the nucleus is found in the atom in nucleosynthesis reactions.
the nucleus is found in the atom in nucleosynthesis reactions.
where is the nucleus found in the atom?
nucleosynthesis reactions
the atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by ernest rutherford based on the 1909 geiger–marsden gold foil experiment. after the discovery of the neutron in 1932, models for a nucleus composed of protons and neutrons were quickly developed by dmitri ivanenko and werner heisenberg. an atom is composed of a positively-charged nucleus, with a cloud of negatively-charged electrons surrounding it, bound together by electrostatic force. almost all of the mass of an atom is located in the nucleus, with a very small contribution from the electron cloud. protons and neutrons are bound together to form a nucleus by the nuclear force.
atomic nucleus
a far more rudimentary form of double fertilization occurs in the sexual reproduction of an order of gymnosperms commonly known as gnetales. specifically, this event has been documented in both "ephedra" and "gnetum", a subset of gnetophytes. in "ephedra nevadensis", a single binucleate sperm cell is deposited into the egg cell. following the initial fertilization event, the second sperm nucleus is diverted to fertilize an additional egg nucleus found in the egg cytoplasm. in most other seed plants, this second 'ventral canal nucleus' is normally found to be functionally useless. in "gnetum gnemon", numerous free egg nuclei exist in female cytoplasm inside the female gametophyte. succeeding the penetration of the mature female gametophyte by the pollen tube, female cytoplasm and free nuclei move to surround the pollen tube. released from the binucleate sperm cell are two sperm nuclei which then join with free egg nuclei to produce two viable zygotes, a homologous characteristic between families "ephedra" and "gnetum". in both families, the second fertilization event produces an additional diploid embryo. this supernumerary embryo is later aborted, leading to the synthesis of only one mature embryo. the additional fertilization product in "ephedra" does not nourish the primary embryo, as the female gametophyte is responsible for nutrient provision. the more primitive process of double fertilization in gymnosperms results in two diploid nuclei enclosed in the same egg cell. this differs from the angiosperm condition, which results in the separation of the egg cell and endosperm. comparative molecular research on the genome of "g. gnemon" has revealed that gnetophytes are more closely related to conifers than they are to angiosperms. the rejection of the anthophyte hypothesis, which identifies gnetales and angiosperms are sister taxa, leads to speculation that the process of double fertilization is a product of convergent evolution and arose independently among gnetophytes and angiosperms.
double fertilization