From our article you will learn what a gamete is. This is a special cell whose functions are strictly specialized. What are they? Let's get it together.
What is a gamete: definition
Translated from Greek, this term means "wife" or "husband." This determines its significance as accurately as possible. Gamete is a reproductive cell. In nature, there are two varieties of it - male and female.
In any case, gametes are formed as a result of division of primary germ cells. At the same time, their diploid set of chromosomes is preserved. This causes an increase in their number. The process of forming male and female gametes has its own significant differences. So, four full-fledged cells capable of fertilization are formed from one primary sperm. In female gametes, only one egg acquires this ability.
The structure of the egg
What is the gamete of the female body? It is always a motionless cell containing a sufficient supply of nutrients necessary for the development of the future organism. It has a round, or spherical shape. The egg is reliably protected by several membranes: vitelline, transparent and external. Her cytoplasm is a real storehouse of yolk inclusions.
Features of male germ cells
Now let's figure out what a male gamete is. Sperm cells are always much smaller than ovules. This is due to the fact that male gametes contain only genetic information. Why are they lacking in nutrients? The fact is that the basis of the future organism is precisely the egg, which has enough of them.
Gametes of plants and animals: similarities and differences
Male gametes of animals are mobile. Sperm cells consist of three parts: the head, neck and tail. The first one contains the core. Its chromosome set is haploid, or single. This structural feature is typical of all germ cells. The sperm head also contains an acrosome, or apical body. This organelle produces a special enzyme that is able to dissolve the protective membranes of the egg. In the neck are centrioles and mitochondria. They produce the energy necessary to set the tail in motion.
Male gametes of plants are called sperm. In the highest seed representatives of this kingdom, they are in the anthers of the stamens. They move with the help of wind, insects or humans. The process of transferring them to the stigma of a pestle is called pollination.
What is a gamete plant and where is it located? If we are talking about an egg, then this, like in plants, is a motionless cell of an oval shape. It is located in the lower expanded part of the pestle of flowers. In order for gametes to merge, two sperm move to the female gamete as the germ tube grows. As a result of their fertilization, a seed is formed.
In higher spore plants, germ cells mature in specialized organs - gametangia. In these organisms, a clear alternation of generations is observed in the life cycle.
Consider this process with the example of mosses. His sexual generation is represented by a green "rug". It consists of individual leafy plants. Gametophytes are formed on them, in which germ cells mature. As a result of the fertilization process, for the implementation of which water is required, an asexual generation grows - sporophyte. It looks like a box on a dry leg. Asexual reproduction cells, called spores, mature in it. They fall into the soil and again give rise to the gametophyte. So the phases of the life cycle replace each other.
Fertilization result
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, the male introduces sperm into the female’s body using copulative organs . The development of the fetus also takes place there, so this method is more progressive.
In plants, the most complex process of gamete fusion is observed in flowering. It is called double, because the female gamete and the central germ cell connect with the sperm. As a result, an embryo is formed, a reserve nutrient called an endosperm, and a peel. And all together - a seed.
The zygote begins to crush. In this case, an embryo is formed. At first it consists of one layer. It is called a blastula. Next, it begins the laying of tissues and future organs. During this period, it is called gastrula. The formation of the embryo continues with the laying of three embryonic leaves from which certain organs and their systems develop.
So, in our article we examined what a gamete and zygote are. These structures are carriers of hereditary information and give rise to a new organism.