primitive and non primitive unit cells

. Such type of unit cells in which particles are present only in the corners are called Simple Unit Cells . But it has been observed that the particles may also be present at some other special positions within the unit cell. Such uni..

It is a diverse group of algae, most of which are fresh water forms. A few are marine forms. The plant body may be unicellular and motile (as in Chlamydomonas) or colonial and motile (as in volvox) or colonial and non motile (as in hydrodictyon) or filamentous (as in Oedogonium and Cladop..

The ovaries lie in the abdomen and are the female reproductive organ. They secrete three steroid female sex hormones Oestrogens, progesterone and relaxin . Ovaries are two almond-shaped glands placed one on each side of the uterus, below the uterine tubes attached to the back of the broad ligamen..

Chemical evolution resulted in the formation of life on earth about 3.8 billion years ago. The primitive cells that resulted from this process gradually gave rise to primitive forms of organisms such as bacteria, algae, fungi and protozoan. These organisms in turn, gav..

They are found abundantly in pteridophytes, gymnosperms and primitive angiosperms. In these groups of plants, the tracheids represent the most active water conducting elements. In advanced angiosperms, the tracheids are found restricted to leaf margin and leaf tip. The tracheids are elon..

Introduction - The first photosynthetic organism probably appeared almost three billion years ago. With the evolution of photosynthesis, however, organisms began to change the face of our planet and, as a consequence, to exert strong influences on each other. Organisms have continued to change the ..

show a primitive type of sexual reproduction called genetic recombination. In this process, the exchange of genetic materials takes place by a process called conjugation . Conjugating bacterial cells are in contact through a hollow tube called pilus. In the higher organis..

Earth is said to have been formed about4.8 billion years ago. Earliest earth was a hot revolving ball of gas. The formation of first cells in planet earth is explained by the theory of chemical evolution proposed by Oparin and Haldane, independently. According to this theory, t..

The division Pteridophyta includes a group of primitive vascular plants, commonly called pteridophytes. The adult plant body in these plants is a sporophyte. It shows differentiation into true roots, stem and leaves. The stem is mostly herbaceous . Leaves may be smaller or larger. Vascula..

. However, it is also seen in lower organisms like the bacteria, Spirogyra (an alga) and Paramoecium (a protozoan). Bacteria show a primitive type of sexual reproduction called genetic recombination. Sexual reproduction involves the fusion of male gamete with the female gamete in a proces..