JAMB Biology Guide: Evolution, Classification, and Life Histories
This guide traces the “Increasing Complexity” of life. In JAMB, questions often focus on which organism is more advanced and why.
1. Kingdom Monera: The Prokaryotic Foundation
Monerans are the simplest living things. They lack a true nucleus (Prokaryotic).
- Key Organisms: Bacteria and Blue-green algae (Cyanobacteria).
- Characteristics: Unicellular, microscopic, reproduce mainly by binary fission.
- JAMB Tip: Blue-green algae are the pioneers of photosynthesis, though they lack chloroplasts (pigments are spread in the cytoplasm).
2. Kingdom Protista: The Eukaryotic Transition
These are the first organisms to have a membrane-bound nucleus.
- Protozoans (Animal-like): * Amoeba: Moves via pseudopodia (false feet).
- Paramecium: Moves via cilia; contains a “contractile vacuole” for osmoregulation.
- Protophyta (Plant-like): * Euglena: The “bridge” organism. It has a flagellum for movement (animal-like) and chloroplasts for photosynthesis (plant-like).
3. Kingdom Fungi: The Decomposers
Fungi are non-photosynthetic and cell walls are made of chitin.
- Examples: Rhizopus (Bread mold) and Mushrooms.
- Life History: They reproduce via spores. They consist of a network of threads called hyphae, which form the mycelium.
- Economic Importance: Yeast is used in baking/brewing; some mushrooms are poisonous while others are edible.
4. Kingdom Plantae: The Conquest of Land
The evolution of plants is a move from “water-dependent” to “water-independent.”
I. Thallophyta (e.g., Spirogyra)
- Simple, aquatic plants. No roots, stems, or leaves.
- Spirogyra reproduces sexually via conjugation.
II. Bryophyta (e.g., Mosses and Liverworts)
- Transition: Known as the “Amphibians of the plant kingdom.” They live on land but need a film of water for their sperm to swim to the egg.
- Structural Note: They have rhizoids instead of true roots.
III. Pteridophyta (e.g., Ferns – Dryopteris)
- First Vascular Plants: They possess Xylem (water transport) and Phloem (food transport).
- Life History: Show clear Alternation of Generations.
IV. Spermatophyta (Seed Plants)
The most advanced plants.
- Gymnosperms: (e.g., Whistling pine, Cycads) Seeds are “naked” (not enclosed in fruit).
- Angiosperms: Flowering plants.
- Monocots: (e.g., Maize, Grass) One seed leaf, fibrous roots.
- Dicots: (e.g., Mango, Water leaf) Two seed leaves, taproot system.
5. Kingdom Animalia: Invertebrates to Vertebrates
The Advancement of Invertebrates
- Coelenterata (Hydra): Simple tissues, radial symmetry.
- Platyhelminthes (Flatworms – Taenia): Bilateral symmetry begins here.
- Nematoda (Roundworms): First to have a “tube-within-a-tube” body plan.
- Annelida (Earthworms): True segmentation and a closed circulatory system.
- Arthropoda (Insects, Spiders, Crabs): * Success Secrets: Exoskeleton (chitin) and jointed appendages.
- Economic Importance: Insects are pollinators (Bees), but also vectors of disease (Mosquitoes – Malaria; Tsetse fly – Sleeping sickness).
- Mollusca (Snails): Soft-bodied, usually with a shell.
The Advancement of Vertebrates (Phylum Chordata)
The trend is toward Homeothermy (maintaining constant body temp) and internal fertilization.
- Pisces (Fish): 2-chambered heart, gills, external fertilization.
- Amphibia (Toads): 3-chambered heart, live on land but breed in water.
- Reptilia (Lizards): 3-chambered heart (mostly), lay Amniotic eggs (land-ready).
- Aves (Birds): 4-chambered heart, feathers, warm-blooded.
- Mammalia: Most complex; have diaphragm, hair, and mammary glands.
Life Span Classification
Plants are also classified by how long they live:
- Annuals: 1 year/season (Maize).
- Biennials: 2 years (Carrot, Cabbage).
- Perennials: Many years (Cocoa, Orange).
JAMB Quick-Fire Revision Table
| Organism | Evolutionary Milestone |
| Bacteria | First life forms (Prokaryotic) |
| Euglena | Plant/Animal link |
| Ferns | First vascular tissues (Xylem/Phloem) |
| Reptiles | First truly terrestrial eggs |
| Mammals | Most advanced brain and parental care |
