VARIATION IN POPULATION Population is a group of organisms of the same specie living in a specified area within a given period of time. Variation refers to the differences which exist between individuals of the same species Types of variations Morphological variation Physiological variation. Morphological variation is the noticeable physical appearance of individuals…
STRUCTURE OF A FRUIT A fruit is a matured fertilized ovary of a flower containing one or more seeds. Contrary to this, some plants do not undergo fertilization for the formation of their fruit. Such fruits are called parthenocarpic fruits e.g. banana and pineapple. Such fruits are seedless. A typical fruit has the following parts…
DEVELOPMENT OF ZYGOTE IN FLOWERING PLANTS, GERMINATION OF SEEDS, ADAPTIVE FEATURES IN A DEVELOPING ANIMAL DEVELOPMENT OF ZYGOTE IN PLANTS Pollination is followed by fertilization and the development of zygote in flowering plants during which the flower changes into a fruit enclosing the seeds. The male and female sex cells that form zygote at fertilization…
COURTSHIP BEHAVIOURS IN ANIMALS Courtship is a reproductive communication between males and females of a species that ends in sexual union. Courtship behaviours in animals include PAIRING: – A form of courtship in which a compatible male and female separate themselves from other in a group to form a mating pair. Pairing occurs in human,…
THE ORGAN OF HEARING Mammals have two ears on each side of the head. The greater part of it is enclosed in the skull for protection. The ear is for hearing as well as for maintaining balance. STRUCTURE OF THE EAR AND THEIR FUNCTIONS The mammalian ear is divided into 3 parts. The outer ear….
SENSORY RECEPTORS All living organisms respond to changes in their environment (stimuli). These changes can be mechanical, electromagnetic, chemical or thermal. Though most cells in the bodies of organisms are sensitive to stimuli, certain cells specialize in detecting a particular type of stimulus, these are called sense cells or sensory receptors which are quite many…
REFLEX AND VOLUNTARY ACTIONS Actions are responses to stimuli. These actions are grouped into two: involuntary (reflex) and voluntary actions. REFLEX ACTIONS Reflex actions are automatic responses to stimuli which do not involve the conscious or higher centre of the brain. These actions are mainly protective, guarding us from dangerous stimuli and helping us…
THE PERIPHERAL NERVOUS SYSTEM These include the sensory system (receptor and nerves leading from all parts of the body to the CNS) and the motor system (nerves running from the CNS to the effectors). The PNS consists of twelve cranial nerves (connecting the brain to the head and neck region) and thirty one spinal nerves…
THE NERVOUS SYSTEM The nervous and hormonal systems co-ordinate various biological activities in the body of multicellular animals, the basic structural unit of nervous system is the nerve cell called neurone. It consists of a dense, cell body and protoplasmic processes called nerve fibres. A bundle of long nerve fibre is called a nerve. The…
HORMONES AND ENDOCRINE GLANDS Hormones are chemical substances produced or secreted by endocrine glands (ductless glands) in response to various stimuli. Hormones are secreted into the bloodstream and circulated to exert their effect on their target organs. This effect could be to speed up or slow down biological reactions. A few hormones like thyroxine and…
STRUCTURE OF THE LIVER The liver is the largest organ in the body of a mammal with a weight of about 1.25kg. It is reddish brown, soft with two lobes and it is located below the diaphragm on the right side of the abdomen. It partly overlaps the stomach and has bile duct connecting it…
HOMEOSTASIS Homeostasis is the process by which a fairly constant internal environment is maintained in an organism. The internal environment of an organism is made up of the body fluid such as blood, lymph and tissue fluid. For efficient functions of body cells and healthy growth, a living organism must be able to adjust to…