Category Zoology

LIVING THINGS – INTRODUCTION

 

 

Our world is home to many millions of living things. From the hot, dry deserts to the frozen Polar Regions, at the depths of the oceans, and even inside the bodies of other creatures! All living things are specially adapted to enable them to survive in their different environments.

Living things may look very different, but they all share some basic characteristic: they need oxygen and ‘nutrients’ for nourishment; they move and grow; they get rid of waste substances; they react to things around them; and they can also reproduce.

 

 

 

 

 

Polar bears are specially adapted to live in the cold extremes of the Polar Regions.

 

 

 

 

 

 

 

Chameleons change the colour and pattern of their skin, to blend in with their surroundings and protect themselves from attack.

 

 

 

 

 

 

 

Lions are camouflaged in the hot, dry plains of Africa.

IS IT ALIVE?

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.

THE VARIETY OF LIFE

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”

EVOLUTION

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.

CELLS

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.

FEEDING AND BREATHING

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.