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Sporozoites move towards the liver, where they spend an incubation period during which they make 2 cycles of Asexual reproduction where the nuclei divide by Schizogony giving many merozoites.
Merozoites migrate to blood infecting the red blood cells, where they pass several cycles of Schizogony.
They produce huge numbers of merozoites that are released together every 2 days with the destruction of the infected red blood cells. Meanwhile, symptoms of Malaria fever appear on the patient (as heat, chill, and sweating).
5. Merozoites give rise to gametocytes, those migrate to the mosquito with patient’s blood.
6. Gametocytes develop to gametes in the mosquito’s stomach where they fuse into the zygote (2N) that transforms to the Ookinete (2N) that penetrates into the stomach`s wall, and grows to the Oocyst (2N).
7. The nucleus of the Oocyst divides by meiosis, this process is known as Sporogony producing numerous Sporozoites (N) that liberate and move towards the mosquito’s salivary glands to be ready for human infection.
So, the life of Plasmodium includes Sexual generation that reproduces by gametes fusion in mosquito followed by Asexual generation that reproduces by Sporogony in (mosquito) and by Schizogony (in Man).
2. Life Cycle of a Fern Plant (Ploypodium):
From the common ferns, Polypodium, which is known in plant nurseries as an ornamental plant, and Adiantum, which grows on well edges and shaded streams. The life cycle of Polypodium starts by the Sporophyte (2N).
Sporophyte carries the leaves, on their lower surfaces there are sori. Sori contain numerous spore cells (2N) which divide by meiosis giving spores (N).
On maturation of these spores, they are released and carried by winds to far distances.
Upon reaching a wet soil, spores germinate, forming several cells, that develop to a flat heart shaped body called the Gametophyte (N).
Gametophyte grows over the soil.
Rhizoids arise from the lower surface extremity of the gametophyte, that penetrate into the soil to absorb water and salts. The genital organs grow from the anterior region of the same surface of the Gametophyte. The male genital organs are called Antheridia, while the female genital organs are called Archegonia.
On maturation of the antheridia, the male gametes (ciliated sperms (N)) liberate and swim over soil water to reach the mature Archegonium for fertilizing its egg (N) forming the zygote (2N).
The zygote divides and differentiates to a new Sporophyte (2N), that grows over the Gametophyte, on which it depends for sometime till developing its own roots, stem, and leaves.
The Gametophyte degenerates, while the Sporophyte grows to repeat the life cycle. So, the Sporophyte (2N) that reproduces Asexually alternates with the Gametophyte (N) that reproduces Sexually in the life cycle of ferns. By such way, it represents a typical example of the phenomenon of alternation of generations in the living organisms.
3. Life Cycle of Schistosoma (Bilharzia):
The life cycle of Schistosoma is an example of alternation of generations in the Animal Kingdom. Adult worms live in Man, and reproduce sexually in his body. The parasite also uses snails as intermediate hosts, where Asexual reproduction occurs. Moreover, both types of reproduction enable the parasite to face the life of parasitism in a better way.
Reproduction in Flowering Plants.
The flowering plants are a large group of seed plants whose seeds develop with a pericarp. It is then called Angiospermae. They are common in various habitats. They vary in size from small herbs to giant trees. The flower in these plants is the specialized organ for reproduction. It is a short stem with the leaves being modified to various floral parts. The flower arises from the axil of either a green or a scale leaf called bract. In some cases flowers occur without bracts. Flowers may be solitary apical as in Tulip, and so stops the growth of the stem, or may be solitary axillary as in Petunia. In other cases, flowers may be grouped on the floral axis into various aggregations called inflorescence as in Beans and Manthur.
The flower and its parts:
The flower emerges from the axil of a leaf called bract that varies in shape and colour from a plant to the other. The flower in some plants is carried on a pedicle and so becomes stalked. In some other plants, it is sessile.
The structure of a typical (complete) flower:
(as in Beans, Apple, Onion, and Petunia)
There are 4 floral whorls:
1. Calyx: It is the outer whorl of the flower, it is formed of green leaves known as sepals these protect the inner parts of the flower against drought, rain, or wind.
2. Corolla: It is the next whorl inside the Calyx. It is composed of one row or more of petals, that help in protection of the floral sexual parts, and they attrract insects so that, the pollination process occurs.
N.B.: In flowers of most Monocot plants as Tulip and Onion, leaves of the Calyx are hardly differentiated from those of the Corolla and so both whorls are called Perianth.
3. Androecium: It is the male organ that consists of numerous leaves called
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| When two filaments contact each other, a protrusion grows inwards between opposite pairs of cells. | | | Stamens. Each stamen consists of a filament which carries an apical |