Wednesday, January 20, 2010

WAEC: 2009 SSCE BIOLOGY PRACTICAL EXAMINATION

LECTURE ON THE SPECIMENS PROVIDED FOR WAEC SSCE BIOLOGY PRACTICAL



THE SPECIMENS PROVIDED

GROUP I

SPECIMEN A: Water Lettuce

SPECIMEN B: Cactus Plant

SPECIMEN C: Amaranthus spp / Talinum spp



GROUP III

SPECIMEN H: Lungs of mammal

SPECIMEN J: Toad/Frog

SPECIMEN K: Maize leaf



CONCEPTION OF THE SPECIMENS

SPECIMEN A: WATER LETTUCE (Hydrophytes)
  • Habitat: Aquatic

  • Class: Angiosperm (flowering plant)

  • Mode of nutrition: Autotrophic (photosynthesis)

  • Mode of reproduction: Asexual (vegetative propagation)

  • Structure for reproduction: Stolon

OBSERVABLE FEATURE

  • it has stolon

  • it has thin cuticle on the leaves

  • it has air storage tissues

  • it has fibrous/adventitious root

  • it has green leaves

  • it has tiny hairs on leaves

STRUCTURAL ADAPTIVE FEATURES

  • Possession of light body for floating

  • Presence of tissues with air space and spongy tissues for flotation

  • Presence of hairy adventitious/fibrous root for water absorption and gaseous exchange

  • Possession of stolon which connects whorls of plants together and for vegetative propagation

  • Swollen leaf for buoyancy

  • Air storage tissues for buoyancy

  • Presence of whorls of spongy leaves for floatation

  • Stomata on upper surface of leaves for transpiration and gaseous exchange

  • Presence of waxy thin cuticle which prevents wetting of the leaves

  • Possession of tiny hairs on leaves which repel water

  • Poorly developed strengthening tissues which makes it flexible and able to withstand wave action

  • Presence of poorly developed conducting tissues

  • Possession of chloroplast for photosynthesis

  • Possession of air bladder for buoyancy

CHARACTERISTICS OF SPECIMEN A HABITAT

  • It has a fluctuating salt content
  • The soil is saturated and lack oxygen
  • The soil is readily washed away by the sea

ECOLOGICAL FACTORS FOR SPECIMEN A HABITAT

The factors that affect Specimen A in its habitat are as follows:

  • Water current
  • Water density and viscosity
  • Depth of water
  • Salinity
  • Dissolved oxygen
  • Light intensity