REPRODUCTION IN LIVING ORGANISMS
What is reproduction?
How reproduction does takes place?
Here you will see the importance of reproduction as concerns living things.
The question that bugs the mind is how does reproduction take place amongst living things?
WHAT IS REPRODUCTION?
Reproduction is the ability of living organisms to be able to give birth to young ones or new individuals of the same species.
The sole of reproduction is to ensure the continuity of life. Follow me as I give you load down on the various types of reproductio
TYPES OF REPRODUCTION
There basically two main types of reproduction. These are sexual and asexual reproduction. These simply means the reproduction involving only organism and the one involving two separate organism of the same species. So take the different types of reproduction as follows
ASEXUAL REPRODUCTION AND SEXUAL REPRODUCTION
Sexual reproduction is the type of reproduction which involves the fusion of the male gametes like the sperm cell, together with the female gametes called egg or Ova to form a Zygote which develops to a young offspring
Sexual reproduction is mostly found with mammals and flowering plants
DIFFERENCES BETWEEN SEXUAL AND ASEXUAL REPRODUCTION
The characteristics of sexual reproduction
i. One parent involved
ii. No gamete formed
iii. No fertilization/fusion of gametes/sex cell/no zygote formed
iv. Offspring are identical, meaning no genetic variation
v. Rapid reproduction mode
vi. More individuals are produced at a time
vii. Meiosis is not involved
The characteristics of asexual reproduction
i. Two parent organisms are involved.
ii. Gametes/sex cell formed
iii. Meiosis cell division is involved
iv. Fertilization/fusion of gametes/sex cell. Zygote is formed
v. Offspring varies genetically
vi. Slower mode of reproduction
vii. Fewer individual are produced
Types of asexual reproduction in animals
There are so many types asexual form of reproduction that can be found in animals. These are as follows
i. Binary fission====Amoeba and paramecium
ii. Budding===Hydra and Obelia
iv. Parthenogenesis===Aphids and Honey bee
vi. Fragmentation===Planaria/Sponges/Hydroid Coelentetrate
GENERAL FORMS OF ASEXUAL REPRODUCTION
Asexual reproduction is one aspect of reproduction that we will not shy away from dealing as it concerns a very technical aspect of producing new offspring for the sole purpose of life continuity.
So there are four major types of asexual reproduction methods. They are binary, budding, spore formation and vegetative reproduction
Binary fission is a type of asexual reproduction in unicellular organisms in which a single cell-parent divides into two or more equal parts by mitosis type of cell division to produce two or more new daughter cells. This can be seen in protozoa like Amoeba, paramecium and bacteria
Budding in reproduction is a type of asexual reproduction in which the parent organism forms an outgrowth known as bud, which then grows into a new organism. The organism later separates from the parent organism. This mainly occur in yeast and Hydra
Spore are asexual reproductive units formed by some lower organisms especially fungi, e.g. Rhyzopus, which produces numerous spores in sporangia that are borne at the ends of upright hyphae called sporangiosphores. When the sporangia becomes mature, they burst and the spores are dispersed by the wind. If the spores falls on a suitable substance, it germinates and gives rise to a new MYCELIUM
What is vegetative reproduction? Vegetative reproduction is the production of new individual from the vegetative parts of plants. The vegetative parts of plants which are involved in this type of reproduction are the stem, roots and the leaves.
TYPES OF VEGETATIVE REPRODUCTION
There are so many types of vegetative reproduction which can be seen here in agricultural science but I will be devoted to the following types of vegetative reproduction
It is worthy of note that there are two types of vegetative reproduction. These are natural and artificial vegetative reproduction. So let’s deal with them one after the other
NATURAL VEGETATIVE REPRODUCTION
Natural vegetative reproduction involves the use of natural or vegetative parts to produce or get new individuals. Such parts used for this method are leaves, roots and stem
There are also other forms of natural vegetative reproduction which are as follows
USE OF MODIFIED UNDERGROUND STEM
Some underground stem such as rhizomes, e.g. the cana lily, ginger,
SUCKERS e.g. banana, plantain, pineapple,
CORM e.g. cocoyam
BULB e.g. onion
These are few of the many forms of natural vegetative reproduction
THE USE OF FLESHY LEAVES
This type of natural vegetative reproduction involves the use of some fleshy leaves of some plants to produce new individual e.g. Bryophyllum
ARTIFICIAL VEGETATIVE REPRODUCTION
Artificial vegetative reproduction involves the use of intelligence by man to grow new plant from cut portion of the vegetative body of an older plant.
Artificial vegetative propagation can be carried out by cutting, layering, budding, grafting and marcotting. Very quickly let’s treat each them one after another
When parts of a plant are cut into portions and planted to in order to produce new plants, such cut portions are called cuttings. Cuttings may come from leaves or stems which solely depends on the types of plant that is been propagated. Plants whose stems produces roots easily are propagated by stem cutting.
Such stem must have two nodes close to the end which will be inserted into the ground. An example of plant that can be propagated by the stem cuttings are cassava, hibiscus, sugar-cane, cocoa, cola and sweet potato
Layering types vegetative propagation happens majorly when a branch or shoot growing near the ground is bent over so that one or two of the nodes could touch the ground. Then a slit is made on the node, and the branch pegged to secure it in place. The nodes are then covered with soil. The adventitious roots will then grow out from the node.
When the roots are well established, the stem is then severed from the parent plant and transplanted to the field to become a new plant. Examples of plant that are propagated through layering are tomato, cocoa, cola and coffee
Budding as a type of vegetative propagation of plants is a skilled technique used when plants do not easily grow from cuttings. Here a bud is cut from a matured plant branch. Attached to the bud is a flat, shield-shaped piece of stem. The stem piece and bud is called the scion
An inverted t-shapes cut is made on another bark of a desirable characteristics called the STOCK and the edges of the cuts are turned back to expose the cambium.
The scion is then inserted into the stock and the two are bonded into position. The joint should be made water proof by the use of polyethylene tape leaving the actual bud exposed. If the stock bonds successfully with the bud, then in about two to three weeks it should begin to develop new shoot.
The top shoot above the union is cut off while all branches below the scion are carefully removed. When fully developed, the budded plant is carefully transplanted to its permanent site
Grafting as a type of vegetative propagation plant is closely related to budding vegetative propagation and is one of the artificial methods of vegetative propagation. It involves the application of a whole shoot or stem (SCION) into another plant called the STOCK.
Grafting brings into close contact the vascular cambia of both the scion and the stock. As in budding, both scion and stock must be closely related on bonded to avoid incompatibility which could result in the breaking of the scion and stock at a later date. The practical and basic operation of the grafting is similar to that of budding
Plants easily propagated from or by grafting is mainly the Citrus, e.g. orange, grape, tangerine etc.
Marcotting as a types of vegetative means of propagation, the roots grow from the part of a branch in which a string of the tissue has been removed. This branch can then grow into a new plant.
Plants usually propagated by Marcotting include garden shrubs, mango tree and lemon
ADVANTAGES OF VEGETATIVE PROPAGATION OF PLANTS
I. YOUNG PLANTS USES FOOD RESERVES OF THE PARENT AS IT BECOMES EASILY ESTABLISHED
II. Growth in the young plant is rapid since there is no resting period
III. Only one parent is needed
IV. Offspring are identical to parents
V. Offspring mature more rapidly
VI. Plants are less susceptible to adverse weather condition
VII. Plants that do not produce seed are therefore propagated vegetatively
DISADVANTAGES OF VEGETATIVE PROPAGFATION OF PLANTS
i. No new varieties of plants are produced
ii. There is no mixing of characters
iii. Offspring and parents compete for light and nutrients since many individual occupies a small space
iv. Vegetative propagation reduces resistance to diseases
v. Vegetative propagation also reduces resistance to weather changes in the environment
vi. Colonization of new localities in unlikely since offspring are always produces to parent plant in vegetative propagation
vii. Diseases of parent plant can easily be transferred to offspring in vegetative propagation
viii. Undesirable character can easily be transmitted to offspring in vegetative propagation
SEXUAL REPRODUCTION AND THE TYPES OF SEXUAL REPRODUCTION
What is sexual reproduction?
Sexual reproduction as can be seen in an average mammal, is the type of reproduction which involves the fusion of the male gametes and the female gametes (ova) to form a zygote which develops into new young offspring.
What sexual reproduction in living things simply means is that offspring are produced by the fusion of two different sex cells known as gametes, which usually comes from two parents
A typical example of this is the process whereby a man and his wife will combine, mate and give birth to a new born baby.
TYPES OF SEXUAL REPRODUCT6ION
There majorly two types of sexual reproduction, they are
ii. Fusion of gametes
What is conjugation?
Conjugation is the simplest form of se4xual reproduction which occurs in some lower animals like mucor, Rhizopus, paramecium and spirogyra
Conjugation is a process by which nuclear materials are passed from cell to another.
In spirogyra for example, conjugation starts with two filaments called conjugants coming together to lie side by side. Lateral outgrowth starts to grow or develop opposite each other from opposite cell in the two filaments. The outgrowth meets and the separating walls dissolves to form a continuous channel called conjugation tube. Meanwhile, the cytoplasm of each cell shrinks away from the cell walls and round up to form a gamete.
One of the gametes regarded as the male migrates through the conjugation tube into the other cell. The cytoplasm of each cells fuse, the nuclei also fuse and a zygote is formed. After sometimes the zygote or the zygosphere will germinate and a new filament is formed
FERTILIZATION- THE FUSION OF GAMETES
Meaning of fertilization
What is fertilization?
Fertilization also known as fusion of gametes is the union of the haploid male and female gametes to produce diploid organisms called zygote;
Therefore the process this union of the gametes to form this zygote is called fertilization
In higher animals, these gametes are formed in special organs called gonads.
The male gametes called spermatozoa or simply sperm are produce in the testes by a meiotic cell division called spermatogenesis. In like fashion, the female which is known as ova or eggs are produced in the ovary also by a meiotic cell division called oogenesis.
These male and female gametes are brought together during mating and they unite together by a process of fertilization to form a diploid zygote which later develops into a new organism
In higher plants, male and female gametes are also produced.
The flowers are the reproductive unit in plants. The male gametes called pollen grains are produced by the anthers while the female gametes called ovules are produced by the ovary of the flower. The pollen grains and the ovules must fused together fertilization to form a zygote.
After the fertilization, the ovules forms the seed while the ovary forms or becomes the fruit. Read here* details of about male and female reproductive systems
THE ADVANTAGES OF SEXUAL REPRODUCTION
i. Sexual reproduction permit variability of individuals
ii. Sexual reproduction enhances survival in new territory
iii. Sexual reproduction gives room for hybrid production
iv. Sexual reproduction enhances the maintenance of chromosomes number from one generation to another
v. Sexual reproduction enhances the formation of new species and also promotes the continuation of old species
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