Escherichia coli (commonly abbreviated E. coli) is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms (endotherms).Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans.The harmless strains are part of the normal flora of the gut, and can benefit their hosts by producing vitamin K2, and by preventing the establishment of pathogenic bacteria within the intestine.ost E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans. The harmless strains are part of the normal flora of the gut, and can benefit their hosts by producing vitamin K2, and by preventing the establishment of pathogenic bacteria within the intestine.
In flowering plants the gametophytes are very reduced in size, and are represented by the pollen and the embryo sac. The sporophyte produces spores (hence the name) by meiosis, a process also known as reduction division that reduces the number of chromosomes in each spore mother cell by half.The resulting meiospores develop into a gametophyte.n flowering plants the gametophytes are very reduced in size, and are represented by the pollen and the embryo sac. The sporophyte produces spores (hence the name) by meiosis, a process also known as reduction division that reduces the number of chromosomes in each spore mother cell by half.
The asexual form, or sporophyte, is represented by the commonly known and cultivated fern plant, and is diploid (2N). Sporophytes can reproduce either by vegetative cloning via their rhizomes or through spore formation. The prothallia are equipped with multiple antheridia (male reproductive organs) and archegonia (female reproductive organs). As heterosporous plants, the fern's antheridium produces free-swimming sperm and its archegonium produces eggs. The products of their unions are zygotes, and fertilization occurs when the sperm swim through an opening (operculum) from each antheridium along a thin film of water to the neck of each archegonium.