RESPIRATION IN TOAD
Tadpole The young toad called tadpole uses gills for gaseous exchange. At the tadpole stage, the animal develops external gills through which direct diffusion of gases takes place between the animal (tadpole) and the respiratory medium (water). Oxygen dissolved in…
OXIDES
Oxides are binary compounds formed when elements combine with oxygen. Binary compounds are compounds containing two elements only. Oxides are classified into several groups, namely, acidic oxides, basic oxides, amphoteric oxides, neutral oxides and higher oxides. 1) Acidic oxides: These…
METAMORPHOSIS IN INSECTS
Metamophosis is defined as the series of gradual changes of form and shape of an insect from the fertilised egg (immature stage) to adult (mature stage of adulthood). Certain organisms when they are hatched from eggs do not directly resemble…
REPRODUCTION IN COCKROACH
The cockroach exhibits incomplete metamorphosis. This starts from fertilised eggs to nymph and finally to adult or imago stage i.e. Egg -> Nymph -> Adult. Mating begins when the male cockroach introduces sperms into the posterior part of the female’s…
IODINE
Iodine was discovered in 1812 by Courtois. Iodides occur in minute quantities in sea water. They are also found as organic compounds in some sea weeds and as deposits of sodium (NaIO3)and calcium trioxoiodates (V), (Ca (IO3)2) in association with…
GRAPHITE
Graphite exists as black, slippery, hexagonal crystals. The carbon atoms in graphite, form flat layers, and are joined together by strong covalent bonds. These layers are arranged in parallel, one above the other, with weak intermolecular forces operating in-between the…
INTRODUCTION TO CARBON
Carbon occurs naturally as diamond and graphite. It also occurs in an impure form as coal and in the combined state as carbon (IV) oxide, natural gas, petroleum and wood. Other sources of carbon are mineral deposits of metallic trioxocarbonates…
DIAMOND
Diamond is the purest form of naturally occuring carbon. It is found as colourless, lustreless solids which can be transformed into brilliant gems. It consists of an array of bonded atoms. No discrete molecules can be distinguished. Diamond crystal is…
OZONE
Ozone is an unstable triatomic molecule of oxygen. In 1866, J. Soret, demonstrated that ozone was an allotrope of oxygen. Ozone is formed from atmospheric oxygen by lightning flashes. Small fractions of ozone are also formed around electrical machinery when…
THE VERTEBRAL COLUMN
The vertebral column, also known as the backbone or spinal column, is the central supporting structure of the skeleton. The vertebral column forms the backbone of vertebrate animals and protects the spinal cord. It is made up of five groups…
OCTANE NUMBER
Octane number (octane rating) is a measure of the performance of petrol in the engine and the rating depends on the percentage composition of branched chain (iso-octane) to straight chain (n – pentane) hydrocarbons in the fuel. Petrol consists of…
CRACKING AND REFORMING
CRACKING Cracking is the process of further treatment of crude oil fractions in which bigger hydrocarbon fractions are broken down into smaller hydrocarbon fractions. It consists of heating the hydrocarbons in the C 15- and- above range under high pressure…
ENERGY TRANSFORMATION IN NATURE
Energy exists in various forms. These forms of energy are inter-convertible, i.e ., one form of energy can be transformed into another form. Such energy transformation are governed by the laws of thermodynamics. In nature, energy transformation is brought about…
REPRODUCTION IN TOAD
In sexual reproduction, the male animal produces the sperm while the female produces the egg or ovum. The fusion of the sperm and the egg in the fallopian tube of the female during mating is called fertilization. The fusion of…
CELL REACTION TO ITS ENVIRONMENT
All living things are capable of responding to internal and external stimuli. The ability to do this is called irritability or sensitivity. By this means, plants and animals are able to detect and respond to changes in their environment. Irritability…
ASPECTS OF GROWTH
It is sometimes very difficult to determine growth in organism. Growth varies from one organism to another. Parameters normally used to measure growth in organisms include: Mass. Length, height or width. Area or volume. a) In most growth studies,…
MEANING OF CROP PEST
A pest can be described as any organism capable of causing damage to crop plant. Types of Crop Pest Important pests of crop plants are grouped into the following classes: insects birds; rodents; monkeys; man; nematodes. Insect pests…
MEANING AND CAUSES OF DISEASES OF CROPS
A plant disease may be defined as a departure or deviation of the plant from the normal state of health, presenting marked symptoms or outward visible signs. In other words, disease is an unfavourable condition caused either by the pathogens…
Study Guide
