Category: A-level Biology
Which one of the following types of bacteria causes the conversion of ammonia into nitrates?
Nitrifying bacteria convert the most reduced form of soil nitrogen, ammonia, into its most oxidized form, nitrate Read More
Describe an experiment to show that more transpiration occurs in the lower epidermis than the upper epidermis of a plant leaf.
Two identical photometers setup are each containing a single leaf from the same potted plant but one smeared with grease on the upper epidermis and ... Read More
Outline the fate of food after absorption
. Glucose, galactose and fructose are oxidized to release energy in the body and formation of cellular structures Lipids are oxidized to produce energy, ... Read More
Adaptation of small intestine for absorption of food
Long to allow food enough time for absorption Villi and microvilli increase surface area for absorption Well supplied by blood to carry away absorbed food ... Read More
Give the importance of organic matter in the soil.
A soil with an adequate level of organic matter will be less erodible, have increased nutrient retention, and also be easier to work and plow. Other ... Read More
Outline precautions undertaken when assembling the potometer for use in a laboratory.
The plant is cut in water to prevent air entering the xylem. Measurement should begin when leaves are dry. Caution should be taken when preparing ... Read More
Distinguish between transpiration and translocation?
Transpiration is the evaporation of water from leaves in the form of water vapor. Translocation is the transportation of synthesized products in plants. Read More
Describe the changes undergone by a protein molecule from the time it is swallowed until its structural molecules are used in a cell of the skin.
Big protein particles are broken down into small particle in the mouth by teeth. In the stomach Enzyme pepsin in presence of HCl breaks down ... Read More
How are the larva, pupa and adult of the butterfly suited to their functions?
Larva has legs for dispersal and to look for food, it accumulates energy to be used during the pupa stage Pupa stage is a dormant ... Read More
Life cycle of butterfly
Butterfly lays eggs that hatch into larva. The larva develop through pupa to adult Read More
Differentiate between incomplete and complete metamorphosis and in each case give two examples of insects.
Complete metamorphosis is the type of insect development that includes egg, larva, pupal, and adult stages, e.g. butter fly, wasps, ants, and fleas, which differ ... Read More
Define the term metamorphosis
Metamorphosis are developmental changes in form that occur as in an animal from hatching or birth to adulthood. Read More
Give the difference in meaning of a reflex action and a voluntary action.
Voluntary actions involve conscious thought (thinking time). Reflex actions do not involve conscious thought (thinking time) and happen very quickly to avoid unnecessary damage to ... Read More
Differences between a motor neuron and a sensory neuron
Effector/motor neurons Sensory neuron 1. Transmit impulse from CNS to the effector Transmit impulse from sense organ or receptor to the CNS cell ... Read More
Who is a carrier in biology?
A carries is an individual who carries one deleterious allele for an autosomal recessive disorder. Read More
Special features of the whale that enable it to retain heat in cold water
have small surface area to volume ratio Small extremities reduce surface area to volume ratio. Using their thick blubber layer as an insulator, Retaining heat ... Read More
Adaptations of the elephant to hot environment
Large ears increase surface area for heat loss Vasodilatation in the ear when hot increase blood flow to the skin surface increasing heat loss Fan ... Read More
Special features of the elephant that enable it to lose heat while in hot climate.
Large ears increase surface area for heat loss Vasodilatation in the ear when hot increase blood flow to the skin surface increasing heat loss Fan ... Read More
What are the 3 pivot joints in the body?
Pivot joints allow rotation, and although you have many joints in your body, there are only three pivot joints. They are located in your neck, your ... Read More
What is the process of putrefaction?
Putrefaction involves the decomposition of proteins, breakdown of the tissues, and liquefaction of the organs. The body is decomposed by the action of putrefying bacteria and ... Read More
What is the main purpose of the larva stages in metamorphosis?
The main purpose of larva stage to consume energy in preparation for the huge morphological changes of the next stage of complete metamorphosis. Read More
Suggest meanings of oviparity and viviparity and ovoviviparity
Oviparity is a mode of reproduction in which animals lay eggs. Ovoviviparity is a mode in which animals lay eggs and keep them inside the ... Read More
Ways by which plants excrete their metabolic wastes products.
Gaseous waste (oxygen and carbon dioxide) by diffusion through the stomata and lenticel Stored solid and liquid waste by shedding leaves, peeling of bark and ... Read More
What is selective reabsorption?
Selective reabsorption is the process whereby useful molecules (e.g. ions, glucose and amino acids), after being filtered out of the capillaries along with nitrogenous waste ... Read More
What is ultrafiltration in biology
Ultrafiltration is the process of filtration of blood in the glomerulus under great pressure during which the liquid part of the blood i.e. plasma along ... Read More
Distinguish clearly between complete dominance and co dominance.
In complete dominance, the dominant gene/allele completely masks the effect of the recessive gene/allele whereas, in co-dominance neither gene/allele in the pair is dominant Or ... Read More
How trees conserve soil.
reduce soil erosion fallen leaves mulch the soil and keep it moist decomposing leaves add humus to the soil Some trees contain symbiotic organism that ... Read More
How deforestation harm the environment
May cause climate change, desertification, soil erosion, fewer crops, flooding, increased greenhouse gases in the atmosphere, and a host of problems for indigenous people It causes ... Read More
Why birds haves rigid skeleton?
To make the skeleton sturdy for attachment of flight muscles so that the thrust (forward force) generated by the wings can lead to maximal lift, ... Read More
Adaptations of birds to flight
Hollow bones reduce weight has feathers to insulate the body during flight a streamlined body – this helps reduce the force of drag wings – ... Read More
Dental formula for antelope
The dental formula is 0/3, 0/1, 3/3, 3/3 = 32. Read More
Dental formula for rabbit
The dental formula for a rabbit is I2/1, C0/0, P3/2, and M3/3, for a total of 28 teeth Read More
Example of aggregate fruits
A type of fruit that develops from a single flower of many simple pistils. Examples are blackberries, strawberries and raspberries where each fleshy lobe is actually an ... Read More
Example of multiple fruits
A multiple fruit is atype of fruit that develops from the ovaries of many flowers growing in a cluster or that are fused together into ... Read More
How does air pollution affect living organisms
Illness such as pneumonia or bronchitis, headache, nausea e.t.c Bad smell Irritation to nose, throat, eyes and skin Cause cancer Damage body organs, liver brain ... Read More
Outline the human activities that cause air pollution
Emission from factories Emission from cars, aeroplane, aerosol cans Cigarette smocking Burning of rubbish Burning fuel such coal, kerosene Read More
What is air pollution?
Air pollution is the presence in or introduction into the air of a substance which has harmful or poisonous effects. Read More
Describe an experiment to show that anaerobic respiration takes place in yeast.
Yeast break down glucose (food) into ethanol, carbon dioxide and releases energy. It is a type of cellular respiration that takes place in the absence of ... Read More
Outline any four (4) functions of the human skin other than temperature regulation.
Provides a protective barrier against mechanical, thermal and physical injury and hazardous substances. Prevents loss of moisture. Reduces harmful effects of UV radiation. Acts as ... Read More
Distinguish between excretion and secretion
Excretion is the removal of waste metabolic products from the body. Secretion is a process by which substances are produced and discharged from a cell, ... Read More
Causes of mutation
Ultraviolent light Chemicals Freezing of cells Read More
Define the term “mutation”
This is a change in the amount or structure of DNA of an organism Read More
Processes in the living organism that involve osmosis
Functions of osmosis Absorption of water by the root hair Absorption of water in the loop of Henle Absorption of water in the intestines Read More
How does the human body defend itself from disease causing germs?
use physical barriers like your skin to prevent entry of germs produce pathogen-destroying chemicals, like lysozyme, found on parts of your body without skin, including ... Read More
with examples explain passive immunity
A type of immunity that occurs when a person is given antibodies rather than making them through his or her own immune system. For example, ... Read More
With an example define what active immunity is?
Active Immunity results when exposure to a disease organism triggers the immune system to produce antibodies to that disease. Active immunity can be acquired through natural ... Read More
What makes an insect are suited for flight; adaptations of insects to flying
have streamline body have strong flight muscles have exoskeletons for attachment of flight muscles have extensive tracheal system that delivers oxygen directly to the muscles ... Read More
Give a detailed description of the mechanism of flight in insects
Locomotion in insects Insects thorax contain two sets of antagonistic flight muscle; a pair of dorso-ventral muscle (indirect muscle- not attached to the wing) run ... Read More
Describe the menstrual cycle in man.
The menstruation/ sexual/ oestrus cycle This cycle found in female; ensures that female reproductive physiology events are synchronised. For the uterus prepares itself for implantation ... Read More
Describe an experiment to show the action of Saliva on cooked starch
Experiment Two test tubes A and B add equal amount of cooked starch To test tube A add 1cm3 of saliva To test tube B ... Read More
Differences between mitosis and meiosis
Mitosis meiosis 1. Homologous chromosomes remain separate Homologous chromosomes pair up 2 There no crossing over Crossing over occurs 3. No formation of ... Read More
Importance or significance of meiosis
Sexual reproduction: Meiosis results in half the number of chromosomes, during fertilization the nuclei of the two gametes fuse to form a zygote restore the ... Read More
Importance or significance of mitosis
Genetic stability: It ensures that the daughter cells carry the exact genetic material as the parent cells Growth: growth results in increase in the number ... Read More
Adaptations of intestine villi to absorption
Villi are thin to increase surface area for absorption Well supplied by blood to carry away absorbed food so as to maintain diffusion gradient The ... Read More
Adaptation of small intestine for absorption of food
Long to allow food enough time for absorption Villi and microvilli increase surface area for absorption Well supplied by blood to carry away absorbed food ... Read More
Which fins do fish use for braking?
The pectoral fins along with the pelvic fins help the fish by acting as brakes and can assist the fish with difficult maneuvers Read More
In which ways does removal of a hand from a hot object differ from plant shoot growth towards light?
Removal of hand from hot object Plant growth towards light Fast Slow Electrical and chemical Chemical Response to heat Response to light It’s effects are ... Read More
State the importance of plant response to gravity.
Negative geotropism in primary shoot allows shoot grow towards light Positive geotropism in the primary root that causes it to grow down into the soil, ... Read More