Chapter 1: Apply principles of classification

In applied biology, the precise classification of collection instruments is essential for accurate identification, monitoring, and assessment of organisms in aquatic and terrestrial environments. Professionals working in water quality labs, environmental consultancies, and research institutions rely on these instruments to collect representative samples that inform public health decisions, conservation strategies, and regulatory compliance. Understanding the principles behind instrument classification ensures that applied biologists select, use, and maintain tools appropriately, thereby upholding scientific rigor and data integrity in Kenyan contexts such as county water departments, hospital laboratories, and agricultural research stations.

1.1 Collection instruments

Collection instruments are the tools a biologist uses to take organisms, parts of organisms and their surroundings from the field or laboratory without damaging them or mixing them up. A specimen taken with the wrong instrument may arrive crushed, contaminated or incomplete, and it can no longer be identified or classified with confidence. Every later step of this unit, from naming a specimen to placing it in a kingdom, depends on a specimen that was collected cleanly, so the choice, specification and care of the instrument come first.

An instrument is chosen for the organism it must take (a floating alga, a soil beetle, a leaf), for the place where it will work (open water, a pond bottom, leaf litter, a tree canopy) and for what happens to the specimen next (identification alive, preservation, culture in the laboratory). This topic describes the instruments themselves. The procedures for using them to collect specimens, and the preservation and labelling of what is collected, belong to Collection of specimens.

Types of collection instruments

The instruments are grouped below by the kind of specimen they take. Each group has a few tools that do the same job in different places.

Instruments are active when the collector works them (nets, grabs, swabs) and passive when they are left to collect on their own (pitfall traps, settlement plates).

Instruments for aquatic specimens

Water is sampled in two ways. A water sampler such as the Van Dorn takes a closed volume from a known depth, so the organisms and chemistry of that layer are preserved together. A net filters a large volume and keeps only what is larger than its mesh, so it concentrates organisms but loses the smallest ones. For that reason a phytoplankton net and a zooplankton net are never swapped: the coarse mesh lets algal cells pass through, and the fine mesh clogs quickly with algae when towed for animals.

Bottom samplers are chosen by the sediment. A grab closes its jaws on soft mud and returns a disturbed bulk sample, while a corer returns a column with the layers in order. Hand nets and kick nets are used in shallow streams and ponds, where the collector wades in and works the net through weed and over the bed.

Instruments for land and air specimens

Instruments for land specimens are matched to where the animal lives. Ground-dwelling animals fall into pitfall traps, soil animals are taken with an auger or by hand sorting of a measured soil sample, and insects on plants are swept or beaten into a net or tray. Flying insects are taken with a light trap at night, in which an ultraviolet or white lamp draws moths and beetles to a sheet or into a collecting funnel, or with a Malaise trap, a tent-like net that guides flying insects up into a bottle.

Small mammals are caught alive in box traps set along a line and checked at fixed times. Bats and birds are caught in mist nets, which are fine nets stretched between poles and watched constantly. Both uses can need written permission from the authority that looks after wildlife and protected areas, so the permit is arranged before any instrument is bought or set.

Instruments for plants and for microbes

A plant specimen is cut with clean secateurs so that the stem is not torn, placed in a plastic bag or a vasculum (a metal field box) to stop it wilting, and later flattened in a plant press. A hand lens of 10× magnification is carried in the field for checking small features such as hairs and flower parts.

Microbial sampling uses sterile instruments only. Swabs, scoops and screw-cap bottles are sterile before the trip (swabs come sterile and single-use) and are opened only at the moment of use, because a single airborne spore or a touch of a finger can add organisms that were never part of the sample. A loop or a sterile spatula takes colonies from a culture plate, and the loop is sterilised in a flame before and after use.

Containers, labels and recording tools

Every instrument is only half of the kit. The specimen needs a container (specimen tubes, vials, jars, paper envelopes for dry material, a cool box for live or microbial samples), a label that survives the journey (pencil on waterproof paper), and a record (a field notebook, a collection sheet, a camera and a hand-held GPS for the position). A killing jar for insects and a vial of 70 percent ethanol are part of the kit for insect work, and fixatives such as formalin are carried only in sealed, labelled containers and handled in a fume cupboard on return.

Specification of collection instruments

The specification of an instrument states what it is made of, its size and capacity, its mesh or pore size, and the conditions it was designed for. Reading it before the trip prevents common mistakes:

• Material: Glass gives a clear view of a sample and is easy to sterilise, but it breaks on rough ground, so plastic or metal is used in the field. Metal that corrodes in salt water, such as untreated steel, is replaced by stainless steel or plastic in coastal work.
• Capacity or size: A water sampler must hold enough water for the tests planned, and a net must have a wide enough mouth and a long enough body to filter without clogging.
• Mesh or pore size: The mesh decides what is kept and what escapes, so it is matched to the smallest organism wanted.
• Sterility: Instruments for microbes are supplied sterile and sealed, or are sterilised in an autoclave before use. Single-use swabs are thrown away after one sample and never cleaned or reused.
• Portability and robustness: A field instrument has to survive a rough journey, and it folds, packs flat or breaks down into parts that fit a field bag.
• Calibration: Where an instrument measures as it collects, such as a depth-marked sampler line or a graduated bottle, its markings are checked against a ruler or a measuring cylinder.

Selecting an instrument

Selection is a decision made in order. The following steps are worked through before every field trip:

1. State what is to be collected, for example aquatic insect larvae from a stream, or soil beetles in a plot, and whether the specimen must stay alive.
2. Describe the place: depth and flow of the water, type of ground, height of the vegetation, and how easily the site can be reached on foot.
3. Match the size of the target organism to the instrument, by choosing the mesh or trap size that keeps the smallest organism wanted.
4. Check the material against the place, choosing plastic or stainless steel where there is salt, mud or rough ground.
5. Confirm that the instrument can be sterilised or cleaned, if the sample will be cultured or tested for microbes.
6. Check what the instrument can legally and safely take: permits for wildlife, protective gloves and boots for work in water or soil, and the means to carry live specimens safely.
7. Count the instruments, spare nets, spare cups and containers, and pack them so that nothing needs to be borrowed in the field.

Example: A survey of invertebrates in a seasonal pond needs a hand net with a fine mesh for the larvae in the weed, a plankton net with a small-mesh cod end for the drifting animals in the open water, sterile bottles if the water is also to be tested for bacteria, and a field notebook, all packed in a bag with a cool box.

Care and maintenance of collection instruments

Care starts at the end of every trip, because dirt left on an instrument contaminates the next sample and corrodes the instrument.

• Rinsing and cleaning: Nets are rinsed in clean water, soaked briefly in mild detergent if they carried mud or algae, rinsed again and dried in shade, because strong sunlight weakens nylon. Metal parts are washed and wiped dry.
• Disinfecting between sites: Boots, nets and samplers that moved between ponds or streams are disinfected, so that organisms and pathogens are not carried from one water body to another.
• Inspection: Mesh is held up to the light for tears, ring joints and seals are checked for wear, and traps are checked for bent doors and broken springs.
• Sterilising: Glassware and metal tools for microbial work are sterilised in an autoclave or a hot-air oven according to the maker's instructions, and are kept wrapped until used.
• Storage: Instruments are dried completely and stored in a clean, dry place off the floor, with nets hung or loosely folded, so that they do not rot or grow mould.
• Replacement: Worn mesh, perished rubber seals and cracked containers are replaced. Consumables such as swabs, labels and preservative are restocked after every trip.
• Records: A register notes each instrument's use, repairs, and sterilisation dates, so that a worn or contaminated instrument is withdrawn before it spoils a sample.

Checks during use

Short checks at the point of use protect the quality of the specimen:

• Cleanliness: Confirm that the instrument and container are clean, and sterile where needed, before each sample.
• Condition: Look for damage that could let a specimen escape or be crushed.
• Fit for the job: Confirm that the mesh or size matches the organism wanted at that site.
• Labelling: Confirm that every container carries its label before it leaves the site, as set out in Collection of specimens.
• Handling: Wear gloves where the sample is soil, water or animal material, and wash the hands after every site.

Chapter Summary

This chapter explored the foundational principles of classification within taxonomical concepts, beginning with an examination of the various instruments used for specimen collection. Students learned how to select and classify appropriate tools based on the nature and requirements of the specimens being gathered. The process of specimen collection was then discussed in detail, emphasizing the importance of accurate handling and documentation, as well as the role of a portfolio of evidence in supporting scientific analysis and verification. The chapter also addressed methods for organizing and maintaining collected specimens, ensuring that records are reliable and can be referenced for future study. Finally, the general classification of specimens was covered, providing students with systematic approaches to group and identify organisms based on shared characteristics. By integrating these core topics, the chapter equipped learners with the skills necessary to apply taxonomical concepts effectively in both academic and field settings. This comprehensive approach ensures that students can confidently manage the entire process from collection to classification, supporting robust and credible scientific outcomes.