biology essay atika

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Biology Paper 1 Questions and Answers - KCSE 2020 past papers

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Instructions to candidates

• Answer  all  the questions.
• Candidates should answer the questions in English.

Answer  all  the questions in the spaces provided.

• Name the taxonomic grouping that contains individuals with most similarities.   (1 mark)
• budding in yeast; (1 mark) 
• enlargement of the eye pupil in dim light.  (1 mark)
• Explain why there is no grass in most dense forests. (2 marks)
• State  one  structural difference between a cell wall and a cell membrane. (1 mark)

• Name the Kingdom to which the organism belongs. (1 mark)
• State the mode of nutrition for the organism. (1 mark)
• Name the part labelled E. (1 mark)
• State  two  functions of the part labelled E. (2 marks)
• State the importance of a well-developed blood capillary network in the alveoli. (1 mark)
• Name the genetic disorder in humans that is characterised by inability of blood to clot. (I mark)

• Account for the shape of the sketch made in (a) above. (2 marks)
• Explain why plants have lower respiratory rates compared to animals. (l mark)
• State  two  situations in plants when the rate of respiration rises more than normal. (2 marks)
• Explain why most plants growing in water-logged areas die before attaining maturity. (3 marks)

• the meaning of the term imbibition (1 mark)
• why the dry mass of the endosperm decreases while that of the embryo increases. (2 marks)
• State  two  characteristic features used to classify members of Class Coniferales. (2 marks) 

• Name the type of growth curve shown. (1 mark)
• Name the Phylum where members show the type of growth curve illustrated. (1 mark)
• State  two  limitations of using fossil records in retracing evolutionary history of living organisms.(2 marks)
• Describe cell biology as an evidence of organic evolution. (3 marks)

• Name the process that takes place around the 14th day. (1 mark))
• Name  two  hormones produced at the follicular phase. (2 marks)
• Under which two conditions would the cycle be interrupted? (2 marks)
• State  two  reasons why blood reaching the glomerulus is always under high pressure. (2 marks)
• the hormone that was deficient in the patient: (1 mark)
• the gland that produces the hormone named in (a) above; (1 mark) 
• the disease the individual was likely to be suffering from. (1 mark) 

• Name enzymes S and T. S (1 mark) T (1 mark)
• Name the part of the alimentary canal where enzyme T is likely to be found. (1 mark)
• Explain your answer in b(i) above. (2 marks)
• Explain the biological significance of completing a dose of antibiotics. (3 marks)
• State  two  reasons why females with Turners' Syndrome are infertile. (2 marks)) 
• Define the term "field of view" as used in microscopy. (1 mark)
• State  two  functions of the body tube of a light microscope. (2 marks)
• Give a reason why it is  not  advisable to use water in cleaning a microscope. (1 mark) 
• Explain the role of blood capillaries in thermoregulation. (2 marks)

• the hormone K (1 mark)
• gland L that produces ecdysone hormone (1 mark)
• State the role of ecdysone hormone in the growth and development of insects. (1 mark)
• Name process M (1 mark)
• Account for the rapid increase in size of organisms immediately after moulting. (2 marks)
• Explain why the leaf of a sisal plant has a thick and shiny cuticle. (2 marks)
• Explain why an individual with blood group AB can only donate blood to an individual with the same blood group. (2 marks)

• process N (1 mark)
• polysaccharide p (1 mark)
• State  two  conditions necessary for the formation of compound Q. (2 marks)
• State  two  environmental conditions necessary for process N to take place. (2 marks)

MARKING SCHEME

• (Asexual) reproduction; Rej sexual
• Irritability/ Response (to stimulus) /Sensitivity
• Form canopies/shadows/shade; which prevent light from reaching grass; grass die/fail to flourish due to their inability to photosynthesis; 
• Cell wall is (fully) permeable while cell membrane is semi-permeable. (cell wall has larger pores while cell membrane has smaller pores)
• Cell wall is (mainly) made up of cellulose (fibres) while cell membrane has a (double) protein layer sandwiching a lipid layer; Acc. lipoprotein
• Cell wall is rigid, tougher ( cannot burst) while cell membrane is weaker (bursts)
• Fungi; Acc. fungi
• Saprophytism/saprophytic/food on dead decaying (organic) matter; Rej. Saprophyte
• Hypha/Hyphae; Acc. mycelium Rhizoids
• Secretes digestive enzymes(for external digestion); 
• Anchors the organism/mushroom (firmly) onto the substrate. Acc. anchorage.
• Absorbs digested food materials/Absorbs water and mineral salts/ions.
• Increases the surface area for (efficient) exchange/transport of respiratory gases ( oxygen and carbon (IV) oxide)
• Haemophilia; Acc. Hemophilia

• The rate of diffusion increases with the increase in temperature; Increase in temperature increases the kinetic energy of the (diffusing) molecules (increasing the rate of diffusion).
• Plants are less active than animals, hence require lower amount of energy than animals.
• During germination (to generate energy required for the process.
• During rapid growth/cell division (at the tips of roots/shoots).
• During active uptake/transport of substances (through the roots).
• Waterlogging submerges the plant root system; Cutting off supply of oxygen to the roots/soil surrounding the roots.
• (Aerobic) respiration in the roots is hampered
• active uptake/transport of materials is affected (leading to the death of the affected plants).
• K- Ulna L- Radius
• (Rapid) absorption of water by (germinating) seed (through the micropyle/seed coat).
• During germination, stored food in the endosperm is broken down/hydrolyzed/oxidized; to provide nutrients for the growing embryo.
• Presence of cones
• Naked seeds, seeds not enclosed in fruits
• Xerophytic characteristics/needle-like leaves/ thick waxy cuticle/sunken stomata.
• Intermittent/staircase (growth curve)
• arthropoda; correctly spelt Acc. arthropoda/Athropoda/athropoda    Rej. Anthropoda/ anthropoda
• Missing links due to complete decomposition of some organisms.  Acc. some parts decomposing
• Distortion of parts during sedimentation.
• Destruction of fossils by geological activities (earthquakes/faulting/mass movement of earth surfaces/volcanicity) 
• Presence of similar cell organelles ( mitochondria, ribosomes,lysosomes);
• Similar biological chemicals(ATP/proteins/DNA); 
• Similar blood pigmentation in tissues of some groups of animals show they have a common phytogenetic origin.
• Follicle stimulating hormone Rej. FSH
• Oestrogen/Estrogen
• Luteinizing hormone  Rej. LH
• (Drastic) change in weather/environment.
• Pregnancy/Implantation/Conception   Rej. fertilisation
• Emotional instability (anger, stress, anxiety).
• Renal artery branches directly from (dorsal) aorta whose blood under pressure
• Afferent arteriole/supplying blood is broader than efferent taking out blood.
• Diabetes mellitus    Rej. Diabetes alone
• S - Pepesin; Acc.  Chymosin/Rennin  Rej. Renin T- Trypsin
• In the duodenum, the medium is alkaline/basic; favouring the optimal working of the enzyme (T) as illustrated
• To completely kill/contain the (targeted) pathogens; Since failure to take full dose accords the pathogens an opportunity to develop resistance to the drug; the pathogen mutates(overtime) giving rise to a new strain; finally the drug becomes ineffective.
• They lack ovaries
• Have small uterus
• Less number of chromosomes.
• A circular area seen (on the stage) when focusing/viewing through the eyepiece of a microscope.
• Holds the revolving nose piece/objective lenses in place
• Holds the ocular/eyepiece (lens) in place
• To avoid rusting
• To avoid interference with visibility of the lens.
• Constrict during cold/low temperatures; to conserve heat
• Dilate during hot/high temperature; to facilitate heat loss
• Juvenile (hormone)
• prothoracic (gland)
• Ecdysone (hormone) causes metamorphosis; or causes the larval stage (of an insect to change/metamorphosize into pupa and pupa into adult.
• Complete Metamorphosis
• During moulting (the tough/hard impermeable) exoskeleton is shed; allowing the (soft permeable) larvae to take in air/water leading to rapid growth (which in turn results to increase in size of the organism).
• (Sisal is a xerophyte) the thick cuticle enables it to conserve water; reduce water loss;
• It is shiny to reflect light,minimizing evaporation by radiation.
• The individuals blood has both antigen A and B; which will coagulate/agglutimate with antibodies a and b; found in individuals with blood groups A,B and O; OWTTE
• Photosynthesis
• Respiratory enzymes
• Absence/little oxygen
• Optimum temperature
• Water/Moisture
• Carbon (IV) oxide

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