biology for grade 7

: Separation of the chromosomes is now complete with paternal and maternal chromosomes having exchanged portions of chromatids. The chromosomes condense again. The chiasmata disappear by sliding towards the tips of the chromatids. This process is called terminalisation. By the time these change..

It is characterised by rounded face, broad forehead, a mongolian type of eyelid fold, projecting lower lip, protruding tongue, short neck, flat hands and stubby fingers. Victim has little intelligence due to malformation of the brain. Gonads and genitalia are underdeveloped. This disease is also c..

It is estimated that in the last 100 years 360 billion tons of CO 2 is added to atmosphere. CO 2 has risen by 7% in the last 30 years. As CO 2 in atmosphere has capacity to trap infrared rays in the band with 2.1 to 15 m m, higher CO 2 in atmosphere has caused global warming (rise in temp..

The following steps can be followed to conserve water 1) Careful and economical use of water for domestic and industrial purposes. 2) Wastage of irrigation water can be minimized by over avoiding over watering, checking leakage in irrigation channels, sprinkler, techniques can be adopted for water..

Accumulation of Wastes - Accumulation of wastes due to its improper disposal is a major problem in our country. The recent Surat plague epidemic is an indication. Population in India has been growing at the rate of 1.7%. With this increase, there has also been an increase in the amount of..

Cyclic Electron Transport System - 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 serve..

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 molecules of pigment, which serve as li..

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 (primitive eukaryotic organisms) 3. KI..

fig. 27.6 Floral diagram and formula of male flower fig.27.7 Floral diagram and formula of female flo..

Golgi complex is represented by several structures like membranes, vesicles and granules. It appears as a central stack of flattened inter communicating sacs called cisternae in a parallel arrangement along with tubules and vesicles. The cisternae are continuously being formed at one end and bud of..