1970-05-23 — Page 26

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英中會考生物科答案

堅道英文書院撰答

Suggested Answers

for

H.K. Cartifieate or Education Examination (English)

Biology (Conventional Questions

(o) The rates of transpiration of a leafy shoot

under different environmental conditions could be measured accurately by a potometer. The whole apparatus was eat up as shown in the diagram below-

・Leafy shoot -Water

Scale

Capillary tube

-Tap of reservoir

In setting up the petometer threë important precautions should be noted: (1) The joints in the apparatus must be greased to make them air tight. (ii) The leafy shoot used in the apparatus must be thoroughly soaked, with water by cutting it in water. (iii) The whole apparatu must be kept air tight and there should be no sir bubble left in the bottle. As the whole apparatus was ready put it under different environmental conditions, and the rate of transpiration was recorded by means or a scale attached to the capillary tube. 195 transpiration took place water filled in the capillary tube withdraw from the end and

ne and and readings taken...

From the readinge obtained, we found that the rate of transpiration is greater in conditiens, where there were sunlight, high temperature, moving air, and low humidity,

3. Give a brief explanation (to to 6 lines) of th

importance of Four of the following:-

fresh fruit and vegetables in our di

water in the germination of seade,

tree planting in Hong Kong

synovial fluid

inguminous plants

regulation of body temperature by the skin of a-mammal.

From the biological point of view, food- stuffs are required by the body for maintain- ing vital activities and normal growth.

ITOBA ITUITAæ such as tomate, lemon, orange and black-currant and vegetables are the best source of Vitamin A and 0 which are essential for the normal growth of the boay, the maintenance of health of epithelial cells and the healthy condition of capillary wallss Furthermore, carbohydrates, the okief energy producing food, are also obtained fron many of succulent fruitEy

(b) The germination or seeds can only be the wor

considerable physiological activities within the seeds. Without the absorption of water, development cannot cours. During this process the water serves to soften the sesa coat and swollen it, and the seed coat finally ruptures. In addition the stored food materials turn into a solution form and more water is drawn into the mood as a result of:

(c) As compare with many other countries, the

percentage of atmospheric carbon dioxide of Hong Kong is likely to become higher. This gas is produced mainly by both animal's breathing and combustion of fuel and coal. Since the trees (green plants) synthesi14

TAGIT COOK Irom atqospheric orbon 10x106 and water by the process of photosynthesis, thus tres planting in Hong Kong is important in removing carbon dioxide present in the atmosphere, Furthermore the oxygen formed

the process of photosynthesis maintaine the constant concentration of atmospherio Dzygen.

(d) The osvity of a movable joint is filled with

a synovial fluid which serves as lubricant. to reduce friction between two bones.

(e) The roots of leguminous plants have swollen root-nodules which are packed with millions of nitrogen-fixing bacteria, eig. Rhizobium. These bacteria are able to convert nitrogen in the soil atmosphere into nitrogenous compounds as food for the plants and at the same time the planta supply carbohydrates to the bacteria. Furthermore the soil is fertilized by the decay of the plants which intensifies the nitrate content in the soil

This is done by the evaporation of sweat, and by the contraction or dilation of the skin capillaries.

During sweating, the activity of sweat glands can be regulated rate of sweating, and

amount of the amount of sweat determines the latent body heat liberated during evaporation. of avsat.

Another way of temperature regulation 19 by the dilation of skin capillaries which gawas more blood to flow near the surface, and thus the heat loses from the epidermis by.

On a conduction, convection and radiation. cold day, the contraction of the skin. capillaries permits only a small amount of blood to flow near the skin surface, thus reducing the Loss of heat.

4. (a) Give an illustrated account of the structure

and life history of Dodder.

(b)

Describe the differences in the mode of fare Dodder from those of fi) a mould and (11) spirogyra,

(a) Dodder 10 a plant parasite round on a variety

of green plants such as olovar, nettle and Gores. Ita thread-like pink stems twine round the stam or it host. At frequent intervála haustoria penetrate the hostis vascular tissuss and enable it to obtain supplies or food and water. Although the pink flowers are so small, but each one has sepals, patala, five stamans and an ovary formed from the bases of two par pels, The early life of the dodder is normal, germination of the seed resulting in the production of a root and a shoot, but, as soon as iom shoot come a in contact with the atin of the host plant and penetrates into the vascular tisause of the host with haustoria, its root dien away

·Scale leaf Haustoria

Stem of Dodder's host -Clusters of

pink flowers

-Stem of

Douder

External Structure of Dodder.

•Stem of Dodder Vascular tissue

of Dodder

Vascular

bundle of host's stem

Haustorium

Internal Structure of the stem

of Dodder

The re-story of Dodder falls into

the following stagasi-

In summer; the clusters of pink bisexual flowere appears at the axial and 11e between the stem and scale leaves, Bacn or these flowers may produce four-seeded fruit.

(11) In autumn, the mature seeds are dis peraed

by wind to soil where they still do not germinate until the host, eig, clover. "well developed.

The germination of seeds usually taken place in the late spring. At first, a Ball root is sent out to absorb water, and

The spiral like stem grow upwarde. whole seedling is very simple showing in feature, for it has no real root and shoot systems. After a suitable host plant is attached by the seedling, it senda out haustoria and twines round the stem of. the host. Then the temporay root of the seedling dies off and finally it de panda on the host for food and water supplies.

Root

(3) A mature plant body

and its host

-Clusters pink flowers.

Soil surface

-Radicle

A germinating

Seed

·shoot

(2) A seedling

Diagrams showing the life-history of Dodder

(b) Doaanr * the parasitic mods of life. arising

from its sten are little diac-like, absorbing organe called haustoria. Each haustorium produces calls which connect the water pipes, (xylem) and food pipes (phloem) of the dodder with those of its host's plant, so that water, mineral salts and complex organzo food can be ebao bad from the host into the dodder.

A mould (e.g, mucor) is known as the #aprophytic mode of life. It lives on the host surface, such as bread, which 18 caused to decay and is destroyed. The reading hyphae of the fungus, by production of certain enzymes, enable the solid starch of the bread to be converted 1030 a sugar? solution which 18 then absorbed through. the walls of hyphae into the proto It also needs to absorb minerals and aitrogen in the form of amino acids for Its growth and reproduction.

1) Spirogyra 18 a green water plant and.......

leads a holophytic mode of lize. It mexes ite food in the same way as other graes plants by the process of photosynthesis, It contains chloroplasts and survives in water containing dissolved ourbon dioxide, so that under the presence of sunlight. staroh 18 manufactured by the procean or photosynthesis. By the formation of this carbohydrate, it can synthesize body naterials sufficiently for its existence and reproduction..

5.(a) List Four animain and Four plants in a named

babitat that you have studied.

(b) Constrüôt a simplified food web diagram for the habitat and describe how the plants and animals there are interdependent for their food supplies.

Four animals and Four planta round 17 a freak water pond are l-

(1) Larvae of mosquito

(11) Tadpoles of Frog

(111) Dragon fly nympha

(iv) certain fishes (e.g. Roaon. Leaches)

(v) Duokweed

(vi) Liverwort (vii) Hornwort (viii) Elodea

A simplified food web diagram to snow wne interdependence of the planta and animale according to their food supplies:-

Large green plants (eg. Duckweed and Elidea)

Fowl

Tadpoles of frog Larvae of mosquito.

Many fishes e.g. Roach Dragon fly nympha

certain Leeches

As in general throughout nature; the praASTY food-producere are the green plants, which.

through photosynthesis, are able to transform the energy present in light in the form of. chemical anergy of sugar. In so doing carbon is assimilated from oarbon dioxide,

The sugar formed can be converted Eato proteins by the plants, provided that the appropriate mineral elements are present, these must be obtained in ponds. The supply of (minorals is replenished as the plants and

animals die and are decomposed by Bacteria.

The herbivorous animals such as tadpoles of frog and large of mosquito feed on the planta and, in their turn, provide food for the carnivores, such as the dragon-fly nymphs and rosch. In the pond if too many of these. carnivores are present, there is likely ultimately to be in difficiency of food, for them, because the plant growth will be Inhibited by lack of minerale,