PHEROMONES

 Hormones are chemical messengers secreted by the endocrine glands. They carry messages, inside the body, through blood stream from one part of the body to the target organ. At the same time, there are also certain chemicals that carry information outside the body to other members of the same species. These are known as pheromones or ecto-hormones. These are chemical substances released by an animal into its surroundings which influences the behaviors or development of the individuals of the same species, e.g, in insects, females release sex attractants, queen bee substance in honey bees, alarm pheromones in termites and bees and trail pheromones in ants, etc.

THE SKELETAL SYSTEM

 The complete framework bones and cartilage together forms the skeletal system. The adult human keleton consists of 206 bones and is divided into two main divisions: (I) Axial skeleton and (II) Appendicular skeleton

(i) Axial skeleton consists of bones that lie along the main axis of the body, e.g., ribs, vertebral column and skull comprises of 80 bones.

(ii) Appendicular skeleton consists of bones which le around or on sides of the main axis of the body. e.g., upper and lower limbs and gridles- shoulder & hip girdle and comprises of 126 bones.