Tag: zoology

Sexual reproduction is a form of reproduction where the two reproductive gametes obtained from both the parents fuse together, to form a zygote. The gametes involve a large ovum (or egg) obtained from female and a male's smaller sperm. Each gamete contains half the number of chromosomes of normal cells.

• Reproduction in man is only sexual. After insemination, there is a fusion of sperm and ovum in the oviduct. This process is called fertilization. After fertilization, implantation takes place in the uterus and the development and the growth of the fetus occurs there.

The type of reproduction in which no gametes are involved and the new organisms emerge from a single parent only is called asexual reproduction. There is no fusion of gametes in asexual reproduction and the chromosome number also remains constant. Various types of asexual reproduction include division, budding, spore formation, etc.

Apospory is the development of gametophyte without meiosis forming haploid spores. 

Sexual reproduction is a characteristic of most of the higher life forms. Sexual reproduction characteristically involves reduction division or meiosis to form haploid cells and syngamy or fertilisation to form a zygote. Asexual reproduction is a means of reproduction without involving meiosis or fertilization. Most of the unicellular organisms show asexual reproduction. Vegetative reproduction is a type of asexual reproduction. The term vegetative reproduction is used in the context of plants only. Plants propagate rapidly through vegetative propagation. For example, suckers, rhizomes, runners etc.

Sexual reproduction involves the formation of haploid gametes. The gametes are produced by a specialised type of cell division called meiosis. The meiosis is a special type of division because it is reductional division and it involves crossing over. The crossing over involves the exchange of chromosomal segments between non-sister chromatids of a homologous pair of chromosome. The crossing over results in new genetic combinations. The rearrangement of genetic material every time crossing over occurs produces new combinations thus leading to the generation of variations in a sexually reproducing population.

• Sexual reproduction involves the formation and fusion of gametes.
• This requires formation of gametes with meiosis in diploid organisms or meiosis taking place in zygote if the organism is haploid. 
• Due to meiosis, only 50% of the genetic material is passed to the next generation and fusion of gametes results in a unique combination of the genome. 
• While asexual reproduction results in offsprings with exact genetic material as their parent reducing chances of variations.

• Reproduction is the process by which new individual organisms or 'offsprings' are produced from their 'parents' and thus, 
• it is a fundamental feature of all known life, each individual organism exists as a result of reproduction.

• Unicellular organisms generally divide by asexual reproduction which involves budding, binary fission, multiple fission, fragmentation, spore formation.
• Multicellular organisms can divide by sexual as well as asexual methods. For example, vegetative propagation in all plants is a means of asexual reproduction while all higher animals reproduce sexually.