8. Faunal Diversity

8. Faunal Diversity

8.1 Protista

Protista is a diverse kingdom of eukaryotic microorganisms that are predominantly unicellular. They are classified based on their nutritional mode and locomotion into three major groups: animal-like protozoa, plant-like algae, and fungus-like slime molds.

Classification of Protista

Protozoa – Classification up to Class

Protozoa are unicellular, heterotrophic, and motile organisms. They are divided into four major classes based on locomotory structures:

1. Sarcodina (Amoeboid) – Move by extending pseudopodia. Example: Amoeba proteus.
2. Mastigophora (Flagellates) – Possess one or more flagella. Examples: Trypanosoma brucei (cause of sleeping sickness) and Euglena gracilis (mixotrophic).
3. Ciliophora (Ciliates) – Use cilia for locomotion and feeding. Example: Paramecium caudatum.
4. Sporozoa (Apicomplexa) – Non‑motile, spore‑forming, obligate parasites. Example: Plasmodium vivax (malaria parasite).

Paramecium caudatum

Habits and Habitat: Free‑living in freshwater ponds, stagnant water, and slow‑moving streams.

Structure: Slipper‑shaped cell covered with rows of cilia; an oral groove leads to the cytostome (cell mouth); two contractile vacuoles regulate water balance; a large macronucleus controls daily functions and a small micronucleus is involved in reproduction.

Reproduction:

• Asexual: Transverse binary fission – the cell divides perpendicular to its long axis, producing two daughter cells.
• Sexual: Conjugation – temporary union of two Paramecia, exchange of micronuclear material, followed by separation and subsequent fission.

Economic Importance: Serves as a food source for micro‑invertebrates; widely used in biological research (e.g., studying ciliary action, osmosis, and genetics).

Plasmodium vivax

Habits and Habitat: Obligate intracellular parasite of human erythrocytes; transmitted by the bite of an infected female Anopheles mosquito.

Structure (Life‑cycle Stages):

• Sporozoite: Infective form injected into human bloodstream.
• Merozoite: Result of schizogony in liver hepatocytes and erythrocytes; invades new RBCs.
• Trophozoite: Feeding stage inside RBCs.
• Gametocyte: Sexual precursor taken up by mosquito.

Reproduction:

• Sexual: Occurs in the mosquito gut – gametocytes fuse to form a zygote → ookinete → oocyst → sporozoites.
• Asexual: Takes place in human liver (exo‑erythrocytic schizogony) and erythrocytes (erythrocytic schizogony).

Life‑cycle Summary: Mosquito bite → sporozoites enter bloodstream → invade liver cells → develop into merozoites → released into bloodstream → invade RBCs → undergo asexual cycles → some differentiate into gametocytes → taken up by mosquito → sexual reproduction → new sporozoites migrate to salivary glands.

Economic Importance: Causes benign tertian malaria; significant public health burden in tropical regions; drives drug resistance research and vaccine development.



8.2 Animalia

The kingdom Animalia comprises multicellular, heterotrophic eukaryotes that lack cell walls. Animals exhibit a hierarchy of structural organization, varied body plans, symmetries, cavity types, and segmentation patterns.

Levels of Organization

• Cellular: Loose aggregation of similar cells (e.g., sponges).
• Tissue: Groups of similar cells performing a specific function (e.g., epithelial tissue).
• Organ: Structure composed of two or more tissue types (e.g., stomach).
• Organ System: Group of organs working together (e.g., digestive system).

Body Plans

• Cell‑aggregate: No true tissues; cells loosely associated (Porifera).
• Blind sac: Single opening serving as both mouth and anus (Cnidaria, Platyhelminthes).
• Tube‑within‑tube: Digestive tract with separate mouth and anus; body wall surrounds the gut (Annelida, Mollusca, Chordata).
• Compartmentalized: Internal body cavities separating organs (e.g., coelom in vertebrates).

Body Symmetry

• Radial: Body parts arranged around a central axis (Cnidaria, Echinodermata).
• Bilateral: Left and right halves are mirror images (most phyla).
• Asymmetric: No plane of symmetry (some sponges).

Body Cavity (Coelom)

• Acoelomate: No body cavity; parenchyma fills space between gut and body wall (Platyhelminthes).
• Pseudocoelomate: Body cavity partially lined with mesoderm (pseudocoel) (Nematoda, Rotifera).
• Coelomate: True coelom fully lined by mesoderm (Annelida, Mollusca, Chordata, etc.).

Segmentation

• Metameric (true segmentation): Body divided into repeating segments each with similar sets of organs (Annelida, Arthropoda, Chordata).
• Non‑segmented: Body lacks distinct repeating units (Mollusca, Echinodermata).

Classification of Phyla (up to Class) with Examples

Phylum	Key Features	Classes (examples)
Porifera	Asymmetrical, porous body, choanocytes, no true tissues	Calcarea (e.g., Sycon), Hexactinellida (glass sponges), Demospongiae (most sponges)
Coelenterata (Cnidaria)	Radial symmetry, cnidocytes, polyp & medusa forms	Hydrozoa (e.g., Obelia), Scyphozoa (jellyfish), Anthozoa (corals, sea anemones)
Platyhelminthes	Dorso‑ventrally flattened, acoelomate, hermaphroditic	Turbellaria (free‑living planaria), Trematoda (flukes), Cestoda (tapeworms)
Aschelminthes (Nemathelminthes)	Round, cylindrical, pseudocoelomate, complete digestive tract	Nematoda (roundworms, e.g., Ascaris), Rotifera (rotifers)
Annelida	Segmented, true coelom, setae or parapodia	Polychaeta (marine worms with parapodia), Oligochaeta (earthworms, leeches), Hirudinea (leeches)
Arthropoda	Jointed appendages, chitinous exoskeleton, segmented body	Insecta (e.g., Drosophila), Arachnida (spiders, scorpions), Crustacea (crabs, shrimp), Myriapoda (centipedes, millipedes)
Mollusca	Soft body, mantle, often shell, muscular foot	Gastropoda (snails, slugs), Bivalvia (clams, oysters), Cephalopoda (octopus, squid)
Echinodermata	Spiny skin, water vascular system, pentaradial symmetry (adults)	Asteroidea (starfish), Echinoidea (sea urchins, sand dollars), Holothuroidea (sea cucumbers)
Chordata	Notochord, dorsal hollow nerve cord, pharyngeal gill slits, post‑anal tail	Subphyla: Urochordata (tunicates), Cephalochordata (lancelets), Vertebrata (fish, amphibians, reptiles, birds, mammals)

Earthworm (Pheretima posthuma)

Habit and Habitat: Moist, organic‑rich soil; cosmopolitan distribution.

External Features:

• Metamerically segmented body (≈100–150 segments).
• Prominent clitellum (glandular thickening) near anterior third.
• Setae (bristles) on each segment for locomotion.
• Prostomium (lip‑like lobe) overhanging the mouth.

Digestive System:

• Alimentary canal: mouth → pharynx → oesophagus → crop → gizzard → intestine → anus.
• Physiology: Pharynx pumps soil; crop stores; gizzard grinds with aid of sand particles; intestine secretes enzymes (protease, amylase, lipase) and absorbs nutrients; peristaltic movements propel food.

Excretory System:

• Three types of nephridia:
  • Septal nephridia – located in each segment behind the septum.
  • Integumentary nephridia – attached to body wall.
  • Pharyngeal nephridia – present in pharyngeal segments.
• Structure of septal nephridia: coiled tubule with an internal nephrostome (ciliated funnel) that collects coelomic fluid; wastes expelled via nephridiopore.

Nervous System:

• Central: Bilobed brain (cerebral ganglia) in segment 3, ventral nerve cord with segmental ganglia.
• Peripheral: Segmental nerves arise from ganglia to body wall and viscera.
• Working mechanism: Simple reflex arc – sensory neuron → interneuron in ganglion → motor neuron → effector (muscle).

Reproductive Systems:

• Male: Paired testes in seminal vesicles, vasa deferentia leading to male pores.
• Female: Paired ovaries, oviducts leading to female pores; spermathecae store received sperm.

Copulation: Two worms align ventral surfaces; exchange of sperm occurs via mutual insertion; sperm stored in spermathecae.

Cocoon Formation: Clitellum secretes a mucous cocoon that slides over the anterior end, collecting eggs and sperm; fertilization occurs inside the cocoon; cocoon deposited in soil.

Economic Importance:

• Soil aeration and mixing – enhances fertility.
• Vermicomposting – converts organic waste into nutrient‑rich humus.
• Used as bait in fishing.
• Assist in sewage treatment by breaking down sludge.



Frog (Rana tigrina)

Habit and Habitat: Freshwater ponds, marshes, and moist terrestrial areas; semi‑aquatic.

External Features:

• Moist, permeable skin for cutaneous respiration.
• Prominent tympanum (eardrum) behind the eye.
• Webbed hind feet for swimming.
• Nictitating membrane (transparent third eyelid) protects eye underwater.

Digestive System:

• Alimentary canal: mouth → pharynx → oesophagus → stomach → small intestine → large intestine → cloaca.
• Digestive glands: Liver produces bile; pancreas secretes enzymes (amylase, lipase, trypsin) and bicarbonate.
• Physiology: Food captured by tongue, moistened by mucus, enzymes break down macromolecules; peristalsis moves chyme; nutrients absorbed in intestine; waste expelled via cloaca.

Blood Vascular System:

• Three‑chambered heart: two atria (left, right) and one ventricle.
• Double circulation: pulmonary circuit (lungs ↔ heart) and systemic circuit (body ↔ heart).
• Additional structures: Sinus venosus receives deoxygenated blood; truncus arteriosus distributes mixed blood.
• Oxygenated blood from lungs enters left atrium, deoxygenated from body enters right atrium; both empty into ventricle where partial mixing occurs before ejection.

Respiratory System:

• Respiratory organs: moist skin (cutaneous), buccal cavity (buccal), lungs (pulmonary).
• Physiology:
  • Cutaneous: Gas exchange across skin; requires moisture.
  • Buccal: Air drawn into buccal cavity, oxygen diffuses across buccal epithelium.
  • Pulmonary: Air inhaled into lungs; alveoli provide large surface area for exchange.
• Ventilation: Buccal pump forces air into lungs; skin diffusion supplements oxygen uptake, especially during hibernation.

Reproductive System:

• Male: Paired testes attached to kidneys; vasa deferentia transport sperm to cloaca.
• Female: Paired ovaries; oviducts (fallopian tubes) transport ova to uterus; uterus expands to hold eggs; cloaca receives both gametes and waste.

Breeding: External fertilization; male clasps female (amplexus); female releases eggs into water, male releases sperm; fertilized eggs develop into tadpoles.



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This concludes the detailed coverage of Protista and Animalia as outlined in the syllabus. The information presented includes definitions, classifications, structural diagrams, functional explanations, and ecological/economic relevance of the representative organisms.