What are Algae?


Seaweeds look like plants. They even make their own food from sunlight, like plants do. But seaweeds are not plants. They do not have true roots, stems, leaves, or flowers. They are special types of living things called algae.



Seaweeds are built well for a life in the sea. They are soft and flexible and can sway in the water without being torn apart. Some seaweeds use a root-like anchor to cling to rocks, shells, or the sea floor. Some have gas-filled swellings to keep afloat. Sargassum weed floats in large masses in the ocean. Eel grass grows in thick beds at the muddy bottom of shallow waters. It looks like a field of waving grass along the shore. There are also underwater forests of kelp that grow up from the shallow sea floor.



Some kinds of algae are so small that you need a microscope to see them. And some of them can move around. They do this by beating little hairs that grow from their surface. Sometimes these tiny algae cling together in chains or gather into jellylike balls.




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What are fungi?


Fungi are living things that are a lot like plants. They grow almost everywhere in nature, including the air. They don’t move around, but they do reproduce. Scientists once called fungi “plants,” but fungi cannot make their own food. They get their food from dead plants and animals. So today, experts put these living things in a group of their own. Mushrooms, mould, and yeast are types of fungi.



Mushrooms and moulds grow from tiny cells called spores. Spores float on the air like dust. When a spore lands on bread or something else it can use as food, it begins to grow. It sends out many tiny threads. Some of these threads grow down, like roots. Others grow upwards, like stems. Bunches of these threads form the spots you see on mouldy fruit or cheese.



Yeast cells look like drops of jelly. They’re so tiny you can’t see them without a microscope. When a yeast cell takes in food, such as sugar, it swells up and splits into two new cells. Then, each new cell takes in food, swells up, and splits in two. Soon, there are millions of new yeast cells. People put yeast in bread dough to help make the bread fluffy.



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Why do plants eat insects?


You probably know that many insects eat plants. But did you know that some plants eat insects? These plants include the sundew and the Venus’s-flytrap. They need to eat insects because their soil does not have enough food to help them grow.



The leaves of sundew plants are covered with little hairs. On each hair there is a drop of sticky liquid. These drops glitter like dew in the sunshine and attract insects. When an insect touches one of the drops, it is stuck! Then all the hairs slowly fold in around the insect. They push the insect down against the leaf. A juice oozes out of the leaf and digests the insect.



The leaves of the Venus’s-flytrap work just like traps. They can open and close like clam shells. Little “claws” surround the edge of each leaf, and tiny hairs grow on the inside. When a fly or other insect lands on a leaf and touches one of the hairs, the leaves quickly close like a trap. Then the plant digests its meal.



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What are unusual plants?


If you think that all plants look and act alike, you’re in for a surprise. Plants come in more shapes and colours and live in more places than you can imagine. They have some unusual ways to get their food and water, too.



New Zealand has a plant that looks like a soft cushion. It’s called a cushion plant. It’s made up of thousands of tiny stems with millions of little leaves. The leaves are covered with tiny hairs. The stems are so close together that the plant looks like one big green cushion. In winter, the plant turns white, giving it a woolly look.



Some plants live by “stealing” food or water from other plants. When the dodder sprouts from the ground, it begins to grow towards the nearest plant. The dodder soon wraps itself around the other plant. It gets its food and water by sucking them out of the other plant. Mistletoe also gets its water this way. Mistletoe grows on many kinds of trees, with its roots sunk deep into the tree’s branches.



Some plants even move! They don’t actually get up and walk around, but they open and close, or fold and unfold. For example, if you touch the leaves of the sensitive plant, they will fold up suddenly and droop. Then, in a short time, they will unfold and straighten up again.



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What are poisonous plants?


Many kinds of berries and seeds are poisonous! People have died from eating mistletoe berries, yew berries, and castor beans. Belladonna, or deadly nightshade, has green or black berries - both are dangerous! Never eat a berry, seed, or nut unless a grown-up says it is safe.



Some plants make you itch and burn if you touch them. You can avoid them if you know what they look like. Poison sumach has white berries that hang down. Poison ivy grows as a vine, with leaves in groups of three. That’s where the cautionary rhyme “Leaves of three, let it be” came from. Nettles have bristles that can make you itch.



Some of the most beautiful plants are poisonous. The oleander can sicken or even kill a person who eats it. Some plants have both poisonous and non-poisonous parts. Rhubarb stems are good to eat, but eating rhubarb leaves can make you very ill!



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How Long Do Plants Live?


Some plants live for only one year. These plants are called annuals. The seeds of annuals sprout in the spring. A new plant grows. The plant flowers and makes new seeds in summer. When winter comes, the plant dies, leaving seeds in the ground to germinate in spring.



Some plants seem to die when winter comes. Their leaves fall off and their stems look dry and lifeless. But in the spring they start growing again. These plants are called perennials. Perennial plants grow back year after year.



A biennial plant lives for two years. The first year, it grows leaves and shoots. As it grows, it stores food, often in a swollen root. When winter comes, the leaves and stems die. The next spring, the plant grows again. It flowers and makes seeds, using the food it had stored up the previous year. Then it dies.



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What are watering plants?


Have you ever seen firefighters using a fire hose? The hose looks stiff and fat while water is running through it. But when the fire is put out and the firefighters turn off the water, the empty hose is limp.



Many plants are something like a fire hose. As long as their roots keep pumping water, their stems and leaves stand up straight and stiff. But a plant loses water through its leaves. If the plant doesn’t get enough water to replace the lost water, it will soon flop over, just like an empty fire hose. Perhaps you’ve seen this happen to potted plants. They begin to droop when they need water.



Plants that live in deserts, where there is very little water; have special ways of collecting and storing water. For example, the roots of some cactus plants grow down deep or spread out very far to find water. Cactus plants store the water in their thick, fleshy stems. When there is no rain, they live off the stored water. 




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What kinds of trees have needles?


The kinds of trees that are often used as Christmas trees are called conifers or needleleaf trees. They are called needleleaf trees because their leaves are thin and sharp, like needles. Pines, spruces, and redwoods are all conifers.



Most conifers are green all year. They are called evergreens. They don’t change colour and lose all their leaves at a certain time each year as deciduous trees do. Instead, they lose a few needles at a time, all year round.



Conifer needles are very tough. They don’t freeze in winter, and they don’t lose water as quickly as other kinds of leaves do. By holding on to the water they have, conifers stay alive and green all winter.



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Why do broadleaf trees lose their leaves?


Many broadleaf trees lose their leaves once a year and later grow new leaves. These trees are called deciduous trees. Oaks, maples, willows, and many other types of trees are deciduous.



In places that have cold winters and warm summers, most deciduous trees lose their leaves in autumn. Leaves need water to stay alive and to make food. A tree gets water from the soil. But in winter, the water in the soil turns to ice. The roots can’t take in this frozen water. There is no water for the trees.



In late summer, the tree begins to prepare for winter. A thick layer grows where each leaf’s stem is attached to the twig. Water can no longer get into the leaves. The leaves dry up, fall to the ground, and die.



In springtime, the ground warms up. The ice melts. The soil is wet again. Then a tree’s roots start taking in water, and the tree grows new leaves.



But not all broadleaf trees are deciduous. In warmer parts of the world, broadleaf trees stay green all year. They are called broadleaf evergreens. They lose just a few leaves at a time. The eucalyptus, or gum, trees of Australia are broadleaf evergreens.



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What are the largest plants?


Can you climb a maize plant or a tulip? Can you swing from a daisy? Of course not! But a tree is a different matter entirely.



Trees are tall, sturdy plants with woody stems called trunks. Branches grow from the trunk, usually quite far off the ground. It’s the trunk that makes a tree so strong. The trunk supports the tree.



The trunk also has several layers, each with an important job to do. Tree trunks are covered with a tough outer skin. Most trees have a hard, dry skin called bark. The bark protects the soft inside part of the tree. The next layer carries food made by the leaves to other parts of the tree. Next to this layer is the part of the trunk that makes the bark and new wood. Further inside is the wood. Some wood carries water around the tree. The inner wood helps support the tree.



In regions where trees make a new layer of wood once a year, the layers form a series of rings. After the tree has been cut down, each year’s layer of wood can be seen as a ring. A tree with 50 rings has lived for 50 years. The rings also reveal the tree’s life story. Narrow rings show that there was not much water or sunlight that year. Wider rings mean more water and sunlight were available, and more growth occurred.




How do plants without seed make new plants?


Not all plants have to make seeds to grow new plants. Some plants can make copies of themselves without the help of another plant.



The good-luck plant grows new plants around the edges of its leaves.



If you plant a potato, a new plant will sprout from it! A potato is a tuber. New stems sprout from a tuber’s bud, called an eye.



The leaves and stems of some new plants grow out of underground buds called bulbs. Flowers such as lilies, tulips, and crocuses grow from bulbs. Onion and garlic plants have bulbs you can eat!



Some plants grow copies of themselves by sending off shoots. Mint and some kinds of grasses have underground stems from which new plants will grow. Strawberry plants produce stems called runners that grow sideways. New plants grow on the runners and root themselves wherever they touch the ground.



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What are the types of engineers?



Our world is full of mechanics that help us use things, go places, and communicate. Engineers help make all this possible. Here are just a few types of engineers and what they do.



Architectural engineers



Architectural engineers develop better ways of building homes and other buildings. They also find ways to make buildings taller. They apply the latest scientific knowledge and technologies to the design of buildings. Architectural engineering as a relatively new licensed profession emerged in the 20th century as a result of the rapid technological developments. 



Chemical engineers



Chemical engineers design ways to end pollution. They create drugs to fight cancer and other illnesses, too. Chemical engineers work mostly in offices or laboratories. They may spend time at industrial plants, refineries, and other locations, where they monitor or direct operations or solve onsite problems. Nearly all chemical engineers work full time.



Civil engineering



Civil engineering is the oldest kind of engineering. Civil engineers design bridges, subways, roads, dams, and canals. Civil engineering is traditionally broken into a number of sub-disciplines. It is considered the second-oldest engineering discipline after military engineering, and it is defined to distinguish non-military engineering from military engineering.



Electrical engineers



Electrical engineers design equipment that produces electric power and sends it to our homes. They also design computer circuits and robots. Electrical engineers work in a very wide range of industries and the skills required are likewise variable. These range from circuit theory to the management skills of a project manager. The tools and equipment that an individual engineer may need are similarly variable, ranging from a simple voltmeter to sophisticated design and manufacturing software



Materials engineers



Materials engineers work out how to make the produces we use better. They develop new materials for making anything from hand tools to huge trains. They also find new ways to use the materials we already have.



Mechanical engineers



Mechanical engineers design new machines. Some mechanical engineers invent better ways of heating and cooling homes and buildings. The mechanical engineering field requires an understanding of core areas including mechanics, dynamics, thermodynamics, materials science, structural analysis, and electricity.



In many ways, engineers are helping to design the future.



 



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How do robots learn new jobs?



With a click and a whirr, a robot keeps busy in the factory. It joins steel panels together. All day long it works on brand-new cars.



Some robots push a metal pin called a rivet through metal sheets to join the pieces together. Others are welders. They heat the edges of the metal very quickly so that they melt and join together.



There are no humans working these robots. These robots work by themselves.



How are robots able to join the parts correctly every time? First, a human teaches the robot to do the job. As the human moves the different parts of the mahine in and out, up and down, reaching out and twisting around, every movement is recorded by the robot’s microprocessor. Now the robot has all these movements in its memory. It knows exactly what to do every time a car is put in front of it. As long as the cars are put in exactly the same place each time, the robot will move into action and carry out exactly the right movements for riveting, welding, or even spray-painting.



 



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How do tall buildings stay up?



Tall trees in the forest sway in the wind. So do tall skyscrapers in the city but you just don't notice it as much. So how do these very tall buildings stay up?



The walls of a skyscraper are made of stone, concrete, glass, or metal. Under the walls is a frame of concrete or steel. This frame is strong enough to hold up the walls and floors. But it can also bend very slightly in the wind-like trees do. A tall tree has deep roots that hold the trunk and branches. Tall buildings have deep foundations. The foundation holds the steel girders in the ground.



The builders dig down until they find solid rock to build. The builders dig down until they find solid rock to build the foundation on. If there is no rock and the ground is soft, the basement is built on piles. Piles are deep holes bored into the ground. The holes are filled with steel and concrete. This gives the building a sturdy base to rest upon.



 



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What material are bridges made of?



Thanks to bridges, rivers and lakes will not interrupt a journey. People build bridges to make it easier to cross rough land or water. There are thousands of bridges in the world, but only five basic kinds: beam, arch, suspension, cantilever, and cable-stayed bridges.



Do you think bridges could be made out of glass? Inventors are working on this idea now. Concrete used in bridges is worn down by salt, ice, and wind. The steel used to make the concrete stronger often rusts. But a special glass called fibreglass is very strong. When glass fibres are held together by a type of "glue" ice, and wind. The steel used to make the concrete stronger often rusts. But a special glass called fibreglass is very strong. When glass fibres are held together by a type of "glue" called resin, they become stronger than steel or concrete. Fibreglass is also lightweight and can be easily shaped.



Beam bridge: This can be made of wood, steel, or concrete.



Arch bridge: A beam bridge can break easily in the middle. But a curving arch helps to carry the load on the bridge.



Suspension bridge: The roadway is suspended, or hung, from long steel cables. This type of bridge can be much longer than other types.



Cantilever bridge: One or more independent beams joined by a centre span make a cantilever bridge.



Cable-stayed bridge: This is one of the newest kinds of bridge designs. It takes less concrete or steel than a beam bridge. And it fits across narrow rivers better than a suspension bridge.



 



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