Category: A-level Biology
Explain why measles vaccine administered at the age of 9 month
The measles vaccine is typically administered at 9 months of age because this is when an infant's immune system is mature enough to respond effectively ... Read More
Explain why the impermeability of an axon membrane to sodium ion in part of a neuron helps to maintain resting potential in that part of the neuron
Impermeability of the membrane prevents entry of sodium ions which would cause depolarization Read More
Explain why sickle cell trait is prevalent in malaria prone areas
Sickle cell trait is caused by a recessive allele in heterozygote state. Malaria acts as a selection pressure for heterozygote promoting their high occurrence in ... Read More
When light and temperature are optimum while carbon dioxide concentration is low, the rate of photosynthesis can’t increase further.
In isolated populations mutations and natural selection occurs differentially leading to evolution of new species Read More
Structure of the earth, continental drift and earthquakes
Physical geography Chapter 1: Structure of the earth, continental drift and earthquakes In the universe we live on planet earth, is the third planet from the ... Read More
Explain the effects of the heterozygote advantage in a population with increasing gene
Increasing gene flow reduces the probability of recessive alleles or disadvantageous alleles in the population as it introduces new alleles. This reduced the selection pressure ... Read More
State four physiological differences between C3 and C4 plants.
Difference between C3, and C4 plant C3 pathway C4 pathway 1 Photosynthesis occurs in mesophyll cells Photosynthesis occurs in mesophyll cells and bundle sheath cells ... Read More
Explain how light influences stomatal opening in a plant that has been previously in the dark.
When exposed to light, starch of the guard cells is converted into malic acid, Malic acid dissociate into malate and H+ ions in the guard ... Read More
Does milk contain iron?
Dairy products such as cheese, cottage cheese, milk and yogurt, although rich in calcium, have negligible iron content Read More
What part is played by the mammalian skin in excretion?
Sweating eliminates urea, a by-product of protein catabolism, excess water and salts Read More
What is the role of stored proteins during seed germination
Provide a source of amino acids and reduced N necessary for synthesis of enzymes, and for formation of structures in developing embryo. some may be ... Read More
Methods to reduce soils erosion are
Afforestation Planting grass cover Mulching Strip cropping Terracing Contour cropping Read More
Types of soil erosion
Sheet erosion: the surface of the soil is removed evenly over the whole surface of a slope Rill erosion: top soil is removed to an ... Read More
What is soil erosion?
It is the washing away to soil Read More
Effects of adrenaline in the body.
increase rate of heart beat increases rate of breathing increases metabolic rate increase blood pressure and increases blood flow to brain and muscle enlarges pupil ... Read More
What’s the difference between endocrine and exocrine glands?
Exocrine glands secrete their substances through ducts onto your body's surfaces. On the other hand, endocrine glands secrete their substances directly into your bloodstream Read More
What are the differences in blood contents between the blood carried by hepatic portal vein and hepatic vein?
Blood in the hepatic portal vein is rich in nutrients from the intestine Read More
Name the constituents of the mammalian blood
plasma, red blood cells, white blood cells, and platelets, water, food nutrients (glucose, amino acids, fatty acids, vitamins), waste products (like urea and ammonia) hormones, ... Read More
How does clay affect the fertility of soil?
Contain plant nutrients Increases soil capillarity Increase soil water retention Provide firm anchorage to the plants Read More
Explain the value/importance of earthworms in maintaining a condition suitable for crop growing.
. Tunnels improve aeration and drainage of soil causes decay and formation of humus source of food to other animals e.g. chicken die and rot ... Read More
Describe an experiment to demonstrate hydrotropism in plant roots and shoots.
Hydrotropism: 1. Hydrotropic movements refer to a plant's movement or growth in response to a water stimulus, while hydrotropism refers to the analogous response to ... Read More
Benefits of studying genetics
helps researchers develop new strategies to treat and prevent human disease. Help to understand more about the genetic basis of human diseases. Genetic engineering such ... Read More
Distinguish between dominant and recessive genes
A dominant gene is the one that expresses itself entirely in heterozygous state while a recessive gene is one masked in heterozygous state Read More
Distinguish between phenotype and genotype
Phenotype is the physical characteristic of an organism determined by the genotype and the environment. Genotype is the genetic constitution of an organism i.e. the ... Read More
Adaptations of fish for locomotion/swimming
Streamline shape reduces friction Eye to see in water Pectoral, pelvic and ventral fins for balancing. Slippery body reduce friction Has gills to extract oxygen ... Read More
What is a multiple allele?
The presence of three or more alleles for a given gene is referred to as multiple alleles. Read More
What are sex-linked genes?
Sex linked genes are those that sit on sex chromosomes and that are inherited differently in males and females Read More
What is codominance
Codominance, in genetics, phenomenon in which two alleles (different versions of the same gene) are expressed to an equal degree within an organism. Read More
What does heterozygote mean?
Heterozygous refers to having different alleles for a particular trait Read More
What happens when onion epidermis is placed in strong sugar solution
The cells of the epidermis placed in strong sugar solution lost water by osmosis, and became flaccid Read More
What happens when onion epidermis is placed in water
The cells of the epidermis placed in pure water gained water by osmosis, swell and became turgid Read More
When mucus fills the Eustachian tube, hearing is impaired. Explain why.
It may causes increase in pressure in the middle air which distorts vibration of the eardrum and ossicles Read More
How does the blockade of Eustachian tube affect hearing?
Obstruction or blockage of the Eustachian tube results in a negative middle ear pressure, which will cause the ear drum to retract (suck in). In ... Read More
What is the function of hair and wax in ear canal
Wax and protects the ear from invasion of organisms and keeps away dirt and debris from the ear drum Read More
Adaptations of insect pollinated flowers and wind pollinated flowers
Note that there is a difference between characteristics and adaptations of flowers Adaptations of Insects pollinated flowers brightly colored petals to attract pollinators scented to ... Read More
The importance of a skeleton to an organism
Hydrostatic skeleton provides support form movement Exoskeleton1.It minimize water loss by evaporation 2.It protects the internal soft tissue 3.It determine maximum size of the organism ... Read More
Types of skeletons
There are three types of skeleton Hydrostatic skeleton Here support is provided by a fluid under pressure and it is found in round worms, earthworm. ... Read More
Parts of motor neuron/nerve
Functions of parts of nerve cell Nerve fibre or axon transmits impulses The myelin sheath protects the axon; it also insulates the axon and speeds ... Read More
Functions of parts of nerve cell
Nerve fibre or axon transmits impulses The myelin sheath protects the axon; it also insulates the axon and speeds up transmission of impulse. Nucleus controls ... Read More
What happens to old red blood cells in the body?
Old or damaged RBCs are removed from the circulation by macrophages in the spleen and liver, and the hemoglobin they contain is broken down into heme ... Read More
What substances are secreted from sweat glands?
urea, water, sodium chloride, lactate Read More
A-level math paper 1 Inequalities
Please double click and download the PDF below A-level math paper 1 Inequalities Read More
Adaptations of a bony fish to movement in water
- has streamline shape to reduce drag force - has tail fin for propulsion - has fins for stability - has slippery body to reduce ... Read More
Differences between bones and cartilages
Differences between bones and cartilages Bones Cartilages 1 Bone is tough and hard Cartilage is soft and flexible 2 Bones cannot bend Cartilages ... Read More
Pentadactyl limb
It is so called because typically has five digits, is found in all four classes of terrestrial vertebrate some of the limbs bone can even ... Read More
The largest section of the human brain is the …
Cerebrum. The cerebrum (front of brain) comprises gray matter (the cerebral cortex) and white matter at its center. The largest part of the brain, the ... Read More
Describe how the various parts of the human digestive system are adapted to their functions
Adaptations of the mouth for digestion Contains space to receive food by ingestion, contains teeth to break food into small particles by mastication contains saliva to ... Read More
Describe the process of fertilization in human beings.
Fertilization occurs when a sperm fuses with Ovum; during intercourse sperms are released from the testis through the urethra into the vagina. The sperm travels through ... Read More
Adaptations of schistosoma mansoni to the parasitic mode of life
has cilia or tails for swimming to find the host has secretory glands for host penetration, has a tegument and glycocalyx for parasite protection/host immuno-modulation, has ... Read More
What is chistosoma mansoni?
Schistosoma mansoni is a water-borne parasite of humans transmitted by water snail, and belongs to the group of blood flukes. The adult lives in the ... Read More
What is parasitism?
Parasitism is a relationship between two species of plants or animals in which one lives in or on another organism benefits at the expense of ... Read More
To which bones is the biceps muscle attached by tendons?
Finally, the short head of the biceps brachii, due to its attachment to the scapula (or shoulder blade), assists with stabilization of the shoulder joint when a ... Read More
What is thigmotropism?
Thigmotropism is a directional growth movement which occurs as a mechanosensory response to a touch stimulus. Thigmotropism is typically found in twining plants and tendrils, however ... Read More
What is a plant body called that has not differentiated into roots stems and leaves?
Thallophytes are any group of organisms, including algae, fungi, and lichens, that show no differentiation into stem, root, or leaf and were formerly regarded as constituting ... Read More
What is an axial skeleton?
Your axial skeleton is made up of the bones in your head, neck, back and chest. Your appendicular skeleton is made up of everything else — ... Read More
Soil components and their uses
Soil components and their uses Soil component Use Air Oxygen is particularly required for respiration of micro organism and plant roots; decomposition of organic matter, ... Read More
An experiment to show that germinating seeds liberate carbon dioxide.
Set up Air is drawn over the germinating seeds using a suction pump for some time. Observation Lime water in conical flask D turns milk ... Read More
Testing for presence of starch in leaves
The leaf is boiled in hot water to kill the protoplasm The boiled leaf is placed in boiling alcohol to remove chlorophyll The leaf without ... Read More
Suggest the main functions and deficiency symptoms of nitrogen, magnesium and phosphorus to the plant
ELEMENT FUNCTION EFFECT OF DEFICIENCY Nitrogen Nitrogen is required by plants to produce amino acids, proteins, and DNA. Nitrogen is necessary because it is ... Read More