商業備華: 周三第張六第日五十月四年巴屣 WAH KIU YAT PO 報日嬌
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英中會考生物科答案 •歷百琴·
Section B
UR,G,FIE, (English) 1969
BIOLOGY
Suggested Answers
(1) Erepain, from the insestinal juice, which
completes the conversion of peptones or peptides into amino-acide.
(ii) Steapsin, from the pancreatic juice, which
changes fats, to glycerin and fatty acide. iii) Ptyalin, from the saliva of man, which
changes starob to maltose.
2.(a) By means of large labelled diagrams show the
external and internal structure of” a named' dicotyledonous seed.
What are the functions of the structures which
you have Labelled in the diagrams?
(b) What is meant. by vegetative propagation? What are the advantages of this process?
(c) By means of large labelled diagramė
illustrate the internal structure of any named bulb.
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TRE TILLED OUld whion stores food in the fleshy #Gale-lanvas arising from a shortened triangula stem. The future leaves and flowers are in the centre of food storing leaves. The annual oyola begins in autumn, the stored food being used in the growth of roots, leaves and flower while the excess food is stored in the aziflarý buda which become the future bèkbu
1.(a) What is digestion? Descride ne processes and
the patha by which the products of digestion are transported to the heart.
(b) What is an enzyme? Name three enzymes and snow)
what part each plays in the process of digestion,
Aria.'
(a) uigestion is the process of intake of food and
preparing it for absorption and assimilation through the blood stream from the villi of the small intestine in mammals.
The food in a mammal's diet is not in a form which can be immediately absorbed and assimilated. It therefore must be subjected to mechanical and chemical changes, called digestion, before it can be absorbed and used in the body of a mammal..
When food enters the mouth, it is ground up and mixed with saliva, a watery liquid produced by a number of salivary glands. In nan, the three pairs of salivary glande secress a saliva of mucin and ptyalin. The water in nucin will dissolve any soluble food as well as to lubricate the food, helping its pasosge from the mouth to the stomach through the oesophagus. The ptyalin digests the starch to soluble maltose. In many other animals, the saliva has little or no digestive function.
The food enters the stomach where it is churned and mixed with the gastric juice by the rhythmic contraction of the stomach wall. Normally liquid only enters into the stomach and pass downwards gradually without allowing to stay in the stomach while the solid food has to stay in the stomach for digestion. The gastric juice secreted by the gastric glanda contains pepsin, rennin and dilute hydro- chloric acid. The pepsin breaks down protein to peptones and proteoses; the rennin bears the responsibility to coagulate milk proteïn. The acid acidifies the stomach contents stopping the action of the ptyalin, but, enabling the pepsin and rennin to function.
At intervals the pyloric sphincter relaxes and the rhythmic movemeur or the stomach forces some of the chyme through inte the duodenum. Here it comes in contact with: (1) Bils, from the liver, emulsifies fata, neutralizes stomach acids and provides correct medium for other enzymes. (ii) Pancreatic juice, from the pancreas, which contains three digestive enzymes, the amylase, which changes starch to maltose; lipase, which changes fats to fatty acids and glycerol and trypsinogen, which combines with enterokinase to be come trypsin. By the action of trypsin, the protein and peptones are digested to amino-acids.
ii) Intestinal juice, from cells of the small intestine contains three carbohydrate- digesting enzymes, the maltase, which converte meltose into glucose; sucrase, which converts sucrose into glucose and fructose; and lactose, which converts lactose into galactose and glucose. The pravein digeeting enzymes in the intestini juice, called erspsin which completes the digestion of protein into amino-acids.
A short time after the food has entered the Ball intestine it is in a liquid. condition and ali digestable food has been digested and is ready for absorption.
The absorption of digested food takes place through the walls of the alimentary canal. The majority of the digested foods are absorbed by the villi in the jejunum and ileum of the small intestine, where the digestion of food is completed.
The digested carbonydrate (simple sugare į and tigested proteins (amino-acids) are absorbed through the epithelial cells into the capillaries of villi. By the way of heyatlo portal vein, the simple sugars and amino-acida in the blood óf villous capillaries are transported to the liver, where the exces8 sugar is converted into glycogan to be stored; the excesв amino-acid is deaminated into ures to be excreted. The required amounts of simple augar and amino-acide are then transported to the heart by the way of inferior vena cava which collects the blood from the hepatic vein of the layer.
The digested fats including fatty acids, glycerin, and droplets of oil enter the lacteals of the villi through the lymphatic vessels which join the blood circulation by the way of the thoracic duct, so that the fate absorbed are also passed into the blood-stream
(b) An enzyme can be defined as an organic protein
catalyst. It is produced by living cells, chiefly by that of the alimentary canal. Each a pecific enzyme acts only on a specific substance or group of substances and has no antagonistic action to each other.
The three named enzymes and their actions in the process of digestion are described as the faller
Ans. (a)
Side view
-Testa-
position
"of the
radicle
Hilum
Front View
position of the micropyle
Testa removes and the two cotyledons separated.
Coty (2017
-plumule
Radicle
Groove in which the plumuje pres
Diagrams illustrating the eternal. and internal structure o Broad Bean
The functions of the various, structures in the diagrams are döşoribed as "tha follown 1. (1) Testa - The outer layer which is thick and
tough, and serves to protect the internal parts of the seed. (11) Hilum - is the scar where the seed wa-
once attached to the fruit.
a tiny opening for the absorption of water for germination.
iii) Miaropyle
(iv) Plumul
-
- On germination, it gives rise to the future shoot of the plant. (V) Radiole On germination, it gives rise to
the future root of the plant vi) Cotyledon - it functions to store food for
the development of the embryo plant and to liberate the plumule by the elongation of it stalk.
(b) Vegetative propagation is the development or a new individual plant from the mother plant of a vegetative structure....e.g. food-storage organ, besides providing for perennation of the plant, may also provides for ita peproduction, by developing from one storage organ several new shoots which way then
become detached from the mother plant and from new individuals. This process of reproduction without producing flovere in called vegetative propagation.
The advantages of vegetative propagation are: (1) New plants develop quickly into perfect
replicas of their parents.
(11) Plentiful food is stored in the
reproductive organ to tide the plant over the early stages of growth. (iii) The new individual may be adapted to the
environment.
(c)
(iv) The process of reproduction is without the
help of the complicated mechanisma,
Flower bud
Triangular
Steak
-Food-Storage
Loaf
-Scale leat Foliage "Teat"
-Axillary bud
•Adventitious roots..
A Longitudinal Section of Tulip Bulb
3. (a) List the general characteristics of insects.
(11) State the methods which can be used to
control the varions atazos. in the life övol] of the mosquito." (0) (1) Why should the housefly be killed?
(11) What is the moonomio importance of the
Jabbage white butterfly?
(a) (13 by hold the sosquito be killed?
Ano.
(a) The general characteristics of insects ares (1) The body of an insect is protected by a
horny szo-skeleton This skeleton consists largely of a substance called chitin.. (2) The whole body of an insect is obviously segmented, and is olearly divisible into three parts. These are the head, thorax and abdomen.
3) At each side of the head of an insect is a large compound eye which is composed of few hundrede of simple eyes. Close to each bye there is an antenna. The mouth parts ar
pecially adapted for either chewing. Bucking or lapping.
4) The thorax consists of three segmenta only.
These are prothorax, mesothorax and. metathorax.
Each segment bears a pair of jointed leg on the ventral side, and one pair or two pairs of wings on the dorsal surface.
5) The number or segments in the abdomen of
the adult is eleven or lean. The terminal end of the last abdominal segment is modified as a genital opening.
6) The spiracies are located along the sides
of the thorax and abdomen. The tracheas leading from the spiracles form many branches in the internal tissue of the body.
(b) (1) The mosquito is considered as a pestiferous.
insect because most of mosquitoes are the carriera of diseases. Tropical dosquitoms (Anopheles) are the carriers of malaria, yellow fever, elephantiasis and dengue feve all of which affect man and in many canes ( can be fatal. The organisms causing the liseases are carried from one host to inother by the female mosquitoes, which thêm, ip while feeding. The economia effent con be very great.
(11) Kethods of control of mosquito are;—
1) Spraying standing water and svamps with
insecticides to kill the larvae.
<) Spraying water with paraffin to
suffocate the larvae.
Introducing fish, whión reed on •10 larva, to the water where the larvas breed,
→ Haluage projects in the breedinë
grounds.
Clearing water of weads to induce a flow of water and thun check thế lira cycle.
6) Spraying buildings, oaves eto, to kill
the hibernating females.
() Treatment of the diseasen carried, w.g.
alaria is treated by the usa of quinine or more recently by mapaQLLUS, and paludrine.
(0) (1) The hibit of the fly of visiting
indiscriminately human food and organis refuse is to some extent responsible for the spreading of diseases, Dysentiry is perhaps the commonest disassa mansad ka Sam
flies, but others are diphtheria, typhoid and anthrax. For above mentioned reasons, therefore the housefly should be killed... (ii) Insects may be either useful karaful, The
cabbage white butterflies are important in pollination of the "lowòring plants, but a great damage can be caused to orope by the larvae of cabbage white butterfly and often complete defoliation will result from a Beyore attack.
-(To be continued)