Comparison table of asexual reproduction and sexual reproduction

asexual reproduction

Sexual germ cells are not formed, but they are formed.

No meiosis, through meiosis.

By fertilization without fertilization.

Early, low-level and primitive reproductive modes have appeared in evolutionary history. Common in lower organisms and plants. There are late, advanced and evolutionary reproductive models in evolutionary history. The main reproduction modes of higher animals and plants.

Without gene recombination, without gene mutation, the genetic material of offspring is exactly the same. Small change. With gene recombination, great changes have taken place in the genetic material of future generations.

The methods are fission propagation, bud grafting propagation, spore propagation, vegetative propagation (grafting, cutting, layering) and so on. Higher plants are double fertilized, while higher animals are common fertilized.

Application: Rapid propagation of excellent fruit tree varieties by grafting, plant tissue culture and other methods. Application: cross breeding

* * * Similarity: Both are about increasing the number of offspring, and both have heredity and variation.

(1) Replication type:

ⅰ. asexual reproduction:

1. Concept: Without the combination of germ cells, a new individual's reproductive mode is directly produced by the mother.

★ Remarks: Asexual reproduction can produce germ cells, but new individuals can only be formed without the combination of hermaphroditic germ cells.

2. Type:

Conceptual example: the reproductive model of splitting a mother's reproduction into two daughters. Spore reproduction of unicellular organisms such as amoeba and bacteria spores (a kind of asexual germ cells) are produced by organisms. Spores can directly form new individuals. Rhizopus and Penicillium germinate and reproduce from the mother at a certain position, and when they grow up, the buds fall off from the mother to form new individuals. The vegetative propagation of yeast and corals is composed of vegetative organs (roots, leaves and stems) of plants.

3. Several special reproductive modes

(1) IVF

General process: in vitro fertilization, after the fertilized egg develops in vitro for a period of time, the embryo is transplanted into the uterus to continue its development.

Essence: It belongs to sexual reproduction. Compared with normal reproduction of human beings, it mainly changes the place of fertilization.

(2) Cloning:

General process: the nucleus of somatic cells is transferred to enucleated eggs, and the combined eggs are transplanted into the uterus, and gradually develop into new individuals.

Essence: Somatic cell culture and reproduction belong to asexual reproduction.

(3) Tissue culture

① Somatic cell tissue culture

General process: In vitro, plant somatic cells gradually form new plants on tissue culture medium through cell division and cell differentiation.

Essence: It belongs to asexual reproduction. Its principle is the totipotency of plant somatic cells.

② anther culture in vitro

General process: Mature pollen is directly cultivated into haploid plants without fertilization.

Essence: Sexual germ cells are cultured into new individuals in vitro, which belongs to sexual reproduction.

(4) virus reproduction

The reproduction mode of the virus is replication, which should belong to asexual reproduction.

Ⅱ. Sexual reproduction:

1. Concept: Two sex cells and pairwise combination form a fertilized egg, and then form a new individual.

2. Type:

Examples of the concept of reproductive species names include two gametes that combine into zygotes through sexual reproduction, and two gametes that combine into zygotes through heterogamy of animals and plants with the same shape and size, such as algae and fungi. However, the two gametes that combine into zygotes through heterogamy are different in shape and size, one is slightly larger and the other is slightly smaller. The egg reproduction of protozoa is made up of sperm and egg cells, and the sperm is particularly small. Although parthenogenesis in higher animals and higher plants has huge egg cells, in sexually reproducing animals, the egg cells independently develop into offspring, such as bees (drones), aphids, Daphnia, dandelion,

3. The sexual reproduction process of angiosperms:

① Formation of pollen grains and sperm:

★ Remarks: Two sperm formed by the same germ cell have the same genetic composition.

② Formation of embryo sac, egg cell and polar nucleus;

③ Double fertilization process (unique phenomenon of angiosperms)

4. Comparison between sexual reproduction and asexual reproduction

The difference between asexual reproduction and sexual reproduction in the project is that germ cells can produce germ cells (such as spores), but they do not produce germ cells through the combination of hermaphroditic germ cells. Generally, parents' traits are maintained by their offspring with little variation, which is a breeding method to maintain parents' excellent traits. Offspring is inherited by parents, with strong variability, which is not conducive to maintaining parents' traits and weak adaptability.