Mosses, Ferns and Conifers

Mosses

Mosses and the closely related liverworts carry spores in stalked capsules. The capsules form only after the union of male and female sex cells. As in ferns the cells need moist condition so mosses flourish mainly in damp environment.

Ferns

Ferns generally carry their spores in little capsules under the leaves. The related horsetails carry their in fleshy cones at the tips of the stems. Although the reproductive process needs water, mature ferns can survive in dry places.

Conifers

Conifers bear sees on the scales of their cones. The cones are small and soft at first, but swell and become woody after pollination. When the seeds are ripe the cones either open slightly or fall to pieces to release them. Conifers are the best known of the cone bearing plants, known as gymnosperms.

The Plants

With something in the region of 300000 different kinds or species, plants make up one of the two great kingdoms of the living world. The chlorophyll they contain is responsible for the essentially green nature of the planet. Unlike animals, plants can manufacture their own food from simple inorganic materials mainly water and the carbon dioxide gas in the air, they are thus the primary producers of food and all terrestrial animal life depends on them, either directly or indirectly, for food.
Most animals stop growing when they reach maturity and each species has a fixed shape. But plants go on growing throughout their lives and although the leaves and flowers of a particular species generally have a fixed shape, the overall shape and size of the plant can vary a good deal according to its situation.

Leaving aside the flowers or other reproductive organs, a typical plant has three main regions – root, stem and leaf. The root anchors the plant and absorbs water and dissolved minerals from the soil by means of osmosis. Growth takes place by elongation of the cells just behind the tip and this forces the root down. Delicate root hairs just behind the growing regions absorb the water and pass it to tubes in the centre of the root.
The stem which may be soft or woody carries water and dissolved minerals from the roots to the leaves through a ring of tubes. Another set of tubes carries manufactured food down from the leaves and distribute it around the plant. The stem also arranges the leaves in the most efficient way for catching sunlight and in flowering plants, displays the flowers in the best position for achieving pollination. The leaves are the plant’s food factories. They are usually flat and have a number of veins. Continues with the tubes in the stems, the veins carry water to the leaf tissues for photosynthesis and also carry away the manufactured food. The undersides of the leaves have thousands of microscopic breathing pores that allow carbon dioxide in and oxygen out. They also release a lot of water vapor by evapo-transpiration.

Truffles, Gills and Pores, Lichens

Truffles

Truffles are subterranean fungi with solid, globular fruiting bodies. They grow mainly in broad leaved woods. The perigord truffle of southern France is a much prized and very expensive delicacy. The traditional way of finding truffles is to train pigs or dogs to sniff them out. Most attempts at cultivating truffles commercially have failed.

Gills and Pores

The typical mushroom gets its food from decaying matter in the ground. Its fruiting body is spherical when it first bursts through the soil, but it quickly expands to form a cap and stalk. The latter, often called the stipe, may have a ring showing where the rim of the cap was originally attached and there may be a cup or volva, at the base. Under the cap, most species bear numerous fragile gills arranged like spokes in a wheel. The gill surfaces release millions of spores, the equivalent of seeds in flowering plants. Other mushrooms looks more like sponges, scattering their seeds from thousands of minute pores.

Lichens

Lichens are among the hardiest of all organisms, growing in some of the hottest and coldest places. They clothe much of the arctic tundra. Each of the many species is actually a combination of a fungus and an alga. The alga can exist along, but the fungus cannot, so lichens are regarded as special kinds of fungi that rely on algae to provide much of their food.

The Fungi

The fungi were once regarded as simple plants, but their chemical makeup is very different from that of plants and they are now placed in a separate kingdom. A fungus consists essentially of a mass of slender threads, called hyphae, which absorb food from other living or dead organisms. The familiar mushrooms and toadstools are the reproductive stages of the fungi and are often called fruiting bodies. They are composed of tightly compacted hyphae and their role is to produce and scatter the dust like spores. If a spore reaches a place with enough food and moisture for survival, it will grow sending out a hypha. The name mushroom was originally used for just one or two species of fungi with edible fruiting bodies, all the other fungi with umbrella shaped fruiting bodies being called toadstools. However, the modern tendency is for all umbrellas shaped fruiting bodies, whether edible or not, to be called mushrooms. Although many species are edible and very tasty, they contain little food value.
Relatively few of the 100,000 or more known fungi are really poisonous but a handful is truly deadly. The death cam probably kills more people than any other fungus. Growing in broad leaved woodlands, this fungus has a greenish cap with white gills. One specimen is more than enough to kill a person, with a slow and painful death. Several related fungi can produce sever illness if eaten although they are not necessarily deadly. These include the fly agaric, common under birch and pine trees, the blusher common I both deciduous and coniferous woodland, and the verdigris fungus common in grass and woodlands.

Convergent Evolution

Convergent evolution is a common phenomenon, in which unrelated plants or animals come to resemble each other because they have adapted to similar ways of life. The similarity of some species of American cacti and certain desert living spurges in Africa is a good example. Seals and Penguins are apparently very different animals, but both are superbly adapted for swimming. Their limbs and general body shapes appear similar when observed in the water.
Few animals have a clear fossil record as the horse. The oldest known fossils of this family, from rocks some 55 million years old, are of a fox sized creature called Hyracotherium. Its teeth indicate that it ate leaves, and it probably lived in the forests. Fossils from successively younger rock layers show that the descendants of Hyracotheium gradually became larger and were represented by several distinct genera before producing the modern horse about two million years ago. Their toes were reduced to one on each foot and their teeth became larger and stronger to deal with tough grasses.

Taxonomy and Evolution

The sequence of bases along the DNA molecule may be compared between species. If the base sequences are similar then the species are closely related. For example, there is a 1.2 percent difference between the DNA of humans and that of chimpanzees, and a 1.4 percent differences between humans and gorillas, making the chimpanzee a closer relative to humans than the gorilla. Humans and orangutans share 97.6 percent of their DNA, but this does not match the 98.8 percent shared by chimpanzee and human.

Evolution is the process of gradual change by which the characteristics of living organization are altered from generation to generation the changes in given organism eventually become so great that it can no longer be regarded as the same species. Fossil records show that such replacement of one species by a more advanced one has been taking place for many millions of years, and that most species have survived for only about ten million years. The idea that living things have all evolved from simple ancestors was first put forward by the ancient Greeks, but until Charles Darwin and Alfred Russel Wallace published their work on natural selection no one could give satisfactory explanation.

Darwin and Wallace noticed that plants and animals produce large numbers of offspring and that there is a struggle for existence among the progeny- competition to find food and avoid predators as well as a struggle against adverse environmental factors. They also realized that the progeny vary, and reasoned that only those most suited to their surroundings would survive. The progressive improvement shown throughout evolution is thus brought about by natural selection of the best in each generation.

Human Chromosomes and DNA Fingerprinting

Every human body cell, except for sperm and egg cells, contain 46 chromosomes.  These contain around 100000 genes that between them determine all of an individual’s characteristics, from hair colour to potential height. Sperm and egg cells each contain 23 chromosomes. When they fuse during fertilization, the chromosome number is restored to 46, or 23 pairs of chromosomes. Thus everybody cell nucleus contains 23 paternal chromosomes paired up with 23 maternal chromosomes. 

 DNA fingerprinting, also known as genetic finger printing this process is used to reveal the genetic identity of an individual. The arrangement of bases within his or her DNA is unique to that individual, just as his or her fingerprints are; the only exceptions are identical twins, who share the same DNA. A tissue sample, usually of blood, is taken from the person and DNA molecules are then cut into small pieces and separated. By adding a radioactive probe, and using an X-ray film, a banded strip is produced, unique to its owner. The more closely two people are related, the greater the similarity between the pattern of bands. Genetic fingerprinting was used to confirm the human remains found in Russia were those of the Romanovs, the Russian royal family, by comparing DNA fingerprints from the remains with those of the Romanovs’  living relatives. Genetic fingerprinting is similarly used to prove paternity. In criminal cases such as rape, DNA extracted from the perpetrator’s semen or other body fluids can be used to confirm his identity.