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TWO STAGES. “In angiosperms the diploid sporophyte is the dominant stage and the haploid gametophyte is completely dependent upon the sporophyte. The flower is part of the sporophyte: it is diploid and through meiosis will produce spores that will undergo mitosis to form gametes. The anthers will produce haploid microspores. These will undergo mitosis and differentiate to form the pollen grains, each of which carries two sperm. The ovules will produce haploid megaspores.” https://lnkd.in/d4Dqxx6 View in LinkedIn

CULTURE. “In contrast to biological evolution, in social evolution acquired characteristics are passed on to subsequent generations. Cultural evolution is essentially a Lamarckian process. The capability of cultural evolution for bringing about effective change on a timescale far faster than biological evolution demonstrates the power of Lamarckian evolution.” https://lnkd.in/dMvAeqz View in LinkedIn

OVERLY COMPLEX. “The angiosperm life cycle is more complex than the life cycles of the other major groups of plants that we have discussed. This is because in addition to having alternation of generations, angiosperms also have a process called double fertilization.” https://lnkd.in/d4Dqxx6 View in LinkedIn

BROAD EVOLUTION. “According to Spencer, evolution is a process giving rise to increasing differentiation (specialization of functions) and integration (mutual interdependence and coordination of function of the structurally differentiated parts). He viewed evolution as the dominant force driving the spontaneous formation of structure in the universe, including the formation of matter, stars, geological formations, biological species, and social organizations. Thus, Darwinian evolution is just. a special case of a broader principle.” https://lnkd.in/dMvAeqz View in LinkedIn

RUNNING THE GAUNTLET. “During this journey, the pollen tube of Arabidopsis, for example, interacts with at least seven different pistil cell types prior to arrival at its final destination inside the ovule. To add complexity, further layers of recognition exist. These include self-recognition and specialized processes to prevent self-fertilization and consequent inbreeding, as well as interspecific barriers, which are poorly understood at the molecular/cellular level.” http://www.sciencedirect.com/science/article/pii/S1674205214608996 View in LinkedIn

DISCRIMINATION. “During the various phases of pollination...angiosperms distinguish self from non-self-pollen and direct and control pollen tube growth through the maternal tissues towards the egg apparatus.” http://www.sciencedirect.com/science/article/pii/S1674205214608996 View in LinkedIn

CONSTANT CROSS-TALK. “During its journey, the angiosperm pollen tube communicates with its environment, allowing the maternal reproductive tissues to recognize and support compatible pollen in order to avoid fertilization failure. The acceptance of compatible pollen and the subsequent steps leading to successful fertilization comprise complex and cooperative processes between the pollen and the receptive pistil.” http://www.sciencedirect.com/science/article/pii/S1674205214608996 View in LinkedIn

TWO PRODUCTS. “The receptive synergid cell degenerates following this interaction, whereas the other synergid cell persists. After their ejection from the pollen tube, the two sperm cells stay immobile between the two female gametes for several minutes and subsequently fuse with the egg and central cells, respectively. These two fusion events give rise to the embryo and to the endosperm, respectively, and the process is therefore termed double fertilization.” http://www.nature.com/articles/ncomms5722?WT.ec_id=NCOMMS-20140829 View in LinkedIn

NUTS AND BOLTS. “In flowering plants, the egg is intimately associated with typically six to eight other haploid cells forming the female gametophyte. These include the central cell representing the second female gamete and two synergid cells that produce the signals, which guide the male gametophyte, or pollen tube, towards the ovule. The pollen tube delivers two non-motile sperm cells whose release occurs by bursting, which in turn is triggered when the tube interacts with the synergid cells.” https://lnkd.in/dXVTT6X View in LinkedIn

RACING POLLEN TUBES. “The reproductive strategy of flowering plants is different and involves competition among growing pollen tubes to enter one ovule and to deliver their sperm cell cargo. The first pollen tube that enters an ovule usually releases its cargo and one sperm cell fuses with the egg cell forming the embryo while the second sperm cell fertilizes the central cell to generate the endosperm. Later-arriving pollen tubes do not enter already targeted ovules.” http://www.sciencedirect.com/science/article/pii/S096098221200468X View in LinkedIn