Collection, Preservation and Observation of Specimens

A Specimen is the whole or part of an organism used in biological studies.

To differentiate between plants and animals, there is need to collect, observe and record the external features of various types of plants and animals.

Reasons for collecting specimens in biology

• For further observations;
• Preservation for future reference;

Precautions during collection, preservation and observation of specimens

• Collect the needed number of specimens only.
• No specimen should be harmed during the process of capture and preservation.
• Poisonous, biting or stinging specimens should be handled with forceps.
• The natural habitats of each specimen should not be damaged or altered.
• The live specimen should be returned to their habitat after observation.

Collection of specimens

Methods and apparatus for collecting specimens include:

• Bait trap-for attracting and trapping small animals like; rats, squirrels, moles and mice.
• Fish net-for catching small fish and other small aquatic organisms like; crabs, prawns and frogs.
• Pair of forceps-for picking up small stinging animals e.g. scorpions.
• Pooter-for sucking small animals from rocks, cracks, crevices in walls and wood or from small holes like; bedbugs.
• Sweep net-for catching flying insects like bees.
• Pitfall trap-for trapping small crawling animals like; ants.

Preservation of specimens

Specimen bottles of different sizes are used.

They may be ventilated or not depending on whether the specimen is needed alive or dead.

Specimen should be put in bottles with perforated covers to avoid suffocating them.

Observation of specimens

This is done either by:

• Using naked eyes.
• Magnifying hand lenses to enlarge the image of small specimens for better observation.
• Light microscope for observing microscopic specimens.

Observation of external features of plants

Procedure

• Cut a few branches of the plants to be observed. Uprooting should only be done when it is absolutely necessary. Plants with medicinal value and the species should not be uprooted.
• Observe the shapes of leaves, type of leaves, different types of stems, roots and flowers of collected plants.

Leaves

• These are green parts of the plants that are attached to the stem or branches.
• The leaf may be oval shaped, arrowhead, round, cordate or linear shaped.
• The leaf may be simple or compound.
• The leaf margin may be smooth, serrated, dentate or crenated.
• The leaf apex may be pointed or rounded.
• The leaf may be arranged forming a network or parallel venation.
• Leaf arrangement on the stem may be whorl, alternate or opposite.

Stem

• This is the aerial part above the ground which bear the branches, leaves and flowers.
• Observe the nodes, internodes, auxiliary buds, leaves, flower buds and flowers.
• Some plants have such organs like thorns for protection, adventitious roots for horizontally growing stems and tendrils for support of weak stems (in passion).
• Other plants have underground fleshy stems for storage of food substances. They include rhizomes (ginger), stem tuber (Irish potatoes) and corms (yams).

Root

• This is the underground part of a plant.
• Different types of roots can be observed in different plants.
• They include fibrous roots in grass; tap roots in herbaceous plants, prop roots in maize and buttress roots in mangrove trees.
• Flower
• This is the coloured or white part produced by a plant before a fruit.
• The flower may be open (wind pollinated), closed (insect pollinated), head shaped, spike shaped, raceme shaped, pinnacle shaped or umbel shaped.

Observation of external features of animals.

Procedure.

• Collect as many animals as possible using sweep nets, pooter, bait traps and fish nets.
• Insects, rats, centipedes, millipedes and earthworms should be put in specimen bottles covered with a perforated cover to avoid suffocating the animals.
• Observe the coat cover, sensory structures, locomotory structures, modes of feeding and mouth parts of collected animals.