Fertilization occurs when the nucleus of both a sperm and an egg fuse to form a diploid cell, known as zygote.
The male gametes are called sperm cells, and the female gametes are called egg cells (ova). During mating, the sperm cell and the egg cell unite to form a fertilized combination of cells called a zygote. This zygote is the first of many cells of a new individual. This zygote will begin to divide into two cells and this continues to be repeated over and over resulting in the development of an embryo. Gametes unite to produce a zygote, which then develops into an embryo. This usually happens inside a seed, protecting the embryo and providing food (cotyledon) for the embryo when growing conditions are right. Plants which are produced, as a result of cross-fertilization, are not identical to either plant. Allogamy, which is also known as cross-fertilization, refers to the fertilization of an egg cell from one individual with the male gamete of another. Autogamy which is also known as self-fertilization, occurs in such hermaphroditic organisms as plants and flatworms; therein, two gametes from one individual fuse. This is the point when fertilisation actually occurs; pollination and fertilisation are two separate processes. The nucleus of the other sperm cell fuses with two haploid polar nuclei (contained in the central cell) in the centre of the gametophyte. Max Image Size: 2880 pixels wide by 2160 pixels high. Description: This medical illustration shows fertilization (conception) and capacitation, the moment in which a single sperm cell and an egg (oocyte) unite, marking the beginning of a human life. This process typically occurs in the fallopian (uterine) tube. X. Angiosperms exhibit double fertilization: one sperm unites with an egg, and a second sperm with the central cell of the embryonic sac, or female prothallium. Fertilization independent of the presence of free water is one of the most important adaptations of seed plants to survival on land. The second stage of the reproductive process—karyogamy, or the union of nuclei—occurs within the asci. Somatogamy is a process characteristic of basidiomycetous fungi. These organisms do not form gametes or gametangia, and plasmogamy occurs when two uninuclear cells, the positive and negative primary mycelia, unite. Human fertilization is the union of a human egg and sperm, usually occurring in the ampulla of the uterine tube. The result of this union is the production of a zygote cell, or fertilized egg, initiating prenatal development. Scientists discovered the dynamics of human fertilization in the nineteenth century. The sperm bind through the corona radiata, a layer of follicle cells on the outside of the secondary oocyte. Fertilization occurs when the nucleus of both a sperm and an egg fuse to form a diploid cell, known as zygote. The successful fusion of gametes forms a new organism Fertilization is the process by which sperm and egg unite. An expanded understanding of the mechanisms that underlie these events has provided insights into an important aspect of early development and also has proven to be a valuable model in which to study cellular function.  Fertilization in humans. The sperm and ovum unite through fertilization, creating a zygote that (over the course of 8-9 days) will implant in the uterine wall, where it will reside over the course of 9 months. This is the point when fertilisation actually occurs; pollination and fertilisation are two separate processes. The nucleus of the other sperm cell fuses with two haploid polar nuclei (contained in the central cell) in the centre of the gametophyte. 1 During sexual reproduction, two haploid gametes join in the process of fertilization to produce a diploid zygote. 2  Meiosis is the type of cell division that produces gametes. 3  It involves two cell divisions and produces four haploid cells. Sexual reproduction occurs in a cycle. Diploid parents produce haploid gametes that unite and develop into diploid adults, which repeat the cycle. This series of life stages and events that a sexually reproducing organism goes through is called its life cycle.
http://edquestscience.com/pdf/cardsBDb.pdf https://en.wikipedia.org/wiki/Fertilisation http://www.nucleuscatalog.com/view-item?ItemID=4631 http://encyclopedia2.thefreedictionary.com/fertilization https://en.wikipedia.org/wiki/Human_fertilisation http://www.nature.com/fertility/content/full/ncb-nm-fertilitys57.html https://en.wikipedia.org/wiki/Fertilisation http://www.ck12.org/user:dGVycnlyQHZhbGxleTI2Mi5vcmc./section/Reproduction-and-Meiosis-%253A%253Aof%253A%253A-The-Cell-Cycle%252C-Mitosis%252C-and-Meiosis/
fertilization occurs when which cells unite