Reproduction
Definition and Purpose: Reproduction is the biological process by which organisms produce new individuals—known as offspring—from their parent(s). Its fundamental purpose is to ensure the survival and continuity of the species across generations.
Asexual Reproduction: This mode involves a single parent and does not involve the fusion of sex cells (gametes). The offspring produced are typically genetically identical to the parent (clones). Examples include binary fission in bacteria, budding in yeast and Hydra, and fragmentation in starfish.
Sexual Reproduction: This mode typically involves two parents (male and female) and the fusion of specialized reproductive cells called gametes (like sperm and egg) to form a zygote.
Genetic Variation: Sexual reproduction is crucial because it introduces genetic variation in the offspring due to the combination of DNA from two parents. This variation is the raw material for evolution and natural selection, allowing a species to adapt to changing environments. Asexual reproduction offers very little to no genetic variation.
Role in Life Cycle: Reproduction is an essential part of an organism's life cycle. While it is the method for producing offspring, cellular division processes like mitosis are also a form of reproduction in single-celled organisms, and are used for growth and repair in multicellular organisms.