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.

FUNGI

The mushrooms and other fungi that can appear overnight in damp places are not plants. They belong to a completely separate group of living things that feed on dead or living plants and animals. Each fungus forms a hidden network of slender stems called a mycelium, and the visible part is just the “fruiting body” that sprouts like an apple on a tree to spread the spores that grow into new fungi.

1. OAK BOLETE A typical mushroom has radiating gills beneath its cap that produce millions of spores. Other fungi, like the oak bolete, have spongy undersides that release spores from tiny holes, or are covered with spore-producing tufts.


2. TURKEYTAIL Fungi are vital to life because they break down and recycle dead organisms. The turkeytail grows on dead wood, rotting it down so the nutrients it contains can be used by growing plants.


3. DEATH CAP Some fungi are extremely poisonous if they are eaten. The well-named death cap has probably been responsible for 90 per cent of all known deaths from mushroom poisoning.


4. SAFFRON MILK CAP Many fungi grow around the roots of certain plants, and provide them with plant foods in exchange for sugars. The saffron milk cap, for example, always grows with pine trees.


5. PARASOL MUSHROOM Some fungi, like the penny bun and parasol mushroom, are good to eat. But if you are not an expert at identifying them, you could be poisoned by a killer like the death cap.


6. FLY AGARIC The fly agaric is one of the best-known “toadstools” — a word often used for inedible or poisonous fungi. The white scales on its red cap are the remains of a thin veil that covered the growing fungus.


7. PENNY BUN The root-like fibres attached to the stem are just a tiny part of the penny bun’s mycelium. This can cover huge areas. The mycelium of a single honey fungus can extend 150,000 sq m (1.6 million sq ft).


8. STUMP PUFFBALL Puffballs are named for the way the ripe fungi puff clouds of dust-like spores when they are kicked or hit by rain. Just one giant puffball can contain an amazing 7 trillion (7,000,000,000,000) spores.

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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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One of the most fascinating aspects about owls is their ability to rotate their heads. Of course, it's a myth that they do a 360-degree turn, but they can rotate it a good 270 degrees. For comparison, we humans can turn our heads only to about 90 degrees left or right. So, how do the owls do it? Let's find out.

Before we get into the details of how owls are able to turn their heads that much, it is important to understand why they need it. Unlike many other creatures, owls have eyes fixed in their sockets, and so, to see, they must move their heads. This helps them look for prey as well as avoid predators. For long, it was a mystery how owls could rotate their heads so much without damaging the blood vessels in the region. It was solved by researchers a few years ago.

So flexible      

One reason for the easy head rotation is the way an owl's head is connected to its body - the joint offers greater movement. Apparently, the birds also have multiple vertebrae, which gives them an extensive variety of motion. But the more important reason lies in the bird's blood vessels. The researchers discovered that "owls have backup arteries, which offer a fresh supply of nutrients when blood vessels get closed off by rapid turning". The arteries also expand to allow the blood flow to continue without any disruption. It's interesting how researchers found this out. They used as many as 12 dead birds for the study, and injected dye into the dead owls arteries to mimic blood flow and manually turned their heads.

It is said that though the owl is most noted for this head-turning ability, it may not be unique to it. For instance, some types of raptors or birds of prey too seem to be able to turn their heads nearly as much as owls do. But, it is perhaps more crucial to owls because unlike many other raptors whose eyes are located on the sides of their heads, owls have their eyes situated in front. And so the birds certainly needed some help in the head-rotation department!

 

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For many people, warm weather is a time for fun-filled outdoor activities. However, hot weather and outdoor activities don’t always mix well, especially during periods of extreme heat— times when temperatures are substantially hotter and/or more humid than average for a location and date.

Warmer temperatures can mean higher ozone levels. Pay attention to the U.S. Environmental Protection Agency’s Air Quality Indexexternal icon when planning outdoor summer activities, especially if you have asthma or another lung disease.

When temperatures are extremely high, take steps to protect yourself and your loved ones:

• Stay in an air-conditioned indoor location as much as you can.


• Drink plenty of fluids even if you don’t feel thirsty.


• Take cool showers or baths to cool down.


• Check on a friend or neighbor and have someone do the same for you.


• Never leave children or pets in cars.


• Check the local news for health and safety updates.

 

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Hypothermia is a medical emergency that occurs when your body loses heat faster than it can produce heat, causing a dangerously low body temperature. Normal body temperature is around 98.6 ºF (37 ºC). Hypothermia (hi-poe-THUR-me-uh) occurs as your body temperature falls below 95 F (35 ºC).

When your body temperature drops, your heart, nervous system and other organs can't work normally. Left untreated, hypothermia can lead to complete failure of your heart and respiratory system and eventually to death.

Hypothermia is often caused by exposure to cold weather or immersion in cold water. Primary treatments for hypothermia are methods to warm the body back to a normal temperature.

When the balance between the body's heat production and heat loss tips toward heat loss for a prolonged period, hypothermia can occur. Accidental hypothermia usually happens after cold temperature exposure without enough warm, dry clothing for protection. Mountain climbers on Mount Everest avoid hypothermia by wearing specialized, high-tech gear designed for that windy, icy environment.

However, much milder environments can also lead to hypothermia, depending on a person's age, body mass, body fat, overall health, and length of time exposed to cold temperatures. A frail, older adult in a 60-degree house after a power outage can develop mild hypothermia overnight. Infants and babies sleeping in cold bedrooms are also at risk.

 

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Heatstroke is a condition caused by your body overheating, usually as a result of prolonged exposure to or physical exertion in high temperatures. This most serious form of heat injury, heatstroke, can occur if your body temperature rises to 104 ºF (40 ºC) or higher. The condition is most common in the summer months.

Heatstroke requires emergency treatment. Untreated heatstroke can quickly damage your brain, heart, kidneys and muscles. The damage worsens the longer treatment is delayed, increasing your risk of serious complications or death.

Heat stroke results from prolonged exposure to high temperatures -- usually in combination with dehydration -- which leads to failure of the body's temperature control system. The medical definition of heat stroke is a core body temperature greater than 104 degrees Fahrenheit, with complications involving the central nervous system that occur after exposure to high temperatures. Other common symptoms include nausea, seizures, confusion, disorientation, and sometimes loss of consciousness or coma.

 

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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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Penguins have adapted to life in the sea rather than in the air. They may not be able to fly and they may look clumsy when they waddle about on land, but in the water they are superb swimmers. In fact, penguins swimming and diving in the sea are so graceful they have been mistaken for dolphins or porpoises.

Penguins have wings, but they are short and stubby compared with the wings of birds that fly. Penguins' wings are stiff at the shoulder too. They do not have elbow joints either. So penguins cannot fold their wings like other birds. But these sturdy little wings make great paddles in the water, where penguins are really at home. They are also useful for helping the birds along on land when they are frightened or just in a hurry. You will see penguins flapping them furiously to get up a bit of speed. For most of their es, though, penguins are well equipped with the wings they have. In any case, flying wings would be useless to them underwater.

 

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Our skin is amazing stuff. It stops bacteria entering our bodies. It keeps in the water that makes up sixty per cent of our total content. Skin shields us from the sun's harmful rays and changes itself to provide extra protection when it is needed. That is why we go brown after sunbathing. Our skin helps control our body temperature. It contains our sense of touch. The outer layer is constantly renewing itself. It can repair itself when wounds happen. One-tenth of our blood circulates through our skin. It is also very crowded. On average, each square centimetre of skin has hundreds of nerve endings, not to mention the blood vessels, hair follicles and sweat glands that are packed in too.

With all this work to do, it is not surprising that our skin accounts for about sixteen per cent of our total weight. The average man is covered by about 1.85 square metres of skin and the average woman by 1.57 square metres.

 

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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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