K.C.S.E Biology Q & A - MODEL 2018PP1QN20
Define the term analogous structures.
answers
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K.C.S.E Biology Q & A - MODEL 2018PP1QN19
The diagrams below illustrate some forms of beaks in birds.
​(a) Which diagram represents the beak from which the others are likely to have evolved?
(b) Explain your answer in (a) above.
answers
​ (a) Beak M
(b) Beak M is simple/basic; original beak; the birds separated to occupy different niches; and specialized for different diets; leading to more complex/developed beaks over time; K.C.S.E Biology Q & A - MODEL 2018PP1QN18
​A tall, light skinned lady with pimples on her face has long hair and limps.
(a) List two features which the lady has that are due to inheritance.
(b) Explain why most recessive genes are expressed phenotypically in male offspring of humans.
answers
​(a) Height (tallness);
Long hair; Skin colour (light); (b) Most of the genes are sex-linked and are carried on the X - chromosomes; boys receive X chromosomes from the mother (and Y chromosomes from the father); if the X carries a recessive gene, it is more likely to be phenotypically expressed in boys;
K.C.S.E Biology Q & A - MODEL 2018PP1QN16
Name the bones that articulate to form a ball and socket joint at the hip.
answers
K.C.S.E Biology Q & A - MODEL 2017PP2QN08
Describe how the mammalian eye is structurally adapted to its function.
answers
K.C.S.E Biology Q & A - MODEL 2017PP2QN05
State how in-breeding leads to reduced hybrid vigour
answer
K.C.S.E Biology Q & A - MODEL 2017PP2QN05
State two advantages of using genetically modified varieties in bean farming.
answers
K.C.S.E Biology Q & A - MODEL 2017PP2QN05
In beans, the gene for purple colour is dominant over the gene for white colour. A pure breeding bean plant with purple colour was crossed with a heterozygous bean plant.
Using the letter P to represent the gene for purple colour, work out the genotypic ratio of the offspring. K.C.S.E Biology Q & A - MODEL 2017PP1QN23
The diagram below represents a set up during an experiment.
​(a) (i) What was, the experiment investigating?
(ii) State the likely identity for substance K (iii) Explain your answer in (a) (ii) above (b) Account for the observations made in flask 2.
answers
​a.) i) To investigate how ants respond to moisture/water hydrotaxis (varied environments with/without moisture water);
ii) Silica gel/anhydrous calcium chloride pellets/pyrogallic acid/dehydrating drying agent; iii) The colour of cobalt (II) chloride paper remained blue/all the moisture water vapour was absorbed/There was no water/moisture in the flask to change the colour of cobalt(II) chloride paper; b.) (More) ants were attracted) moved into the flask; due to the presence of moisture/water vapour; (evidenced by the change of cobalt (II) chloride paper to pink)
K.C.S.E Biology Q & A - MODEL 2017PP1QN20
State three methods of fossil formation.
answers
​i. Petrification/change into rock;
ii. Entire organism or parts preserved; iii. Impressions (e.g. casts/moulds); K.C.S.E Biology Q & A - MODEL 2017PP1QN18
Below are diagrams representing developmental stages of three different vertebrates.
​(a) State the evidence of evolution illustrated by the vertebrates in the diagram.
(b) Suggest why the structure labelled J has been retained throughout the evolution of fish. (c) State two major advantages evolution has given humans Over most of the other animals.
answers
K.C.S.E Biology Q & A - MODEL 2017PP1QN16
The following are text messages on a celiphone that represent gene mutation.
​(a) Identify the type of gene mutation represented in each case
I II (b) State Mendel’s First Law. (c) State two disadvantages of genetically modified plant products.
answers
​a. I — Deletion;
II- Inversion; b. The characteristics /traits of an organism are determined by internal factors/ genes (which occur in pairs). Only one of the genes can be carried in a gamete/ passed onto the next generation; c. Most have lost most of the original (desirable) qualities e.g taste; Poor/undesirable qualities are perpetuated through subsequent generations; Products’ qualities are irreversible- can’t get original species/qualities; K.C.S.E Biology Q & A - MODEL 2017PP1QN12
Explain the survival values of the following tropic responses to plants.
(a) Geotropism (b) Phototropism
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K.C.S.E Biology Q & A - MODEL 2016PP2QN07
Using a relevant example in each case, describe simple and conditional reflex actions.
answers
Simple reflex action eg. withdrawal of finger from a sharp object/ hot object; its an automatic response to a specific stimulus; when the finger touches sharp object/ hot object, the pain receptors/ thermoreceptors in the skin are stimulants; and trigger off a nerve impulse; the nerve impulse is transmitted via the senses neurone; to the grey matter of the spinal cord/ CNS/ brain; the impulse is then transmitted via synapse; to the relay neurone; and then through another synapse; to the motor neurone; and then through another synapse; to the motor neurone; the impulse is then transmitted to the effector muscles in the hand; ace - efferent neurone for motor neurone Afferent neurone for sense neurone intermediate/ associative/ connector/interauncial neurone - for relay. The effector muscles/ biceps contract; and the finger is withdrawn from the hot object/ sharp object;
Conditioned reflex action - salivation in a dog/ human being (ace. any other relevant example) student in response to sound; it is an automatic response evoked from an animal by unrelated stimulus; substituted for the one which normally elicits the response; it develops from a past experience; and involves modification of behaviour/involves learning; it weakens with time; and must be reinforced by repeating the related stimulus; the dog/ student salivates when the bell (for meals) rings; because they have learnt to associate the ringing of the bell at meal time with food; everytime it rings (accept use of other relevant examples) they are offered food. K.C.S.E Biology Q & A - MODEL 2016PP2QN03
The diagram below represents bones at a joint found in the hind limb of a mammal.
​(a) Name the bones labeled X, Y and Z
X Y Z (b) (i) Name the substance fi)und in the place labeled W. (ii) State the function of the substance named in (b) (î) above. (c) Name the structure that joins hones together at the joint. (d) State the difference between ball and socket joint and the one illustrated in the diagram above. (e) Name the structure at the elbow that performs the same function as the patella.
ANSWERS
​(a) X- Femur
Y- Tibia Z- Fibula (b) (i) Synovial fluid (ii) Lubrication of the joint/ shock absorption Distribution of pressure (c) Ligament (d) Ball and socket joint allows movement in all planes while the illustrated allows movement in one plane only. Accept 360 for all planes 180 for one plane (e) Olecranon process
K.C.S.E Biology Q & A - MODEL 2016PP2QN02
Explain why people with sickle cell trait have an adaption survival advantage over normal individuals in malaria endemic regions.
ANSWERS
K.C.S.E Biology Q & A - MODEL 2016PP2QN02
Differentiate between sickle cell anaemia and sickle cell trait.
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K.C.S.E Biology Q & A - MODEL 2016PP2QN02
How is sex determined in man?
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K.C.S.E Biology Q & A - MODEL 2016PP1QN29
Name two tissues in plants that provide mechanical support
ANSWERS
K.C.S.E Biology Q & A - MODEL 2016PP1QN29
State a characteristic that is common to all cervical vertebrae
ANSWER
K.C.S.E Biology Q & A - MODEL 2016PP1QN06
Explain continental drift as an evidence of evolution.
answer
K.C.S.E Biology Q & A - MODEL 2016PP1QN01
Name the type of muscles found in the following organs.
Stomach Bone
answers
​Stomach - Visceral muscles/ smooth muscle.
Bone - Skeletal muscles K.C.S.E Biology Q & A - MODEL 2015PP2QN05
In an experiment to investigate a plant response, the set up shown in the diagram below was used.
(a) Name the type of response that was being investigated.
(b) If the Klinostat was not rotating: (i) state the observations that would be made on the seedlings after three days; (ii) explain the observations in (b) (i) above. (c) If the experiment was repeated with the Klinostat rotating: (i) state the observation that was made on the seedlings after three days; (ii) give a reason for the observation made on the seedlings.
ANSWERS
​(a) Geotropism/Gravitropism;
(b) (i) The shoot tip/plumule curved upwards; root tip/radicle curved downwards; (ii) Auxins migrated downwards to lower side; Higher concentration on the lower side; caused more growth on the lower side than on the upper side in shoots inhibited growth on the lower side than on the upper side in the roots; (c) (i) The seedling will continue growing horizontally; (ii) There was even distribution of auxins (on the tips);
K.C.S.E Biology Q & A - MODEL 2015PP2QN03
A female with sickle cell trait marries a normal man. The allele for sickle cell is HbS and the normal allele is HbA. Determine the probability that their first born will have the sickle cell trait. Show your working.. |
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