SEXUAL REPRODUCTION
TABLE OF CONTENTS
- WHAT IS SEXUAL REPRODUCTION
- INTRODUCTION
- SEXUAL REPRODUCTION IN FLOWERING PLANTS
- PARTS OF A FLOWER
- POLLINATION
- SELF POLLINATION
- CROSS POLLINATION
- FERTILISATION
- SEXUAL REPRODUCTION IN ANIMALS
- MALE AND FEMALE
- GAMETES
- ZYGOTE
- FERTILISATION
- TYPES OF FERTILISATION
- ADVANTAGES OF SEXUAL REPRODUCTION
WHAT IS SEXUAL REPRODUCTION
Sexual reproduction is a way of reproduction which requires the fusion of the haploid female gamete, which is the egg cell and the haploid male gamete, which is the sperm cell. Sexual reproduction tales place by the union of special reproductive cells known as the sex cells. These sex cells are of two types , male sex cells and the female sex cells (these come from two different parents which are a male and a female). These sex cells are commonly known as gametes. Thus the cells required in sexual reproduction are known as gametes.
INTRODUCTION
The gametes are of two types: male gametes and female gametes. In the sexual reproduction, a male gamete fuses with a female gamete to form a new cell known as the zygote. This zygote then is grown and developed into a new organism in a certain amount of time. This should be noted down that the sex cells or the gametes are sometimes also known as the germ cells. And in total there are two types of germ cells that exist male germ cells and female germ cells.
SEXUAL REPRODUCTION IN FLOWERING PLANTS
The plants in which the sex organs are taken within the flowers and the seeds are surrounded by in a fruit are called angiosperms . Angiosperms are frequently known as flowering plants. The flowering plants reproduce by ‘sexual reproduction ‘ procedure. This clearly signifies that two sexes (female and male) are involved in reproduction in flowering plants.
Just like the human beings , plants also have male and female sex organs , although they are different in form from humans beings. The reproductive organs of a plant are in its flowers . We can also say that flowers consist of the sexual reproductive organs of a plant . In plants mostly the same flower consists of the male organ as well as the female organ. In different words , flowers consist of the sexual reproductive organs of a plant.
In most of the plants, the major number of plants are bisexual which have the male and female reproductive organs in the similar plant or same flower. And in fact the reproductive part of the inflated plants is the flower.
The main purpose of the flower is to build male and female gametes and to ensure that fertilization will occur to build new seeds for the reproduction of plants. The most common way of reproduction in flowering plants is by sexual reproduction.
For the sexual reproduction to occur , it occurs in the flowers. A flower develops both the male and female gametes required for sexual reproduction in the plants.
PARTS OF A FLOWER
The main parts of a flower are listed below as follows :
These are receptacle , sepals , petals , stamen and carpel. These are all explained briefly below.
- RECEPTACLE – The base of the flower to which all the slices of a flower are attached is known popularly as the receptacle.
- SEPALS – The green , leaf-like bits in the outermost circle of a flower are known as sepals. When taken altogether, all the sepals are known as calyx. The main purpose of the sepals is the protection of the flower in its early stage when it’s in the form of a bud.
- PETALS – The glowing parts of the flower are known as petals. The petals are placed inside the sepals. All of the petals when counted all together are known as corolla. Usually the petals are scented. They smell beautiful. The main features of the petals is to attract the insects for pollination and also to protect the reproductive organs that are in the middle of the flower.
- STAMEN – The small stalks with swollen up tops just on the internal ring of petals in a flower are known as stamens. The male reproductive organ of the plant is the stamen. Pollen grains are produced by the stamen.
The Stamen is formed by two parts : the filament and the anther. The bundle of stamen is known as filament and the swollen up top of the stamen is known as the anther. It is usually the anther of a stamen that forms the pollen grains and keeps them. The pollen grains are yellow , powder-like substances which appear as this. The male gametes are contained into the pollen grains of the plant. The male gametes of a plant are formed in the anther of the stamen. A flower typically has a lot of stamens in it. - CARPEL- The carpel lies at the centre of the flower in a flask shaped organ. The female reproductive organ of the flower is known as the carpel. A carpel is made up of three parts : stigma , style and ovary. The stigma is the toppest part of the carpel. For receiving the pollen grains the stigma is present from the anther of stamen during pollination. The stigma is made sticky for the pollen grains to stick to it. The style is the middle part of the carpel. Style is a tube shaped structure which makes a connection between stigma to the ovary. The ovary is the swollen part at the bottom of the flower below the carpel . Ovules are made by the ovary and stored. Ovules consist of the female gametes of the plant. There are typically many ovules in the ovary . Each and every ovule consists of only one female gamete of the plant. The female gamete of the plant that is near the inner part of the ovule is known as the ovum or the egg.
The Female gametes of a plant are formed in the ovary of the carpel. The female organ of a plant is called by two different names : carpel and the pistil. The female organ known as the carpel is nearby a number of male organs known as the stamens in the flower.
The flowers that contain only single sex organ , either stamens or the carpels are known as unisexual flowers. Unisexual flowers include the flowers if papaya and watermelon plants. But the flowers in which both both sexe organs are contained which are the stamens and the carpels , they are typically known as the bisexual flowers.
Some examples of bisexual flowers are mustard plants and Hibiscus flowers.
A newly formed seed of the plant at the time when the gamete is present in a pollen grain unites with the female gamete that is present in the ovule.
This occurs in two different ways : pollination and fertilization.
POLLINATION
To the male gamete to be able to merge with the female gamete , it is compulsory that the pollen should firstly grain from the anther of stamen and hence should be taken to the stigma of carpel.
This transfer of the pollen grains from the anther to a stamen to the stigma of a carpel is known as pollination. Therefore pollination is said to occur when the pollen grains are taken from anther to the stigma of the flower. Pollination is conducted by insects like bees and butterflies , birds , wind and water. Pollination can happen in two different ways : self pollination and cross pollination.
SELF POLLINATION
When the pollen grains from the anther of a flower are transported to the stigma of the same flower or another flower on the same plant it is known as self pollination.
CROSS POLLINATION
When the pollen grains from the anther of a flower on one plant are transported to the stigma on another similar plant, this technique is called cross pollination. Cross pollination is carried by insects as follows:
At the time of when an insect sits on the flower of a plant for sucking nectar , then the pollen grains from the anther of this flower adhere to its body.
And thus when this insect sits on another flower of another plant , then the pollen grains adhered to the insect’s body are transported to the stigma of this second flower.
FERTILISATION
After a pollen grain has fallen on the stigma , he next pace is fertilization. Fertilisation is said to occur when the male gamete present in the pollen grain has joined with the female gamete or the egg present in the ovule.
SEXUAL REPRODUCTION IN ANIMALS
MALE AND FEMALE
A man or a boy is male and has male sex organs while a woman or a girl is a female which has female sex organs.
The male sex cells are called the sperms while on the other hand , the female sex cells are known as ova eggs.
GAMETES
Sexual reproduction occurs by the contribution of special reproductive cells known as the sex cells. These sex cells are also called as gametes. In different words, gametes are the sexual reproductive cells.
Gametes are of two different types :
Male gametes and female gametes .
Male gamete is called as sperm and the female gamete is called as the ovum or the egg.
Sperms and ova are highly small cells that can be viewed only by the help of a higher power microscope.
ZYGOTE
The fusion of two gametes , has given rise to a single cell known as the zygote. In other words, the cell that has formed by the fusion of male gamete and a female gamete is known as the zygote.
FERTILISATION
For the sexual reproduction to occur, a male gamete must have to fuse with a female gamete. The fusion of the male and female to form a zygote during the sexual reproduction is known as fertilisation.
In other words we may call it the fusion of a sperm with an ovum or an egg which can lead to the formation of a zygote during sexual reproduction is known as fertilisation.
The procedure of fertilization gives rise to a new cell known as the zygote.
The zygote is the fertilized ovum or the fertilized egg. The zygote then evolves and matures to form a bew baby. The unborn baby in the uterus in initial stages of maturation is known as the embryo.
TYPES OF FERTILISATION
- INTERNAL FERTILISATION
Internal Fertilisation can be called that has occured inside the female’s body. In all mammals including human beings, birds and reptiles , the fertilisation occurs inside the female body itself.
In internal fertilisation, the male animal has to place the sperms into the female animals body. The transformation of sperms from male to the female is known as copulation or mating. During the procedure of copulation, a large number of sperms are discarded into the female body. - EXTERNAL FERTILISATION
External fertilisation can be explained as the one that occurs outside the female body. In external fertilisation, the eggs of the female animal are fertilized outside the body of the female. This occurs in amphibians like frogs , toads, fishes . The fertilisation of eggs of the female occur outside the female animal’s body. In external fertilisation, the sperms and eggs are released by the male and female ib the water where they collide and fertilisation takes place.
ADVANTAGES OF SEXUAL REPRODUCTION
The sexual reproduction has many advantages over the asexual reproduction. In the case of sexual reproduction, the children or the offsprings are almost similar to their parents as they have the same genes.
Therefore much of genetic variation is not possible in asexual reproduction. Thus it can also be counted as an disadvantage as it stops the further evolution of the organism.
But in the case of sexual reproduction, the offsprings are almost similar to the parents but are not identical to them or to one another. This can be marked due to the fact that the offsprings receive some genetic material from the father and some from the mother.
Due to this mixing of the genes, from the father and mother of the offsprings, a lot of genetic variations can be seen . Also sexual reproduction leads to a lot of genetic variety in the population. This clearly means that the species can very fast adapt to the changes in the surroundings.