Home BIOLOGY TOPIC 6: REPRODUCTION ~ BIOLOGY FORM 3

TOPIC 6: REPRODUCTION ~ BIOLOGY FORM 3

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Concept of Reproduction

Reproduction is the ability of living organisms to form new individuals of the same species from those already in existence. Here, the new organisms replace those that have died and so life continues. It can also be defined as the process whereby organisms produce new individuals of the same species. It is one of the important features of living things.

The Merits and Demerits of Sexual and Asexual Reproduction

Explain the merits and demerits of sexual and asexual reproduction

Sexual Reproduction

This is a type of reproduction in which new organism is produced when a male gamete fuses with a female gamete. Sexual reproduction involves the fusion of two gametes. The process of fusion of gametes is called fertilization.

These two gametes differ in form and function and each is produced from a different organ. In animals the gametes producing organs are called gonads. These include the ovaries and testes. In flowering plant structures concerned with the production of gametes are the ovaries and anthers. The testes and anthers produce the male gametes while ovaries produce the female gametes.

Merits of Sexual Reproduction

  1. It ensures genetic stability
  2. It ensures perpetuation of life
  3. It brings variation
  4. Leads to the interaction among organisms

Demerits of Sexual Reproduction

  1. Offspring have a great chance of inheriting diseases from the parent
  2. The reproduction takes long time
  3. It needs energy
  4. The sexual reproduction produces few numbers of offspring
  5. It depends on presences of two parents
  6. It leads to great chance of spreading diseases
  7. It takes a long time until offspring are produced

Asexual Reproduction

This is the type of reproduction whereby production of offspring is from single organism without the production of gametes. There is no fusion of gametes.

Examples of organisms who produce asexually are amoeba and bacteria. Asexual reproduction involves only one individual organism. That means no change of genetic material is passed from a parent to an offspring. The offspring are also identical to their parents.

In this kind of reproduction, in same organisms, body part such as roots, stems or leaves may become reproductive body organs.

Depending on the type of organisms asexual reproduction may be of different forms or ways such as:

  • Fission
  • Sporulation/Spore formation
  • Budding
  • Fragmentation
  • Vegetative propagation
  • Binnary Fission (Splitting)
  • Suckers
  • Bulbils

Binary Fission (Splitting)

This is an asexual reproduction in which an organism divides into two equal parts, which are identical to each other.

Each part then grows to attain the original size of the parent cell and hence become a separate and independent organism.

Fragmentation

This is a form of asexual reproduction in which organisms (parent) breaks into two or more parts. Fragments grow and develop into a new organism with identical features as the parent. Example worms such as Nematodes and flat worms.

Sporulation/Spore formation

Sporulation is asexual reproduction by the use of spores. The spore develops from single cell as a result of mitosis, forming a structure known as sporangium. When the sporangium is truly developed, the wall bursts to release the spores which when placed in suitable area they germinate into new organisms.

Other organisms, which reproduce by sporulation, are ferns and mosses.

Budding

Budding is a type of asexual reproduction in which a new organism arises as an outgrowth (bud) of the older organism (parent). The bud later separates from the parent and grows to become an independent organism to attain the size of the parent. Examples: yeast and hydra

Some flowering plants reproduce through the formation of structure called buds. Roots may form such buds, leaves or underground stems and such buds sprout to form new independent plants.

Vegetative propagation

Vegetative propagation is a form of asexual reproduction found in plants in which a bud grows and develops into a new plant. The detached plant, root, stem or leaves at some stages grows and develops into an independent plant.

Artificial vegetables propagation: This is vegetative propagation, which occurs through man’s manipulation. Man can learn from plants’ natural vegetative propagation and can intervene and make propagation of plants artificially.

Natural vegetative propagation: Vegetative propagation involves different parts of plants as discussed below. Such as:

Bulb

In this type each bud grows to form a shoot, which produces a new bulb at the end of the growing season.

Bulb is a modified underground shoot having fresh strong leaves

Tubers

These are short swollen underground storage organs formed from a stem or a root. New tubers are made at the end of the growing season but do not arise from old tubers.

Stem tubers

These are short swollen underground stems, which store food, such as starch. Normally, yam plants form a number of tubers each of which can rise to a new plant. Such new plant continues to live after the death of the parent.

Root tubers

These are swollen adventitious underground roots. Roots tubers such as sweet potatoes and cassava store their food in root tubers and do not bear leaves or bud.

Rhizomes

These are horizontally growing underground stems, bearing leaves, buds and adventitious roots. Examples are lilies, ferns and grass.

Stolons

These are slender stems, creeping horizontally as they grow along the ground surface. Examples: strawberries, black currant and oxalis.

Suckers

These are short horizontal branches, arising from the main stem or just below ground level. Suckers contain food reserves. Examples: Bananas, sisal and pineapples

Tap root

A taproot is the main root that arises from a radical. Tap roots may become swollen and act as storage organs.

Tillers

These are collection of shoots. Grass plants consist of a number of tillers. Each tiller has a number of leaves, which arise from the stem of nodes at the base of the leaves.

Leaves

Some plants such as cactus propagate vegetative using leaves. When the leaves fall off from a plant they develop adventitious roots and buds, which later may grow and develop into mature plants.

Merits of Asexual Reproduction

  1. Asexual reproduction results into an individual with the same genetic constitution as their parent.
  2. Its offspring matures faster than sexually reproduced organisms
  3. It does not depend on processes of pollination, seed or fruit dispersal

Demerits of Asexual Reproduction

  1. Asexually reproducing organisms are at a great risk to perish or get destructed when environmental conditions are unfavorable
  2. The parents may pass undesirable characteristics to the offspring since only one individual organism is involved in asexual reproduction
  3. Competition for resources such as food and shelter may occur due to large number of organisms being produced

Meiosis and Reproduction

The Meaning of Meiosis

Give the meaning of meiosis

Reproduction involves the transmission of genetic materials from one generation to the next insuring that species survive. The process of reproduction involves meiosis.

Meiosis is the type of cell division, which occurs in the reproductive organs to produce sex cells known as gametes.

In this type of cell division the parent cells has diploid number of chromosomes. However the daughter cell arising from the cell division has the half number of chromosomes a condition known as haploid state.

Therefore meiosis reduces the chromosomes number into half means from 2n to n.

The Significance of Meiosis in Relation to Reproduction

Explain the significance of meiosis in relation to reproduction

Meiosis leads to the formation of reproductive cells (Gametes) such as ova and sperms each with half number of chromosomes of the parent cells in organisms reproducing through sexual reproduction.

It involves the possibility of exchange of pieces of genetic information between the paternal and maternal chromosomes of each pair leading to new combination of characteristics in the gametes.

It brings about variation when the members of each pair of chromosomes are separated from each other independently (Random assortment)

Meiosis leads to new combination of genes through the process of independent assortment of chromosomes occurring during meiosis I

Meiosis involves number of processes from prophase, metaphase, anaphase and telephase. There are two meiotic divisions, the first and the second division. All the above named processes occur in both the first meiotic division and the second meiotic division.

First Meiotic Division

 

Maternal and Child Care
The Concept of Maternal and Child Care
Explain the concept of maternal and child care
A pregnant mother needs a lot of care and consideration for the best of her health and that of the child. Basically there are two types of care given to pregnant mother. These are pre-natal and post-natal care. The care given before birth is called pre-natal care and the care given during birth is called natal care. But a pregnant mother also needs a care and support after birth of the child; this kind of care and support provided after birth is called post-natal care.
Maternal care during pregnancy (Pre-natal care)
Pre-natal care means before birth; therefore pre-natal care means a care given to a pregnant woman before delivery.
Things to be done by a pregnant mother
  • Visit ante-natal clinic for counseling
  • Maintain general body cleanliness all the time
  • Have enough rest
  • Wear lose-fitting dresses and low heeled shoes for comfort
  • Eat well balanced diet containing all types of food
Things to be avoided by a pregnant mother
  • Doing tiresome and manual work. Example lifting heavy loads
  • Taking any medicine not prescribed by the doctor
  • Taking drugs such as alcohol, cigarettes which could be detrimental to the unborn baby
  • Tight clothes and high heeled shoes
  • Avoid situations leading to chances of contracting venereal diseases such as gonorrhea, syphilis and AIDS which might affect the baby
  • Avoid stressful situation
Care during natal period
Natal period is the period when the pregnant mother gives birth to the child she has been carrying in her womb for about nine months. A number of things need to be considered during natal period:
  • An expectant mother needs to undergo labor under supervision of a trained nurse or trained birth attendant whenever this is possible
  • If any complications occur that can not be solved by either a trained nurse or a trained birth attendant arises, an expectant mother should be referred to the health center or hospital for medical assistance
  • Most births are perfectly normal but problems can and do occur. When problems arise, modern delivery facilities or techniques such as Caesarean section and vacuum extraction are used. Care should be taken not to damage any organ of the baby or the mother
  • In case a newborn baby is pre-mature appropriate services should be given to it so as to help it accomplish a normal pattern of growth and development
Post-natal services to the mother and the child
These are care and services provided to the mother and the newborn child after birth. After birth a mother has another big responsibility and role of breast-feeding the child.
Also a mother should attend post-natal clinic for medical checks and immunization of the child Balanced diet should be supplied to a lactating mother so as to ensure that she gets enough nutrition for her benefit and ultimately that of the child.
Proper nutrition will help her to restore the tissue worn out during the natal period. This helps also the newborn baby to have enough milk from its mother. The health of both the mother and her child should be seriously taken care of.
Child health care
Mothers should breast-feed the child whenever possible, mother’s milk is better than any other food because of the following:
  1. It contains antibodies that are much needed to the child
  2. In case the mother has no health problems such milk is free from contamination
  3. Mother’s milk also contains much proteins and vitamins which are very important for the child’s growth
  4. Breast milk is easily digested than other milk example bottled milk. Therefore children who take milk from their mother rarely suffer from constipation
  5. Mother’s milk is said to contain some chemicals which help in development of the nervous system of the child
  6. Regular attendance of post-natal clinic for the child is very important. The child should also get immunized against different infections and diseases such as polio, measles and other diseases
  7. The mother should follow medical advice on how to handle the child and in case of any problems report it to the personnel concerned
Social-Cultural Factors which Affect Maternal and Child Care in the Family and Community
Mention social-cultural factors which affect material and child care in the family and community
These include the following:
  • Female Genital Mutilation (FGM):This is the practice of circumcising women. It is said to have effects during childbirth. It causes women to experience pain, bleeding, and shock and may lead to infection.
  • Local Belief:These are certain local beliefs and taboos such as banning women to eat certain types of foods such as protein rich foods, which could help to build their health and that of the child.
  • Working especially hard work such as cultivation: Hard work may cause several problems to the pregnant woman such as miscarriage or pain.
  • Alcohol Consumption during pregnancy:In most cultural practices taking alcohol is considered as a normal behaviour. But alcohol during pregnancy affects both the health of the mother and that of the child.
Appropriate Ways of Providing Maternal and Child Care for People Living with HIV/AIDS (PLWHA
Suggest appropriate ways of providing maternal and child care for people living with HIV/AIDS (PLWHA)
These include the following:
  1. To ensure frequent medical check up for both maternal and child
  2. To ensure they get well balanced diet
  3. Avoid sharing sharp objects like razor blades
  4. Counseling in order to help them deal with their feelings of loss and grief
  5. To avoid discrimination for people living with HIV/AIDS
  6. Ensure the use of polite language when providing care to them
  7. Wearing of gloves when cleaning their bodies and clothes

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