UACE Biology paper 2011
Answer all questions
30
20
40
10
Height.
Ear size.
Blood groups.
Finger length.
Figure 2 shows the banding pattern of a myofibril when relaxed.
Which one of the following occurs in reference to the A band when the myofibril is contracted?’
-4400 kPa
4400 kPa
5400 kPa
-5400 kPa
Duplication
Translocation
Monosomy
Polyploidy
4.22.
5.0.
4.90.
7.65.
Animals |
Volume |
Surface area |
|
/cm3 |
/cm2 |
A |
1 |
6 |
B |
8 |
24 |
C |
64 |
96 |
D |
64 |
28 |
Which one of the organisms would need a specialized respiratory system
In which pyramid does the primary consumer make most efficient use of the producer?
A two replications of DNA occur during meiosis.
D chromatids do not separate during meiosis.
Which curve is most likely to be that of an active flying bird?
C Protandry.
Solution
2.C 12.D 22.B 32.A
4.C 14.A 24.A 34.B
5.A 15.D 25.D 35.D
6.B 16.D 26.C 36.B
7.D 17.B 27.D 37.C
9.A 19.D 29.B 39.C
10.D 20.C or D 30.C 40. NONE
Explanation for the answers for section A
Baryophytes undergo alternation of generation in which a haploid gametophyte generation alternates with a diploid spo rophyte generation. Production of gametes by the gametophyte is by mitosis so that the gametes are also haploid. The gametes then fuse to form a diploid zygote which grows into a diploid sporophyte. The sporophye produces spores by meisosis and so the spore are also haploid. Spores then germinate and grow into the gametophyte.
Diffusion of materials across an epithelium occurs across the thickness of the cells constituting the epithelium. Being thin and delicate, the cells of the squamous epithelium shorten the diffusion distance, i.e. the distance across which materials have to move during diffusion.
According to the rules of base pairing, guanine (G) pair with cytosine (C) and adenine (A) pairs with thymine (T).
As such the ratio of G:C is 1:1 and that of A : T is also 1:1 thus, if G is 40%even C is 40%.
As such A and T constitute 20% which they share in a ratio 1:1 thus, A constitutes 10% and T also 10%
The graph indicates discrete values of the character with no intermediate, i.e. separate bars. This is a representation of discontinuous variation. Such variation is only possible for qualitative characteristics such as Blood groups; tongue rolling; skin colour; eye colour etc.
Note: continuous variation occurs for quantitative characters such as height. Ear size, finger length etc. such characters can take on any value and may have intermediate values. Continuous variation is represented by a histogram. i.e.
Glucose is a polar molecule which is capable of forming hydrogen bonds water is also polar and forms hydrogen bonds with itself and other polar molecules. This property facility the dissolution of glucose in water which it is transported.
During skeletal muscle contraction the actin and myosin filaments slide parallel to one another.
This shortens the sarcomere. The 1-band (the A- band in the question) becomes narrower.
7.The answer is D
The nucleus of a cell controls all the metabolic activities of the cell and such, the size of the nucleus of a cell is directly proportional to the metabolic activity of the cells.
The companion cell is a site of intense metabolic activity and thus has a large nucleus.
Note:
Although the sieve element is metabolically inert., it is just mere speculation that the companion cell provides for its metabolic needs.
Refractory period is the period of inexcitability that accompanies the recovery phase of the axon. It is divided into two: an a absolute refractory period during which the axon completely cannot transmit an impulse and relative refractory period during which it is possible to generate an impulse provided that the stimulus is stronger than usual, i.e. of higher voltage.
Note:
During this period, the sodium ion channels are closed.
Inhibitory post synaptic potential is concerned with synaptic transmission only.
Water potential (Ѱ), solute potential (Ѱs) and pressure (Ѱp) are related by the following equation.
Ѱ = Ѱs + Ѱp (the cell equation)
Ѱs is negative while Ѱp is positive.
Hence the water potential of the cell is -4400kpa
Non-disjunction is the failure of sister chromatids to separate during meiosis.
As a result, some gametes are produced with a diploid genetic constitution while others are empty. When such gametes fertilized, a higher degree of chromosome complement is formed. For example, triploid and higher chromosome complements are formed. This is called polyploidy.
Volume of sweat, Vs = 1dm/ day.
Lu of sweat = 2. 45kJcm-3
=>heat lost in sweat, Q out = Vs x L v
= (1000 x 2.45)
Q out = 2450kJ/day
Energy intake, Q in = 50,000 KJ/day
50000
energy loss = 4: 90%
Hence percentage energy loss during work is 4;90 %
An organism that most needs a specialized respiratory system is one that the least surface area to volume ratio. In such an animal, diffusion alone cannot suffice its respiratory needs.
The surface area to volume ratio of these different animals are as shown;
Animals |
S.A / V ratio |
A B C D |
6/1 =6 24/8=4 96/ 64 = 1.5 28/64 = 0.4374
|
Hence animal that has the least surface area to volume ratio and therefore needs specialized respiratory system.
13 The answer is B
I energy pyramid, bars are proportional to the total energy utilized to each trophic level. Those shown indicate three trophic levels: producers, primary consumer and secondary consumers. In this case, the larger the size bar that corresponds to primary consumers, the more the energy they obtain from the producer and therefore the more efficient they utilize their producers.
This is show by pyramid B.
Algae are photosynthetic organism. As such factors limiting their population so by limiting their photosynthetic activity.
The pond surface is usually covered with a layer of lower plants which limit the amount of light reaching the bottom of the pond. Therefore, the greatest limiting factor of population growth of a algae at the bottom of the pond is light.
In a mutualistic relationship both organism involved benefit and no harm is done to either organism.
If any of the organism does harm to the other, then relationship becomes non-mutualistic. Therefore, that the bacteria in the gut of ruminant animals are preyed on them is a non-mutualistic role.
16 The answer is D
Photosynthetic bacteria also obtain energy from sunlight like the green plants. However, they differ from green plants in that source of their hydrogen is hydrogen sulphide instead of water which is used by green plants.
Gametes are haploid because homologous chromosomes separate during anaphase I of meiosis
In the second division, which occurs without further duplication of DNA, each chromosome is divided into two chromatids that move to two different daughter cell.
Hence each (daughter cell) gametes has half the genetic material of that of the parent cell, i.e. is haploid.
When a fish is taken out of water, the gills clamp up together. This reduces their effective surface area for gaseous exchange. Therefore, the immediate problem to a fish when taken out of water is insufficient oxygen supply.
According the competitive exclusion principle, no two organism of the same species can occupy the same ecological niche. That is similar species of organisms that compete with each other for the same resources cannot co-exist.
However, they may impose restriction on their range of living or develop aggression towards each other. Otherwise, they may evolve into new separate species needing different resources, hence to extinction of the competing strains.
Parthenogenesis is the development of a new individual from an unfertilized egg. There are two kinds of parthenogenesis: diploid and haploid parthenogenesis. In diploid parthenogenesis, the eggs (gametes) are diploid because they are formed by mitosis while in haploid parthenogenesis the eggs (gametes) are haploid because they are formed by mitosis.
No fertilization is necessary and only one sex is necessary. Also some degree of genetic mixing occurs due to crossing over at prophase 1 of meiosis.
In a sexual reproduction, no gametes are formed and there is no genetic mixing.
Mimicry, predation and human activities are some of the factors that affect the distributions o organism.
Note:
Speciation is the process by which one or more species arise from previously existing species. It only affects the number of species present in an area but does not affect distribution and abundance of a given species of organisms.
The liver is the major organ that regulates the blood glucose level. One way in which it reduces the blood glucose level when it is higher than normal is by synthesizing glycogen from glucose.
Note:
When the blood glucose level is lower than normal, the liver can increase the glucose level by; breakdown of glycogen to glucose, and break drown of proteins and fats to produce residues that can be used to synthesize glucose by the process of gluconeogenesis
Active transport is the process by which materials are transported across a living cells membrane against a concentration gradient, using metabolic energy in form of ATP.
As such, active transport:
Note:
Although active transport it takes place across a semi permeable membrane, this is not major requirement. The most important requirement is metabolic energy in form of ATP. This is why it cannot take place in non-living cells even though their membranes may still be semi-permeable.
A physiological homeostatic process involves:
Note:
Positive feedback is a destabilizing mechanism which creates more instability of a system and therefore cannot be used as a homeostatic mechanism. The normal mechanism employed in physiological homeostatic process is negative feedback. Here, a change in the value of the controlled factor initiate a series of processes that bring back the factor to normal.
Iodine is the most important regent in the formation of thyroxine. Thyroxine is an important metabolic hormone that is also important in influencing the growth of bones.
Cretinism is a condition in which the amount of thyroxine is very low in blood as a result of iodine deficiency in the diet. it is characterized by:
This condition is diagnosed in infancy. If it goes unnoticed, it results in myxedema later in life. This is characterized by slow mental activity, decreased metabolic rate and swelling of face, tongue and loss of scalp hair.
Given 2n = 12
= 3x 6
= 18
Artificial selection is the process by which human encourage the breeding of animals with desired qualities while preventing those with undesired qualities from breeding. This is done by:
Note:
Cross-breeding is part of artificial selection but is not a means of preventing individual with undesired qualities from mating.
Fats have a higher caloric valve, i.e. yield more energy per unit mass on oxidation than carbohydrates. This is because fats possess a higher proportion of hydrogen and an almost insignificant proportion of oxygen compared with carbohydrates. The hydrogen is used in the respiratory chain in the mitochondria to form ATP
Fossil fuels yield carbon dioxide when burnt. Carbon dioxide is an acid gas. It dissolves is rain water to form acid rain. The other gas produced from the use of fossil fuels is sulphur dioxide which is also acidic and causes acid rain.
Note:
Coal mining does not yield any gas but use of coal as a\ fuel yield carbon dioxide which is an acidic gas
Sewage disposal in water bodies only causes eutrophication but does not cause acid rain.
Commercial farming reduces the incidence of acid rain production because the plant the absorb the excess carbon dioxide from the atmosphere.
According to medal, characteristics of diploid organism are controlled by alleles occurring in pair and of a pair of such alleles. Only one be carried in a single gamete, i.e. each parent has only a one variety of an allele of each pair.
Also. Each offspring inherits one allele of each pair, one from each parent.
Each allele s transmitted from generation to generation in a discrete unit.
Tropism is a growth movement of part of a plant in response to a directional stimulus.
In tropic responses, the direction of the response is related to that of the stimulus and ,in almost all cases, the plant part moves towards or away from the stimulus. each response is named according to the nature stimulus.
Thus:
Stimulus |
Names of response |
Example |
Air Light Gravity Water Chemical
touch |
aerotropism phototropism geotropism hydrotropism chemotropism
thigmotropism |
Pollen tubes away from air Plant shoots towards light Plant roots grow downwards Plant roots towards moisture Fungal haphae grow towards nutrients Tendrils od peas twin a round their support. |
Note:
The other objectives indicate nastic responses; movement od a plant to non-directional or diffuse stimulus
Both tropic responses and nastic responses occur in plants
Fresh water fishes are liable to osmotic influx of water across the gills part and lining of the mouth and pharynx..
The overcome this problem in three ways:
A active flying bird demands much energy and therefore has high metabolic rate. To supply oxygen to the tissue rapidly, their haemoglobin must release it readily. This is the reason why it has its dissociation curve to the far right of all the organisms represented.
Note:
Mudfish, live in muddy water logged burrow where oxygen tension is very low. Its haemoglobin has very high affinity for oxygen and is represented by curve R, i.e. lies to the far left.
Foetal haemoglobin has higher affinity for oxygen than for an adult human because it has to pick oxygen from maternal blood; its curve is to the left of that o an adult human. Thus curve S represents foetal haemoglobin while T is for adult human.
Variation in flowering plants occurs as a result of cross-fertilization. Therefore, any feature of flowering plant that prevent cross-pollination limits variation. Hermaphrodism is one such character that encourages self-pollination and therefore limits chances of variation
Note:
Dioecism, protandry and self-incompatibility encourage cross-fertilization and therefore promote variation.
Competition is one of the factors that constitute environment resistance. others include, predation, diseases, etc. Therefore, reduction in competition reduces environmental resistance and thus encourages population growth.
In resting state, the axon members are polarized with the outside positive and the inside negative.
During an action potential, the cell membrane becomes more permeable to sodium ions so that there is an influx of sodium ions in the cell. This depolarizes the membrane; the inside becomes positive while the outside negative.
`38. The answer is A
Establishment evolutionary relationship on basis of structure similarities and difference among organism is called comparative anatomy. Under this:
Homologous structures are structures common origin modified in various ways to adapt animals to different modes of life. For example, the pentadactyl limb system.
This is case of divergent evolution
Analogous structures have different origin but are adapted to perform similar functions.
For example, wing of birds and insects. This is a case of convergent evolution.
Social behaviors animals have the following advantages
Its disadvantages include;
High incidence of cannibalism
Increased susceptibility to diseases.
Increased competition for resources
A centipede belongs to phylum Arthropoda, subphylum myriapoda and class chilopoda
Note:
Diplopoda is the class to which millipedes belong
Class Arachnida include the tick and spider
Class Crustacea include a wide range of aquatic arthropods, e.g. crayfish, water flea and the wood louse.
SECTION B
(a) outline the feature of the fungi made it necessary to place them in their own kingdom
(b) explain why the fungi are wide spread and in vast numbers.
(c ) what is the economic importance of fungi?
Solution :
They are heterotrophic feeders.
Others
Others
They can feed parasitically on other living organism, both plants and animals.
Yeast is also used in baking of bread.
Most mould decompose organic matter may lead to rotting of fruit and food
Others
Some fungi are agents of diseases in both plants and animals
Penicillins produced penicillium natatum, a fungus, is an antibiotic.
The fungus in mycorrhiza relationships provides plants with mineral salts and water.
(b) State four conditions that must be fulfilled in order for the principle to hold true
(c ) Brown eyes in a human population is caused by a dominant. If in a population, 84% of the people have brown eye, using Hardy-Weinberg formula, determine the percentage of the population who are.
Solution
There is continued movement of gene (gene flow) within the population due to breeding but the overall gene frequencies remain constant. This stability is referred to as genetic equilibrium.
Mating must be random
The population must be large.
No emigration or immigration from or into the population should occur
Others
Generations should not overlap
All genotypes should be equally fertile, so that no selection occurs.
The allele for other eye colour be b
Frequency of allele B be p
Frequency of allele b be q
Given BB+ Bb constitute 84%
The hardy-Weinberg equation states
P2 +2pq + q2 = 1
given p2 + 2pq = 0.84
q2 = 1 – 0.84
q2 = 0.16
=>q = 0.4
Also p + q = 1
P = 1-0.4
P = 0.6
=> (0.6)2 + 2pq = 0.84
2pq = 0.84-0.36
2pq = 0.48
Hence 0.48% of the population are heterozygous.
(ii) from above
P = 0.6
=> BB = p2 = (0.6)2
.; BB = 0.36
% 0f BB = 36%
hence, the percentage of individual homozygous dominant for eye colour is 36%
(i) Stratified tissue
(ii) Collagen tissue
Solution
forming a tough impervious barrier.
External skin surface
Others
Lining of the buccal cavity
Lining of the vagina
Lining the upper third of the esophagus
(ii) Collagen consist of three polypeptide chains coiled round each other to form triple helix.The chains are interlinked by hydrogen bonds which makes the entire structure tough and inextensible. This provide great tensile strength
It is found in tendons
Other structure proteins with parallel polypepetide chains-linked at many points are collagen and elastic. They are both found in muscles.
(b) State two difference and two similarities between pollen grains of a flowering plant and the spore of moss.
(c ) How are ferns better adapted to live on land than mosses?
Spore |
Pollen grains |
Can germinate into an independent plant structure Not gametes Others: Remain viable over a long period of time |
Cannot form an independent plant structure. Male gametes
Are viable for only a limited time |
They are both formed by meiosis
They are both haploid
Others
They are both light and dispersed by wind.
Others:
They are delicate and small.
They lack a cuticleThey can easily be subjected to desiccation in drier environment
They depend on water for the movement of male gamest towards female gametes during fertilization.
Have chlorophyll and are therefore capable of photosynthesizing
They grow in clusters and therefore strengthen their positions on the soil.
They reproduce both sexually and a sexually. This increases their chances of survival on land
Solution:
Carbon dioxide uptake increase initially at low light intensities and the decreases gradually at higher intensities, to reach constant valves.
Differences
Light plants |
Shade plants |
– Initial rate of carbon dioxide uptake is high at low light intensities – Carbon dioxide uptake starts below zero. – reach a constant at a higher light intensity. – higher saturation value |
– Initial rate of uptake carbon dioxide is high at low light intensities – Carbon dioxide uptake starts at zero – reach a constant at a lower light intensity. – lower saturation value |
Explanation
The rate of respiration of the plants is higher than photosynthesis. There is more food breakdown than synthesis.
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..
………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………..
Solution
Differences
Fish A |
Fish B |
-oxygen concentration of blood is above 50% at the end of the gill plate. – water always has a higher oxygen concentration than blood
Other Oxygen concentration of the blood increase linearly along the gill plate.
|
-oxygen concentration of the blood is about 50% at the end of the gill plate. Initially water has a higher oxygen concentration, but at the end of the gill plate, the oxygen concentration blood and water are the same. Oxygen concentration of the blood increase first rapidly then decreases gradually and reaches a constant valve at 50%
|
Fish A maintains a steep concentration gradient between the water and blood that the fish picks up enough oxygen from the water and deposits sufficient quantities of excess carbon dioxide in it.
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