One of the largest, highly diverse and widely distributed groups in the animal kingdom • Very abundant - numbers extremely high (more than 60,000 described species (with an estimated 500,000 more still undescribed) • Habitat - both aquatic and terrestrial (many free-living & parasitic

Includes crabs, lobsters, prawns, barnacles, pill bugs, copepods, crayfishes, water fleas, shrimps, etc

Active body cells require lots of oxygen for energy production in aerobic respiration as we learnt in Lecture IV. A major by product of aerobic respiration is carbon dioxide. Carbon dioxide dissolves in water to form carbonic acid and hence disturbs acid base balance in the body. Accumulation of carbon dioxide is therefore toxic to the cells as it may cause acidosis. Living cells have mechanisms of intake of oxygen and elimination of carbon dioxide. The two gases are known as respiratory gases. In small organisms such as protozoans the body surface provides an adequate surface area for the exchange of respiratory gases by diffusion. In mammals and other higher animals there are specialized systems for exchange of respiratory gases.

Once an insect hatches from the egg it is usually able to survive on its own, but it is small, wingless, and sexually immature. Its primary role in life is to eat and grow. If it survives, it will periodically outgrow and replace its exoskeleton (a process known as moulting). • In many species, there are other physical changes that also occur as the insect gets older (e.g., growth of wings and development of external genitalia)

Five classes of Uniramia are recognized: 1. Class Diplopoda (millipedes) 2. Class Chilopoda (centipedes) 3. Class Symphyla (sympylids) 4. Class Pauropoda (pauropods) 5. Class Insecta (insects) Centipedes, millipedes, symphylids and pauropods are collectively called myriapodous arthropods (Myriapods). All have long trunks with many segments and appendages, most of which are walking legs.

Insect Hormones • A hormone is a chemical signal sent from cells in one part of an organism to cells in another part (or parts) of the same individual. They are often regarded as chemical messengers. • Typically produced in very small quantities, but cause profound changes in their target cells • Their effect may be stimulatory or inhibitory • In some cases, a single hormone may have multiple targets and cause different effects in each target • Examples of processes controlled by hormones include moulting, metamorphosis, oocyte development (vitellogenesis), colour change and diurnal rhythms of activity

An amazing variety of life exists in the soil ecosystem -from microscopic mites to small mammals. • Most of the soil biota have barely been studied • Soil arthropods and soil fungi - two of the largest groups in the soil have received more attention • Importance of this below-ground ecosystem and its biodiversity is just beginning to be appreciated • Soil ecosystem is very much alive, dynamic and incredibly complex

Trends in human population growth: • Population has grown from an estimated 1 billion in 1800 to about 8 billion in 2022 • Annual global human population growth is estimated at 83 million (about 1.1percent ) • It is expected to rise to about 11.2 billion by the year 2100.

Surveying is defined as taking a general view of, by observation and measurement determining the boundaries, size, position, quantity, condition, value etc. of land, estates, building, farms mines etc. and finally presenting the survey data in a suitable form. This covers the work of the valuation surveyor, the quantity surveyor, the building surveyor, the mining surveyor and so forth, as well as the land surveyor. • Another school of thought define surveying as the act of making measurement of the relative position of natural and manmade features on earths surface and the presentation of this information either graphically or numerically.

The mammalian body is made of essentially non-living matter that is constituted and organized into forms that can contain and maintain life. The matter is in form of chemical compounds known as the chemicals of life. A description of these chemicals constitutes what is known as the chemical basis of life. There are two classes of chemical compounds in the mammalian body namely: a) Organic compounds. These are compounds that contain the element carbon covalently bound to other elements especially hydrogen, oxygen and nitrogen. b) Inorganic compounds. These are various types of salts/electrolytes in the body. Organic compounds There are four main classes of organic compounds in the body and these are referred to as macromolecules or biomolecules. They are: Carbohydrates. These are energy rich compounds that are readily broken down to release energy that runs the body’s life processes. They are also known as the biological fuel molecules. Carbohydrates are made of the elements carbon, hydrogen and oxygen and are simply abbreviated as CHO. Carbohydrates are synthesized by plants through the process of photosynthesis. Animals acquire carbohydrates by feeding on plants. There are two subdivisions of carbohydrates in the body depending on complexity as explained below: a) Sugars Sugars are small carbohydrate molecules found in the diets and in the bodies of animals. Sugars are also known as saccharides. Some saccharides consist of a single sugar molecule and are known as monosaccharides. The most common and well known monosaccharide in the mammalian body is glucose. A few saccharides consist of two sugar units joined together and are known as disaccharides or double sugars. Examples of disaccharides in mammalian diets are sucrose (cane sugar), lactose (milk sugar) and maltose (a breakdown product of starch). b) Polysaccharides -These are large carbohydrate molecules consisting of large numbers of sugar molecules joined together. Examples of polysaccharides in animal diets are starch, glycogen and cellulose.