiny pores (ostia), with a large opening (osculum) at the top; whose body wall has two layers of cells; that live in water fixed to one place; that take in water and food through the ostia and send waste out through the osculum; and that can regenerate from broken pieces. These are the sponges, such as Spongilla and Sycon.

Platyhelminthes (tapeworm, liver fluke) and Annelida (earthworm, leech).

Similarity: most of both are parasites (and neither has a body in segments).

Difference: a flatworm’s body is flat, and its gut has no anus; a roundworm’s body is round (cylindrical), and its gut has both a mouth and an anus. (Also: flatworms are hermaphrodite; roundworms have separate sexes.)

• i.They have a soft, moist body.
• ii.They have one muscular foot for moving.
• iii.Most have a hard shell covering the body.

(Also: many have tentacles on the head; they live in water and on land.)

i.

ii.

iii.

iv.

Draw each with a pencil and label it:

• Amoeba (Figure 3.23): an irregular blob with blunt pseudopodia; label the nucleus, cytoplasm, pseudopodia and a vacuole.
• Earthworm: a long, round body made of many rings; label the head (front) end, the segments, the clitellum (the pale band near the front) and the tail end.
• Snail (Figure 3.37): label the shell, muscular foot, head and the two pairs of tentacles (eyes on the long pair).
• Hydra (Figure 3.27): a tube with a ring of tentacles round the mouth at the top and a base at the bottom; label the tentacles, mouth, body, a bud and the base.

Both are long and round, but their bodies are built differently. The earthworm’s body is divided into segments (rings), it has setae, a moist skin through which it breathes, and both sexes in one animal: it belongs to Annelida. Ascaris’s body is not segmented; it is smooth and covered with a cuticle, it is a parasite, and males and females are separate: it belongs to Nemathelminthes. Animals are sorted by how their bodies are built, not just by how they look from far away.

They live only in the sea.

• i.Their body is covered with a spiny skin; the spines are made of calcium carbonate.
• ii.They have no clear head, and they move with tube feet.

(Also: most can regenerate lost arms.)

A, the snail. It has two pairs of tentacles on its head, with eyes on the tips of the longer pair.

C, the starfish. Its five arms grow from a central disc, and it has no head.

B, Paramecium. Its whole body is one cell.

D, the tapeworm. It lives in the intestine and soaks up the food its host has already digested.

The organelle that controls all the activities of a cell is the nucleus.

The powerhouse of the cell is the mitochondria (one is a mitochondrion).

The organelle that helps in making food is the plastid (the chloroplast).

The half-liquid substance between the nucleus and the cell membrane is the cytoplasm.

A cell is the smallest living unit of which the body of every living thing is made. It is the structural and functional unit of life: the body is built of cells, and the work of life is done in them.

Because every living thing is made of one or more cells (the cell is the building block of the body), and every life process, such as respiration, digestion, growth and reproduction, takes place in cells. Nothing smaller than a cell can live on its own. New cells come only from cells that already exist.

The mitochondrion. It carries out respiration: it breaks down food using oxygen and releases the energy stored in it, which the cell uses for all its work. Like a power station supplying a town with energy, it supplies the cell with energy.

Draw them as in Figure 3.47.

Plant cell: draw a box-like cell with a thick double outline. Label the cell wall (outer line), cell membrane (inner line), cytoplasm, one large vacuole in the middle, the nucleus pushed to one side with its nucleolus, chloroplasts (green ovals), mitochondria, endoplasmic reticulum, ribosomes and the Golgi body.

Animal cell: draw a rounded, irregular cell with a single thin outline. Label the cell membrane, cytoplasm, the nucleus near the middle with its nucleolus, mitochondria, endoplasmic reticulum with ribosomes, the Golgi body, small vacuoles, lysosomes and the centrosome near the nucleus.

An animal cell has a cell membrane, cytoplasm, a nucleus (with nuclear membrane, nucleoplasm, nucleolus and chromatin), mitochondria, endoplasmic reticulum, ribosomes, a Golgi body, lysosomes, a centrosome, and small vacuoles (in some).
Of these, the centrosome and the lysosomes are found only in animal cells.

Any four of: mitochondria, plastids (in plant cells), vacuoles, endoplasmic reticulum, ribosomes, Golgi body, lysosomes, centrosome (in animal cells).

• i.Plant cells are fairly large, with a regular shape, and their thick cell wall shows each cell’s outline clearly.
• ii.They are easy to get: an onion peel is only one cell thick, so it can be put straight on a slide without cutting.
• iii.They take up stains well, so the nucleus and the wall show up clearly under an ordinary school microscope.

• i.P: mitochondrion; Q: nucleus; R: chloroplast (a plastid).
• ii.P, the mitochondrion, carries out respiration: it breaks down food and releases energy for the cell.
• iii.P, the mitochondrion.
• iv.Because it has a thick, stiff cell wall made of cellulose round it, which doesn’t change shape. (The full vacuole pressing outwards from inside also keeps the cell firm.)
• v.Because of the chloroplasts (R). Their chlorophyll traps sunlight, and the plant uses it to make food from carbon dioxide and water, giving out oxygen. So plants take carbon dioxide out of the air and put oxygen back, which animals and people breathe. This keeps the amounts of oxygen and carbon dioxide in the air in balance, and the food plants make feeds every other living thing.