Leaves are a plant’s powerhouse, using sunlight to join water and carbon dioxide to make sugar, the plant’s fuel.
Leaves are broad and flat to catch maximum sunlight.
Leaves are joined to the stem by a stalk called a petiole.
The flat part of the leaf is called the blade.
The leaf blade is like a sandwich with two layers of cells holding a thick filling of green cells.
If you hold a leaf blade up to the light, you can clearly see the pattern of its veins.
The green comes from the chemical chlorophyll. It is this that catches sunlight to make sugar in photosynthesis.
Chlorophyll is held in tiny bags in each cell called chloroplasts.
A network of branching veins (tubes) supplies the leaf with water. It also transports the sugar made there to the rest of the plant.
Air containing carbon dioxide is drawn into the leaf through pores on the underside called stomata. Stomata also let out water in a process called transpiration.
To cut down water loss in dry places, leaves may be rolled-up, long and needle-like, or covered in hairs or wax. Climbing plants, such as peas, have leaf tips that coil into stalks called tendrils to help the plant cling.
Muscles are special fibers that contract (tighten) and relax to move different parts of the body.
Voluntary muscles are all the muscles you can control by will or thinking, such as your arm muscles.
Involuntary muscles are the muscles you cannot control at will, but work automatically, such as the muscles that move food through your intestine.
Most voluntary muscles cover the skeleton and are therefore called skeletal muscles. They are also called striated (striped) muscle because there are dark bands on the bundles of fiber that form them.
Most involuntary muscles form sacs or tubes such as the intestine or the blood vessels. They are called smooth muscle because they lack the bands or stripes of voluntary muscles.
Most muscles are arranged in pairs, because although muscles can shorten themselves, they cannot make themselves longer. So the flexor muscle that bends a joint is paired with an extensor muscle to straighten it again.
This microscopic cross-section shows striated, or striped, skeletal muscle. It is so-called because its fibers are made of light and dark stripes.
The heart muscle is a unique combination of skeletal and smooth muscle. It has its own built-in contraction rhythm of 70 beats per minute and special muscle cells that work like nerve cells for transmitting the signals for waves of muscle contraction to sweep through the heart.
Your body’s longest muscle is the sartorius on the inner thigh.
Your body’s widest muscle is the external oblique which runs around the side of the upper body.
Your body’s biggest muscle is the gluteus maximus in your buttocks (bottom).
You have more than 640 skeletal muscles and they make up over 40% of your body’s entire weight, covering your skeleton like a bulky blanket. This illustration shows only the main surface muscles of the back, but your body has at least two, and sometimes three, layers of muscle beneath its surface muscles. Most muscles are firmly anchored at both ends and attached to the bones either side of a joint, either directly or by tough fibers called tendons.
Most muscles are long and thin and they work by pulling themselves shorter – sometimes contracting by up to half their length.
Skeletal muscles, the muscles that make you move, are made of special cells which have not just one nucleus like other cells do, but many nuclei in a long fiber, called a myofiber.
Muscles are made from hundreds or thousands of these fibers bound together like fibers in string.
Muscle fibers are made from tiny strands called myofibrils, each marked with dark bands, giving the muscle its name of stripcy or ‘striated’ muscle.
The stripes in muscle are alternate bands of filaments of two substances: actin and myosin.
The actin and myosin interlock, like teeth on a zip.
When a nerve signal comes from the brain, chemical ‘hooks’ on the myosin twist and yank the actin filaments along, shortening the muscle.
The chemical hooks on myosin are made from a stem called a cross-bridge and a head made of a chemical called adenosine triphosphate or ATP.
ATP is sensitive to calcium, and the nerve signal transmitted from the brain that tells the muscle to contract does its work by releasing a flood of calcium to trigger the ATP.
Muscles, such as the biceps and triceps in your upper arm, work in pairs, pulling in opposite directions to one another.
Berries are fleshy fruit which contain lots of seeds. The bright colours attract birds which eat the flesh. The seeds pass out in the birds’ droppings and so spread.
Bananas, tomatoes and cranberries are all berries.
Many berries are bright red and
Cloudberries are aggregate fruits like shiny to attract birds. raspberries. The tiny amber berries grow close to the ground in the far north, and are collected by Inuits and Sami people in autumn to freeze for winter food. 194
Cloudberries are also known as salmonberries, bakeberries, malka and baked appleberries.
Cranberries grow wild on small trailing plants in marshes, but are now cultivated extensively in the USA in places such as Massachusetts.
Wild huckleberries are the American version of the European bilberry. But the evergreen huckleberry sold in florists is actually a blueberry.
Me strawberry tree’s Latin name is unedo, which means ‘I eat one. The red berries are not as tasty as they look.
According to Greek mythology, the wine-red mulberry was once white but was stained red by the Hood of the tragic lovers Pyramus and Thisbe, whose story is retold in Shakespeare’s Midsummer Night’s Dream.
Like butterflies, moths belong to the insect group Lepidoptera.
Most moths have fat, hairy bodies, and feathery or thread-like antennae.
Many moths fly at dusk or at night. By day, they rest on tree trunks and in leaf litter, where their drab color makes them hard for predators such as birds to spot. However, there are also many brightly colored day-flying moths.
Tiger moths give out high-pitched clicks to warn that they taste bad and so escape being eaten.
The biggest moths are the Hercules moth and the bent wing ghost moth of Asia, with wingspans of over 25 cm.
Night-flying moths shiver their wings to warm them up for flight.
Hawk moths are powerful fliers and migrate long distances. The oleander hawk moth flies from tropical Africa to far northern
Europe in summer. The caterpillars of small moths live in seeds, fruit, stems and leaves, eating them from the inside.
The caterpillars of large moths feed on leaves from the outside, chewing chunks out of them.
When threatened, the caterpillar of the puss moth rears up, thrusts its whip-like tail forward, and squirts a jet of formic acid from its head end. Every caterpillar spins silk, but the cloth silk comes from the caterpillar of the white Bombyx mori moth, known as the silkworm.
Democracies are countries with governments elected every few years by popular vote.
Most democracies have a constitution, a written set of laws saying how a government must be run.
Democracies like France are republics. This means the head of state is an elected president. In some republics like the USA, the president is in charge; in others, the president is a figurehead and the country is run by a chancellor or prime minister.
Monarchies are countries which still have a king or queen — like Britain. But their power is usually limited and the country is run by an elected government.
In autocracies a single person or small group of people holds all power, as in China and North Korea.
Most governments are split into the legislature who make or amend laws, the executive who puts them into effect and the judiciary who see they are applied fairly.
Most countries are capitalist, which means most things capital — are owned by individuals or small groups.
A few countries like Cuba are communist, which means everything is owned by the community, or the state.
Socialists believe the government should ensure everyone has equal rights, a fair share of money, and good health, education and housing.
Fascists believe in rigid discipline and that they and their country are superior to others, like Hitler’s Germany in the 1930s. There is no openly fascist country at present.