biology for grade 7

It is the process in which materials either waste products or secretions are eliminated from a cell. The process involves the substance being surrounded by a membranous vacuole or vesicle. It moves to the surface of the cell and fuses with the cell membrane. The substance gets released to outside. ..

In this type, the females have two homomorphic sex chromosomes XX and hence they are homogametic. The males have one sex chromosome and are represented as XO. If the X-carrying ovum is fertilised by a X-carrying sperm, the resulting zygote XX will develop into a female. If the sperm carrying no sex..

It is a disease caused by the deficiency of vitamin D, calcium and phosphorus. Calcium and phosphorus form the bones and teeth. However, absorption of these minerals can take place only in the presence of vitamin D. Vitamin D or calciferol is formed by the body in the presence of sunlight from ..

1. Mildew Pathogen seen as a growth on the surface of the host. 2. Rust Small pustules of spores, usually breaking through the hoot epidermis. 3. Smuts Pustules larger than those of the rusts. 4. Scab Roughed appearance of the diseased organ. 5. Colour change Change of colour from the normal. 6. H..

Growing consumption and non renewablity fossil fuel necessitate the conservation of this natural resource of to help in this effort many measures have been advocated. 1) Use of oil should be minimized so as to save it for future use. Public transport should be used as far possible. 2) More efficie..

. Some organisms prefer alkaline medium (more than pH 7). For example prtozoans and molluscs, where as some organisms prefer acidic (less than pH 7) For example euglena and other pyhtoflagellates flourish in water having pH 2.8. Still other forms can survive in a wide range of p..

Cylic reaction transport occurs only occasionally when synthesis of carbohydrate is curtailed due to limited supply of CO 2 and NADPH 2 starts accumulating. At this time, there would be no need for additional NADPH 2 . Moreover, the cyclic electron transport serves the purpose of more production of..

Photochemical and Biosynthetic Phases - Light Phase consists of photochemical reactions which are carried out by two different photo systems, PS-I and PS-II. In the thylakoids, chlorophyll and other molecules are packed into units called photo systems. Each photosystem unit contains from 250 to 400..

Five Kingdom Classification - The present trend in biology is to follow the five kingdom classification proposed by R.H.Whittaker in the year 1969. Whittaker classified the living organisms into five kingdoms namely. 1. KINGDOM: MONERA (prokaryotic organisms) 2. KINGDOM: PROTISTA (primiti..

Prop roots e.g., Ficus benghalensis (Banyan) : In banyan the adventitious roots arise from the horizontal branches and grow vertically downwards. After reaching the soil they become thick and woody. Thus, they function as pillars giving mechanical support to the branches. Hence, they are also kno..