Category Biology

                  Fungi used to be considered as part of the plant kingdom, but they are now thought to be quite different. The main part of the fungus is a mass of tiny threads called a mycelium. Fungi live on other organic matter. In the soil, fungi are the most important agent in the breakdown of dead plant and animal material, recycling it so that plants can use the nutrients.  Fungi live in damp areas or in water because they have no method of preventing their fragile threads from drying out – they cannot survive dry atmospheres. Some fungi are parasites, attacking animals or plants.

                Mushrooms are the reproductive organs of some types of fungi, in which the threads of the mycelium compact together to produce the familiar umbrella-shaped mushroom. Microscopic spores, which are produced on the underside of the mushroom cap, spread in the wind to start new fungal colonies.

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                  Lichens are peculiar organisms in which algae and fungi live together. They are usually flat and crust-like, with no roots and often grow on roofs, rocks or tree branches, and are frequently brightly coloured. The main structure of a lichen is the fungal part, but it also contains algae cells which contribute food through photosynthesis. Reindeer moss is a form of lichen that is very common throughout the Arctic. It forms the main diet of the caribou and other grazing animals. Lichens grow very slowly, but can eventually cover very large areas. Some individual ones are extremely old, and some lichens growing in rocks in Antarctica are thought to be 10,000 years old — they are the oldest living organisms.

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                  Ferns differ from flowering plants mainly in the way that they reproduce. They have fronds instead of true leaves, and some ferns grow into a tree-like form that can be 24 m tall. Microscopic spores are produced on the underside of the fronds, and these are scattered by the wind. When the spores land in a suitably damp area, they sprout and grow into a tiny flat plant that develops small reproductive structures. Sperms fertilize the egg cell, which begins to grow as the tiny plant shrivels and dies, and the complete fern begins to develop. Ferns’ delicate reproductive parts can only survive in a moist atmosphere, so these plants only grow in damp places.

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                        Giant kelp looks like a kind of seaweed, but it is in fact is the largest-known kind of algae. It grows in very long strands up to 65 m in length, and is fastened to the sea-bed with a root-like organ called a holdfast. Small air bladders help to keep the kelp floating upright and spreading across the water’s surface. Kelp is harvested and used for various industrial purposes. One substance extracted from it, is called algin, and is commonly used to make ice cream.

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                      The impressions of fossilized leaves are commonly found in coal. The most common fossils are of ferns, mosses and horsetails, all of which still grow on the Earth today. Coal was formed in shallow bogs, where plants died and were gradually buried by more material, until pressure and time converted them into coal. The oldest coal was formed 350 million years ago, and the process still continues in swamps and bogs. Peat is the earliest stage in the formation of coal. It has not yet been subjected to the pressure that will eventually turn it into a hard material.

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                    Algae are the most primitive form of plant life. Most algae are aquatic, and they range in size from microscopic single-celled organisms to seaweed that is several metres long. Algae photosynthesize, like other plants, and they are responsible for providing most of the world’s oxygen. Algae are very varied, but even the large forms, such as kelp and other seaweeds, lack the true leaves, stems and roots found in other plants. Not all algae use the green chlorophyll found in other plants in order to photosynthesize; some use red or brown pigments for this purpose.

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