JAMB Biology Note- Evolution Among Organisms

Topic

Evolution Among Organisms

Sub-Topics

1. Monera (Prokaryotes): e.g., bacteria, blue-green algae
2. Protista (Protozoans and Protophyta): e.g., Amoeba, Euglena, Paramecium
3. Fungi: e.g., mushrooms, Rhizopus
4. Plantae (Plants):
   • Thallophyta: e.g., Spirogyra
   • Bryophyta: e.g., Brachmenium, Merchantia
   • Pteridophyta: e.g., Dryopteris
   • Spermatophyta: Gymnospermae and Angiospermae
5. Animalia (Animals):
   • Invertebrates: e.g., coelenterates, Platyhelminthes, Nematoda, Annelida, Arthropoda, mollusks
   • Vertebrates: e.g., pisces, amphibia, reptiles, aves, mammalia

Table of Contents

• Topic
• Sub-Topics
• A. Monera (Prokaryotes)
  • Examples
  • Characteristics
  • Evolutionary Significance
  • Structural Complexity
• B. Protista (Protozoans and Protophyta)
  • Examples
  • Characteristics
  • Evolutionary Significance
  • Structural Complexity
• C. Fungi
  • Examples
  • Characteristics
  • Evolutionary Significance
  • Structural Complexity
• D. Plantae (Plants)
  • 1. Thallophyta
  • 2. Bryophyta
  • 3. Pteridophyta
  • 4. Spermatophyta
    • a. Gymnosperms
    • b. Angiosperms
    • 1. Thallophyta
    • 2. Bryophyta
    • 3. Pteridophyta
    • 4. Spermatophyta
• E. Animalia (Animals)
  • 1. Invertebrates
  • Differences Among Invertebrates
  • 2. Vertebrates
    • a. Pisces
    • b. Amphibia
    • c. Reptilia
    • d. Aves
    • e. Mammalia
• Radial Symmetry vs. Other Types of Symmetry
  • • 1. Invertebrates
    • 2. Vertebrates
• Evolutionary Trends
  • 1. Increasing Structural Complexity
  • 2. Gradual Transition from Water to Land
  • 3. Advancements in Reproductive Strategies
• Economic Importance and Environmental Roles

A. Monera (Prokaryotes)

Examples

• Bacteria and blue-green algae (cyanobacteria).

Characteristics

• Unicellular organisms lacking membrane-bound organelles and nucleus.
• Genetic material exists as a circular DNA strand (plasmids may also be present).
• Reproduce asexually through binary fission.

Evolutionary Significance

• Represent the earliest life forms on Earth (~3.5 billion years ago).
• Cyanobacteria played a critical role in oxygenating the Earth’s atmosphere via photosynthesis.

Structural Complexity

• Simple structure with evolutionary features such as:
  • Flagella for movement.
  • Specialized membranes (e.g., thylakoids) for photosynthesis.

Prokaryotes: Organisms with no membrane-bound nucleus or organelles.

Plasmids: Circular DNA molecules found in prokaryotes, often carrying genes for antibiotic resistance.

Binary Fission: Asexual reproduction in which a cell divides into two genetically identical cells.

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B. Protista (Protozoans and Protophyta)

Examples

• Amoeba, Euglena, Paramecium.

Characteristics

• Unicellular eukaryotes with membrane-bound organelles and a defined nucleus.
• Nutrition:
  • Euglenoids exhibit both autotrophic (photosynthesis) and heterotrophic modes.
• Reproduction:
  • Both asexual (binary fission) and sexual (conjugation).

Evolutionary Significance

• Serve as a bridge between prokaryotes (Monera) and more complex eukaryotes (fungi, plants, and animals).
• First to exhibit cellular compartmentalization and advanced cell structures.

Structural Complexity

• Evolved movement and feeding mechanisms:
  • Cilia (Paramecium) and pseudopodia (Amoeba).

Eukaryotes: Organisms with membrane-bound nuclei and organelles.

Autotrophic Nutrition: Mode of nutrition in which organisms produce their own food (e.g., photosynthesis).

Heterotrophic Nutrition: Nutrition by consuming organic material from other organisms.

Pseudopodia: Temporary projections of cytoplasm used for movement and feeding in amoebas.

Cilia: Hair-like structures on the cell surface aiding in movement and feeding.

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C. Fungi

Examples

• Mushroom, Rhizopus, yeast.

Characteristics

• Can be unicellular (e.g., yeast) or multicellular (e.g., mushrooms).
• Lack chlorophyll; nutrition is:
  • Saprophytic (decomposers) or parasitic.
• Body composed of hyphae, forming a network called mycelium.

Evolutionary Significance

• Represent a distinct kingdom diverging from plants.
• Crucial in ecosystems as decomposers and symbionts (e.g., mycorrhizae).

Structural Complexity

• Developed reproductive structures (e.g., spores) for dispersal.
• Form complex symbiotic relationships (e.g., lichens with algae).

Hyphae: Thread-like filaments that form the mycelium of fungi.

Mycelium: Network of hyphae in fungi, responsible for nutrient absorption.

Saprophytic: Mode of nutrition where organisms feed on decaying organic matter.

Parasitic: Organisms that feed on living hosts, often harming them.

Spores: Reproductive cells capable of developing into a new organism without fusion.

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D. Plantae (Plants)

1. Thallophyta

• Example: Spirogyra.
• Characteristics:
  • Simple, multicellular, and non-vascular.
  • Reproduce by fragmentation or conjugation.
• Evolutionary Significance:
  • Represent early autotrophs and ancestors of land plants.

2. Bryophyta

• Examples: Mosses (Brachythecium), Liverworts (Marchantia).
• Characteristics:
  • Non-vascular plants requiring moist environments.
  • Exhibit alternation of generations (gametophyte and sporophyte stages).
• Evolutionary Significance:
  • First plants to colonize land.
  • Lack true roots but developed rhizoids for anchorage.

3. Pteridophyta

• Example: Ferns (Dryopteris).
• Characteristics:
  • Vascular plants with roots, stems, and leaves.
  • Reproduce via spores, lacking seeds.
• Evolutionary Significance:
  • Pioneered vascular tissue development, enabling larger size.

4. Spermatophyta

a. Gymnosperms

• Examples: Cycads, Conifers.
• Characteristics:
  • Produce naked seeds (not enclosed in fruits).
  • Adaptations like needle-like leaves for dry environments.
• Evolutionary Significance:
  • Advanced vascular system and seeds for survival.

b. Angiosperms

• Examples: Monocots (Maize), Dicots (Waterleaf).
• Characteristics:
  • Flowering plants with seeds enclosed in fruits.
  • Efficient pollination mechanisms (insects, wind).
• Evolutionary Significance:
  • Most diverse and dominant plant group.

1. Thallophyta

• Thallus: Simple, undifferentiated plant body without true roots, stems, or leaves.
• Fragmentation: Asexual reproduction where parts of an organism grow into a new organism.
• Conjugation: Exchange of genetic material between two cells, often in algae.

2. Bryophyta

• Rhizoids: Root-like structures in bryophytes, used for anchorage and water absorption.
• Alternation of Generations: Life cycle involving a multicellular haploid gametophyte and a multicellular diploid sporophyte stage.

3. Pteridophyta

• Vascular Plants: Plants with specialized tissues (xylem and phloem) for transporting water and nutrients.

4. Spermatophyta

• Gymnosperms: Seed-producing plants with naked seeds not enclosed in fruits.
• Angiosperms: Flowering plants with seeds enclosed within fruits.

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E. Animalia (Animals)

1. Invertebrates

• Coelenterates (e.g., Hydra): Radial symmetry, simple tissues.
• Platyhelminthes (e.g., Taenia): Bilateral symmetry, parasitic adaptations.
• Nematoda: Unsegmented, complete digestive systems.
• Annelida (e.g., Earthworms): Segmented bodies, closed circulatory systems.
• Arthropoda (e.g., Insects): Exoskeletons, jointed appendages, advanced sensory organs.
• Mollusca (e.g., Snails): Soft-bodied, developed organs.

Differences Among Invertebrates

Feature	Coelenterates (e.g., Hydra)	Platyhelminthes (e.g., Taenia)	Nematoda	Annelida (e.g., Earthworms)	Arthropoda (e.g., Insects)	Mollusca (e.g., Snails)
Symmetry	Radial symmetry	Bilateral symmetry	Bilateral symmetry	Bilateral symmetry	Bilateral symmetry	Bilateral symmetry
Body Segmentation	None	None	None	Segmented	Segmented body with jointed appendages	None
Circulatory System	None	None	None	Closed circulatory system	Open circulatory system	Open circulatory system
Digestive System	Incomplete or absent	Incomplete	Complete	Complete	Complete	Complete
Nervous System	Simple nerve net	Simple nerve cords	Simple nerve ring	Ventral nerve cord	Highly developed sensory organs	Simple nervous system
Body Covering	Soft body with no exoskeleton	Soft and flat	Cylindrical, unsegmented	Soft, segmented with setae or bristles	Hard exoskeleton made of chitin	Soft body, sometimes covered by a shell
Mode of Nutrition	Carnivorous or filter feeders	Parasitic	Parasitic or free-living	Detritivorous or predatory	Varied (herbivorous, carnivorous, etc.)	Mostly herbivorous or filter feeders
Reproductive System	Asexual and sexual reproduction	Hermaphroditic	Sexual reproduction	Sexual reproduction, some hermaphrodites	Sexual reproduction	Mostly sexual reproduction

2. Vertebrates

a. Pisces

• Examples: Sharks (cartilaginous), Bony fish.
• Adaptations for aquatic life: Gills and fins.

b. Amphibia

• Examples: Toads, Frogs.
• Transition between aquatic and terrestrial life with lungs and limbs.

c. Reptilia

• Examples: Lizards, Snakes.
• Adaptations for dry land: Scales, amniotic eggs.

d. Aves

• Examples: Birds.
• Adaptations for flight: Feathers, lightweight skeleton, high metabolism.

e. Mammalia

• Examples: Humans, Whales.
• Features: Hair, mammary glands, advanced brain functions.

Radial Symmetry vs. Other Types of Symmetry

Feature	Radial Symmetry	Bilateral Symmetry	Asymmetry
Definition	Body parts arranged around a central axis.	Body parts divided into two mirror-image halves by one plane.	No definite symmetry in body structure.
Examples	Coelenterates (e.g., Hydra, jellyfish), echinoderms (e.g., starfish).	Most animals, including humans, insects, and vertebrates.	Sponges (e.g., Porifera).
Plane of Symmetry	Multiple planes of symmetry through the central axis.	Only one plane of symmetry (left and right sides).	No plane of symmetry can divide the body.
Movement and Adaptation	Suited for sessile or slow-moving organisms; can interact with the environment from all sides.	Suited for active movement; associated with cephalization (development of a head region).	Not specialized for movement or symmetry.
Body Organization	Circular or cylindrical body plan.	Distinct anterior (front) and posterior (back) ends.	Irregular body structure.

1. Invertebrates

• Coelenterates: Radially symmetrical animals with simple tissues (e.g., Hydra).
• Bilateral Symmetry: Body plan with a single plane of symmetry, dividing the body into mirror halves.
• Segmented Body: Body divided into repeating units, as in annelids (e.g., earthworms).
• Exoskeleton: Hard outer covering providing support and protection, as in arthropods.

2. Vertebrates

• Cartilaginous Fish: Fish with skeletons made of cartilage (e.g., sharks).
• Amniotic Egg: Egg with a protective shell and internal membranes, allowing development on land.

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Evolutionary Trends

1. Increasing Structural Complexity

• From unicellular (Monera) to multicellular forms (Fungi, Plantae, Animalia).
• Specialization of tissues, organs, and systems.

2. Gradual Transition from Water to Land

• Bryophytes as pioneers.
• Amphibians as the first vertebrates adapting to terrestrial habitats.

3. Advancements in Reproductive Strategies

• From spores (Bryophyta, Pteridophyta) to seeds (Gymnosperms, Angiosperms).
• Internal fertilization in higher animals (e.g., mammals).

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Economic Importance and Environmental Roles

• Insects: Pollinators and crop pests.
• Plants: Food sources, oxygen production.
• Fungi: Decomposers, used in food and medicine.
• Animals: Ecological balance, food chain roles.