Category: A-level Biology

Differences between inhaled air and exhaled air

05/02/2021 3

Differences between inhaled air x and exhaled air Inhaled air x Exhaled air y Contains more oxygen Contains less oxygen Contains little carbon dioxide Contains ... Read More

Hearing o-level

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Hearing o-level Sound funnels into the ear canal and causes the eardrum to move. The eardrum vibrates with sound. Sound vibrations move through the ossicles ... Read More

Accommodation of the eye

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Accommodation of the eye Is the ability of the eye to near and far objects To see near objects, the ciliary muscle contract releases the ... Read More

Functions of active transport

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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

Adaptations of spongy mesophyll of a leaf

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Adaptations of spongy mesophyll of a leaf - loosely packed to allow free movement of air - contains chloroplast for trapping light energy and carry ... Read More

Adaptation of the leaf cuticle

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Adaptation of the leaf cuticle - thin to allow easy penetration of light - transparent to allow passage of light - perforated to allow exchange ... Read More

Adaptation of leaves to photosynthesis

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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

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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

Adaptations of halophytes to their habitat

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Adaptations of halophytes to their habitat Possess succulent leaves and/or stem for storage of water Have salt glands to secrete excess salts Have thick cuticle ... Read More

Evidences for transportation of organic materials in the phloem

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Evidences for transportation of organic materials in the phloem When phloem is cut, the sap exudes is rich in organic material such as carbohydrate. The ... Read More

What is physiological effect Small body size  of animal on oxygen dissociation curve

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What is physiological effect Small body size  of animal on oxygen dissociation curve Small body size shifts the oxygen dissociation curve to the right Physiological ... Read More

State the effect and advantage of rising body temperature on oxygen dissociation curve.

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Effect and advantages of raising temperature on oxygen dissociation curve. Increased body temperature lowers affinity of hemoglobin to oxygen or shifts oxygen dissociation curves to ... Read More

The adaptations of blood in terrestrial animals living at high altitude

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The adaptations of blood in terrestrial animals living at high altitude At high altitude the oxygen tension is very low. Thus, the adaptations of blood ... Read More

Adaptations of blood in terrestrial animals to extreme oxygen tension

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Adaptations of blood in terrestrial animals to extreme oxygen tension Extremes of oxygen tension can the very high or very low values of oxygen partial ... Read More

Describe how the pH of blood and tissue fluids in mammals is maintained.

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Describe how the pH of blood and tissue fluids in mammals is maintained. pH of blood and tissue fluids is maintained by mechanisms operating in ... Read More

How is blood flow maintained in such a system?

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How is blood flow maintained in such a system? Blood flow is maintained by pumping of the heart at high blood pressure and one way ... Read More

What is a closed circulatory system?

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What is a closed circulatory system? A closed circulatory system is where blood is confined in blood   Please Subscribe to promote this website. Subscription ... Read More

Adaptation of xylem to its function

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Adaptation of xylem to its function (i) Lack of end walls reduces resistance to flow (ii) Lignin makes cell walls impermeable to water that reduces ... Read More

How are red blood cells suited for its functions?

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How are red blood cells suited for its functions? (i) The biconcave shape increases surface area for absorption of oxygen (ii) Lack of nucleus increase ... Read More

Outline adaptations of animals that live in environments of low oxygen tension

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Outline adaptations of animals that live in environments of low oxygen tension Increased affinity of their haemoglobin for oxygen. Increased haemoglobin concentration in their blood. ... Read More

Explain why breathing in air rich in carbon dioxide is dangerous.

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Explain why breathing in air rich in carbon dioxide is dangerous. It increases the acidity of the blood and tissue fluids, inhibiting enzymes and stopping ... Read More

Explain why breathing in pure oxygen at higher pressures than atmospheric is dangerous

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Explain why breathing in pure oxygen at higher pressures than atmospheric is dangerous The tissue metabolizes rapidly at first to keep with the oxygen supply. ... Read More

Explain the physiological advantage of a high concentration of myoglobin in skeletal muscles

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Explain the physiological advantage of a high concentration of myoglobin in skeletal muscles Myoglobin has a higher affinity for oxygen compared to haemoglobin. It holds ... Read More

What is the effect of carbon dioxide concentration on oxygen dissociation curve?

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What is the effect of carbon dioxide concentration on oxygen dissociation curve? High carbon dioxide levels in the tissues cause a shift of the oxygen ... Read More

What is the effect of temperature on hemoglobin oxygen dissociation curve?

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What is the effect of temperature on hemoglobin oxygen dissociation curve? Increase in environment temperature causes a right shift of the oxygen dissociation curve. This ... Read More

What is Bohr effect?

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What is Bohr effect? Bohr effects is a rightward and downward  shift of the haemoglobin oxygen dissociation curve that as a result of increased carbon ... Read More

Give the meaning of Chloride shift

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Give the meaning of Chloride shift Chloride shift is the movement of chloride ions into red blood cells as bicarbonate ions leave during carbon dioxide ... Read More

How is the skin of an adult frog adapted for gaseous exchange?

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How is the skin of an adult frog adapted for gaseous exchange? The skin of the frog is moist. Respiratory gases can easily dissolve in ... Read More

Describe how a gill is structurally adapted as a respiratory surface

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Describe how a gill is structurally adapted as a respiratory surface Highly folded into filaments to increases surface area gaseous exchange It is covered with ... Read More

Advantages and disadvantages of ectotherm

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Advantage of ectotherms Low food consumption since it is not used to maintain body temperature. Bodies are less affected by wide environmental temperature variation   ... Read More

Advantages of being endothermic animals

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Advantages of being endothermic animals Survives in a wide range of environmental temperatures Metabolic reactions in the body are always carried out effectively no matter ... Read More

Response of endotherms e.g. man to cold conditions

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Response of endotherms e.g. man to cold conditions The hair is raised and brought into a more-or- less vertical position by contraction of erector pili ... Read More

Response of endotherms to hot conditions.

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Response of endotherms to hot conditions.   The hairs are lowered: by relaxation of erector pili muscles, so they lie flat against the surface of ... Read More

Adaptations of endotherms to cold environment.

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Adaptations of endotherms to cold environment. The animals develop large volume to surface ratio. i.e. the extremities such as ear tend to be small and ... Read More

Adaptations of endotherms to Hot environment.

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Adaptations of endotherms to Hot environment. Have thin subcutaneous fat layer to promote heat loss Are small compared to their counterpart in cold region to ... Read More

What is lower critical temperature?

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The lower critical temperature. The lower critical temperature is the environment temperature below which physical mechanism such as insulation cannot maintain body temperature. The lower ... Read More

What is Upper critical temperature?

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What is Upper critical temperature? The upper critical temperature (290C for man) is the environment temperature above which physical mechanism such as sweating, lowering hair ... Read More

Explain body size contribute to the survival of mammals in cold habitats

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Explain body size contribute to the survival of mammals in cold habitats Mammals in cold habitats usually have a large body size as a result ... Read More

Strategies of the camel to overcome heat stress

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Strategies of the camel to overcome heat stress include: Possession of tissues which are tolerant to wide ranges of temperature. The camel stores heat in ... Read More

Why should body temperature be kept constant?

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Why should body temperature be kept constant? Temperature must   be maintained   at a value optimum for the action of enzymes upon which the organized   functioning ... Read More

How does meiosis contribute to variation?

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Contribution of meiosis to variation Production of unique gametes by crossing over between homologous chromosomes separates linked gene at metaphase I of meiotic division. When ... Read More

Describe the mechanism which limit inbreeding in plant

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Means employed by plants to limit self-fertilization in plants Dichogamy: anthers mature and stigma become receptive at different times Protandry: anther mature before the stigma ... Read More

What is the effects of inbreeding in a population?

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Examples of defects seen with inbreeding include: Reduced fertility. Reduced birth rate. Higher infant and child mortality. Smaller adult size. Reduced immune function. Increased risk ... Read More

Give an outline of the life cycle of a named pteridophyte

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Give an outline of the life cycle of a named pteridophyte. Life cycle of a fern The gametophyte (prothallus) bears special gamete-forming organs; antheridia which ... Read More

(b) How does the development of Embryo sac in flowering plants differ from oogenesis in humans?

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Differences between development of embryo sac and oogenesis Development of embryo sac Oogenesis 1.      Develops primarily by mitosis from dedicated haploid functional mega spore cells. ... Read More

Outline the events that lead to the formation of pollen grain in flowering plants

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Outline the events that lead to the formation of pollen grain in flowering plants This question requires that you describe what happens in the anthers ... Read More

Outline the events which take place after fertilization

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Outline the events which take place after fertilization After fertilization The zygote divides mitotically, growing and developing into the embryo. The embryo consists of a ... Read More

Describe the process of fertilization in higher plants

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Describe the process of fertilization in higher plants  Fertilization is the fusion of male and female to produce a zygote    In higher plants, the ... Read More

Under what circumstances may variation not occur in sexually produced individuals 

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Under what circumstances may variation not occur in sexually produced individuals  When fertilization occurs between closely related individuals, When crossing over does not occur during ... Read More

Under what circumstances may variation occur in asexually produced individuals.

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Under what circumstances may variation occur in asexually produced individuals. mutations Environment effects In case haploid parthenogenesis Please Subscribe to promote this website. Subscription is ... Read More

Explain how sexual reproduction cause variation among offspring.                

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Explain how sexual reproduction cause variation among offspring.                 Variation in sexual reproduction is caused Crossing over that allows ... Read More

Explain how asexual reproduction produces offspring identical to the parent.

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Explain how asexual reproduction produces offspring identical to the parent In asexual reproduction there is no mixing of genetic materials since cells that result in ... Read More

What is meant by double fertilization in flowering plants? 

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What is meant by double fertilization in flowering plants?  Double fertilization refers to occurrence two independent nuclear fusions during fertilization in the embryo sac of ... Read More

Give one reason why dioecious plants are rarer than monoecious plant 

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Give one reason why dioecious plants are rarer than monoecious plant  The chance of pollination and reproduction are limited as they are usually depend on ... Read More

Explain why nearly all dioecious plants are wind pollinated

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Explain why nearly all dioecious plants are wind pollinated Male and female flowers occur on different plants thus wind pollination increases chances of pollination where ... Read More

Explain why in dioecious plants, male plants are usually associated with dry soils while female plants are associated with moist soil is 

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Explain why in dioecious plants, male plants are usually associated with dry soils while female plants are associated with moist soil is  Male plants are ... Read More

Ecological significance of Dioecious state

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Significance of Dioecious state Increases chances of genetic variation among offspring with increased chances of survival in different habitats. Please Subscribe to promote this website. ... Read More

Give ecological importance of each monoecious kind of a plant

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Give ecological importance of each monoecious kind of a plant Increases chances of pollination and seed production Please Subscribe to promote this website. Subscription is ... Read More

Explain why dormancy is more common in weeds than in tropical forest trees

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Explain why dormancy is more common in weeds than in tropical forest trees - weed seed are small and have little food reserves thus can ... Read More

Suggest three ways of breaking seed dormancy.

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Suggest three ways of breaking seed dormancy. – breaking the seed coat - Stratification/subjecting the seeds to an obligatory period of cold - removal of ... Read More