What is gamete and zygote: features of the structure

From this article you will learn what gamete is. This is a special cell whose functions are strictly specialized. What are they? Let's understand together.

What is gamete: definition

In translation from Greek, the term means "wife" or "husband". This determines its significance as accurately as possible. A gamete is a sex cell. In nature, there are two of its varieties - male and female.

In any case gametes are formed as a result of division of primary sexual cells. At the same time, their diploid set of chromosomes is preserved. This causes an increase in their number. The process of formation of male and female gametes has its significant differences. So, from one primary spermatozoon four full cells are formed, capable of fertilization. In female gametes, this ability is acquired only by one egg.

Structure of the egg

What is the female gamete? It is always a fixed cell containing a sufficient supply of nutrients necessary for the development of the future organism. It has a round, or spherical shape. The egg cell is safely protected by several membranes: vitelline, transparent and external. Its cytoplasm is a real storehouse of vitelline inclusions.

Features of male sex cells

Now let's figure out what a male-type gamete is. Spermatozoa always have much smaller sizes in comparison with ovules. This is due to the fact that the male gametes contain only genetic information. Why are they deprived of nutrients? The fact is that the basis of the future organism is the egg, which has them in sufficient quantity.

Gametes of plants and animals: similarities and differences

Male gametes of animals are mobile. Spermatozoa consist of three parts: the head, neck and tail. The first one contains a kernel. Its chromosomal set is haploid, or single. This feature of the structure is typical for all germ cells. The sperm head also contains an acrosome, or an apical body. This organelle produces a special enzyme that is able to dissolve the protective shells of the egg. In the neck are centrioles and mitochondria. They generate the energy needed to set the tail in motion.

Male gametes of plants are called spermatozoa. In the higher seminal representatives of this kingdom they are in anthers of stamens. They are moved by the wind, insects or man. The process of transferring them to the stigma of the pistil is called pollination.

What is the gamete of plants and where is it located? If we are talking about an egg, then this, as well as in plants, is an immovable oval cell. It is in the lower extended part of the pistil flowers. In order for the gametes to merge, the two sperm move to the female gamete as the germinal tube grows. As a result of their fertilization, a seed is formed.

In higher spore plants, the sex cells mature in specialized organs - gametangia. In these organisms, a clear alternation of generations is observed in the life cycle.

Consider this process using the example of mosses. His sex generation is represented by a green "rug". It consists of separate leaf-stalk plants. They form gametophytes in which germ cells mature. As a result of the fertilization process, which requires water, an asexual sporophyte grows. It looks like a box on a dry stem. It ripens the cells of asexual reproduction, which are called spores. They fall into the soil and again give rise to the gametophyte. So the phases of the life cycle change.

The result of fertilization

A fertilized egg is called a zygote. Her chromosome set is already diploid, or double. In animals, fertilization is external and internal. In the first case, it occurs outside the body of the female. This method is typical for fish and amphibians. With internal fertilization, male with the help of copulatory organs introduces spermatozoa into the female organism. There is also development of the fetus, so this method is more progressive.

In plants, the most complex process of fusion of gametes is observed in flowering plants. It is called double, because with female sperm the female gamete and the central embryonic cell are connected. As a result, the embryo is formed, a reserve nutrient called endosperm and skin. And all together - a seed.

The zygote starts to crumble. In this case, the embryo is formed. First it consists of one layer. It is called a blastula. Next, it begins the laying of tissues and future organs. In this period it is called a gastrula. The formation of the embryo is proceeding by the laying of three embryonic leaves, from which certain organs and their systems develop.

So, in this article we have examined what the gamete and the zygote are. These structures are carriers of hereditary information and give rise to a new organism.