8. Faunal Diversity
Protista
The kingdom Protista comprises a diverse group of eukaryotic microorganisms that are predominantly unicellular. Though simple in organization, protists exhibit a wide range of nutritional modes, locomotory structures, and ecological roles. They are traditionally grouped into three major categories based on their resemblance to animals, plants, or fungi.
Classification of Protista
- Animal‑like protists (Protozoa) – heterotrophic, motile, unicellular.
- Plant‑like protists (Algae) – photosynthetic, possess chlorophyll, range from unicellular to multicellular seaweeds.
- Fungus‑like protists (Slime molds) – decomposers, exhibit spore formation and amoeboid feeding phases.
Protozoa
Protozoa are unicellular, heterotrophic organisms that move using specialized structures such as pseudopodia, flagella, or cilia. They inhabit freshwater, marine, and terrestrial environments, often playing crucial roles in food webs and nutrient cycling.
Classification up to Class
- Sarcodina (Amoeboid) – locomotion via temporary extensions called pseudopodia. Example: Amoeba proteus.
- Mastigophora (Flagellates) – possess one or more whip‑like flagella. Examples: Trypanosoma brucei (causes sleeping sickness) and Euglena gracilis (mixotrophic).
- Ciliophora (Ciliates) – move by numerous short cilia. Example: Paramecium caudatum.
- Sporozoa (Apicomplexa) – non‑motile, spore‑forming, obligate parasites. Example: Plasmodium vivax (malaria parasite).
Paramecium caudatum
Paramecium caudatum is a classic model ciliate used in laboratory studies.
Habits and Habitat
Found in freshwater ponds, lakes, and stagnant water bodies rich in decaying organic matter. It is free‑living and feeds on bacteria and small algae.
Structure
- Shape: Slipper‑shaped, asymmetrical.
- Locomotory organelles: Dense covering of cilia that beat in coordinated waves.
- Oral groove and cytostome: A ventral indentation leading to the cell mouth where food vacuoles form.
- Contractile vacuole: Expels excess water to maintain osmotic balance.
- Nuclei: A large macronucleus governing daily functions and a small micronucleus involved in sexual 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.
The rate of asexual proliferation can be expressed as:
N = N₀ × 2ⁿ
where N₀ is the initial population, n is the number of fission cycles, and N is the final population.
Economic Importance
- Serves as a food source for micro‑invertebrates and larval fish.
- Widely used in research on cell biology, genetics, and toxicology due to its simple culture and observable behaviors.
Plasmodium vivax
Plasmodium vivax is a protozoan parasite responsible for benign tertian malaria in humans.
Habits and Habitat
Obligate intracellular parasite of human erythrocytes; transmitted by the bite of an infected female Anopheles mosquito.
Structure (Life‑cycle Stages)
- Sporozoite: Motile, inoculated into human skin during mosquito bite.
- Merozoite: Result of schizogony in liver hepatocytes and erythrocytes; invades new red blood cells.
- Trophozoite: Feeding stage within RBCs, appears as a ring‑form.
- Gametocyte: Sexual precursor taken up by mosquito; develops into gametes in the mosquito gut.
Reproduction
- Sexual (in mosquito gut): Gametocytes fuse to form a zygote → ookinete → oocyst → sporozoites.
- Asexual (in human host):
- Liver stage (exo‑erythrocytic schizogony): sporozoites → schizonts → thousands of merozoites.
- Blood stage (erythrocytic schizogony): merozoites → ring trophozoites → schizonts → release of merozoites.
Life‑Cycle Overview
- Infected mosquito bites human → sporozoites enter bloodstream.
- Sporozoites travel to liver → invade hepatocytes → undergo schizogony.
- Merozoites released into bloodstream → invade erythrocytes → repeat asexual cycles.
- Some parasites differentiate into male and female gametocytes.
- Mosquito ingests gametocytes during blood meal → sexual reproduction in gut → sporozoites migrate to salivary glands.
Economic Importance
- Causes malaria, a major public health burden in tropical and subtropical regions.
- Leads to anemia, fever, and socioeconomic losses due to morbidity and mortality.
- Emergence of drug‑resistant strains complicates treatment and control efforts.
Animalia
Kingdom Animalia encompasses multicellular, heterotrophic eukaryotes that lack cell walls. Animals exhibit a hierarchical organization from cells to organ systems, diverse body plans, symmetries, cavities, and segmentation patterns.
Levels of Organization
- Cellular: Loose association of independent cells (e.g., sponges).
- Tissue: Groups of similar cells performing a specific function (e.g., epithelial tissue).
- Organ: Structures composed of two or more tissue types (e.g., stomach).
- Organ system: Integrated group of organs working together (e.g., digestive system).
Body Plan
- Cell aggregate: Cells loosely associated, as in sponges.
- Blind sac: Single opening serving as both mouth and anus (e.g., cnidarians).
- Tube‑within‑tube: Digestive tract with separate mouth and anus, surrounded by body wall (e.g., nematodes, annelids).
- Compartmentalized: Internal organs housed in distinct body cavities (e.g., vertebrates).
Body Symmetry
- Radial: Body parts arranged around a central axis (e.g., jellyfish, sea stars).
- Bilateral: Left and right halves are mirror images (e.g., insects, vertebrates).
- Asymmetric: No plane of symmetry (e.g., some sponges).
Body Cavity
- Acoelomate: No body cavity; mesoderm fills space between gut and body wall (e.g., flatworms).
- Pseudocoelomate: Body cavity not fully lined by mesoderm (e.g., roundworms).
- Coelomate: True coelom completely surrounded by mesodermal lining (e.g., earthworms, vertebrates).
Segmentation
- Metameric (segmented): Body divided into repeating units called metameres (e.g., earthworms, arthropods).
- Non‑segmented: Body lacks true metameric repetition (e.g., molluscs, cnidarians).
Classification of Animal Phyla (up to Class)
| Phylum | Key Features | Classes (Examples) |
|---|---|---|
| Porifera | Asymmetrical, porous body, choanocytes for water flow | Calcarea, Hexactinellida, Demospongiae |
| Coelenterata (Cnidaria) | Radial symmetry, cnidocytes, polyp & medusa forms | Hydrozoa, Scyphozoa, Anthozoa |
| Platyhelminthes | Dorso‑ventrally flattened, acoelomate, hermaphroditic | Turbellaria, Trematoda, Cestoda |
| Aschelminthes (Nemathelminthes) | Round, cylindrical, pseudocoelomate | Nematoda, Rotifera |
| Annelida | Segmented, true coelom, setae (in many) | Polychaeta, Oligochaeta, Hirudinea |
| Arthropoda | Jointed appendages, chitinous exoskeleton, molting | Insecta, Arachnida, Crustacea, Myriapoda |
| Mollusca | Soft body, mantle, often shell, muscular foot | Gastropoda, Bivalvia, Cephalopoda |
| Echinodermata | Spiny skin, water vascular system, radial symmetry (adult) | Asteroidea, Echinoidea, Holothuroidea |
| Chordata | Notochord, dorsal hollow nerve cord, pharyngeal gill slits | Subphyla: Urochordata, Cephalochordata, Vertebrata |
Earthworm (Pheretima posthuma)
The common earthworm is a vital soil organism that contributes to nutrient cycling and soil structure.
Habit and Habitat
Found in moist, temperate soils worldwide; prefers organic‑rich environments and avoids waterlogged or extremely dry conditions.
External Features
- Segmented body: Consists of 100‑150 similar metameres.
- Clitellum: Thickened glandular segment involved in reproduction.
- Setae: Small chitinous bristles projecting from each segment, aiding locomotion.
- Prostomium: Lobelike structure overlying the mouth.
Digestive System
The alimentary canal is a straight tube running from mouth to anus, with specialized regions:
- Mouth → Pharynx (muscular, creates suction)
- Oesophagus (transports food)
- Crop (storage)
- Gizzard (muscular, grinds soil and organic particles)
- Intestine (major site of digestion and absorption, typhlosole increases surface area)
- Anus (egestion)
- Types: Septal nephridia (in each septum), integumentary nephridia (in body wall), pharyngeal nephridia (in pharynx).
- Structure of a septal nephridium:
- Nephrostome – ciliated funnel opening into coelom.
- Coiled tubule – site of filtration and reabsorption.
- Bladder – stores urine before release via nephridiopore.
- Male: Paired testes in early segments, seminal vesicles for sperm storage, vas deferens leading to the male genital pore.
- Female: Paired ovaries, oviducts leading to female genital pore, spermathecae that store sperm received during copulation.
- Soil aeration and improvement of texture through burrowing.
- Vermicomposting – conversion of organic waste into nutrient‑rich compost.
- Used as bait in fishing.
- Assist in sewage treatment by breaking down sludge.
- Moist skin: Glandular, facilitates cutaneous respiration.
- Tympanum: Circular ear membrane behind the eye.
- Webbed feet: Aid in swimming.
- Nictitating membrane: Transparent third eyelid protecting the eye underwater.
- Cutaneous: Gas exchange across moist skin (major contributor at rest).
- Buccal: Exchange in the lining of the mouth cavity.
- Pulmonary: Exchange in the lungs (important during activity).
- Male: Testes located near kidneys, vasa efferentia transport sperm to the kidneys, then via vas deferens to the cloaca.
- Female: Paired ovaries, oviducts (with anterior uterus-like region) leading to the cloaca; the uterus stores eggs temporarily before laying.
Physiology involves secretion of enzymes (proteases, amylases, cellulases) and peristaltic movements that mix food with digestive juices.
Excretory System
Excretion is carried out by nephridia, tubular structures that filter coelomic fluid.
Nervous System
Consists of a cerebral ganglion (brain) linked to a ventral nerve cord with segmental ganglia; peripheral nerves innervate body wall and organs.
Working mechanism: a simple reflex arc – sensory neuron → interneuron in ganglion → motor neuron → muscle contraction.
Reproductive Systems
Copulation
Two earthworms align ventral surfaces, exchange sperm via the male pores, and store received sperm in spermathecae.
Cocoon Formation
The clitellum secretes a mucous cocoon that slides over the anterior end, collecting eggs and sperm; fertilization occurs inside the cocoon, which then deposits in the soil.
Economic Importance
Frog (Rana tigrina)
The Indian bullfrog is a semi‑aquatic amphibian that exhibits typical vertebrate organ systems.
Habit and Habitat
Inhabits freshwater ponds, marshes, and paddy fields; requires moist skin for respiration and spends time both in water and on land.
External Features
Digestive System
The alimentary canal: Mouth → Pharynx → Oesophagus → Stomach → Small intestine (duodenum, ileum) → Large intestine → Cloaca.
Digestive glands: Liver (produces bile), Pancreas (secretes enzymes and bicarbonate). Physiology involves enzymatic breakdown of proteins, lipids, and carbohydrates, followed by absorption in the intestine.
Blood Vascular System
Features a three‑chambered heart: two atria (right and left) and a single ventricle. Oxygen‑poor blood from the body enters the right atrium, oxygen‑rich blood from the lungs enters the left atrium; both empty into the ventricle which pumps blood to the lungs and body via the truncus arteriosus. The sinus venosus collects venous blood before it enters the right atrium.
Double circulation ensures partial separation of oxygenated and deoxygenated blood, increasing metabolic efficiency.
Respiratory System
Respiration occurs through three surfaces:
Ventilation is driven by buccal pumping; oxygen diffuses into blood and carbon dioxide diffuses out.
Reproductive System
Fertilization is external; the female releases eggs into water, the male releases sperm simultaneously, and fertilization occurs in the surrounding medium.
This concludes the detailed treatment of Protista and Animalia as required for the chapter. All subtopics have been addressed with definitions, examples, classification, and illustrative diagrams where appropriate.