Category Plants & Animals

When is a butterfly formed?

            A caterpillar starts to become a butterfly as soon as it enters the chrysalis stage, by wrapping itself in cocoon. During this phase, known as pupation, the insect gradually develop all the butterfly characteristics, including wings. For some butterflies the transformation may be completed in one or two weeks. But others need many months before they are ready to leave the cocoon and     fly away.

            From the time it is hatched to the time it starts the pupation stage, a caterpillar or larva does little more than eat, grow larger and moult several times. This larval stage varies according to the species. Small caterpillars will complete their development in a week but some large varieties will take us two years or more.

            When this period is over the caterpillars spins a cocoon under a leaf or even underground, and enters it to begin the transformation. Many cocoons are of silk.

Why do many flowers have a sweet scent?

The sweet scent of flowers is designed to attract insects who seek food in the shape of pollen and the fragrant-smelling nectar. This nectar is a solution of sugars produced in little sacs called nectarines at the base of the flower petal.

     The insects have a part in the process of fertilization. Almost all plants perpetuate themselves by means of sexual reproduction, during which a male reproductive cell or sperm fuses with female reproductive cell or egg.

     When bees or other insects visit flowers in search of the sweet-smelling nectar, parts of their hairy bodies become dusted with pollen which contains the male reproductive cells. This rubs off on the flower’s carpels which contain the egg or ovule.

Insects seem to be strongly attracted by sweet scents. In fact, some flowers, such as the meadow sweet, are so highly scented that insects are attracted to them although they have no nectar to offer. Most insect-pollinated flowers have evolved wonderful devices for guiding the movements of that pollen is dusted over the insect’s body

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.

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.