Practical 1: Non-chordates

1. Study of Protozoa Whole Mounts
2. Reproduction in Paramecium (Slides)
3. Examination of Pond Water for Protista
4. Study of Museum Specimens (Non-chordate Phyla)
5. Study of Ctenophora Specimen
6. Mounts from Periplaneta (Cockroach)

1. Study of Protozoa Whole Mounts

This exercise involves identifying and drawing prepared slides of common protozoans.

A. Amoeba

Principle: To observe the key features of an amoeboid protozoan.
Observation: Look for an irregular, shapeless mass of protoplasm.
Identification Points (Draw and Label):
- Pseudopodia: Finger-like, blunt extensions of the cytoplasm (ectoplasm and endoplasm) used for locomotion and feeding.
- Plasma Membrane: The thin outer boundary.
- Nucleus: A single, large, disc-shaped nucleus, usually stained dark.
- Contractile Vacuole: A clear, spherical vacuole for osmoregulation.
- Food Vacuoles: Small, dark vesicles containing food particles.

[Image of Amoeba proteus labeled diagram]

B. Euglena

Principle: To observe the features of a flagellated protozoan, which is a connecting link between plants and animals.
Observation: Look for a small, green, spindle-shaped organism.
Identification Points (Draw and Label):
- Pellicle: A flexible outer covering, maintaining its shape.
- Flagellum: A single, long, whip-like structure at the anterior end for locomotion.
- Stigma (Eyespot): A small, reddish pigment spot that is light-sensitive.
- Chloroplasts: Green, elongated structures for photosynthesis.
- Nucleus: A large, centrally located nucleus.
- Contractile Vacuole: A vacuole at the anterior end.

[Image of Euglena labeled diagram]

C. Paramecium

Principle: To observe the features of a ciliated protozoan.
Observation: Look for a slipper-shaped organism, often stained pink or purple.
Identification Points (Draw and Label):
- Shape: "Slipper-shaped," with a blunt anterior and pointed posterior.
- Cilia: Numerous small, hair-like projections covering the entire body for locomotion.
- Oral Groove: A large depression on one side leading to the cytostome (mouth).
- Macronucleus: A large, kidney-bean-shaped nucleus controlling metabolic functions.
- Micronucleus: A small, spherical nucleus (often hard to see) involved in reproduction.
- Contractile Vacuoles: Two "star-shaped" vacuoles (one at each end) for osmoregulation.

[Image of Paramecium caudatum labeled diagram]

2. Reproduction in Paramecium (Slides)

A. Binary Fission (Asexual)

Principle: To observe the transverse binary fission in *Paramecium*.
Observation: Look for a single *Paramecium* that is elongated and "pinched" in the middle.
Identification Points:
1. The macronucleus elongates and divides amitotically.
2. The micronucleus divides mitotically.
3. A transverse furrow (constriction) appears in the middle of the cell.
4. The cell divides into two smaller daughter cells (a proter and an opisthe).

[Image of Paramecium binary fission stages]

B. Conjugation (Sexual)

Principle: To observe sexual reproduction in *Paramecium* for genetic recombination.
Observation: Look for two *Paramecium* individuals fused together along their oral grooves.
Identification Points:
1. Two cells (conjugants) are attached.
2. The macronucleus degenerates (disappears).
3. The micronucleus undergoes meiosis to form haploid pronuclei.
4. A migratory (male) pronucleus from each cell crosses over and fuses with the stationary (female) pronucleus of the other.
5. This forms a diploid zygote nucleus (synkaryon).
6. The cells then separate (exconjugants) and undergo further divisions to restore the normal nuclear setup.

3. Examination of Pond Water for Protista

Principle: To observe the wide diversity of living protists and other microorganisms in a natural aquatic ecosystem.
Requirements: Pond water sample (ideally with algae or decaying leaves), microscope, glass slide, coverslip, dropper.
Procedure:
1. Collect a pond water sample.
2. Place one drop of the sample on a clean glass slide.
3. Gently lower a coverslip over the drop, avoiding air bubbles.
4. Observe under the microscope, starting with low power and then moving to high power.
5. Reduce the diaphragm aperture (light) to increase contrast, making transparent organisms visible.
Observation: Look for, identify, and draw various moving organisms. Common examples include:
- Ciliates: *Paramecium*, *Vorticella* (bell-shaped, on a stalk), *Stentor* (trumpet-shaped).
- Flagellates: *Euglena*, *Volvox* (large, green, spherical colonies).
- Amoeboids: *Amoeba*.
- Algae: Diatoms (geometric shapes), *Spirogyra* (spiral chloroplasts).
- Metazoans: Rotifers (wheel-like ciliary organs), *Daphnia* (water fleas), *Cyclops*.

4. Study of Museum Specimens (Non-chordate Phyla)

This is a "spotting" exercise. You must identify the specimen, classify it (Phylum and Class), and list 2-3 key reasons for your identification.

Phylum	Specimen Example	Key Identification Points (Comments)
Porifera	Sycon (Scypha)	1. Vase-shaped body. 2. Attached to a substratum. 3. Body surface is porous with spicules. 4. A large opening (osculum) at the top.
Cnidaria	Obelia (Colony)	1. Plant-like, branching colony (polymorphic). 2. Shows polyps (hydranths for feeding) and blastostyles (for reproduction).
Cnidaria	Aurelia (Jellyfish)	1. Bell-shaped or umbrella-shaped medusa. 2. Four oral arms and marginal tentacles. 3. Four horseshoe-shaped gonads are visible.
Platyhelminthes	Taenia solium (Tapeworm)	1. Dorsoventrally flattened, ribbon-like body. 2. Body divided into scolex (head), neck, and proglottids (segments). 3. Scolex has suckers and hooks for attachment.
Platyhelminthes	Fasciola hepatica (Liver Fluke)	1. Dorsoventrally flattened, leaf-like body. 2. Shows two suckers (oral and ventral) for attachment. 3. Incomplete digestive tract.
Nemathelminthes	Ascaris (Roundworm)	1. Long, cylindrical, unsegmented body, pointed at both ends. 2. Sexual dimorphism: Female is longer and straight; Male is shorter with a curved posterior.
Annelida	Nereis (Clamworm)	1. Metamerically segmented body. 2. Each segment (except head and tail) bears a pair of fleshy, paddle-like appendages called parapodia for swimming.
Annelida	Hirudinaria (Leech)	1. Dorsoventrally flattened, segmented body. 2. Lacks setae and parapodia. 3. Has an anterior sucker (oral) and a posterior sucker for attachment and locomotion.
Arthropoda	Palaemon (Prawn)	1. Body has a hard exoskeleton. 2. Body divided into an anterior cephalothorax (head and thorax fused) and a posterior abdomen. 3. Has jointed appendages.
Arthropoda	Limulus (King Crab)	1. "Living fossil." 2. Body is boat-shaped, covered by a hard carapace. 3. Has a long, spike-like telson (tail).
Mollusca	Pila (Apple Snail)	1. Asymmetrical, soft body. 2. Body is enclosed in a spirally coiled shell. 3. Possesses a muscular foot for creeping.
Mollusca	Octopus	1. Soft, unsegmented body with a large head and a bag-like visceral mass. 2. Shell is absent. 3. Head bears 8 long, flexible arms (tentacles) with suckers.
Echinodermata	Asterias (Starfish)	1. Pentamerous radial symmetry (star-shaped). 2. Body has a central disc and five arms. 3. Spiny-skinned (exoskeleton of calcareous plates). 4. A small, button-like madreporite is visible on the aboral (upper) surface.

5. Study of Ctenophora Specimen

Specimen Example: Pleurobrachia (Sea Gooseberry)
Principle: To identify the features of the phylum Ctenophora (comb jellies).
Identification Points:
1. A transparent, gelatinous, pear-shaped body.
2. Possesses eight ciliated comb rows (ctenes) on the body for locomotion, which may be visible.
3. Has a pair of long, branched tentacles that are retractile into sheaths (unlike Cnidaria).
4. Lacks stinging cells (nematocysts).

6. Mounts from Periplaneta (Cockroach)

This involves observing prepared permanent slides or fresh mounts of dissected cockroach parts.

A. Mouth Parts (Biting and Chewing Type)

Observation: Look for the five major components arranged around the mouth.
Identification Points (Draw and Label):
1. Labrum: The flat, flap-like "upper lip."
2. Mandibles: A pair of hard, toothed, pincer-like jaws for grinding food.
3. Maxillae: A pair of accessory jaws, each with a 5-segmented palp (maxillary palp) for holding and sensing food.
4. Labium: The "lower lip," formed by fused secondary maxillae, bearing a pair of 3-segmented palps (labial palps).
5. Hypopharynx: A tongue-like structure within the mouth.

B. Digestive System

Observation: A long tube divided into three distinct regions.
Identification Points (Draw and Label):
1. Foregut: Includes the pharynx, esophagus, a large crop (for storage), and a muscular gizzard (proventriculus) for grinding.
2. Midgut (Mesenteron): A narrower tube. At its junction with the gizzard are 6-8 finger-like hepatic caeca (for digestive enzymes).
3. Hindgut: At its junction with the midgut are numerous thin, thread-like Malpighian tubules (excretory organs). The hindgut consists of the ileum, colon, and rectum.

[Image of Periplaneta (cockroach) digestive system labeled]

C. Nervous System

Observation: A "ladder-like" nervous system typical of arthropods.
Identification Points (Draw and Label):
1. Supra-oesophageal Ganglion (Brain): A large ganglion located above the esophagus.
2. Circum-oesophageal Connectives: Nerves that loop around the esophagus, connecting the brain to the sub-oesophageal ganglion.
3. Ventral Nerve Cord: A double nerve cord running along the ventral side of the body.
4. Segmental Ganglia: Paired, fused ganglia in each thoracic and abdominal segment, giving it a ladder-like appearance.

[Image of Periplaneta (cockroach) nervous system labeled]