State the importance of magnesium in plant metabolism.
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.
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.
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.
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.
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?
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?
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?
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.
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
UACE BIOLOGY PAPER 2 2005 marking guide (UNEB)
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UACE BIOLOGY PAPER 1 2005 marking guide (UNEB)
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UACE BIOLOGY PAPER 2 2006 marking guide (UNEB)
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Suggest the factors that would cause immigration of new species to a virgin island.
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
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
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
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
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.
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
Compare DNA and RNA molecules
Similarities between DNA and RNA Both contain purines adenine and guanine and the pyrimidine base cytosine Both contain phosphate groups. They both have a basic ... Read More
Describe the role of mRNA in the protein synthesis in a cell.
mRNA caries genetic information in form of nitrogenous bases from chromosomal DNA in the nucleus to the ribosomal RNA in the in the cytoplasm. It ... Read More
How does the molecular structure of proteins relate to their functions?
According to molecular structure, proteins can be classified as follows in relation to function; Fibrous proteins from a long, tough, fibre insoluble in water. ... Read More
Discuss how structure and function are related for voluntary muscle tissue
Voluntary muscle tissues in animals act as a component of the locomotory apparatus. They are usually attached to bone, a strategic for to be involved ... Read More
What is meant by water stress in relation to plants?
a Water stress is a condition in which a plant greater tendency to lose water to the environment through transpiration than it can obtain by ... Read More
What is the effect of water stress in green plants?
It causes wilting It causes reduction in rate of photosynthesis It may lead to shedding of plant leave I cause rapid closure of stomata. Read More
Outline the structural adaptation of the xylem vessel for long distance transport to water and mineral salts?
Science Had elongated cylindrical cells connected end- to –end to form a continuous pipe/ vessel. Has a dead cell with no protoplasm to create room ... Read More
Outline the cause of gene reshuffling
a - Crossing over prophase 1 in meiosis - independent assortment at metaphase 1 of meiosis - Random assortment of chromosomes in metaphase I - ... Read More
In what way may variation resulting from gene reshuffling differ from that caused by mutation?
Gene reshuffling new combination of the same alleles and as a result leads to variation in combinations of the same characters. Mutations lead to formation ... Read More
What is the importance of variation in a population?
May lead to emergence of new species. Increase chances of organisms to survive in different habitats. Increase chance of resistance of organisms to diseases and ... Read More
State two effects of DDT to organisms.
It interferes with the conduction of nerve impulses in the nervous system. In birds, it interferes with proper formation of egg shells. DDT has a ... Read More
Explain how a pest sprayed with a pesticide may flourish afterwards.
May eradicate predators The pests may mutate breed pesticide- resistant progeny. These survive and become selected for and flourish in increasing numbers as the ... Read More
UACE BIOLOGY PAPER 1 2006 marking guide (UNEB)
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Describe how hormones from the ovary and pituitary gland interact to control the human menstrual cycle.
Hormones produced by the ovary include progeserone and oestrogen while the pituitary gland produces luteinizing hormones (LH) and follicle stimulating hormone (FSH) which interact as ... Read More
Describe how adrenaline affects the metabolism of carbohydrate
It increases the rate of conversation of glycogen to glucose. This increases the blood sugar content. It increases the rate of production of glucose from ... Read More
Describe how insulin affects the metabolism of carbohydrate
- it increases the rate of uptake of glucose by muscle and fat cells through a number of glucose channels in the cell surface membrane. ... Read More
What is meant by negative feedback in body processes?
Negative Feedback: is a mechanism whereby deviation from a set norm causes a corrective mechanism to restores the norm. For example, increase in the ... Read More
Explain how the epithelial is adapted for its functions.
In this question you should point out the structural modifications of epithelial tissue to suit the different functions. One cell thick reduce diffusion distance in ... Read More
Outline the functions of a cell nucleus.
The nucleus contains the DNA It controls the process of the cell division. It controls all the metabolic activities of the cell by controlling the ... Read More
Explain the significance of mitosis and meiosis in organisms.
Significance of mitosis Ensures genetic stability by producing daughter cells identical to parent cells Enables growth Is a basis of asexual reproduction Enables regeneration ... Read More
UACE BIOLOGY PAPER 2 2007 marking guide(UNEB)
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What are the limitations of measuring leaf as a way of measuring growth in a plant?
It does not account for girth or volume Different parts of the plant may grow at different rates The method is not accurately measured using ... Read More
Why is it important to estimate population size?
To monitor population change To establish feeding relationship within a habitat To construct food chain, food web and pyramid of numbers To determine carrying capacity ... Read More
In capture-recapture method to estimate the population size of fish, state two assumption that were made.
That fish mix randomly within the population. That organisms disperse randomly within the geographical area of the population. That change in the population size due ... Read More
Give ways in which animals avoid predation.
ce Mimicry Keen eye-sight Adoption of nocturnal life Alarms Fast runner Glossy body surface Production of poisonous substance as is the case of toads and ... Read More
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Outline the events that lead to the formation of pollen grains in flowering plants.
This question requires that you describe what happens in the anthers during formation of pollen grains from the meristematic cells to mature pollen grains. However, ... Read More
How does the development of the embryo sac in flowering plants differ from oogenesis in humans?
In this question you should compare the events that occur during either process up to and including the products of each process. Development of ... Read More
Using an example, explain an effect of gene mutation in humans.
In this questions, first show your understanding of the term gene mutation. Then using suitable examples outline the effect of this process in humans. A ... Read More
What is the significance of mutation in crop husbandry?
In this question you should point out how the effect of a mutation is of importance in crop husbandry. Mutations can induce polyploidy in plants ... Read More
Describe the structure of the phloem and cardiac tissues.
Structure of phloem This is a vascular conducting tissue whose structure is composed of sieve tubes, phloem parenchyma and companion cells. Sieve tubes are living, ... Read More
Explain how the structures of the phloem and cardiac muscle are related to their functions
In this question, examine the structure of particular parts of the tissue and relate this to the function. Phloem The sieve tube cells are elongated, ... Read More
Explain how light may affect the activities of organisms.
In this question you should outline how the activities, (both physical and physiological) of both plants and animals are affected by light. Light is ... Read More
Why does transpiration occur mainly through leaves other than other parts of a plant?
Transpiration is the process by which plants lose water vapour through their aerial part. It may occur through leaves, green stems and lenticels of woody ... Read More
Using example, explain the ecological importance of each of the group chemoherotrophic in an ecosstem.
The importance of bacteria in the ecosystem depends on their activities in the ecosystem; (i) Saprophytic bacteria include nitrosomonas, nitrobacter and denitrifing bacteria derive organic ... Read More
What are chemoherotrophic bacteria?
Are bacteria unable to manufacture their own food, but obtain nourishment and energy from the chemicals in their organic chemical Read More
UACE BIOLOGY PAPER 1 2008 marking guide (UNEB)
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What is meant by apical dominance?
Apical dominance is a phenomenon that occurs in plants where the presence of the apical bud inhibits the growth of lower axillary buds, yet when ... Read More
What is the ecological importance of seed dormancy?
Enable the seeds to survive unfavorable conditions like drought. Prevents the seeds from developing in the pods Allows for seed dispersal, which ensures colonization of ... Read More
What is the ecological importance of apical dominance
Enable the plant to grow first vertically so as to access sunlight. Enable the plant to outcompete other individuals in the vicinity for sunlight. In ... Read More
Explain the absence of a yolk sac in the development of a human foetus while it is an important structure in the development of birds.
The yolk sac produces red blood cells in the human embryo but its function is quickly taken over by the liver in the foetus. It ... Read More
State the reproductive adaptation of birds to terrestrial life.
Fertilization is internal. This increases chances of success of the process of fertilization. They lay eggs with shells in which the embryo grows with all ... Read More