Science of reproduction

BY MICHAEL JOHN UGLO

GOOD day all and welcome to our ninth lecture on the topic of reproduction in the lecture series of the Science of Organisms.
Looking at the nature of reproduction as a preamble, there are basically two forms and these are sexual and asexual forms of reproduction. All plants, animals and microbes undergo these two forms.
In plants the principal form of reproduction apparently is asexual. When unfavourable climatic conditions as well as adverse environmental catastrophes strike, then that subdues plant life thriving at that period. A non-existent time of the plant life at that instant exists and lasts until a favourable environmental condition returns, then the plant life can now come back to life from the sprouting of the seeds that were held dormant for that unfavourable time period.
So in totality, plants can be said to be hermaproditic. That is, plants have both male and female parts on them to reproduce sexually as well as asexually such as vegetative reproduction both giving rise to a diploid organism.
Plant and animal life you see around you have existed since the dawn of time as sheer stochastic events. Thus they all have an inalienable right to exist. No one has any right to subdue them according to his egoistic perceptions. No one is to dictate to anyone just because you have the resources such as money.
However, change the bad habits in the society and fix them with good habits.
As a rewording of Aristotle, the more you own, the more you owe to the society. What does this mean? Find out because you owe the people of this nation in the same measure corresponding to how much you accrue from this nation through whatever means.
If you are campaigning to ameliorate the lives of the people even when you are tempted by their riches, then, that is good. You are elected to parliament not to become Mr Ten Per Cent, but a channel for the people’s prosperity and their wellbeing.
Reproduction
The process that leads to new individuals, whether plants, animals or microbes is called reproduction. This can also be called procreation or breeding. Every living thing that once existed and is currently living is as a result of reproduction. In reproduction, an individual can produce an exact copy of itself as a diploid organism without genetic diversity for their somatic cells or an individual that has a gene mixing because of gene cross overs known as haploid organisms.
Their gametes which are their ova and the spermatozoa (sperm) contain halved chromosomes in the nucleus of the germ cells.?There are two kinds of reproduction commonly known as asexual reproduction and sexual reproduction. There are some individuals that are known to have both sexual organs for a male and a female and are known as hermaphrodites. An earthworm for instance has both male and female reproductive organs. Some organisms can reproduce both asexually and sexually depending on circumstances.
For instance, some plants can reproduce asexually with an exponential growth in population given favorable environmental conditions such as plentiful food and nutrient supplies. Once when that is depleted, they will have to meet the setback and experience population decline and to extremes population crash.
Also, when biotic and abiotic environmental factors are not right, like the introduction of an exotic species that takes over native species, predators, lengthy drought and wet seasons, fire, volcanoes, cyclone, tsunami and waterlogging, the plants can die off. In such situations, they can resort to sexual reproduction using their pollen grains and their egg cells from their ovaries. They can even produce hard shelled seeds or spore capsules that will be very hard to break and last a lengthy period awaiting favorable seasons before they can break open and spring back to life.
Asexual reproduction is normally practised by plants such as use of rhizomes like gingers, suckers like bananas and other vegetative methods using runners like pumpkins and sweet potatoes. The young from these methods of reproduction involve mitosis where the new individuals are very similar copies of the parent. There is no genetic diversity.
Sexual reproduction is the next method of reproduction that involves two individuals of the male and the female gametes in the flowering plants. Flowers are the organs for sexual reproduction in plants. The pollen grains supported by the anthers extended from filaments are the male sex cells. They are transported by wind or an insect and placed on the stigma of the female part of the plant in a process called pollination.
The stigma is supported by a tube-like structure called style that extends from the ovary which are the female parts of the plant. This will allow the pollen grains to pass down through it to meet the egg cell called ova (ovum for one) at the ovary at its basement.
Once a pollen grain successfully meets an egg cell at the ovary it is called fertilisation. A fertilised egg is called a zygote. The zygote eventually develops into a seed when the ovary becomes the fruit enclosing the seeds inside.

Non-flowering plants like conifers reproduce by their cones which become like the sex organs. They produce pollen which fall on the carpel which is the female part of the plant. Once fertilised they produce new conifers.
Other coniferous plants have male and female parts on different coniferous plants. It is the wind or insect movements that transport the pollen grains to the carpels of these female coniferous plant to the male plant that allow the cross-pollination to take place for fertilization to take place.
The others reproduce by spores and are called sporophytes. Spores are enclosures that contain the reproductive cells to reproduce new individuals. Living things that reproduce through the use of spores include the fungi, algae, mosses, lichens and ferns.
Organisms that employ the method of budding to produce new individuals include hydra, amoeba and yeasts. In budding there is a swelling on the side of an adult organism like the hydra. The bulge swells and grows bigger until a new young, pops its head out and then suddenly buds off and becomes a new individual. The young is left to fend for itself as no parental care is given.
In other organisms such as the birds, the male and female mate before fertilized eggs are laid. The eggs are warmed by the mother bird until, the small birds hatch. Parental care is needed so the mother bird has to feed the small birds until they mature and become adult birds and are able to fly to fend for themselves.
Other organisms use the methods of external fertilisation. These living things include the amphibians such as frogs and the fish. The male partners get on top of the female whose eggs are matured to be released for spawning. Then the male touches the female back in courtship and the female releases the eggs. At the same time the male releases its sperm. Some lucky sperm many eggs and become fertilized for the development of new individuals. Little or no parental care is given so not many fertilised eggs are able to hatch and survive to adulthood.

In reptiles as well as the arachnids, their mating is internal fertilisation. The female then lays a fertilised egg. There is little care given to their young. Most of their young have a good likelihood of surviving. In some species of spiders, after mating, the female spider which is bigger in size kills and eats up the male mating partner.
In hermaphroditic organisms like some annelids such as earthworms, they have both male and female sex organs. Theirs is internal fertilisation. Two earth worms can mate in such a way as the male and female sex organs are swapped for sperm to be deposited into each other for internal fertilisation to take place.
In humans, the female hormone called estrogen is responsible for the sexual maturity of females with their secondary characteristics development. These includes development in the vocal cord for high pitched voice, development of breasts, pubic hair growth and broadening of hips.
The male hormone responsible for the development of secondary sexual characteristics is the testosterone hormone responsible for the broadening of shoulders, growth of beard, deepening of the voice and growth of the pubic hair.

The testosterone hormone also helps in development of the gametes which are the spermatozoa (sperm cell) produced from the gonads called the testicles which is enclosed by the scrotum and channeled by the vas deferens which then passes onto the urethra in preparation for ejaculation.
It has gone through a meiosis process of cell division to form a haploid cell for genetic variation. The egg cell or ova (ovum for one) are produced from the female gonads called the ovaries (ovary for one) also undergone meiosis cell division to form a haploid egg cell.
Once matured and ready, the egg is stimulated by the female hormone progesterone when its level is high during ovulation when the egg cell is released from the ovary to pass through the fallopian tube to be implanted on the thick blood lined capillary uterine wall of the uterus awaiting a sperm to be fertilised.
Once fertilised, it undergoes another process of cell division and thus multiplication of genetically identical cells called mitosis and becomes a zygote (fertilised egg) and grows and develops into a fetus. The fetus then develops into a new baby during pregnancy when the progesterone level spikes.
The baby is born after a nine-month gestation period which is also called the labour period. The birth is called parturition. The new born baby is almost helpless and depends on the mother for total care such as breast feeding and warmth for survival.
When the egg is not fertilised, it degenerates and the thick blood lined uterus breaks and comes out as menstruation. The menstruation cycle is controlled by the progesterone hormone.

In the mammals, their fertilisation method is also internal. Female marsupials keep their offspring in their pouches for care and warmth and protection from danger. All young are given parental care particularly by their mothers until they are matured. They all have hair and breast feed their young for nourishment.
My Prayer for PNG today is: “Yahweh, I know you are near. Standing always at my side. You guard me, from the foe and you lead me, in ways everlasting…”
Next week: Microbiology in science and technology