👶BIO101. REPRODUCTION

 *REPRODUCTION*

 *Reproduction* is a biological process by which an organism reproduces an offspring that is biologically similar to the organism.

 Reproduction enables and ensures the continuity of species, generation after generation. It is the main feature of life on earth.

*Reproduction* is the process of producing offspring that are biologically or genetically similar to the parent organism.”

 Let us have a detailed overview of reproduction, its types and the modes of reproduction in plants and animals.

 *TYPES OF REPRODUCTION*

 There are basically two types of reproduction:

1 Asexual Reproduction

2 Sexual Reproduction

*ASEXUAL REPRODUCTION*

 *Asexual reproduction* refers to the type of reproduction in which only a single organism gives rise to a new individual.

 *Asexual reproduction* does not involve the fusion of gametes, and therefore, the offsprings produced are genetically identical to the parent.

The organisms produced by asexual reproduction are less diverse in nature. This type of reproduction is practised widely by *unicellular organisms*

 

 Take note of the key words in the slide✍️

 The process involves rapid population growth and no mate is required for the process. However, a lack of genetic diversity makes organisms more susceptible to diseases and nutrition deficiencies

 

 Asexual reproduction is further divided into:

 1. *BINARY FISSION:* In this, the cell splits into two each cell carrying a copy of the DNA from the parent cell. For eg., amoeba.

 *2 BUDDING:* In this, a small bud-like outgrowth gives rise to a new individual. The outgrowth remains attached to the organism until it is fully grown. It detaches itself and lives as an individual organism. For eg., hydra

 *3 FRAGMENTATION* : In this, the parent organism splits into several parts and each part grows into a new individual. For eg., Planaria

 *4 SPOROGENESIS* : In this type of reproduction, a new organism grows from the spores. These can be created without fertilization and can spread through wind and animals

 *SEXUAL REPRODUCTION*

 *Sexual reproduction* is a type of reproduction that involves the production of an offspring by the fusion of male and female gametes.

  In sexual reproduction, male and female gametes are formed to produce an offspring. These gametes are either formed by the same individual or by different individuals of the opposite sex.

 Can u remember in ur secondary school then  

Dis is the part most students like to hear😂😁😅

 This process is usually slow and complex compared to asexual reproduction. The organisms so produced are genetically diverse. Thus, they can evolve along with the changing climatic conditions. Humans and many multicellular organisms exhibit a sexual mode of reproduction.

 *REPRODUCTION IN ANIMALS*

 *Animals reproduce sexually as well as asexually.*

 Sexual reproduction involves the fusion of male and female gametes. This process is known as fertilization. Fertilization can be external or internal. External fertilization is the process in which the male sperm fertilizes the female egg outside the female’s body. On the contrary, in internal fertilization, the fusion of male and female gametes takes place inside the body of the female.

 Asexual reproduction involves reproduction processes such as binary fission, budding, fragmentation, etc. The organisms have no reproductive systems and therefore no formation of male and female gametes takes place.

 *REPRODUCTION IN PLANTS*

 *Plants reproduce by sexual and asexual means.*

 Vegetative reproduction is the main mode of plant reproduction. Roots such as a corm, stem tuber, rhizomes and stolon undergo vegetative propagation.

 *Sexual reproduction* in plants takes place through pollination in which the pollen grains from the anther of a male flower transfer to the stigma of the female flower.

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 Define Reproduction

Define Asexual Reproduction

What are the types of Asexual Reproduction?

What are the advantages of Sexual Reproduction.

What is the difference between sexual reproduction and asexual reproduction?

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 Bacteria divide asexually via *binary fission* ; viruses take control of host cells to produce more viruses; Hydras (invertebrates of the order Hydroidea) and yeasts are able to reproduce by budding. 

These organisms often do not possess different sexes, and they are capable of "splitting" themselves into two or more copies of themselves. Most plants have the ability to reproduce asexually and the ant species Mycocepurus smithii is thought to reproduce entirely by asexual means.

Let's dwell more on the sexual reproduction

*DEFINITION OF SEXUAL REPRODUCTION*

*Sexual reproduction* is the process in which new organisms are created, by combining the genetic information from two individuals of different sexes.

The genetic information is carried on chromosomes within the nucleus of specialized sex cells called *gametes*

In males, these gametes are called *sperm*😌😌😌 and in females the gametes are called *eggs* 🥚🥚🥚. 

During sexual reproduction the two gametes join together in a fusion process known as *fertilization* , to create a *zygote* , which is the precursor to an embryo offspring, taking half of its DNA from each of its parents.

In humans, a zygote contains *46 chromosomes: 23 from its mother and 23 from its father.*

 The combination of these chromosomes produces an offspring that is similar to both its mother and father but is not identical to either.

Phenotype traits, such as physical adaptions to an organism’s environment and genotype traits, such as resistance to disease, are passed down from each parent during sexual reproduction.

Natural selection, whereby individuals with favorable adaptions to their environment are able to survive and successfully reproduce, drives the evolution process

Sexual reproduction increases the diversity of genotypes and phenotypes within a population, allowing natural selection to select for the individuals best suited to an environment.

*Sexual reproduction* differs from asexual reproduction, which only requires one parent. 

In asexual reproduction, unlike sexual reproduction, there is no fusion of gametes, so the offspring are genetically identical to their parents and are therefore clones.

Asexual reproduction does occur in some animals, although it is rare; most asexual reproduction occurs in bacteria, fungi, starfish, corals, hydras (jellyfish) and some flowering plants such as strawberries

*TYPES OF SEXUAL REPRODUCTION*

Which one be type of sexual reproduction again bayi 😂

*ALLOGAMY*

*Allogamy* occurs when the gametes which join together during fertilization come from two different individuals. 

The female gamete is usually in the form of an egg or ovum while the male gamete takes the form of a sperm.

Both egg and sperm are cells specialized to perform the task of reproduction; each sex cell contains only 23 chromosomes (these are called haploid cells) rather than the normal 46 chromosomes present in other cells of the body 

The two haploid cells fuse together to create a diploid cell which then undergoes mitosis, in order to grow and form an individual organism. Mitosis is the division of one cell into two, after the DNA has been replicated within the nucleus

Because genes of individuals are passed down through sexual reproduction, and survival of genes is controlled by natural selection, individuals are driven to choose mates based on their ability to produce offspring likely to survive and live to reproduce themselves

*INTERNAL FERTILIZATION*

Internal fertilization is the fertilization of the egg by the sperm within the body of one of the parents, usually by means of sexual intercourse.

 Internal fertilization usually takes place within the female body, after the male implants sperm.

However there are exceptionally rare examples, such as seahorses (Sygnathidae), where the female implants her eggs into the male and the zygote is formed within the male’s body.

The next step in internal fertilization depends on the species.

Some creatures, such as birds, insects and reptiles, then lay an egg containing the cells, which are undergoing mitosis, and a reserve of yolk to feed and support growth of the embryo. 

After a period of time (often having been incubated) a fully formed individual will hatch from the egg. This is known as oviparity.

The embryos of most mammal species grow and develop within the body of their mother, resulting in the live birth of a fully formed offspring: this is called viviparity

Embryos are supported by the placenta, which provides nutrient uptake, waste removal and thermo-regulation in placental organisms (most mammals).

A third form of development is ovoviviparity, in which embryos develop in eggs stored within the body of the parent until they are ready to hatch, giving the appearance of a live birth.

*EXTERNAL FERTILIZATION*

External fertilization occurs when a sperm cell and an egg cell join outside of the body.

Most amphibians and fish and many invertebrates use external fertilization, producing anything from hundreds to billions of gametes at a time into close proximity. 

The quick release of gametes into aquatic environments this is called spawning. However, sometimes females will lay eggs on a particular substrate which are subsequently fertilized by males

The sex cells of creatures which reproduce through external fertilization often have special adaptions for movement, such as the addition of strong flagella for independent movement.

*AUTOGAMY*

Autogamy, also known as self-fertilization or self-pollination, is the fusion of male and female gametes, which are produced by a single individual. Species which are able to produce both male and female gametes are called hermaphrodites.

Although autogamy is similar to asexual reproduction, in that there is no input of genetic diversity from a partner, the recombination of chromosomes from the male and female gametes results in offspring with slightly altered genetic information, which can therefore look phenotypically different from their parents. Most plants and earthworms reproduce by autogamy. It is sometimes possible for hermaphrodites to reproduce with other hermaphrodites. In this case, genetic diversity does increase within the population.

*ADVANTAGES OF SEXUAL REPRODUCTION*

Deleterious mutations accumulate within DNA over time, through cell mitosis. Organisms which produce asexually simply pass these mutations on to their offspring, while organisms which combine their DNA through sexual reproduction allow only a portion of their deleterious mutations to pass to their offspring, increasing their chances of survival.

This effect is increased through natural selection, where individuals with exceptionally harmful mutations are unable to pass on their genes through sexual reproduction.

Increased diversity of genes within a population also allows natural selection to improve an organism’s ability to adapt to environmental changes. Random mutations, which are of no use to one generation, may become key to survival in future generations under a change of environmental pressures. This is the driving force behind speciation.

*Chromosomes* – The structure within the nucleus of a cell, containing the proteins and nucleotides that make up DNA.

 *Embryo* – The unborn developmental stage of a eukaryotic organism

 *Sexual Intercourse* – Sexual contact between individuals, which can result in the exchange or transfer of cells, and therefore sexual reproduction.

*Quiz* 

1. How many chromosomes does a female egg contain before fertilization?

2. What is an advantage of sexual reproduction?

A. Larger size

B. Increased genetic diversity

C. More sexual partners

3. Sexual selection may result in:

A. Better camouflage

B. Brighter colored feathers

C. Ability to run faster

D. All of the above

4. Viviparity involves:

A. Internal gestation

B. Laying eggs

C. External fertilization

D. Pollination

 *Written by:* 

            Miss Victoria

✍️ *FLASHPEE EDUCATIONAL TEAM*