My Science School

Imagine you were looking at a waxwork model of a child. They model might confuse you at first. It may look very realistic and even share many of the physical features of a child. But you would soon be able to tell that the waxwork was not a living thing.

A real child can move. A child needs to eat and breathe to survive, and gets rid of waste materials, like faeces and urine, from its body. A child can see and hear things happening nearby and will act accordingly. Eventually the child will grow and may even have children of its own. The waxwork model may appear to be very lifelike but it can do none of these things.

Living things can move about, sometimes very quickly, like these human sprinters.

 

 

 

Living things need nutrients for nourishment. This hummingbird is feeding on flower nectar, a good source of sugar. In turn, the flower has been feeding on sunlight and nutrients from the soil.

 

 

 

 

 

 

 

 

We plant many kinds of trees, shrubs and flowers in public places and in our gardens.

There are about two million different types of living things today! Although they share similar features, there are also great differences between them. People have found it useful to sort living things into groups. The two largest groups are the plant and the animal kingdoms.

 

Within these groups there are many different types, or ‘species’. So scientists divide the plant and animal kingdoms into smaller groups. Animals are firstly divided into those that have backbones, the ‘vertebrates’, and those that do not, the ‘invertebrates’. Plants have also been divided into many different groups that distinguish between their structure and their leaf or flowering cycles.

 

The animal kingdom

Most animals are invertebrates (without a backbone). For example, earthworms, butterflies, spiders and crabs are just a few invertebrates. Vertebrates can be put into five groups: fish, amphibians (vertebrates which spend part of their lives in water and part on land), birds, reptiles and mammals. Mammals are the only animals which produce milk to feed their young.

 

Continue reading "THE VARIETY OF LIFE"

Where did all the different types of living things come from? Nobody knows for certain, but many scientists think that plants and animals have gradually developed, or ‘evolved’, over millions of years. As they have changed, they have become better adapted to survive.

For example, millions of years ago plants had no flowers. They relied solely on the wind and the rain to transport their pollen to other plants, so that new seeds could develop. But over time, plants developed simple flowers to attract insects. Insects accidently pick up sticky pollen as they feed on flower nectar, and carry it to nearby plants, helping the flowers to reproduce.

 

 

Human beings may have evolved from ape-like animals. These developed the ability to stand upright on just two feet, so that they could then use their hands for other things. Over millions of years they learnt how to use tools and developed these to become successful hunters.

 

 

 

 

 

 

Fossils are the remains of plants and animals that have been preserved in rock. They give us clues about the life of ancient living things. Scientists can work out the age of fossils by dating the rocks in which they are found.

 

 

 

 

 

Insect-pollinated plants tend to have fragrant, brightly coloured flowers to attract insects.

All living things are made up of tiny building blocks called ‘cells’. Cells are too small to see without a microscope. Some living things have one cell, but the human body consists of about a hundred trillion cells!

Almost all cells contain a nucleus. The nucleus is very important as it controls everything that happens inside the cell. Around the nucleus is a jelly-like substance called ‘cytoplasm’. Here, lots of chemicals are stored. Around the cytoplasm is a very thin ‘skin’ called the cell membrane? This holds the contents of the cell together and controls what enters and leaves the cell. Plants and animals have different types of cells. These cells are all designed for a particular job.

 

 

 

 

 

Plant cells

Plant cells are each surrounded by a ‘cell wall’ made of cellulose, which gives the plant structure and support. They each have a nucleus and cytoplasm. Plant cells usually have a very regular shape.

Animal cells

Animal cells don’t have any cell walls (just a cell membrane). This is because animals use other ways of supporting themselves, such as skeletons. Animal cells are usually irregular in shape.

 

 

 

 

 

 

Special cells have caused pigmentation in these zebras’ coats, creating a striped camouflage.

 

 

 

 

 

 

 

A leaf under a microscope clearly shows the structure of a plant cell.

Living things need certain substances to move, grow and keep themselves alive. Animals eat plants or other animals as their main source of nutrition.

This food is chemically complicated and must be reduced to simpler materials by a process called “digestion”. Chemicals in the body break down the nutrients in food, which the body then uses for growth and energy. Waste materials are then excreted by the body.

 

 

 

 

Photosynthesis

Plants and animals depend on each other for feeding and breathing. Plants take carbon dioxide from that air and absorb water and minerals from the soil. They use the Sun’s energy to convert these simple substances into sugars and starches and produce oxygen. This is called “photosynthesis”.

Animals, like gorillas, use plants as a source of food. They also breathe in the oxygen that plants release. Animals produce carbon dioxide which they breathe out and they excrete waste water and chemicals from their bodies. Plants depend on all these substances.

 

 

 

 

 

Plants need oxygen in order to carry out certain life processes. Plants use photosynthesis to produce oxygen but they also absorb oxygen from the soil (through their roots) and from the air (through small holes in their leaves).

 

At night, plants take oxygen from the air because there is not enough sunlight for photosynthesis to take place. During the day plants produce their own oxygen – much more than they need. This excess oxygen is released into the air.

 

Plants provide oxygen for humans and animals to breathe.

 

 

 

 

Squirrels need to eat about a pound of food a week to maintain an active life.

Most animals have to move to find their food and to avoid predators and other dangers. Many of these animals have muscles to help them move. Muscles help fish to swim, birds and insects to fly and many animals to walk and run.

Plants move by growing in different directions. When water is in short supply, plant roots grow deeper into the soil to find it. Shoots grow taller to find more sunlight. Plants also need to move their pollen and seeds. Pollen and seeds are ‘dispersed’ – spread around – from their parent plant so that they have their own space to grow. They may be carried by animals, water or the wind.

 

 

 

 

Most snakes get from place to place by throwing their bodies into curves. When a snake moves, waves of muscular contraction flow from head to tail. Its sides also push against irregularities on the ground (represented by the orange arrows in the diagram).

 

 

 

 

 

 

 

Virtually every part of a cheetah’s body has been adapted to maximize its running speed.

 

 

 

 

 

 

 

Climbing plants, like ivy, use walls for support, and grow towards the sunlight.

 

 

As plants and animals develop, they grow and get larger and heavier. How does this growth take place? We know that living things take substances, like food, into their bodies. Some of these substances become part of body cells. Cells get bigger until they cannot grow anymore and they divide into two. As more cells are formed, a living thing grows.

 

When living things are fully developed they are able to ‘reproduce’ and create new members of their species. Most living things in the animal world reproduce when special ‘sex cells’ from the mother and father join together. As this cell grows and divides, a new living thing develops.

 

 

 

 

This cell is ready to divide. The threads inside its nucleus, called “chromosomes”, have been duplicated. The nucleus now starts to divide and each new nucleus gets a complete set of chromosomes. The cell membrane then divides to form two separate cells. These are identical to the original cell with the same number of chromosomes. They will grow and eventually divide themselves into two new cells.

 

 

 

 

 

 

 

This calf will grow and develop for up to seven years before it becomes fully-grown.

 

 

 

 

 

 

 

Yew trees take 1,000 years to mature, while pine trees only take 30 years.

The waves that crash on to a seashore are very strong. Seashore plants and animals must hold on tight to keep themselves safe. If they let go, they could be washed away or smashed on the rocks.

 

 

These limpets are holding on to a rock.

Seashore animals have different ways of holding on. Limpets use their strong foot to grip tightly on to rocks and stop them from being washed away. Some animals, like sea urchins, cling on to rocks with lots of tiny feet that look like tubes. Mussel shellfish anchor themselves down to rocks with tough threads.

 

 

 

 

This seaweed grips on tightly to the rocks.

Seaweeds anchor themselves on to rocks to stop them from being washed away by strong waves. Large seaweeds grip on to rocks with strong, finger-like rootlets called holdfasts. During storms, seaweed is ripped off rocks.

 

 

 

 

 

Sea otters wrap themselves in seaweed.

When sea otters sleep, they wrap themselves in giant kelp seaweed. They grab a floating end of kelp and spin around in the water. The kelp wraps around the otter and anchors it down. It stops the sea from carrying the sea otter away in its sleep.

 

 

 

Many plants live on the seashore. Seaweeds are seashore plants that can live in salty seawater. Some seashore plants can only live on the land. They grow high up the shore, out of the reach of the waves.

 

 

 

 

 

This seaweed floats in the water.

Bladder wrack seaweed has pockets of air and jelly to help it float in the water. Its tough leathery leaves are covered in a slippery, gummy substance to protect it from drying out at low tide. Bladder wrack can survive out of water while the tide is out.

Rainforests are important to all of us, so we must save them. Many groups of people raise money to protect and restore rainforests. The money might be spent replanting trees or teaching farmers how to look after the forest.

Growing crops in small patches helps to protect the soil.

If local farmers learn to grow their crops in a similar way to the forest people, they can stop the thin soil wearing out. Growing patchworks of different plants and trees, instead of just one type, restores nutrients to the soil. Using the land sustainably means that farmers will not need to move on and cut down more rainforest.

 

 

 

People can visit this protected rainforest.

Some rainforests have been turned into National Parks or reserves where it is against the law to cut down the trees. This helps to keep the animals, plants and people that live there safe. Many tourists visit the parks to see the rainforest wildlife.

 

 

Continue reading "Rescuing the rainforests"

 

 

People who live in rainforests know how to find everything they need. The forest gives them food, shelter, clothes and medicine. In return, they treat the forest with great respect. They take only what they need, without causing any damage.

 

 

 

 

This man is weaving a roof using palm leaves.

Rainforests throughout the world have been home to various tribes of people for thousands of years. They build their homes using rainforest plants and they hunt for meat, gather fruit and nuts and grow useful plants in their gardens. They use the rainforest in a sustainable way that does not destroy it.

 

 

 

 

Rainforest is cleared to make cattle farms.

Many people have moved into rainforests, but they use the forest in ways that destroy it. Huge areas of rainforest have been cut down to make way for farmland. But because the nutrients in the thin soil soon wear out, farmers move on to destroy new parts of the forest, leaving behind a bare, infertile piece of land.

 

 

 

 

This hillside was once covered in trees and packed with wildlife.

When a rainforest is nut down, plants, animals and rainforest people lose their homes. Many species may die out and become extinct. Without the cover of the trees, the thin soil dries up and is washed away by the rain. The land is left like a desert and it is very difficult for rainforest to ever grow there again.

 

Rainforests only cover a small part of the Earth’s surface but they are sometimes called the lungs of the world. They help control the world’s weather and affect the air we breathe.

Rainforests help to recycle gases in the air.

Trees and other plants breathe in the opposite way to humans and animals. Trees breathe in carbon dioxide (which we breathe out) and breathe out oxygen (which we breathe in). This helps to balance gases in the air and ensures there is plenty of oxygen for us to breathe.

 

 

 

Rainforests soak up the heat from the Sun.

Dark green rainforests absorb the heat and strong sunlight that shines in the tropics. When rainforests are cut down and lighter coloured vegetation grows instead, it creates a mirror effect. Sunlight and heat are reflected back up into the atmosphere causing it to warm up.

 

 

 

 

 

 

 

Cutting down rainforests is helping to make the Earth warmer.

When rainforests are destroyed, there are fewer trees to remove carbon dioxide from the air, so it starts to build up. Too much carbon dioxide in the atmosphere traps heat from the Sun like the glass in a greenhouse. This is called the greenhouse effect and it is making the Earth warmer.

 

Many of the things that we use and eat every day come from the rainforest. New animals and plants that could be useful in the future are being discovered all the time.

All of these things come from rainforest plants.

Many of the foods that we eat come from the rainforest. Banana, coffee and avocado plants first grew wild in rainforests and are now grown in large plantations. Some foods, such as Brazil nuts are still collected from trees growing in the rainforest.

 

 

 

 

 

 

 

 

 

Continue reading "Rain forest Nature’s superstore"

 

 

The rainforest floor is covered with a thick layer of fallen leaves called leaf litter. Millions of insects, tiny creatures and fungi help to break down the leaves. Anything that falls to the forest floor is not there for long!

 

 

 

 

 

Everything that falls to the ground is recycled.

The hot, wet conditions in the rainforest are perfect for rotting, or decomposing. Insects and fungi help to break down dead plants and animals into simple nutrients. These are quickly absorbed by the shallow roots of trees and plants. Rainforests are so good at recycling that 99 percent of nutrients never leave the cycle!

 

 

Continue reading "Rainforest recyclers"

 

The forest floor is the darkest and warmest part of the rainforest. Very little sunlight reaches the ground so few plants grow here. The forest floor is home to many insects and the animals that like to eat them, such as lizards!

 

 

 

 

 

 

This huge rainforest spider is as big as a dinner plate.

The Goliath bird-eating spider is the largest spider in the world. It lives on the rainforest floor and hides in burrows or under logs during the day. At night, it comes out to hunt for lizards, frogs, insects and small birds, which it bites with its poisonous fangs.

 

 

Continue reading "Life at ground level in rainforest"