Home BIOLOGY TOPIC 1: CLASSIFICATION OF LIVING THINGS ~ BIOLOGY FORM 3

TOPIC 1: CLASSIFICATION OF LIVING THINGS ~ BIOLOGY FORM 3

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Kingdom Plantae, Division Coniferophyta (Conifers)

General and Distinctive Features of the Division Coniferophyta

Division Coniferophyta or the conifers belong to Kingdom Plantae. These plants are gymnosperms meaning non-flowering.

They are non-flowering but seed bearing plants. They have vascular tissues. They are woody plants majority being evergreen trees. Few varieties are shrubs
What are the general and distinctive features of the Division Coniferophyta?

General characteristics

1. They have secondary growth whose thickening can be observed in cross section of a stem revealing annual rings. Secondary Growth is the result of growth Lateral Meristems (Vascular Cambium & Cork Cambium).

2. Most of the members of Coniferophyta live in cool climates where they form evergreen forests. They keep their leaves year-round.

3. They have a large amount of internodal elongation which allows them to grow faster than the other higher plants.

4. They are Xeromorphic, a characteristic that help to protect them from excessive loss of water and therefore adapt survival in extreme habitats.

5. Most are large trees while a few are shrubs and other small plants.

6. Most of them have hard barks which protect inner softwood.

Distinctive characteristics

1. Conifers are non-flowering but seed producing plants.

2. They have seeds born in cones shaped structures rather than in fruits.

3. They are gymnosperms which mean naked-seed plants because they produce seeds in cones rather than inside an embryo.

4. The leaves are needle-shaped and have a thick cuticle for protection and to decrease water loss.

The Structure of Pinus

Pines are evergreen, coniferous resinous trees growing 3–80 m tall. The bark of most pines is thick and scaly. They have needle like leaves.

Pines are among the most well- known coniferous trees in the world. They thrive in temperate mountainous regions, but can also survive in tropical spots in the northern hemisphere. Pines live relatively long time than other coniferous plants. They may live between 100 and 1,000 years

The Stem

The bark of most pines is thick and scaly, but some species have thin, flaking bark. The branches are produced in regular whorls appearing like a ring of branches arising from the same point.

Leaves

A cross-section of pine stem has several concentric rings with distinct borders between each ring. The center of the stem is called pith. These rings are called annual rings because they grow seasonally and they help a plant to undergo secondary thickening. Generally adult pines have needle-shaped leaves which are green and photosynthetic. The leaves are in bundles or clusters. The leaves (cotyledons) on seedlings are borne in a whorl of 4–24. Juvenile leaves, which follow immediately after seedlings, have single, green leaves arranged spirally on the shoot. They also have non- photosynthetic scale leaves, similar to bud scales. They are arranged spirally like the juvenile leaves.

Cones

A cone is an organ of pines that contains the reproductive structures. The woody cone is the female cone, which produces seeds. The male cones, which produce pollen, are usually herbaceous and much less conspicuous.

Amazing facts about Siberian pine tree
pines tree

The Advantages and Disadvantages of the Division Coniferophyta

Advantages of Conifers

1. Conifers are very important for our economy because of their softwood, which is used for paper and timber, as well as cedar which many people use for their homes because of its beauty and resistance to insects. They have a large economic use as softwood in furniture. In temperate and tropical regions, they are fast-growing softwoods that will allow harvesting in close succession.

2. Decoration and ceremony Many pine species make attractive ornamentals. They are planted in parks and larger gardens. Some varieties are suitable for smaller spaces. Pines are also commercially grown and harvested for Christmas trees.

3. As medicine, Pines and cypress are rich in vitamin; their branches cones and oils can be extracted and used as nutrient supplements.

4. Due to its soft texture conifers are widely used to manufacture Play wood.

5. As other higher plants conifers are source of heat energy, used as firewood and charcoal.

6. Thick forests of conifers form green belts that modify the climate.

7. Conifers form a large arena for Biological research Ecological studies.

8. Food uses: Some species have large seeds, called pine nuts that are harvested and sold for cooking and baking. The soft, moist, white inner bark (cambium) found clinging to the woody outer bark is edible and very high in vitamins A and C. It can be eaten raw in slices as a snack or dried and ground up into a powder for use as bread flour. Also White Pines are rich in Vitamin A and C; flour can be made from the Pine tree’s inner bark. By chewing bark of pine you can eliminate bad breath. Pines can reduce the pain of skin infections by applying warm pine sap.

Division Angiospermophyta ( Flowering Plants )

Angiosperms are flowering plants under kingdom Plantae and division Angiospermophyta. This group of plants is sometimes called Magnoliophyta. Angiosperms are the most abundant land plants.

Like gymnosperms, angiosperms are seed-producing plants but they are distinguished from gymnosperms by their characteristic of producing flowers. These plants produce fruits that contain seeds instead of cones like it is in gymnosperms. The term angiosperm means a plant that produces seeds within fruits.

Angiosperms life cycle

The ovary has ovules that contain mega-sporocyte. Mega-sporophyte has four haploid megaspores; three megaspores disintegrate and the remaining one divides by mitotic divisions to produce eight nuclei in an embryo sac. The three nuclei are organized into the egg whereby one cell is the egg cell; the two others are egg helpers. Although these three cells look are similar, only the egg cell continues to develop to an embryo sac. The embryo sac at this stage is the female gametophyte or mega-gametophyte.

Pollination and fertilization

The pollen from the anther is transported to the stigma of a flower. In the stigma pollen tube emerges. The mature male gametophyte therefore is a germinated pollen grain, pollen tube and three sperm nuclei. The pollen tube grows downward toward the ovary through the style and penetrates the embryo sac. After discharging its contents one of the sperm nuclei fuses with the egg nucleus and form a zygote, the other sperm fuses with the polar cell of the ovary, forming the endosperm nucleus. This is what is known as double fertilization. Fertilization in angiosperms begins very soon after pollination.

Note: In gymnosperms, fertilization can occur up to a year after pollination.

Double fertilization

Double fertilization is a distinctive characteristic of the angiosperms and results in a polyploid endosperm tissue. In double fertilization each ovule receives a pollen tube that delivers two sperm cells to the embryo sac. One sperm fertilizes the egg cell to form the diploid zygote, while the other sperm fertilizes the central polar cell to form triploid endosperm. After double fertilization, the ovule develops into a seed and the ovary into a fruit.

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