Life cycle of a typical fern
A typical fern is homosporous meaning that it produces a single type of spore which looks and spreads like a seed. In nature, spores have single cells containing only one copy of each chromosome (haploid). In its breeding site, the spore develops into gametophyte that survives through photosynthesis. At this stage, these gametophytes produce both sperm and egg which undergo maturation at different times to promote cross fertilization between the gametophytes.
For this fertilization to take place, the fern sperm has to swim by help of flagella through moisture from antheridia to eggs in the archegonia. As a result, a zygote is formed which is diploid, with two copies of each chromosome. The fertilized egg develops through mitosis into a young plant the sporophyte which grows out of an archegonium of its parent. Eventually, the new sporophyte grows into a mature fern which has reproductive leaves (sporophylls). Underneath of the leaves are spots called sori with clusters of sporangia. Mature sporophyte releases sporangium and through the process of meiosis, they burst to release spores and the whole process repeats.
Life cycle of typical conifers
Reproduction starts by undergoing meiosis which involves transformation of microsporophylls comprising of microsporocytes into microspores. The ovules originating from the female cone scales produces megasporocytes that transforms into megaspores. A pine tree is sporophyte since it produces through spores. Reproduction starts by undergoing meiosis which involves transformation of microsporophylls comprising of microsporocytes into microspores.
The ovules originating from the female cone scales produces megasporocytes that transforms into megaspores. This Meiotic cell division produces a tetrad of microspores that grows into a pollen grain. It is through a pair of air-filled bladders that pollen grain move and meets with megagametophyte within an ovule. The process of meiosis produces four megaspores, of which only one survives. Essentially, only one megaspore which is fully functioning is left.
The two sperm cells that are contained in the pollen grain comprises of the tube cell and the generative sperm cell. Pollination takes place through penetration of pollen grain into the female’s microphyl. The tube cell draws out after the process of pollination, and becomes a pollen tube finally becomes the egg cell after a couple of years.
Following the migration of the sperm cell in to the pollen tube, fertilization is considered to have occurred. The sperm cell meets the egg a process that produces a diploid zygote. Embryo develops out of the zygote while still in the naked seed. Germination occurs in presence of favorable environmental and hormonal conditions. Finally, a tree or a diploid sporophyte is developed which matures with time, after which diploid female and male cones appears, and the cycle reaches the end.
Similarities of the life cycles are that, meiosis is used as the basis for cell division and both cycles incorporates asexual form of production. In addition, the male and female gametes originate from the same parent plant and occur in green and non flowering plants.Some notable differences are that spore of a fern plant grow underneath the fronds (Leaves) while that of confers is grows on the cones.The gametophyte of a fern sustains itself through photosynthesis unlike in the cycle of a conifers.In confers, the male gamete is transferred through an elongated tube cell to the egg, while in that of fern, the sperms have flagella for movement to the eggs in the archegonia
Advantages of cycles of plants with seeds and spores include flowering plants producing seeds through double fertilization of two sperm nuclei from a pollen grain (the microgametophyte), rather than a single sperm. This is important for it helps in nourishing the developing embryo. Seeded plants in most cases are green and hence they use sunlight for photosynthesis, thus, promoting continued supply of energy that provides food. Spore bearing plants produce numerous spores hence a high chance of reproduction. Some seeds germinate only when there are favorable environmental cues. Others become dormant and fail to germinate even under favorable weather.