K.C.S.E Biology Q & A - MODEL 2006PP1QN27
Name the end products of the light stage in photosynthesis.
K.C.S.E Biology Q & A - MODEL 2006PP1QN26
The chart below represents a simplified nitrogen cycle.
What is represented by X,Y, and Z?
X- Denitrifying bacteria/ denitrification
Y- Animals/ Herbivores; accept primary consumers
Z- Nitrogen fixing bacteria ( in soil) accept Azotobacter.
K.C.S.E Biology Q & A - MODEL 2006PP1QN25
A dog weighing 15.2kg requires 216kj while a mouse weighing 50g requires 2736kj per day. Explain.
K.C.S.E Biology Q & A - MODEL 2006PP1QN24
State four ways in which respiratory surfaces are suited to their function.
K.C.S.E Biology Q & A - MODEL 2006PP1QN23
State the function of each of the following parts of human ear.
a) Ear ossicles
c) Semi circular canals
d) Eustachian tube.
K.C.S.E Biology Q & A - MODEL 2005PP1QN19
How is the human eye adapted to its function?
Adaptations of the eye.
The presence of:-
K.C.S.E Biology Q & A - MODEL 2005PP1QN18
Describe how gaseous exchange takes place in terrestrial Plants.
Gaseous exchange in terrestrial plants.
Gaseous exchange in plants involves two main respiratory gases: carbon IV oxide and oxygen.
During daytime green plants take in carbon IV oxide for photosynthesis and oxygen for respiration. During photosynthesis oxygen is given out as a by product and released to the atmosphere. In plants such as the flowering plants stomata in the leaves and lenticels in the woody stems and pneumatophores/breathing roots in aquatic woody plants provide the surface for gaseous exchange. Gaseous exchange taken place by diffusion across the respiratory surface.
These are located mainly in the leaves and in younger parts of the stem. The opening and closing of stomata is controlled. Mainly by the intensity of light. They are normally open during the day and closed during the night. Several theories explaining the mechanism of stomata opening and closing have been put forward.
1. Photosynthetic theory
Guard cells have chloroplasts. During daylight, they carry out photosynthesis producing surges. The surges increase the osmotic pressure of the cell sap. This causes water to more into guard cells from the neighboring epidermal cells by osmosis.
The results is an expansion and increase in turgidity of the guard cells causing the stomata to open.
In darkness photosynthesis stops. The sugar in the guard cells is converted to starch. This lowers the osmotic pressure of guard cells causing the to lose water to neighboring cells by osmosis.
The guard cells become flaccid and the stomata close.
The guard cells become flaccid and the stomata close.
2. Starch – sugar interconversion:
The enzymatic conversion of starch to sugar proceeds more readily in an alkaline environment(high PH).The conversion of sugar to starch occurs more readily in an acidic environment (low Ph).During the night, when photosynthesis is not taking place, carbon dioxide accumulates in leaf cells it combines with water to form carbonic acid. This lower the PH in the guard cells leading to conversion of sugar to starch this decreases the osmotic pressure in the guard cells causing them to lose water to the neighboring epidermal cells. The guard cells become flaccid and the stomata close.
During daylight, when photosynthesis is taking places, the concentration of carbon dioxide in the leaf cells, raising their PH, and favouring the conversion of starch to sugar. This increases the osmotic pressure in the guard cells causing them to take in is an expansion and increase in turgidity of the guard cells causing the stomata to open.
3. Potassium Ion (K+) mechanism
When guard cells are exposed to light, their chloroplasts manufacture ATP. The ATP drives at K+ pump in the cell membrane of the guard cells. This causes an active uptake of K+ into the guard cells from surrounding epidermal cells.
Accumulation of K+ in guard cells increases the osmotic pressure of their cell sap. This causes water to move into the guard cells from neighbouring epidermal cells by osmosis. The result is an expansion and increase in turgidity of the guard cells causing the stomata to open.
-At the onset of darkness, chloroplast stop making ATP and its concentration in guard cells falls rapidly stopping K+ pump, K+ migrate from the guard cells
Causing them to lose water to the neighbouring cells by osmosis. The guard cells become flaccid and the stomata close.
-Water molecules are pumped into the guard cells from adjacent epidermis cells.
-A small extent of gaseous exchange takes place in the stem through structures called lenticels.
These are small gaps in the bark usually circular or oval & slightly raked on the bark surface.
The cells in these area are thin walled and loosely packed leaving air space which communicates with air spaces in the cortex. Hence 02 for respiration is taken up & C02 is given out.
K.C.S.E Biology Q & A - MODEL 2005PP1QN17
After an ecological study of feeding relationships students Constructed the food web below.
a) Name the process through which energy from the sun is incorporated into the food web.
b) State the mode of feeding of the birds in the food web
c) Name two ecosystems in which the organisms in the food web live
d) From the information in the food web, construct a food chain with the large bird as a quarternary consumer.
e) What would happen to the organisms in the food web if bird N migrated?
f) Not all the energy from one trophic level is available to the next level. Explain
g) (i) Two organisms which play a role in the ecosystems are not included in the food web. Name them.
(ii) State the role played by the organisms named in g(i) above.
h) i) State three human activities that would affect the ecosystems.
ii) Explain how the activities stated in h(i) above would affect the ecosystems.
b)Heterotrophic – holozoic
c) Small fish pond / dam, rain forests.
d) Algae Zoo plankton small fish bird large bird.
e)-Snails would increase in number
-Bird M would increase in number.
-Green plants would decrease in number
f) The energy to be passed on from one trophic level to the next is contained in food materials. Most of the food taken in by consumers passed on from one trophic level to the next is consumers passes through the digestive track as undigested matter that is removed as faeces. The digested materials are absorbed in to the bloodstream and conveyed to various tissues of the body. Most of the absorbed food materials are used in respiration, to Produce is lost as heat during sweating, evaporation and transpiration in plants.
g)i) Scavengers e.g. vultures
Decomposers e.g. bacteria
ii) Scavengers feed on dead bodies of herbivores and carnivore / the consumers.
-Decomposers act upon the remains of the producers, consumers, & Scavengers causing decay, to release inorganic materials, which are later re-used by producers to make new organic compounds.
h) i) -Deforestation
-Poor waste disposal // Environmental pollution
Lack of trees leads to reduced number producers in an ecosystem.
Many animals eat away and trample the vegetation hence reducing / depleting the number of producers.
-Lead to gully erosion hence carrying away some of the underground and crawling animals (Consumers)
K.C.S.E Biology Q & A - MODEL 2004PP1QN19
Explain how a biotic factors affect plants
In windy conditions the rate of transpiration increases; wind disperses fruits/ seeds; is an agent of pollination; acc. Spores for seed.
Changes in temperatures affects the rate of photosynthesis and other biochemical reactions/ metabolic reactions/ enzymatic reactions/ enzymatic reactions, temperature increases rate of transpiration;
Plants need light for photosynthesis, some plants need light for flowering/ photoperiodism/ seeds like lettuce require light for germination.
When humidity is low, the rate of transpiration increases;
Each plant requires a specific pH to grow well/ acidic/ alkalinity/ neutral;
Plants with salt tolerant tissues grow in saline area, plants in estuaries adjust to salt fluctuations;
North facing slopes in temperature lands have more plants than south facing slope
Plants on windward side have stunted/ distorted growth;
Comparisons of mountains and valleys
Description of other areas with other topographies e.g. River valley rainfall/ water
- Fewer plants in areas/ semi arid and
- Water is needed for germination/ is a raw material for photosynthesis/ dissolves/ minerals salts/ provides turgidity for support/ fruits/ seeds
Variation in atmospheric pressure affect availability of CO+2+ which affects photosynthesis and low pressure increase rate of transpiration; and affect amount of oxygen; for respiration
Mineral salts/ trace elements
- Affects distribution of plants in the soils
- Plants thrive well where there are mineral salts in the soil
Plants living in the soil deficient in particular mineral element have special methods obtaining it; for example legumes obtaining from nitrogen by fixation or carnivorous.
K.C.S.E Biology Q & A - MODEL 2004PP1QN18
How is the mammalian skin adapted to its functions?
K.C.S.E Biology Q & A - MODEL 2003PP1QN19
Describe how fruits and seeds are suited to their modes of dispersal.
Water dispersed fruit / seeds
K.C.S.E Biology Q & A - MODEL 2003PP1QN18
Describe the functions of the various parts of the human eye.
Sclerotic layer – (made up of collagen fibres thus) protects the eye maintains shape of eyeball.
Lens – Refracts light rays / focuses light on retina
Vitrerous aqueous humour once.
Aqueous Humour – Nourishes cornea / lens Refracts light
Irus – ( pigmented thus) – gives the eye its colour / absorbs light controls amount of light entering the eye / adjusts size of pupil impulses.
Pupil – light enters the eyes through pupil.
Retina – has photoreceptor cells / rods / cones / image formation ;l generates impulses.
Fever / yellow spot – visual acuity / most sensitive part of retina with only cones.
Blind spot – point where nerve fibre emerges from the optic nerve / where the optic nerve leaves the eye / point where blood vessels & nerve fibres enter the eye.
Optic nerve – transmit impulses to brain.
K.C.S.E Biology Q & A - MODEL 2003PP1QN17
Some students used a model to demonstrate the effect of sweating on human body temperature. Two boiling tubes A and B were filled with hot water. The temperature of water in the tubes was taken at the start of the experiment and then at 5 minutes interval. The surface of tube A was continuously wiped with a piece of cotton wool soaked in methylated spirit. The results obtained are shown in the table below.
a) On the same axes, plot graphs of temperature of water in the tubes against time.
b) At what rate was the water – cooling in tube A?
c) Why was tube B included in the set up?
d) Account for the rate of cooling in tube A.
e) State two processes of heat loss in tube b.
f) What would be the expected results if tube A was insulated?
g) What would the insulation be comparable to in:
h) Name the structures in the human body that detect:
i) External temperature changes
ii) Internal temperature changes
b) 80 – 18 = 62; 2.48C /Min
d) Rate was faster in tube A; because the film of methylated sprit evaporated; removing heat from the tube;
e) Convection ; radiation
f) Lower rate of heat loss;
g) i) birds
h) i) external temperature changes
ii) Internal temperature changes
K.C.S.E Biology Q & A - MODEL 2002PP1QN20b
Describe how the cervical, lumbar and sacral vertebrae are suited to their functions.
K.C.S.E Biology Q & A - MODEL 2002PP1QN20
Name three types of skeletons found in multicellular animals