My Science School

PLANKTON

The sunlit surface waters of many oceans teem with life, most of it microscopic that drifts with the currents. The whole drifting community is called the plankton. It is made up of plant-like phytoplankton, which uses the energy of sunlight to make food from carbon dioxide and water, and zooplankton — animals that feed on both the phytoplankton and each other.

• DIATOMS The phytoplankton consists of microscopic organisms such as diatoms and cyanobacteria. Diatoms have shells of glassy silica that fit together like tiny boxes with lids, and they exist in a dazzling variety of forms. They thrive in cool seas, where they turn the water grey-green and often multiply into vast cloudy “blooms” that are visible from space.


• CRAB LARVA Among the members of the zooplankton are the eggs and young of animals that have very different shapes and lives when adult. They include the eggs of reef corals and infant fish, molluscs, and crustaceans like this crab larva. Drifting in the plankton provides them with food and helps them disperse through the oceans to find new places to live.


• CYANOBACTERIA Once known as “blue-green algae”, these simple organisms were among the first forms of life to appear on Earth, more than 3.5 billion years ago. They still flourish in the oceans where, like diatoms, they turn carbon dioxide and water into sugary carbohydrates.


• COPEPODS Many animals spend their entire lives as members of the zooplankton. They include the tiny shrimp-like copepods, which form dense swarms in many seas, providing food for shoals of fish and giant filter-feeding whales.


• ARROW WORMS These long, almost transparent animals prey on the other creatures of the zooplankton, including copepods. They are named for the way that they shoot forward through the water to catch their victims.

FRUITS

All plants produce fruits that contain their seeds. Some fruits are dry husks, but others are juicy and tasty. These attract animals, which eat them and carry the seeds in their stomachs. The tough-skinned seeds are not digested, but are scattered far away from the parent plant in the animals’ droppings, and grow into new plants. The fruits are cultivated types that have been specially bred for their size and flavour.

1. ORANGE An orange has very soft juicy flesh contained in many segments, which are enclosed by a hard rind. Each segment usually contains a seed, or pip. An orange is technically a type of berry, which develops over the winter from the single ovary of an orange flower. Green at first, it turns orange as it swells to full size.


2. BANANA The bananas that are cultivated in the tropics have been bred to be seedless, but the wild bananas of Southeast Asia have small fruits containing many big, hard seeds. They grow in bunches on large plants with huge leaves that sprout straight from the ground.


3. NUTS All nuts are large seeds, which the plant has equipped with a store of concentrated plant food. This ensures that the seedlings get a good start in life. The nut is surrounded by a hard shell, which is technically a fruit, but tough and fibrous rather than soft and juicy.


4. DURIAN To attract fruit-eating mammals, many fruits are fragrant. The Southeast Asian durian fruit is famous for its strong aroma, which some people like and others hate. Animals such as forest pigs and orang-utans seem to love both its smell and taste.


5. GRAPES Some fruits such as grapes grow as clusters of soft, edible, thin-skinned berries. Each berry has several seeds embedded in its flesh, although many cultivated varieties of grapes are seedless. Berries are often vividly coloured to attract birds, which have excellent colour vision.


6. PEACH The juicy flesh of a peach, plum, or cherry encloses a hard “stone” that contains a single seed. This type of fruit is called a drupe. The fleshy part is meant to be eaten, so animals spread the seeds, but some animals such as parrots can crack the stones and eat the seeds, too.


7. BROAD BEAN The edible part of a broad bean plant is its seeds, and its fruit is the entire pod. The wild ancestors of such beans do not attract animals. Instead, their pods dry up and split open with explosive force, so the seeds shoot out and are scattered on the ground.


8. TOMATO Not all fruits are edible. Some of the wild relatives of tomatoes are extremely poisonous. They include deadly nightshade, which is lethal to humans, although some animals can eat the berries without coming to harm. Tomatoes are also related to chilli peppers.

ANIMAL KINGDOM

All living things fall into one of five categories, or “kingdoms” — bacteria and protists (single-celled organisms), fungi, plants, and animals. The animal kingdom is made up of many groups of invertebrates (animals without backbones, such as insects) and a few groups of vertebrates, such as mammals. They all share the ability to move and sense their surroundings, and the need to find food.

1. INSECTS Small animals with hard external skeletons, all insects have six legs when adult and, in most cases, two pairs of wings. They include creatures such as butterflies, wasps, flies, and beetles. Many are very attractive, but some can sting, bite, and carry deadly diseases.


2. WORMS There are many types of worms. They include tapeworms, which live inside other animals, flatworms, and roundworms. Most familiar are segmented worms like the earthworms that burrow in soil, marine worms that live on tidal shores, and leeches.


3. AMPHIBIANS Soft-skinned amphibians, such as frogs and toads, lose body moisture easily. To avoid drying out, nearly all frogs live in damp places, often near a pond. Most lay their eggs in water or other damp places, and this hatch into fish-like young, such as tadpoles.


4. BIRDS These highly specialized, warm-blooded vertebrates are superbly equipped for flight, and some may stay airborne for most of their lives. They are the only animals with feathers, which stop them losing body heat, enable them to fly, and are often brightly coloured.


5. MAMMALS Like birds, mammals are warm-blooded, meaning they can control their body temperature. The females feed their young on milk. Most eat plants, but some, such as lions, are meat eaters. Humans belong to the mammal group.


6. ARACHNIDS The spiders, scorpions, ticks, and their relatives are eight-legged invertebrates with hard external skeletons but no wings. Spiders kill their prey with venomous fangs, and scorpions have stings in their tails, some of which are powerful enough to kill a human.


7. MOLLUSCS Most molluscs are soft-bodied animals that live in water and have protective shells. They include mussels, clams, and whelks. The only molluscs able to live on land are the snails and slugs. Octopuses and squids are also molluscs, but they are highly evolved, with well-developed brains and eyes.


8. CRUSTACEANS Like insects, crustaceans have hard external skeletons with several segments, and strong jointed legs. All are aquatic, apart from woodlice. They include tough-shelled animals like crabs and lobsters, as well as more delicate shrimps and water fleas.


9. MIRIAPODS Named for their many legs, miriapods have long bodies divided into segments. Centipedes have a single pair of legs on each segment, while millipedes have two pairs. Some millipedes have more than 90 segments, and more than 180 pairs of legs. Millipedes eat mainly dead material, but centipedes are speedy hunters.


10. FISH Fish were the first vertebrates, and the ancestors of all amphibians, reptiles, mammals, and birds. They are perfectly adapted for life in water, which supports their bodies and provides them with vital oxygen. There are two main fish groups: those with bony skeletons, and the sharks and rays, which have skeletons of flexible cartilage.


11. ECHINODERMS Sea urchins, starfish, feather stars, and sea cucumbers are echinoderms, meaning “spiny skinned”. Their bodies tend to be wheel-shaped, with a central mouth. Feather stars trap food that floats through their feathery arms, but most searches for food on the seabed.


12. REPTILES Although cold-blooded like amphibians, reptiles such as snakes and lizards have waterproof, scaly skins that allow them to live in dry places such as deserts. Most are active hunters, and some snakes have powerful venom, which they use to kill their prey and for defence, if threatened.

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TREES

Trees are the tallest, heaviest, and oldest of all living things. The Californian giant sequoia known as General Sherman weighs approximately 6,000 tonnes - 30 times as much as the biggest animal, the blue whale. The oldest living bristlecone pine tree, which also grows in California, is nearly 5,000 years old. Yet even these ancient giants can still produce tiny seeds that grow into new trees.

LEAVES Like all green plants, trees absorb sunlight through their leaves and use its energy to turn air and water into sugar. A tree’s leaves are its food factories.

COMPOUND LEAVES Most trees have simple leaves of various shapes, but some have compound leaves, made up of many leaflets. These either sprout from a long stalk (pinnate) or fan out from a single point (palmate).

NEEDLES AND SCALES Thin leaves make food efficiently, but they are easily damaged by hot sunshine or frost. So many trees that grow in very hot or cold places have thicker, tougher needles or scales.

FRUIT The flowers of some trees turn into juicy fruits that contain seeds. If birds eat the fruit, the seeds pass through them unharmed and are scattered far away.

TREE RINGS Every year a tree adds a layer of new wood to its trunk. If the tree is cut down, each year’s growth shows as a visible ring, so the number of rings gives its age.

FLOWERS All trees produce flowers, but some may not be obvious because they do not have colourful petals. Other trees, however, such as apples, have showy flowers that attract insects.

SEEDS AND NUTS Some trees have tiny seeds, but others produce the bigger seeds we call nuts. Animals eat them, but also bury and forget them, so they grow into new trees.

CONES Coniferous trees such as pines have woody cones that contain small papery seeds. When the cones open up in the sun, the seeds fall out and blow way.

DECIDUOUS LEAVES Many trees lose their leaves in winter, and grow new ones in spring. Before they fall, the old leaves lose their green colour and turn yellow, brown or even red.

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FLOWERS

Many plants produce beautiful flowers, often vividly coloured and fragrant. These intricate structures form the reproductive parts of plants and have evolved so that they attract insects and birds to sip the sugary nectar at the flower’s centre. While feeding, the insect or bird is dusted with pollen, which is produced by the stamens and contains the male sex cells. The pollen is deposited on the sticky stigma of another flower. This is pollination. A pollen tube then grows down the style to the ovary and fertilizes an ovule. This is fertilization. Some plants, such as grasses and many types of trees, rely on the wind to carry their pollen and their flowers do not need showy petals or fragrant nectar to attract animals. Since this is a less efficient system, they must produce far more pollen, which can fill the air and cause hay fever.

1. Flower Structure A typical flower develops inside a bud at the end of a stalk. When the bud opens, it reveals a ring of petals, each of which secretes nectar from its base. At the centre of the flower lie the male structures that produce pollen. These surround the female structures that hold the ovules, or egg cells. An outer ring of green sepals may protect the flower when it is in bud.


2. Carpel An ovary, a style, and a stigma form the main parts of a carpel. At the heart of the flower lie the ovules, enclosed in a case called an ovary. The top of each ovary extends into a style that carries a sticky pad called a stigma. The flowers of some plants have man carpels, each with their own stigma, but this lily has just one.


3. Stamen The tiny, dust-like pollen grains that contain the male cells are produced by stamens. These usually form a ring around the central carpel or carpels. Each stamen has a long filament, which supports a club-like anther that produces the pollen.


4. Transferring Pollen Insects such as butterflies often drink nectar from one type of flower. Hummingbirds do the same, because their bills are the right shape to reach the nectar. The bird and the insect get dusted with pollen in the process, and carry it directly to another flower of the same type.


5. Fertilization If a hummingbird sips nectar from this lily, it will pickup pollen on its breast feathers. If the bird visits another lily, the sticky central stigma may pick up the pollen. Each pollen grain then sprouts a long tube that grows down through the carpel to reach an ovule. The male cell moves down the tube to fertilize the ovule so it can develop into a seed.

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PLANTS

All green plants use the energy of sunlight to make sugary carbohydrate food from water and carbon dioxide in the air. This is why they grow well only in sunlit, moist places. The food fuels growth and is used to make cellulose — the tough, fibrous tissue that helps support all the various parts of the plant, from its stems and leaves to its flowers.

1. GERMINATION A bean plant begins life as a seed with two halves, called cotyledons. In spring when the weather is mild, the seed starts to absorb water through a minute hole in its outer coating (the testa). The seed swells and about three days later a root grows to hold the plant in place, and a shoot appears above the ground. This process is called germination.


2. ROOTS The plant’s roots absorb water from the soil. The water is used by the leaves to make food. The water also contains dissolved mineral salts, such as nitrates and phosphates, which are essential for growth.


3. STEM The strong stem of the plant supports its leaves in the sunlight. It also contains bundles of tubes or veins. These allow water containing dissolved nutrients to flow up from the roots to the leaves, and also carry sugary food from the leaves to other parts of the plant.


4. LEAVES The leaves are the plant’s food factories. They act like solar panels, as the green chlorophyll enables the plant to absorb the energy of sunlight and use it for photosynthesis - the process in which the plant takes carbon dioxide from the air, and combines it with water drawn up by the roots to make sugar. Oxygen is also produced in the process and released into the air.


5. TRANSPIRATION As sunlight warms a plant; water in the leaves is lost as water vapour, through pores called stomata. The leaves then take in water from the stem, which in turn draws more water up into the plant from the roots. The water carries nutrients from the soil with it.

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In our fight against global warming and climate change, trees are considered part of the solution. But emerging research suggests that trees are also part of the problem.

Trees are carbon sinks locking up vast amounts of carbon dioxide from the atmosphere. This way, they help protect the planet from the harmful effects of the greenhouse gas. But there seems to be another face to trees, that scientists have uncovered only recently. They find that trees emit methane, which is a greenhouse gas 45 times more potent than carbon dioxide at warming our planet. Scientists unofficially call this treethane (tree methane). However, it's currently unknown just how much of methane is emitted by trees.

Emission of methane from cottonwood trees was first observed in 1907, but the finding was reported mainly as a novelty and was largely ignored. Subsequent research has picked up only recently, but in a big way. An expanding network of researchers has discovered methane release from trees from the vast flooded forests of the Amazon basin to Bomeo's soggy peatlands, from temperate upland woods in Maryland and Hungary to forested mountain slopes in China.

Source of methane

Some lowland forest trees such as cottonwood emit flammable methane directly from their stems, which is likely produced by microbes living within. Scientists think trees may also be emitting methane from a direct photochemical reaction thought to be driven by the ultraviolet wavelengths in sunlight Research in this area is still in its early stages and so there is a lot left to be understood.

But understanding why, how and which trees emit the most methane is crucial, as trillions of trees are being planted across the world in an effort to mitigate climate change. However, scientists point out that the amount of methane emitted by trees is generally dwarfed by the amount of carbon dioxide they take in over their lifetime. Forests are still key to maintaining a safe climate, they point out.

 

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Though dreams are understood to be linked to mental functioning, their deeper implications continue to remain a mystery. Even today it is not clear what exactly causes dreams or what their roles and impacts are. While the experience is universal, is it unique to humans? Maybe not.

Initially, it seemed as if it would be difficult to ascertain if animals had dreams. However, over the last few decades, scientists have been getting closer and closer to finding that out. In fact, recent research would have us believe that it is likely that animals do have dreams.

In 2015, a team of researchers discovered that when lab rats are shown food and then go to sleep, certain cells in their brains seemed to map out how to get to the food", and the team likened this to a dream (of "their path to a reward"). Decades before this study, another study had found that cats were perhaps seeing images during their rapid-eye movement or REM sleep.

Interestingly, humans dream during REM sleep, and most mammals, and even certain birds and reptiles are said to go through REM sleep. A 2012 study showed "cuttlefish exhibit a sleep-like state accompanied by color changes, twitching, and rapid eye movements similar to REM sleep".

And, something similar has been exhibited by the octopus too - as revealed in a study published this March that could be linked to dreams. A footage shot by scientists in Brazil showed that an octopus delightfully named Marshmallow-lying at rest at the bottom of her tank, was "suddenly shifting in color from a pale white-green to brown and then orange, as her muscles twitch, suckers contract and her closed eyes shift around". These sophisticated creatures experience at least two different types of sleep, and one of them is "active sleep", similar to REM. The scientists say that the footage raises "the intriguing possibility that, like humans, octopuses experience dreams".

 

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The snowdrop has also been called the fair maid of February and it is not uncommon to see these little white flowers poking their heads above ground at the coldest part of the winter.

Snowdrops have been doing the same thing for millions of years ever since they appeared for the first time. But they were not growing in northern Europe then. Snowdrops originally came from the eastern Mediterranean and from North Africa. The climate in those regions is different from ours. As holiday advertisements keep reminding us, the summers are long, hot and dry. Most of the rain falls there in winter and early spring.

Snowdrops and flowers like them need moisture to grow. So they hide underground when the weather is hot and dry, living on food they have stored in their swollen bases, or corms: When the winter rains come, the snowdrops begin to grow and eventually flower, despite the cold.

Snowdrops have spread far and wide from their first home but they have never lost their pattern of growth and they are still the first flowers to appear in most parks and gardens.

 

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The idea seems crazy, but scientific experiments have shown that some plants really do behave differently when they are exposed to sound especially music.

Ancient legends from India say that the god Krishna used music to make plants grow. Modern experiments in India seem to confirm that plants like music. In the early 1960s a scientist working in a university near Madras made an astonishing discovery. He found that playing the violin or playing Indian music produced plants that were taller and stronger than plants that grew without music. So he tried his experiment on rice growing in paddy fields. He played them Indian music, and the rice plants loved it. They grew strong and healthy and produced masses of rice. Harvests went up between twenty-five and sixty per cent!

A few years later another researcher working in Denver in the USA went a stage further. She experimented with different types of music to find out which her plants preferred. It turned out that the plants were terribly conservative. Rock music, especially acid rock, had them leaning as far from it as they could. They also drank much more water than plants played other music. In one experiment all the plants died when a really heavy number was played.

On the other hand, they adored the classics. An identical group of plants could not get enough of the Beethoven, Brahms, Schubert and Haydn she played them. Some plants burst into flower, others leaned right over to the hi-fi speakers. The experiments continued. Bach proved to be a big hit. So did jazz. But the number one spot again belonged to Indian music. When she played this the plants were leaning at 60° angles towards the speakers. Krishna was right. Plants may not be able to hear as we do, but they have got very set tastes when it comes to music.

 

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If there is one thing a nettle sting does, it makes you try very hard to avoid being stung a second time. This is just what nature intends. The nettle's sting is its means of protection. It stops animals trying to eat the plant.

If you look at a stinging nettle leaf under a microscope, you will see that the small hairs covering it are really tiny tubes. These are filled with poison. They have brittle tips that snap off at the slightest touch, leaving a jagged edge. This can easily penetrate skin so that the poison can get inside it. You probably do not need reminding that stinging nettle poison can create a prickling feeling that lasts for several hours. So you would have to be pretty desperate to sting yourself deliberately, but Roman soldiers are said to have rubbed nettles on their bodies in cold climates to try to keep warm.

 

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The flowers of most plants produce a sweet scent and we are very grateful to them for creating the lovely smells that fill our gardens. Much as we enjoy them, the scents are not meant for our benefit. Plants produce them to attract far more important visitors insects, particularly bees.

When insects crawl inside flowers to sip their nectar, they pick up pollen as well. As they move from flower to flower, the insects transfer the pollen. This ensures that the plants are pollinated and will produce seeds from which other plants will grow the following year.

Not all plants attract insects with sweet scents. Some, like the suitably named Stinkhorn fungus, produce awful smells. This has a smell like rotting flesh to attract large flies which carry away its, spores to produce more plants.

The Stinking Corpse lily smells just as bad, as you might imagine. It needs to attract flies to pollinate it. That is especially important for this tropical plant because it produces the world's largest flower, which can measure up to ninety centimetres across.

 

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Mushrooms belong to the group of plants known as fungi. They are different from other plants because of the way they grow. Instead of growing from seeds, fungi grow from very simple organisms called spores. The hit rate of successful spores is very low. So fungi have to produce literally millions to be sure that some will grow into new plants. One large mushroom can produce 16,000 million spores, but only a few of these will germinate and grow into new mushrooms.

If a spore lands on a suitable piece of ground, it sends out fine branching threads known as hyphae. They form a dense network underground. Small white bumps grow from this and eventually appear on the surface as mushrooms. Once the new mushrooms open out into their familiar umbrella shapes, they start shedding spores of their own to continue the growing process.

Mushrooms are delicious. Other varieties of fungi can be eaten too. Be warned, however. There are some that are terribly poisonous. So we should not eat any of them until we have identified that they are safe.

 

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Some plants do. They do not eat large animals, which is just as well for us. But they do trap insects and consume them. Insects provide these plants with their food. One of the most well known is the Venus fly trap. Any insect unlucky enough to crawl in triggers a mechanism in the plant which snaps it shut. The insect is trapped inside. Then juices in the plant get to work and dissolves it.

The Pitcher plant is another insect eater. It is shaped like a jug, or pitcher – which is how it got its name. Inside the plant is so rough and uneven that a trapped insect cannot crawl out again. In the end it drops exhausted to the bottom of the plant, where it is digested by the plant’s juices.

 

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 Amazingly, yes they can. Some kinds of primitive plants living in water have very small tentacles which they thrash around in the water to propel themselves along. Looking at them, you might they were animals, not plants. But even ordinary plants are on the move all the time – only very slowly.

Roots burrow into the earth in search of moisture. Tendrils reach out for something to cling to and climb. When they find a support, they quickly curl round it and soon become firmly attached. Flowers turn towards the sun. The sunflower even has an Italian name meaning ‘turning with the sun’, because it follows the sun round during the course of a day. And many flowers, like the daisy, open their petals in the morning when the sun shines on them, and close them again at the end of the day, when the light fades.

 

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