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2015 WAEC Biology Theory (a)(i) What is sewage? (ii) State five effects of releasing untreated sewage into a stagnant...

Biology
WAEC 2015

(a)(i) What is sewage?
(ii) State five effects of releasing untreated sewage into a stagnant water body.

(b) Explain surface terracing as a soil conservation method.

(c) Explain the term adaptation.

(d) Explain two ways each by which the following organisms adapt to their habitats:
(i) hydrophytes
(ii) xerophytes. 
 

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Explanation

(i) Sewage : Waste matter/ feaces, urine, waste water from animals/industrial/domestic sources; that is dissolved/ suspended in water.

(ii) Effects of releasing untreated sewage into a stagnant water body;

  • Spread of water-borne diseases/correctly named diseases/microbes/pathogens
  • May be toxic/poisonous to aquatic life/organisms
  • Makes water unfit for consumption/use
  • Increased decomposition
  • Increased concentration of nutrients
  • Rapid growth of algae/aquatic plants/algal bloom/eutrophication
  • Depletion of oxygen
  • Suffocation/death of aquatic animals
  • Generates offensive odour/air pollution
  • Nutrient/nitrate/phosphate enrichment/accumulation in a water body; as a result of breakdown by bacteria. 

(b) Surface terracing as a soil conservation method :
A method of controlling erosion on a gentle/steep slope of hill; flat horizontal areas are constructed on which crops are cultivated; following the contour; steps/walls are built along the contous; plughing is also done along the contours; reduces the speed of water running down the slopes. 

(c) Adaptation : Is the possession of the characteristic/trait/behaviour/structure/feature; that evolved over a period of time; enable an organism to survive and reproduce; in response to changes in the environment/habitat.

(d) Adaptation of; 
(i) Hydrophytes

  1. Some hydrophytes lack/have reduced roots/root hairs/root caps
  2. do not need firm anchorage in water/wetland
  3.  presence of large air space parenchyma in roots/leaves; provide support for buoyancy
  4. Presence of hairs on the leaves; to prevent blockage of the stomata
  5.  stomatal pores; occur only at the upper epidermis of the leaves to aid transpiration/loss of water
  6.  numerous adventitious roots and root hairs; aid the absorption of water/mineral salts
  7. small size of the plant; for buoyancy/floating in water
  8. waxy upper surface of the leaf; to prevent clogging of the leaf by water
  9.  long petiole/leaf stalk to support/ expose the broad lamina for photosynthesis
  10. long flower stalk/pedicel; to expose flower for pollination/ pollinating agents
  11. presence of breathing roots/pneumatophores; for breathing/gaseous exchange.

Xerophytes

  1. possession of thick succulent leaves/stem; for storing water
  2. reduction of leaves to spines; to reduce water loss/rate of transpiration
  3. thick waxy cuticle on epidermis; to reduce water-loss/transpiration
  4. possession of long tap root system; tp obtain water from great depth of soil
  5. presence of sunken stomata; to reduce water loss
  6.  reduced number of stomata; to prevent excessive water loss
  7.  possession of multiple epidermal layers; for water conservation/to reduce water loss. 

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WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
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WAEC May/June 2024 - Practice for Objective & Theory - From 1988 till date, download app now - 99995
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC offline past questions - with all answers and explanations in one app - Download for free