Biological Reproduction Methods and Embryonic Development

Biological Reproduction and Development

Reproduction is the function by which progenitor individuals give rise to new individuals, called descendants, which are like them.

Phases of Biological Development

• Reproduction: In this phase, the organisms produce a cell, or group of cells, from which a new individual forms.
• Embryonic development: The cell formed in reproduction, called a zygote, gives rise to a complete individual through a series of divisions.
• Growth: In this phase, there is maturation and an increase in body size.

Asexual Reproduction Methods

• Vegetative Reproduction: Based on the ability of plants to form new individuals from a fragment of them, called a bud.
• Spore Reproduction: From a cell of an individual, whose nucleus divides repeatedly, more cells originate.
• Division or fragmentation: This involves the breakage of the parent into two or more parts, each of which gives rise to a new individual.
• Budding: It consists of the formation of a bud or bulge on the animal's body.

Sexual Reproduction and Gametes

Males and females develop specialized organs for reproduction called gonads, where they form gametes.

• Unisexual: Each individual has only one type of gonad. Most animals are unisexual.
• Hermaphrodites: Each individual has both types of gonads, male and female. Hermaphroditism is common in certain animals.

Fertilization and Embryo Development

Fertilization is the union of an egg and sperm, with the fusion of their nuclei to form the egg cell or zygote.

Types of Fertilization

• External: Usually occurs in most aquatic animals. It takes place outside the maternal organism in the external environment.
• Internal: Occurs in some fish and in most terrestrial animals. It takes place inside the female reproductive tract.

Embryonic Development Categories

• Oviparous: The development of the embryo occurs outside the mother's body in an egg, and it feeds on substances contained in the reserve.
• Viviparous: The embryo develops inside the mother, who provides protection and nourishes it during its development.
• Ovoviviparous: The development of the embryo takes place inside the mother, but it draws on the reserve substances of the egg.

Postembryonic Development

Postembryonic development refers to the growth of the individual until it reaches the adult state, at which point it acquires the capacity to reproduce.

• Direct: At birth, the offspring have a similar appearance to the adult, so this is a simple process of growth.
• Indirect: The offspring is born as a larva, an underdeveloped stage that looks and behaves much differently than the adult.

Plant Reproduction and Spores

Spore Reproduction: From a cell of an individual, whose nucleus divides repeatedly, several cells called daughter spores originate.

Pollination: Pollination is the process by which pollen grains, found in the anthers of the stamens, reach the pistil of the same flower.