Gametes are the sexual cells of multicellular organisms (made up of several cells). There are male and female gametes, their union being necessary for the fertilization process to occur that will give rise to a zygote.
What is a gamete in animals and plants?
Gametes are the reproductive cells present in animals and plants. They are produced through a process called gametogenesis through miosis, this process occurs in the gonads (gamete-generating organs) of animals or in the gametangia in the case of plants.
Gametes contain a line of chromosomes loaded with the genetic characteristics of the individual. Unlike other cells that contain 46 chromosomes, gametes only have 23, which is why they must join with another gamete to form a new being.
That is why for the union of two gametes a sexual act is first needed; In animals, it occurs through intercourse, and in plants through pollination. Thanks to this process, fertilization will take place, which will finally form a zygote.
Thus, from the formation of the zygote an embryo will originate that will develop to an adult state, said individual will inherit the genetic characteristics of its parents from a physical point of view.
It is important to note that depending on the species, the development of the embryo can occur both inside the mother, as in the case of mammals or plants, and it can also occur outside, as in the case of oviparous animals.
Types of gametes in male and female
Gametes are of two types (male and female), the union of both being necessary to achieve reproduction.
– Male gametes : In animals, they are called “sperm” and in plants it is the “pollen” grains that contain the gametes.
In the case of sperm, they are formed in the testicles and come out through the urethra in the seminal fluid. They are small, highly mobile cells made up of 3 parts: a head (contains 23 chromosomes), a neck and a tail.
In plants, the pollen grain is called the male gametophyte. Once the pollen enters the pistil of the plant through a pollen tube that leads to the ovary, it deposits its sperm, which will give rise to an embryo.
– Female gametes: In animals they are called ovules and in plants they are called “oosphere”, where both have similar characteristics and are designed to receive the male gamete.
Eggs are produced in the ovaries and are characterized by being the largest cell with a spherical shape, it does not have mobility. It contains a nucleus that integrates the maternal genome, a vitelline membrane (which allows the sperm to enter) and a cytoplasmic membrane.
In plants, the pistil is the female sexual organ and the ovules are enclosed in its ovary. The pollen granule is deposited in the upper part of the pistil (stigma) and then travels and deposits the male gametes so that fertilization can take place.