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K.C.S.E Biology Q & A - MODEL 2011PP1QN19
Apart from the lungs, name two gaseous exchange surfaces in a frog.
answers
K.C.S.E Biology Q & A - MODEL 2010PP1QN15
A potted plant was kept in the dark for 48 hours, Two leaves X and Y were treated as shown in the diagram below.
The experimental set-up was kept in sunlight for 6 hours after which a starch test was carried out on the two leaves. .
(a) What were the results of the starch test on leaves X and Y’? X Y (b) Give reasons for your answers in (a) above.
answers
a) X — Starch present;
Y-Starch absent; b) X - Acts as a control; Y - CO2 absent absorbed by potassium hydroxide pellets; Explain why it is not advisable to be in a poorly ventilated room with a burning charcoal stove.24/6/2020
K.C.S.E Biology Q & A - MODEL 2010PP1QN14
Explain why it is not advisable to be in a poorly ventilated room with a burning charcoal stove.
answer
K.C.S.E Biology Q & A - MODEL 2010PP1QN05
State three ways in which a respiratory surface is adapted to its function.
answers
K.C.S.E Biology Q & A - MODEL 2009PP1QN16
How is the surface named in (a) above suited to its function
ANSWERS
K.C.S.E Biology Q & A - MODEL 2009PP1QN16
Name the gaseous exchange surface in insects
ANSWER
K.C.S.E Biology Q & A - MODEL 2008PP2QN08
Describe the mechanism of gaseous exchange in a mammal
answers
Breathing in
External intercostals muscles contract; internal, intercostals muscles relax lifting/ raising the ribcage upwards and outwards; muscles of diaphragm contract. It flattens the volume of the thoracic cavity increases; pressure decrease; higher air pressure in the atmosphere forces air into the lungs Breathing out External intercostals/ muscles relax; internal intercostals muscles contract moving the ribcage downwards and inwards; the muscles of diaphragm relax, the diaphragm assumes dome shape; volume of thoracic cavity decreases; while pressure increases; higher pressure forces air out of the lungs
K.C.S.E Biology Q & A - MODEL 2008PP2QN08
State four characteristics of gaseous exchange surfaces
answers
K.C.S.E Biology Q & A - MODEL 2008PP1QN18
How is the epidermis of a leaf of a green plant adapted to its function
ANSWERS
K.C.S.E Biology Q & A - MODEL 2007PP2QN01
The diagram below represents some gaseous exchange structures in humans
​(a) Name the structures labeled K, L, and M
K……………………………………………………………………………. L……………………………………………………………………………. M…………………………………………………………………………… (b) How is the structure labeled J suited to its function? (c) Name the process by which inhaled air moves from the structure labeled L into blood capillaries
ANSWERS
​( a) K- Pleural membranes
L- Alveolus M- Intercostal muscles (b) Has c- shaped cartilage rings that support it preventing it from collapsing and allow free flow of air Inner lining has secreting cells that trap fine dust particles and micro- organisms Inner lining has hair like structures called cilia that enhance upward movement of the mucus to the larynx (c) Diffusion
K.C.S.E Biology Q & A - MODEL 2007PP1QN12
Name two structures for gaseous exchange in aquatic plants
ANSWERS
K.C.S.E Biology Q & A - MODEL 2006PP1QN24
State four ways in which respiratory surfaces are suited to their function.
answers
State two ways in which floating leaves of aquatic plants are adapted to gaseous exchange.19/6/2020
K.C.S.E Biology Q & A - MODEL 2006PP1QN05
State two ways in which floating leaves of aquatic plants are adapted to gaseous exchange.
answers
​K.C.S.E Biology Q & A - MODEL 2005PP1QN18
Describe how gaseous exchange takes place in terrestrial Plants.
answers
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. Stomata 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 2005PP1QN11
The diagram below represents a part of the rib cage.
​a) Name the parts labeled W, Y and Z.
W …………………………………………………… Y ……………………………………………………. Z …………………………………………………….. b) How does the part labeled Z facilitates breathing in?
answers
​a) W – Spinal column / reutebral column
Y – Sternum Z – Intercostal muscles. b) The external intercostals muscles contract while the internal intercostals. Muscles relax. This movement pulls the ribs upwards and outwards. The diaghragm muscles contracts (flattens).The thoracic volume increase while the pressure reduces, leading to atmospheric air rushing into the lungs through the nose and trachea hence inflating the lungs. |
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