From the fertilized egg, it has to undergo vegetative growth and reproductive growth.

1. Reproduction, development and growth

Reproduction is the process by which organisms produce offspring. For sexually reproducing organisms, the formation of fertilized eggs means the beginning of the next generation of life. It is a developmental process from fertilized egg division to sexually mature organism formation. Therefore, growth and development is a continuation of the reproductive process, and it is a process in which the life possibility of a fertilized egg becomes a biological reality. The development process includes individual growth, which is a process from quantitative change to qualitative change. In the process of individual growth, through the accumulation of quantity, when sexual maturity, qualitative change is realized, thus completing the individual development process. The growth and development of animals are coordinated and orderly under the control of neurohormones.

2. Individual development, embryonic development and post-embryonic development

The individual development of an organism refers to the process that a fertilized egg undergoes cell division, tissue differentiation and organ formation until it develops into a mature individuals. This process can be divided into two stages, namely embryonic development and post-embryonic development.

(1) Embryo development;

Animals: The process by which a fertilized egg develops into a larva. Like frogs from fertilized eggs to tadpoles.

Angiosperms: The process in which fertilized eggs and fertilized polar nuclei develop into seeds in ovules (in essence, fertilized eggs develop into embryos of seeds).

(2) Postembryonic development:

Animals: The process in which larvae hatch from the egg membrane or are born from the mother and develop into sexual mature individuals. This process is abnormal in some animals, such as frog tadpoles developing into frogs; Some are incomplete metamorphosis, such as the development process of locusts, and some are non-metamorphosis, such as cattle and sheep.

Angiosperms: the seeds germinate and grow into adults; After reproductive growth, it develops into a sexually mature individual.

3. The difference between polar nucleus and polar body, embryo sac and blastocyst.

Polar body is a daughter cell formed by simultaneous meiosis of animal oocytes and eggs. Due to the lack of cytoplasm and nutrients, the polar body cannot develop and is finally absorbed by the mother. Of the three polar bodies produced by an oocyte, two (produced by the first polar body) have the same genetic material, and the other is the same as the genetic material in the oocyte. Polar bodies and egg cells contain half as many chromosomes as this species.

Polar nuclei are two nuclei released from the embryo sac of angiosperms, which combine with sperm to form fertilization polar nuclei and develop into endosperm in the future, providing nutrition for the development of young embryos. A megaspore mother cell in the ovule undergoes meiosis to produce a megaspore, and the megaspore undergoes three mitoses to produce eight cells (the structure including these eight cells is called embryo sac), one of which is an egg cell and two polar nuclei, so the genetic material of the two polar nuclei is the same as that of the egg cell, and the number of chromosomes contained is half that of this species. An embryo in which an animal fertilized egg divides to form a blastocyst cavity is called a blastocyst.

4. The relationship between chromosomes and genotypes in plant development.

In order to facilitate the memory of chromosomes and genotypes in various parts of plants, we can summarize the following laws to understand and master, namely "two divisions":

(1) In terms of chromosome number: (assuming that the chromosome number of normal somatic cells is 2N), except for sperm, egg cells and polar nuclei (one polar nucleus), the chromosome number is n; Except for fertilized polar nuclei and developing endosperm cells, the chromosome number of other cells is 2N.

(2) As far as genotype is concerned, except fertilized eggs and developing embryos, its genotype consists of an egg cell and a sperm; Except for fertilized polar nuclei and developing endosperm cells, the genotype of cells consists of one sperm and two egg cells, and the genotypes of other cells are the same as those of the mother.

5. Vegetative growth and reproductive growth

Vegetative growth refers to the growth of vegetative organs such as roots, stems and leaves of plants. Reproductive growth refers to the growth of reproductive organs such as flowers, fruits and seeds of plants. Vegetative growth is the material basis of reproductive growth, but both vegetative growth and reproductive growth consume and compete for organic matter, thus affecting or changing the distribution of organic matter in plants. Therefore, for cultivated leaves, stems, root vegetables and grasses, measures should be taken to promote vegetative growth and inhibit reproductive growth; For plants that harvest cereals, rapeseed and fruits, measures should be taken to promote reproductive growth while vegetative growth, or to control vegetative growth and promote reproductive growth when vegetative growth reaches a certain level.

6. The evolutionary significance of amniotic membrane

Amphibians can't get rid of water restrictions. The reproduction and development (initial stage) of amphibians must be in water and directly depend on the external water environment. Therefore, amphibians are not really terrestrial vertebrates. Amniotic membrane is the structure that reptiles began to appear. There is enough liquid in the amniotic membrane, which ensures the requirements of embryonic development on the water environment, thus reducing the dependence of individual development on the external water environment. Amniotic membrane lays the foundation for the complete terrestrial life of vertebrates. At the same time, amniotic fluid in amniotic membrane can buffer shock and prevent mechanical damage of internal embryos.