Category: O-level Biology
Multiple alleles
Multiple alleles Multiple alleles are two or more alternative forms of a gene controlling a particular characteristic, of which any two may occupy the same ... Read More
Sex linkage
Sex linkage Sex linked characters are those whose genes that are carried on sex chromosomes usually X-chromosomes and is inherited along with sex e.g. colorblindness, ... Read More
Back cross
Back cross This is a cross between hybrids in F1 generation with one of the parents or an organism genetically equivalent to the parents. Back ... Read More
Test crosses in genetics
Test crosses in genetics This is the crossing of an individual having homozygous recessive genotype with an individual showing a dormant trait to determine whether ... Read More
Mendel’s laws of inheritance
Mendel's laws of inheritance Mendel’s first law of segregation states that an organism’s characteristics are controlled by two genes (alleles) and only one can be ... Read More
Alleles (Allelomorphs)
Alleles (Allelomorphs) This is one of the pair of a gene that occupy the same locus (position). Alleles are genes that are responsible for the ... Read More
What is a gene?
A gene This is the basic unit of hereditary and occupies a discrete position on the chromosomes. The gene controls the production of enzyme which ... Read More
Adaptation of animals to low oxygen tension
Adaptation of animals to low oxygen tension High haemoglobin concentration in blood Have myoglobin that store oxygen Fish e.g. trout store oxygen in swimming bladder ... Read More
Adaptations of the alveolus to efficient gaseous exchange
Adaptations of the alveolus to efficient gaseous exchange They are very numerous that they offer a big surface area for gaseous exchange Alveolar epithelium is ... Read More
Structure of alveolus
Structure of alveolus Please Subscribe to promote this website. Subscription is free Share with a friend Your comments are highly welcome Thank you so much Read More
Adaptations of fish gill to gaseous exchange
Adaptations of fish gill to gaseous exchange Gills are red- rich blood supply many tiny gill filaments increase surface area for gaseous exchange Gill lamellae ... Read More
Adaptations of insects to effective gaseous exchange
Adaptations of insects to effective gaseous exchange It has got tracheal system that ramify the whole body delivering oxygen to each cells. The extent of ... Read More
Specialized gaseous exchange surfaces
Specialized gaseous exchange surfaces The specialised gaseous exchange surfaces provide large surface area by developing flaps, sac or tubes. Examples Body surface is usually sufficient ... Read More
Processes of urine production
Processes of urine production Filtration: This occurs in glomerulus into the Bowman’s capsule. The filtration pressure is due to the fact that afferent blood vessel ... Read More
Parts of a nephron
Parts of a nephron Please Subscribe to promote this website. Subscription is free Share with a friend Your comments are highly welcome Thank you so ... Read More
Urinary system
Please Subscribe to promote this website. Subscription is free Share with a friend Your comments are highly welcome Thank you so much Read More
Excretory organs and their excretory product
Excretory organs and their excretory product Excretory organ Products of excretion Lungs Carbon dioxide Skin Urea, ammonia Kidney Urea ammonia and uric acid Please Subscribe ... Read More
The principle endocrine glands of mammal, hormones and functions of the hormones
The principle endocrine glands of mammal, hormones and functions of the hormones Gland Hormone main function a. Thyroid Thyroxine Raise basal metabolic rate Calcitonin Opposes ... Read More
Sensory neuron
Sensory neuron transmits impulses from the receptor to the brain Please Subscribe to promote this website. Subscription is free Share with a friend Your ... Read More
Motor neuron
Motor neuron transmits impulses from the brain to effect Please Subscribe to promote this website. Subscription is free Share with a friend Your comments are ... Read More
Difference between nervous and endocrine system
Difference between nervous and endocrine system Nervous system Endocrine system 1. Fast acting slow acting 2. It’s effects are localized It’s effects are ... Read More
Fat soluble vitamins
Fat soluble vitamins are ADEK Please Subscribe to promote this website. Subscription is free Share with a friend Your comments are highly welcome Thank ... Read More
Vitamins and their deficient diseases
Vitamins and their deficient diseases Vitamin A Night blindness K Delayed clotting E Reduced fertility in rats Vitamin C scurvy Please Subscribe to promote ... Read More
Testing for Vitamin C
Testing for Vitamin C It decolorizes DCPIP. Please Subscribe to promote this website. Subscription is free Share with a friend Your comments are highly welcome ... Read More
Functions of vitamins
Functions of vitamins protect the body against diseases formation of coenzyme that facilitate enzyme reactions blood clotting components of visual pigment Please Subscribe to promote ... Read More
Testing for proteins
\ Testing for proteins They coagulate on heating They coagulate on addition of Melon’s reagent and on heating they form a pink precipitate. They form ... Read More
Advantage of storing fats over carbohydrate
Advantage of storing fats over carbohydrate Has high energy content than carbohydrates It is lighter It is compact and requires less space It is a ... Read More
Testing for lipids
Testing for lipids They form a translucent mark on paper that does not disappear when the paper is dried on a flame. Emulsion test When ... Read More
Physiological functions of lipids
Physiological functions of lipids Source of metabolic water Store fat soluble vitamins (ADEK) Source of metabolic water Raw materials for hormones Please Subscribe to ... Read More
Structural functions of lipids
Structural functions of lipids Make up cell membrane Protection: lipids are constituents of the waxy cuticle of plants and insects Lipids are water repellant thus ... Read More
What are lipids?
Lipids Lipids are made of fats and oils. Fats are solids at room temperature while oils are liquids at room temperature Please Subscribe ... Read More
Functions of carbohydrates
Functions of carbohydrates Glucose, galactose and fructose are oxidized to release energy in he body Glyceraldehyde is an intermediate molecule in photosynthesis. Ribose is component ... Read More
Testing for reducing sugars
Testing for reducing sugars When a solution containing reducing is boiled with Benedict’s or Fehling’s solutions the color changes from blue to green to yellow ... Read More
Testing for non-reducing sugars
Testing for non-reducing sugars 1.When boiled with Benedict’s solution or Fehling’s’ solution, the color remains blue. 2.When boiled with HCl, the solution cooled, neutralized by ... Read More
Examples of disaccharides
Examples of disaccharides Disaccharides Composition Source Maltose glucose + glucose malt Lactose Glucose + galactose milk Sucrose Glucose + fructose Sugar cane Sugar beets Cellubiose ... Read More
Uses of water to the animals
Uses of water to the animals A medium of transport Evaporation cools the animal Lubricates joints, eyes, lungs Constituent of protecting fluids such as tears, ... Read More
Uses of water to the plants
Uses of water to the plants Aid seed dispersal Provide support to herbaceous plants Breaks up the testa of a seed during germination Reagent in ... Read More
Uses of water to living organisms
Uses of water to living organisms It makes up structures of organism It is a solvent It is a reagent in hydrolysis Provide support for ... Read More
Functions of parts of the cell
Functions of parts of the cell nucleus control activities in the cell mitochondria produces energy cell membrane protect inner parts of the cell and also ... Read More
Differences between plant and animal cells
Differences between plant and animal cells Plant cell Animal cell Has a cell wall Lacks a cell wall Has a big vacuole Lack a vacuole ... Read More
Functions of active transport
Functions of active transport Absorption of minerals in the stomach Absorption of minerals in ascending loop of Henle Absorption of mineral in the root hair ... Read More
Evidences to show that active transport require energy
Evidences to show that active transport require energy It is only found in living system which are continuously producing energy by respiration. Increase in temperature ... Read More
Active transport
Active transport It energy-consuming transport of molecules or ions across a membrane against a concentration gradient. Substances usually transported across cell membrane by active transport ... Read More
Functions of osmosis in living organism
Functions of osmosis in living organism Absorption of water by the root hair Absorption of water in the loop of Henle Please Subscribe to ... Read More
Factors that affect the rate of diffusion in living organisms
Factors that affect the rate of diffusion in living organisms Distance over which diffusion occurs: the bigger the distance the lower the rate of diffusion ... Read More
Functions of diffusion in living organisms
Functions of diffusion in living organisms Gaseous exchange at the lungs Absorption of glucose and amino acids from intestine Absorption of water from colon Uptake ... Read More
Differences between mitosis and meiosis
Differences between mitosis and meiosis Mitosis meiosis 1. Homologous chromosomes remain separate Homologous chromosomes pair up 2 There no crossing over Crossing over occurs ... Read More
Importance of Autotrophic nutrition
Importance of Autotrophic nutrition Sugars resulting from autotrophic nutrition constitute structures of plants and animals Sugars obtained from autotrophic nutrition are source of energy Hyman ... Read More
Internal structure of a leaf or cross-section of a leaf
Internal structure of a leaf Functions of tissues in dicotyledonous leaves Tissue Structure Function 1. Upper and lower epidermis One cell thick External walls covered ... Read More
Adaptation of the leaf cuticle for photosynthesis
Adaptation of the leaf cuticle for photosynthesis - thin to allow easy penetration of light - transparent to allow passage of light - perforated to ... Read More
Adaptation palisade layers of leaves for photosynthesis
Adaptation palisade layers of leaves for photosynthesis - cell have high concentration of chloroplast to increase light absorption - cell closely packed cells to increase ... Read More
Adaptations of spongy mesophyll layer of leaves
Adaptations of spongy mesophyll layer of leaves - loosely packed to allow free movement of air - contains chloroplast for trapping light energy and carry ... Read More
Modification of leaves in hot area
Modification of leaves in hot area - hairy to reduce water loss - thick cuticle reduce water loss - become fleshy for water storage -stomata ... Read More
An experiment to show carbon dioxide is necessary for photosynthesis (i) A potted plant is kept in the dark for 24 hours to remove starch ... Read More
Experiment to show that oxygen is produced during photosynthesis
Experiment to show that oxygen is produced during photosynthesis Method The apparatus is filled with carbonated water to enrich it with carbon dioxide and ... Read More
Adaptation of leaves to photosynthesis
Adaptation of leaves to photosynthesis The leaf is only a few cells thick for easy penetration of light and gases. Wax cuticle prevent excessive water ... Read More
Testing for starch in the leaves
Testing for starch in the leaves A leaf is boiled in water to kill protoplasm and burst starch granule present Then, it is boiled in ... Read More
Chemicals of life (O-level biology)
Chemicals of life Overview All cells are made up of a variety of substances some of which organic while others are inorganic. Water forms the ... Read More
Enzymes (biology)
Enzymes Specific objectives The learner should be able to: Describe the criteria for naming enzymes using the type of substrate and type of reaction Explain ... Read More