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3.1. The inheritance and transmission of characters

The inheritance and transmission of characters

Reproduction and inheritance

Living things cannot last forever, so it is necessary that they have to give offspring similar to themselves through reproductionIn reproduction, one or two parents take part that will give rise to one or more descendants to whom they transmit the genetic information. Two types of reproduction are distinguished:
  • Asexual reproduction: The new living being reproduces from a single organism. The descendants are genetically identical to their parent, they are natural clones. The bacteria or sponges reproduce asexually. Others, like plants, can reproduce sexually, through seeds, for example, and asexually, as when a new plant is generated from a piece of potato.
  • Sexual reproduction: Each of the two parents provides specialized cells for reproduction (gametes), which after their union (fertilization), originate a new individual with genetic information from both parents. Children are different from parents and their siblings.

Gametes are formed by meiosis from diploid cells. They are haploid (n) cells, with half the chromosomes. Thus, when fertilization occurs, it will give rise to a new diploid cell (egg or cogote cell) from which the new individual will emerge.

Remember that male and female gametes are different:

  • Male gamete: the sperm (in animals) and anterozoid (in plants) is smaller than the female and mobile, because it has to travel a path to find the female gamete.
  • Female gamete: the ovule (in animals) and oosphere (in plants) is immobile and much larger than the male, since it contains the necessary nutrients for the first phases of the new individual.

What type of reproduction has more advantages, asexual or sexual?

The asexual reproduction is very appropriate for species well adapted to living in a stable environment. But if the environmental conditions change and become adverse, all organisms can die, since they are genetically the same as their progenitor. On the other hand, as in sexual reproduction, different individuals are produced, with different characteristics, and if the conditions become adverse, there may always be someone who is capable of surviving in the new conditions. For this reason, most of the more evolved and complex species have sexual reproduction.

The genetic

Bateson, in 1906, was the first to refer to genetics as the science that studies heredity and variation in living things. The term comes from the Greek "gene", which means origin. At present, the science that studies the nature, organization, function, expression, transmission and evolution of the encoded hereditary information of organisms is known as genetics.



         

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Biology and Geology teaching materials for Compulsory Secondary Education (ESO) and Baccalaureate students.