The most important property of living organisms is the ability to reproduce and reproduce. Most animals have nothing special in this process, they have external genitals, reproducing sexually: the male's sperm enters the female's egg, fertilizing it, the female becomes pregnant and gives birth to young.
In highly organized animals, there is basically only one way of reproduction, which is carried out with the participation of germ cells.
There are a number of animals that do not have external sexual characteristics (almost all birds), as well as hermaphrodites containing both male and female sex glands.
Breeding features of some animals
There are only females in the goldfish population, since this species is unisexual. Females are fertilized by other fish, the spermatozoa of which give development to the eggs of female goldfish.
Some low-organized animals are capable of reproduction without fertilization; in them, sexual reproduction exists alongside development without fertilization. For example, if the eggs of a bee are not fertilized, they become drones. The same thing happens with lizards living in rocks.
The kangaroo is the only animal that has a huge difference in size between mother and cub. A kangaroo is born the size of a pea.
Pigs become sexually mature by about eight months, however, they are able to give healthy offspring and reproduce fruitfully only at an age older than a year. Females have a regular sexual cycle, accompanied by excitement, estrus, sexual intercourse, ovulation and inhibition. If pregnancy does not occur after fertilization, the cycle repeats again.
The birth of little rat pups is very interesting. For two weeks of observation, you can see how a born blind, deaf, bald creature is rapidly turning into a fluffy nimble animal. Rats heat up every four to five days, with the exception of pregnancy, and they are fertile at the age of five weeks. Only extreme cold or heat can slow down the rapid reproduction process in these animals.
Fertilization methods
The planet is full of a variety of living creatures that inhabit land, sky, sea, and they all reproduce in different ways. In some animals, fertilization is preceded by a long period of courtship and choice of partners. Some choose to mate for the rest of their lives. There are all sorts of ways to breed animals, but more often they do it like humans.
For example, dogs have sex like humans only twice a year, when females are in heat. Many have observed "dog weddings", when a herd of males runs after a female, and she mates with them in turn, and then gives birth to puppies.
A similar process of "courtship" occurs in cats: cats fight, run after the female, but only one cat at a time can fertilize her. However, when re-mating with another male, the cat can give birth from both at once.
Reproduction and fertilization methods in artiodactyls (horses, cows) are similar.
