Life Sciences

This article explains the reason why sperm and eggs only contain one genome: human somatic cells have two genomes, female cells contain 46 23 pairs of homologous chromosomes, and male cells contain 46 22 pairs of homologous XY; the single genome of germ cells originates from meiosis, which halves the genome, including steps such as chromosome duplication and synapsis.

This article focuses on "Why is the nucleus the 'headquarters' for manipulating cell activities" and points out that the orderly activity of organelles in living cells depends on the nucleus as the core. Enucleated eggs cannot develop, and single cells cannot survive. Most eukaryotic cells contain nuclei, and the life activities of multicellular differentiated cells are all under the unified command of the nucleus.

This article focuses on "a cell is an independent kingdom" and introduces that a cell is composed of a cell membrane, cytoplasm, organelles and nucleus. The cell membrane is similar to a border line to regulate the entry and exit of substances. The mitochondria convert chemical energy into biological energy. The lysosomes clear waste and poisons. The ribosomes synthesize proteins, and each structure and function are clear, confirming that the cell is an independent kingdom with complete functions.

This article focuses on "Are all cells invisible to the human eye?" and points out that Hooke first discovered cells through a microscope. Most of the cells were 10-100 microns in diameter and were invisible to the naked eye; although nerve cells were 1 meter long, they were extremely thin and colorless. It also showed that chicken egg cells, etc. are also difficult to be seen by the naked eye, and egg shells and protein are not components of egg cells.

Discovery and cognitive process of cells

This article focuses on "Who first proposed that cells are the basic unit of organisms?" and introduces the exchange of research on animal and plant cells between German botanist Schleidan and zoologist Schwang in 1838, establishing that cells are biological structures, functions, and reproductive units, forming the cell theory. This theory was listed by Engels as one of the three major discoveries in natural science in the 19th century.

This article introduces the process of continuous adjustment of the biological classification system with the development of cognition: from Linnai's two-boundary classification, to Haeckel's proposal that the protozoa realm should form three realms after the invention of the microscope, to Whitaker's five-boundary theory and Riedel's four-boundary adjustment, there is still controversy in the academic community in the 21st century about whether viruses are independently bounded, reflecting that the classification system is based on scientific understanding of biological evolution.

In the 18th century, Lin Nai and other scholars established a classification ladder centered on realm, phylum, class, order, family, genus, and species, making it clear that species are the basic unit.

This article focuses on the issue of whether mankind will die out, and mentions two serious biological extinction events in history: a large-scale lava explosion in Siberia 250 million years ago caused 95% biological destruction, and a near-Earth asteroid hit the earth 65 million years ago caused the extinction of dinosaurs; It also quoted Princeton University's Gott's calculation based on the Copernican principle, pointing out that there is a 95% probability that humans will become extinct between about 641025 and 97.5 million years ago, and believes that humans can survive for a long time.

There has been controversy over the evolution of humans for hundreds of years. Most scientists agree with Darwin's theory of evolution and believe that the ancestors of modern humans were Australopithecus, which is the best species in the genus Homo studied by scientists from many countries. Human evolution has gone through stages such as Australopithecus and Homo habilis, and adapting to the grassland environment such as upright walking has promoted evolution.

This paragraph explains how natural selection creates single-celled animals and plants. It mentions Darwin's point of view that 2.5 billion years ago, single-celled organisms in the primitive ocean showed two types of mutations due to lack of food and increased carbon dioxide. Natural selection won and multiplied, forming primitive single-celled animals and plants, amoebas, etc. or their descendants.

Natural selection is the core reason driving evolution.