Bio 1262 Tutorial Uwi

1)Land plants all have heteromorphic (anisomorphic) alternation of generations, in which the sporophyte and gametophyte are distinctly different. All bryophytes, i.e. liverworts,mosses and hornworts, have the gametophyte generation as the most conspicuous. In all bryophytes the gametophyte generation is dominant and the sporophyte is dependent on it As an illustration, consider a monoicous moss. Antheridia and archegonia develop on the mature plant (the gametophyte). In the presence of water, the biflagellate sperm from the antheridia swim to the archegonia and fertilisation occurs, leading to the production of a diploid sporophyte. The sporophyte grows up from the archegonium. Its body comprises a long stalk topped by a capsule within which spore-producing cells undergo meiosis to form haploid spores.

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3) In flowering plants the flowers are essential in the sexual reproductive cycle, with the pollen (the male gametes) from one flower typically being carried to another by some agency, most commonly wind or insects. Once the pollen has been deposited it will fertilize the eggs in the receiving plant. Bryophytes have neither pollen nor flowers and rely on water to carry the male gametes (the sperm) to the female gametes (the eggs). The bryophytes are therefore restricted to moist habitats.

The pteridophyte (fern) species live in a wide variety of habitats, from remote mountain elevations, to dry desert rock faces, to bodies of water or in open fields. Ferns in general may be thought of as largely being specialists in marginal habitats, often succeeding in places where various environmental factors limit the success of flowering plants. The typical fern, a sporophyte, consists of stem, leaf, and root; it produces spores; and its cells each have two sets of chromosomes, one set from the egg and one from the sperm. The sporophyte of most ferns is perennial (it lives for several years) and reproduces vegetatively by branching of the rootlike underground stem,...