Category: A-level Biology

Describe ecological effects of drainage of nitrate fertilizers into rivers and streams.

03/06/2022 3

Accumulation of nitrates in the streams (eutrophication) encourages proliferation of protists and algae on the surface of water. When the algae die, bacterial decomposers use ... Read More

Give three ways in which plants use the nitrates they have absorbed.

03/06/2022 0

Synthesis of chlorophyll Synthesis of enzymes, and hormones Synthesis of nucleic acids They are determinant of osmotic pressure of the cell sap They are determinant ... Read More

Describe how plants absorb nitrate from the soil.

03/06/2022 0

Plants absorb nitrates through root hairs using passive and active mechanism. The nitrates cross the cortex of the root through the apoplast, symplast and vacuolar ... Read More

Advantages and disadvantages of vegetative propagation

03/06/2022 0

Involve use of plant materials other than seeds such as cutting (sweet potatoes, cassava) suckers (pineapple, banana), stem tubers (iris)   Advantages Take short time ... Read More

Describe how new species of organism may arise

03/06/2022 3

The process by which new species arise in known as speciation. Speciation to occur their must genetic isolation of a pollution for enough time to ... Read More

Describe how new species of organism may arise

03/05/2022 0

The process by which new species arise in known as speciation. Speciation to occur their must genetic isolation of a pollution for enough time to ... Read More

Describe what would happen in an individual who develops a malfunctioning liver.

03/05/2022 0

  Solution The liver is the largest organ and center of metabolic activity in the body. Its failure to function properly it fails the following ... Read More

Describe how vascular cambium bring about growth in higher plants

03/05/2022 0

This is located between xylem and phloem and its activity causes secondary growth or increase in girth. The vascular cambium consists of two types of ... Read More

Describe how apical meristem bring about growth in higher plants

03/05/2022 0

The apical meristem consists of the tunica and corpus The cells of the tunica region divide repeatedly by mitosis, perpendicular to the surface. This results ... Read More

How does growth in mammals differ from that in flowering plants?

03/05/2022 0

Growth in mammals Growth in plants Growth occurs in all body parts Growth is limited to particular parts called meristem Growth is limited for some ... Read More

State three ways in which water has similar functions in both plants and animals.

03/05/2022 0

water is a reactant in metabolic reactions Water is solvent Water provides support in plants and animals Evaporation of water from plants and animals causes ... Read More

Behavioural means of minimizing water loss in plants

03/05/2022 0

Behavioural means of minimizing water loss in plants some plants shade off their leaves during water shortage to reduce surface area for transpiration. Some plants ... Read More

Physiological means of minimizing water loss in plants

03/05/2022 0

Some rise the osmotic pressure of their roots e.g. taking up salts from the soil actively to increase the rate of water uptake to replace ... Read More

State assumptions, and two precautions, which are taken into account while using this capture recapture method in estimating population size

03/05/2022 0

Assumptions The organisms are randomly distributed The organisms do not show sudden changes in population size due to migration, immigration or emigration Negligible predation Marks ... Read More

UACE BIOLOGY PAPER 2 2000 marking guide

03/05/2022 0

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UACE BIOLOGY PAPER 1 2000 marking guide

03/05/2022 1

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UACE BIOLOGY PAPER 2 2001 marking guide

03/04/2022 1

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Give three ways in which ions are regulated in the body

03/04/2022 0

Hormone regulate the concentration of ions by (i) controlling uptake of ions from the gut (ii) controlling release of ions from storage organs such as ... Read More

The pH of blood and tissue fluid I human remains constant at about 7.4 in spite of metabolic activities which produce hydrogen ions. Explain how this constancy is maintained by the kidney.

03/04/2022 0

In the cells of proximal convolute tubule, carbon dioxide reacts with water to form carbonic acid. the reaction is catalyzed by carbonic anhydrase enzyme Carbonic ... Read More

How vertebrates are adapted to terrestrial life

03/04/2022 0

Their vertebral column and limbs provide support and aid movement They have bones, joints, ligaments and muscles to effect movement They have well developed osmoregulatory ... Read More

Importance of bacteria

03/04/2022 0

Harmful effects Bacteria are agents of disease of animals and plants such as syphilis, cholera, tetanus Bacteria cause milk and food deteriorate Denitrifying bacteria such ... Read More

Nutritional groups of bacteria

03/04/2022 0

Bacteria are heterotrophic or autotrophic There are two main groups of autotrophic bacteria; photosynthetic bacteria and chemosynthetic bacteria Photosynthetic bacteria utilize light energy to build ... Read More

Differences between eukaryotic and prokaryotic cells

03/04/2022 0

    Prokaryotic cell Eukaryotic cell 1. DNA not enclosed in membrane DNA enclosed in a double membrane nucleus 2. Has small ribosome (70s) Has ... Read More

How muscle contract

03/04/2022 1

Skeleton muscle contraction is initiated by arrival of a nerve impulse at the nerve muscle junction. Arrival of the nerve impulse cause influx of calcium ... Read More

How a skeletal muscle differs from a smooth muscle

03/04/2022 0

Skeletal muscle Smooth muscle -          Cell are multi nucleated Each cell contain a singe nucleus -          Many striations of alternating light and dark bands Not ... Read More

Adaptations of plants to capturing maximum light

03/04/2022 0

Cells in upper layer contain numerous chloroplast Leaves provide large surface area to trap light Leaves are arranged in mosaic manner to expose each leaf ... Read More

UACE BIOLOGY PAPER 2 2002 marking guide

03/04/2022 0

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UACE BIOLOGY PAPER 1 2002 marking guide

03/03/2022 0

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What consideration must be made before application of a biological pest control method? 

03/02/2022 0

Sc Whether the control egent is specific to intended pest Rate of reproduction of both pest and control organism Control organism should feed on all ... Read More

structural and physiological functions of fats

03/02/2022 0

Structural functionsof fats Make up cell membrane Protection: lipids are constituents of the waxy cuticle of plants and insects Lipids are water repellant thus prevent ... Read More

describe structural and biochemical adaptations of red blood cells

03/02/2022 0

Structural adaptation of red blood cells Thin membrane to reduce diffusion distance of gases Biconcave shape increase surface area for gaseous exchange Lack of nucleus ... Read More

Describe the trend of succession that would take place on a bare rock.

03/02/2022 0

  Succession on bare rock is called primary succession and occurs in three stages. Pioneer stage Bare rock breaks down physically and chemically during the ... Read More

Outline the flow of energy in the climax community 

03/02/2022 0

  Energy in form of light from the sun is used for photosynthesis to produce organic molecules. The initial amount of energy fixed by ecosystem ... Read More

Adaptations of flowering plants to gaseous exchange

03/02/2022 0

Has many stomata on leaves and  lenticel to allow gaseous exchange Broad leaves gives provide large surface area for gaseous exchange Cells in mesophyll layer ... Read More

Adaptation of an insect for efficient gaseous exchange

03/02/2022 0

Has highly branched tracheal system that ramify the whole body up to individual cells Tubules open to atmosphere to receive oxygen through spiracles Tracheoles have ... Read More

Qualities of gaseous exchange surface

03/02/2022 0

Has large surface area Moist Thin to reduce distance for diffusion Freely permeable to respiratory gases Has good blood supply Has good ventilation Read More

UACE BIOLOGY PAPER 2 2003 marking guide (UNEB)

03/02/2022 0

Please download PDF: UACE BIOLOGY PAPER 2 2003 marking guide   Read More

State the importance of  magnesium in plant metabolism.

02/28/2022 0

It is a constituent of chlorophyll It activates enzymes in protein synthesis It is co-factor for many enzymes e.g. ATPase Read More

State the importance of  calcium in plant metabolism.

02/28/2022 0

It activates several enzymes e.g. ATPase It is important for translocation of carbohydrate It is a constituent of the plant walls It is important in ... Read More

State on indicator in the environment where there is prevalence of high levels of sulphur dioxide in the atmosphere.

02/28/2022 0

Disappearance of lichen and mosses Discoloration and damage to building, sculptures and fabric Chlorosis and necrosis of vegetation Read More

Describe the how terrestrial plants overcome the challenges of terrestrial environment.

02/28/2022 0

They have shinny leaf surfaces to reflect much of the incident light rays do avoid overheating. They have a thick, waxy cuticle impermeable to water. ... Read More

Discus the factors that affect the rate of diffusion at a respiratory surface.

02/28/2022 0

Surface area of the respiratory surface; the larger the surface area across which diffusion can occur, the higher the diffusion rate. A large surface area ... Read More

How are the conditions for efficient gaseous exchange fulfilled in mammalian lungs? 

02/28/2022 0

The lungs have numerous alveoli which represent a highly folded respiratory membrane to provide a large area for diffusion of the gases. Lungs have a ... Read More

The diameter of capillaries is smaller than the diameter of the red blood cells passing through them. How does this relationship help in gaseous exchange in lungs?

02/28/2022 0

The red blood cell membrane is in close association with the capillary membrane all through its passage. This reduces the distance across which gases diffuse ... Read More

What is the effect of inbreeding in a population? 

02/28/2022 0

It reduces variations in a population Lethal or useful characteristics are retained in the population Promotes desired characteristics in population Read More

Describe the mechanisms which limit inbreeding in plants.

02/28/2022 0

In some plants, the stigma matures before the anther so that it gets ripe before the anther is able to produce mature pollen grains. Thus ... Read More

Suggest the factors that would cause immigration of new species to a virgin island.

02/26/2022 0

Availability of food on the island. Favorable environmental conditions on the island. Accidental movement of organisms to the island. For example flying and swimming organisms ... Read More

Describe the physiological changes that occur in a seed during germination 

02/26/2022 0

Germination starts with the rapid uptake of water by the seed through the micropyle by a process called ambition. Water then moves from cell by ... Read More

Giving reasons, suggest suitable conditions under which seeds for planting should be stored 

02/26/2022 0

dry condition; too much water may cause rotting dry seeds; seed with high content promotes diseases optimum temperature; high temperature promotes pests and diseases low ... Read More

Describe the adaptations of blood in terrestrial animals living in the following environmental conditions

02/26/2022 0

Extreme oxygen tensions (08 marks) Extremes of oxygen tension can the very high or very low values of oxygen partial pressure. In all these conditions, ... Read More

Explain the factors that influence the type of nitrogenous waste excreted by animals

02/26/2022 0

Availability of water; animals in fresh water bodies have enough water available for dissolving any water products. They are able to dilute and excrete ammonia. ... Read More

Describe osmoregulation in a terrestrial insect.

02/26/2022 0

Water must be carefully conserved since most terrestrial insects are unable to drink and depend on metabolic water During excretion, the urine passes from the ... Read More