Also known as reproduction. It refers to the phenomenon that organisms produce offspring and continue their race, which is one of the basic characteristics of life. There are many kinds of biological groups in the biological world, and so are the ways of reproduction. Virus particles with noncellular structure replicate themselves through nucleic acid replication and protein synthesis system in host cells. Prokaryotes and eukaryotes can be divided into asexual reproduction and sexual reproduction. Asexual reproduction is a primitive way of reproduction, and its offspring are the direct continuation of the mother, with a large number, less variation and less vitality. Sexual reproduction is a common way of reproduction in biology, and its offspring is the recombination of parental genetic material, which has strong vitality and variability and is of great significance in biological evolution.

asexual reproduction

A reproductive mode in which the mother directly produces offspring without the combination of germ cells. The most common ways of asexual reproduction are fission reproduction, budding reproduction, vegetative reproduction and spore reproduction. They directly develop into more than two new individuals from vegetative cells or local tissue cells of vegetative bodies; Or derived from vegetative cells into germ cells specialized in morphology and function, and developed into new individuals from this germ cell (spore) without gender differentiation. Therefore, the daughter is the direct continuation of the mother. The process of asexual reproduction doesn't go through complicated stages of fertilization and embryo development, which is beneficial to the reproduction of human race. There is no recombination of genetic material in the process of asexual reproduction, and the genetic information of offspring is basically the same as that of the mother, so the variation of offspring is less, which is conducive to maintaining the excellent characteristics of the mother. However, when continuous asexual reproduction is carried out, the viability of its offspring tends to decline. Asexual reproduction is a primitive way of reproduction, and prokaryotes and protists usually reproduce in this way.

divide

Schizophrenia for short. Reproductive mode in which a mother splits into two or more offspring. The fission of unicellular organisms such as bacteria, unicellular algae and protozoa is actually a kind of cell division. The cell division mode of bacteria and cyanobacteria is transverse division; Amoeba cells divide into two new individuals through one mitosis; The cell division mode of paramecium is transverse division, mitosis in small nucleus and amitosis in large nucleus. The cell division mode of Euglena and diatom is longitudinal division. When the trophozoite of plasmodium matures, it undergoes many nuclear divisions and forms many merozoites.

Destructive reproduction

Reproductive mode in which an organism leaves its mother to produce two or more offspring. For example, oscillatoria in cyanobacteria and Spirogyra in green algae can be broken down into several parts, and each fragment becomes a new population after cell division. Lower invertebrates, such as anemones and planarians, can also produce new individuals through division or lateral division.

Germination propagation

Short for sprout. The organism gives birth to a bud from a certain part of the mother, which gradually grows and separates from the mother, forming a reproductive model of a new individual living independently. Short for sprout. The budding process of yeast begins with the cytoplasm and cell wall of the mother cell protruding outward, and then the nucleus is divided into two subnuclei through mitosis. One subnucleus remains in the mother cell, the other subnucleus moves to the protruding part, and then the cell contracts in the protruding part to produce buds. The buds are temporarily connected with the mother cells, and the above process can be repeated to form a group with multiple buds connected with each other. When the bud is close to the size of the mother cell, it falls off from the mother cell and becomes a complete new individual. The emergence of hydra is that its body wall protrudes outward and gradually grows to form buds. The bud has drooping lips, mouth and tentacles, and its digestive cavity communicates with the mother, and finally the base contracts and separates from the mother. When coral buds grow up, they don't separate from their mothers and form a group.

spore reproduction

Spores without sex differentiation are produced by the mother, and each spore can directly develop into a new individual's reproductive mode without pairing. Protoalgae, such as Chlamydomonas and Chlorella, grow vegetative cells and thicken cell walls to form sporangia, and protoplasts in sporangia divide many times to form multiple asexual spores. Cladosporium forms reproductive branches at the top of algae, and sporangium developed from reproductive branches produces a large number of spores.

The aerial hyphae of various Aspergillus can produce reproductive branches and form sporangia. Penicillium and other reproductive branches re-developed into conidiophore, and its end was broken many times to form conidia. The gametes of plasmodium combine in mosquitoes to form zygotes, which penetrate into the stomach wall and develop into sporangia (i.e. oocysts). After many nuclear divisions, many spores were formed. Spores enter the human body with mosquito saliva and develop into trophozoites in liver cells.

vegetative propagation

Propagation mode from vegetative organs such as roots, stems and leaves of higher plants to new individuals. Such as tuber propagation of sweet potato, creeping propagation of strawberry, rhizome propagation of bamboo, reed, white spear and lotus, tuber propagation of potato, bulb propagation of lily and onion, bulb propagation of narcissus and taro, and leaf bud propagation of begonia are all natural nutrition propagation. In agriculture, forestry and horticulture, rooting, cutting, layering, grafting and other methods are often used to separate a part of plant vegetative organs from the mother body and make them develop into new individuals, which belongs to artificial nutritional reproduction. Tissue culture is also a method of artificial nutrition reproduction. Asexual reproduction can enable offspring to maintain the excellent characteristics of their parents. Therefore, flowers, fruit trees, tea, sugarcane, bamboo and other artificially cultivated plants all adopt this propagation method. However, the long-term vegetative propagation of plants will gradually reduce their viability and must be rejuvenated through sexual reproduction.

tissue culture

Cell culture in vitro is one of the important methods to study living cells. Specifically, it is to cultivate animal and plant cells in vitro under aseptic conditions and give them proper nutrition, so that cells can continue to survive and grow. Its advantage is that cells of different tissues can be isolated and cultured under specific conditions, and the morphology and growth activities of living cells can be directly observed, so as to understand the various conditions required by various cells in a certain physiological state and their responses to various conditions.

Now, due to the improvement of technology, in plant cell culture, not only can callus (a group of undifferentiated cells) be formed, but also can differentiate into complete plants and blossom and bear fruit. For example, many plants, such as tobacco, carrot and Petunia, have been cultured from protoplasts into regenerated plants.

sexual reproduction

Male and female germ cells are produced by parents, and the bisexual germ cells combine to form fertilized eggs, which develop into a new individual reproductive mode. Sexual reproduction can be divided into three basic ways: gamete reproduction, zygote reproduction and parthenogenesis, mainly gamete reproduction. The production of hermaphroditic germ cells must undergo meiosis, and hermaphroditic germ cells are randomly combined into zygotes through fertilization. From fertilized eggs to new individuals. Because both parents can provide a set of genetic information for the formation of offspring through germ cells, offspring have the advantages of parents and can better adapt to the external environment. Due to the random combination of heterogeneous germ cells, there are many variation types in offspring, which provide rich original materials for species evolution. Sexual reproduction is a common way of reproduction in biology, especially in animals.

gametogony

Sexual germ cells are produced by parental gametes. Pairs of opposite sex gametes fuse with each other to form a zygote, and the zygote develops into a reproductive model of a new individual. Gamete reproduction is the main way of sexual reproduction, which can be divided into three types according to the gender differentiation and morphological characteristics of gamete cells: homogamy, heterogamy and egg reproduction.

combine

When some fungi, bacteria, green algae and protozoa reproduce sexually, two cells approach each other to form a joint, and the protoplasts fuse to produce a zygote, which develops into a new individual. This mode of reproduction is called zygotic reproduction. For example, E.coli has two sex lines. When individuals of different sex lines hybridize, somatic cells of positive bacteria contact with somatic cells of negative bacteria, forming connecting tubes on the sides of the three cells, and DNA of positive bacteria cells flows into negative bacteria cells through the connecting tubes to form zygotes; The fertilized egg undergoes cell division to form two Escherichia coli. During the conjugation of Spirogyra, all the protoplasm in the positive conjugation cell reached the negative conjugation cell through the conjugation tube, and the protoplasm of the two cells fused to produce zygote. After meiosis, the zygote produces two sexual spores each, and the sexual spores germinate into vegetative bodies of Spirogyra. When paramecium reproduces, the large nucleus of each insect disappears, and the small nucleus meiosis produces four nuclei, three of which disappear, and the remaining one is divided into dynamic nucleus and static nucleus; The moving nuclei are exchanged by conjugated membranes and fused with the stationary nuclei on the other side respectively; After joining, the two worms separated, each undergoing three nuclear divisions and two cytoplasmic divisions, forming four new individuals. The sexual reproduction mode of zygotic bacteria is also zygotic reproduction.

homogamy

A simple method of sexual reproduction in which two opposite sex gametes combine to form a fertilized egg. Most algae and molds can produce new individuals through gamete fusion, such as haploid vegetative cells of Chlamydomonas, which will form gametophytes in unfavorable living environment. Cell division in different gametes produces opposite gametes, and two opposite gametes fuse into zygotes (2n). The zygote undergoes meiosis to form haploid vegetative cells, and each vegetative cell is a new individual of Chlamydomonas. In the life history of mold, the haploid propagated by zoospores forms a gametophyte at the top of its upright mycelium, and the cells in the gametophyte divide to form opposite gametes, and the two opposite gametes fuse into zygotes and develop into diploid hyphae.

Heterogamy reproduction

Sexual reproduction in which two heterogametes combine to form a zygote. For example, Porphyridium is generally a hollow colony composed of 32 cells similar to Chlamydomonas. In the process of sexual reproduction, some cells of some groups divide many times, producing 64 slender gametes with two flagella; In other populations, some cells only produce a large spherical gamete with flagella. Some populations can produce two kinds of gametes. After the gametes mature, they don't separate temporarily, leave the original population and enter the water, and then separate from each other. With the help of flagella, they can enter the population as large gametes. Macrogametes can neither swim nor leave the group. Each small gamete combines with a large gamete to form a zygote, and then the zygote develops into a new spherical population through meiosis.

Elliptical replication

Parents produce sperm and egg cells with great differences in morphology and fluidity, which fuse to form a zygote, and then the zygote develops into a new sexual reproduction model. For example, when Volvariella volvacea has sexual reproduction, some cells in the population divide many times to form seminal vesicles composed of many spindle-shaped sperm, which have two flagella. Sperm from the same seminal vesicle are combined and separated from each other after leaving the group, so they can swim actively. A few cells in the population can form egg cells. Every big egg cell is wrapped in an oocyst, and it can't swim without flagella. When the sperm enters the oocyte, the sperm and the oocyte fuse to form a fertilized egg. The zygote forms a thick wall in the matrix, and the matrix is separated from the matrix after disintegration. Under suitable conditions, zygotes undergo meiosis and develop into a new Volvariella volvacea population. Most animals and humans, as well as some algae and higher plants, sperm and egg cells fuse to form zygotes, and they do not undergo meiosis and directly develop into new individuals.

parthenogenesis

Also known as parthenogenesis. Sexual reproduction refers to the direct development of the eggs of sexually reproductive animals and plants into new individuals without fertilization, which can be divided into natural parthenogenesis and artificial parthenogenesis. The male individuals in bees and ants are directly developed from unfertilized eggs, and the summer breeding population of Daphnia and aphids is parthenogenesis with only females and no males. Dandelion, Kentucky bluegrass and other plants can also parthenogenesis. Many animals, such as sea urchins, silkworms, fish, frogs, etc., can induce egg cells to directly develop into new individuals under artificial conditions. Haploid plants can be induced by placing mononuclear anthers or ovules of angiosperms on artificial culture medium under aseptic operation conditions, which also belongs to artificial parthenogenesis. The new individuals produced by parthenogenesis are haploid.