Self-Pollination vs Cross Pollination
(Similarities and Differences between Self Pollination and Cross Pollination)
Pollination is a process in sexual reproducing plants by which the pollen grains from the anther is transferred to the stigma of the gynoecium and thereby enable fertilization. Pollination is an essential step for sexual reproduction in seed plants (Spermatophytes – Gymnosperms and Angiosperms) to produce the seeds. In plants (typically in Angiosperms), the pollination and the completion of sexual reproduction can be achieved by two methods – Self-pollination and Cross-pollination.
Self-pollination: Pollen from the anther of a flower is deposited on the stigma of the same flower or a different flower of the same plant.
Cross-pollination: Pollen from the anther of a flower is deposited on the stigma of a flower borne on another plant of the same species.
Nature favor cross-pollination since, it enables a better chance for creating variability in the progenies. Moreover, in order to prevent self-pollination, plants have evolved several structural and genetic methods such as the production of unisexual flowers, the positioning of male and female parts to avoid self-pollination, self-incompatibility and maturation of male and female parts in different types (protandry and protogyny).
Asexual Reproduction vs Sexual Reproduction
(Similarities between Sexual and Asexual Reproduction)
Reproduction is a biological process by which new individuals (progenies) are formed from their parents. There are two types of reproductions in organisms: sexual reproduction and asexual reproduction.
Asexual reproduction: A method of reproduction, usually present in lower animals and plants where progenies are produced from a single parent without the formation of gametes and fertilization. Example: division of bacteria by binary fission, budding of Hydra and yeasts, and vegetative reproduction in plants.
Sexual reproduction: A method of reproduction where the progenies are produced by two parents of separate sexes. These parents produce morphologically and sexually different gametes. The union of gametes results in the formation of zygote. The zygote develops into new progeny.
Properties of Alpha Rays, Beta Rays and Gamma Rays
Unstable atoms on radioactive decay emit particles such as alpha particles, beta particles and gamma rays. These are energy particles, and by producing these energy-rich particles the unstable radioactive atom tries to attain atomic stability. The present post discusses the chemical, physical and biological characteristics of alpha, beta and gamma particles.
Ø They are also called alpha rays, designated as α2+.
Ø Alpha rays consist of two protons and two neutrons bound tougher into particles.
Ø They are identical to the helium nucleus.
Ø They are produced by the alpha decay of radioactive materials.
Ø They are positively charged particles.
Ø Contain 2 positive charges.