Thursday, October 30, 2008


Reptiles are air-breathing vertebrates which have limbs (except snakes and some lizards), are cold-blooded and have horny covering of scales or horny plates. There are about 3,000 species. The four orders of modern reptiles are the crocodiles and alligators, tortoises and turtles, snakes and lizards and the Tuatara.

The last-named order means break headed, and the Tuatara, which is a Maori name, is the only survivor of it. Looking rather like a lizard with a beaked face it lives on some of the lonely islands off the coast of New Zealand. It is truly a precious living fossil, since this reptile order goes back to the time of the dinosaurs. The Tuatara seems to be slow in everything it does, even to its movements. It lives in underground burrows, often in company with a sea-bird, a species of petrel. The reptile sleeps there by night and the bird by day. The eggs have a long incubation period and it is sometimes as much as eighteen months before the young hatch out.


These are plants which grow in or near water and are adapted according to whether they live on the surface, or are submerged, or grow in the mud at the edge of the water.Some are a combination of all these and have several different types of leaves. Some hydrophytes (for example water lily) are anchored to the bottom by roots, and send up leaves on long stems until they reach the surface, when they unfold and spread out. The giant water lily(Victoria regia) is an extreme example of this. The flowers too come up on a long stem and open out above the water.

Some water plants are not rooted to the bottom and merely float on the surface (for example duckweed)or under the surface (for example bladderwort).Such water plants can only live in still waters but some submerged plants are anchored to the bottom by roots and produce long growth with small leaves and these are better adapted to life in running water. The leaves of most water plants have large air cavities in them to act as 'water wings', and some produce large bladder-like swellings for the same purpose(for example water hyacinth).

The water crowfoot is amphibious, that is it can live both in water or at the edge in the damp mud. It has surface leaves which are flat and large compared to the submerged leaves which, when living in water, are finely divided with narrow lobes. These smaller leaves disappear if the water level drops and the plant is left at the edge.

Parasites and Saprophytes

These are plants which depend entirely or partly on other organisms. We have already dealt with the fungi, which are the largest group of parasites and saprophytes in the plant kingdom. But there are other plants which exist on living material (parasites) or make use of dead organic substances (saprophytes) Parasites may be total or partial that is they either get the whole of their food materials from the host plant on which they live, and have no green parts, or they have chlorophyll of their own and can manufacture a certain amount of their own food, but also need some from the host.

Dodder, in the Convolvulus family is a total parasite and can be seen on the stems of plants such as gorse and heather. This is a stem parasite but other plants such as broomrape are root parasites and penetrate and live on the roots of a host plant.

Mistletoe is another good example of a parasite which occurs on the stems and trunks of trees, while several members of the foxglove family live on the roots of grasses in meadows. Saprophytes make use of decaying matter and usually occur in woodlands where there is plenty of rotting vegetation. The bird's nest orchid can be seen growing in woods and is a brownish plant which only appears above ground when it sends up a flowering stem. The roots actually live in association with a fungus which breaks down the rooting materials it lives on into soluble substances. The fungus also penetrates the roots of the orchid and gains some of its materials from the cells there, while the orchid gets its supplies of food materials through the fungus. Thus the two plants are living together and depending on each other for their existence, this being called symbiosis.

Insect eating plants

Although green plants are self-supporting as far as their food requirements go, some plants do rely to a certain extent on other living creatures. One group of these, known as insectivorous plants (plants which live on insects), gain part of their nourishment by trapping insects in various ways. The plants digest the insect's bodies and take the dissolved proteins into their systems. Several of these interesting plants occur in Europe, and there are many others in tropical countries, often large and with weird methods of trapping insects. Insectivores are usually plants of marshes and bogs where the soil is poor in the nitrogen compounds so necessary for their continued healthy existence. Although they are mostly green plants, producing some of their own food, they do need the proteins of the insects to make up the lack of nitrogenous food.

Some plants produce hollow leaves containing liquid in which the insects drown, the Sarracenia being an example of this. The leaves are rather funnel-like with a lid to the opening at the top. The rim of the funnel has nectar to attract insects, and the whole plant is often brightly colored. Inside the funnel is a slippery area, and downward pointing hairs, which prevent any insects crawling out again. Nepenthes, the pitcher plant, produces curious pitcher-shaped extensions to the leaves which act in the same way as Sarracenia. They are usually climbing plants rather than bog plants, and are widely grown in greenhouses in hanging baskets. In both of these plants, the insects bodies are decomposed in the watery fluid at the base of the pitcher, which contains many bacteria, the plant then using the dissolved substances.


These are the plants of the deserts or other dry places. For this reason they must have some method of withstanding long periods of drought, very bright light, strong winds and, perhaps, very high temperatures – although not all deserts are hot.

There are various ways in which plants can overcome these conditions. With annual plants, the seeds often have a long life and will only germinate after rainfall. They then grow very rapidly and complete their life cycle before the drought occurs. On the other hand perennial plants have to exist through bad spells and usually have some method of storing up moisture to tide them over. Cacti are a good example of this with their swollen fleshy growth.

Large thin flat leaves would be of no use in the desert as they would evaporate too much moisture from their surfaces, so leaves are often very small or narrow, and usually have very thick outer layer (cuticle), preventing water loss. They might even be reduced in size to hard spines as in many cacti and succulents. The Yucca has leaves which are narrow and with a very tough cuticle to withstand the desert conditions in America.

Roots may be adapted to store water, becoming thick and fleshy, and it is noticeable that in drier parts of the world, such as the Middle East, there are many plants which produce underground bulbs, corms or tubers. Leaves can also be thick and fleshy for water storage, or develop only during the rainy season, to drop off again when the dry summer comes.

Some grasses can roll their leaves inwards from the edges in dry spells, thus leaving a smaller surface exposed to the sun, while acacias in Australia can turn their leaves sideways on to the sun so that it does not scorch down on to the flat surfaces. Leaves sometimes have dense coverings of hairs to protect them from sun and drying winds.

Plants which grow in places where the soil is very salty, such as by the sea, in river mouths or salt lakes inland, and have adapted themselves to overcome the peculiar conditions, are called halophytes. Most normal land plants are killed by salt in the soil but these plants are so successful that they can be important to man when trying to reclaim new land from the sea.


Some plants which may be mistaken for stem parasites are the Epiphytes which grow in trees usually in tropical areas, and many of the mosses come into this group. The difference is that epiphytes are normal green plants which have taken to a life of growing on the bark of tress but do not gain any of their nourishment from them. They live entirely on what food materials happen to be lodged in the crevices of the bark and a lot of orchids which live in this way send out thick white roots capable of extracting water from the damp tropical atmosphere.

Tuesday, October 07, 2008


The liver is the largest organ inside our body weighing  nearly 1.4kg. fifteen per cent of the total blood in the human body would be circulating at anytime in the liver alone. It is so substantial that even at rest, 2.5 pints of blood passes  through the liver. It has a wonderful regeneration power. Even if 75 per cent of the cells inside get damaged, it regenerates them within  a week . The liver's capacity to remove toxins from our blood stream is tremendous. Any man made machine of the same size cannot accomplish the task of toxin removal at the same rate as liver.