Lifecycle of Living Things

Introduction

Living things go through a sequence of changes from one form to another and from one generation to another, in the process of growth and reproduction. Mammals, for example, develop from a fertilized egg to an adult. Adults then produce new sex cells, known as gametes, which fertilize new egg cells to initiate the same development process again. This specific and repeated pattern of developmental stages is called the Lifecycle of that organism. All plants and animals undergo a lifecycle unique to them. Two important lifecycles are explained here.

Plant Lifecycle

Flowering plants and trees start life as a seed which contains the embryo and a protective layer. A seed needs fertile soil to germinate by breaking the outer layer and growing roots, shoots, and leaves. This is the beginning of a new plant or tree, known as a seedling. When the plant has grown to maturity it grows flowers. Male flowers contain pollen and female flowers have ovaries. Natural elements, like the wind or bees, carry the pollen from one flower to the ovary of another flower and start the process of pollination. The cells in the ovary (ovules) are fertilized and new seeds are produced. These seeds get dispersed by wind, water, animals to new soil where the process of germination starts afresh.

Non-flowering plants, such as moss or fern, don’t produce seeds. They produce spores which get carried by the wind to new moist soil to begin life after germination.

Insect Lifecycle – Metamorphosis

Insects – houseflies, moths, butterflies – undergo transformation through strikingly distinct stages from an egg to adulthood. Typically, this is a four-stage process called a Metamorphosis.

1. The egg
2. The larva or caterpillar
3. The pupa or chrysalis
4. The adult

The lifecycle begins with the egg in which the embryo forms. These insects lay eggs on plants or on decaying organic matter which provides food for the next stage of development, called the larva. In butterflies and moths, the larva is also known as a caterpillar, while in houseflies it is referred to as a maggot. A larva is simply a fleshy worm-like creature, with or without hair, and with a sucking mouth. They have no wings.

The larva or caterpillar grows wings, limbs, tissue, and all the beautiful colors of an adult butterfly or moth. It emerges by breaking the shell of the pupa and after resting awhile it slowly starts flapping its wings to become a fully developed adult. The adult then goes on to find a mate and repeats the process of laying eggs and having them fertilized to form a new lifecycle.

Check Point

1. The process of growth and development from egg to adult in any living organism is known as its ______.
2. Put in the correct order the flowering plant stages –
   1. Flowering
   2. Germination
   3. Seedling
   4. Pollination
3. Non-flowering plants do not produce ______, they produce ______ instead.
4. Put in the correct order the metamorphosis stages –
   1. Larva
   2. Adult
   3. Chrysalis
   4. Egg
5. Other words for larva in butterflies and houseflies are ______ and ______ respectively.

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