Comprehensive Study Guide: Biodiversity, Species Classification, and Ecosystem Dynamics

Fundamentals of Biodiversity

• Definition of Biodiversity: Biodiversity refers to the overall variety of living organisms found on Earth, encompassing plants, animals, fungi, and microorganisms.

• Definition of Species: A species is defined as a set of individuals that share the same distinct characteristics and possess the ability to mate and produce fertile offspring.

• The Three Levels of Biodiversity:

  • Genetic Diversity: Refers to the total variety of genes or inheritable characteristics present within a specific population of organisms.
  • Species Diversity: Refers to the total number and relative abundance of different species present within a specific geographical area.
  • Species Richness: The specific number of different species represented in a particular area.
  • Species Evenness: The relative abundance and distribution of individual members belonging to each species within a particular area.
  • Ecosystem Diversity: Refers to the variety of physical habitats and biological communities distributed across a landscape, including ecosystems such as forests, wetlands, grasslands, and aquatic environments.

• Ecological Niche:

  • An ecological niche is the totality of an organism's way of life, representing how it interacts with its environment and survives.
  • Core components of an ecological niche include:
  • Habitat: The physical place where the organism lives.
  • Diet: The types of food and nutrient sources consumed.
  • Activity: The behavioral patterns and timing of life functions.
  • Interspecific Interactions: How the organism interacts with other species within its community.

• Classification of Organisms by Ecological Role:

  • Specialist Species: Organisms that depend strictly on a specific habitat or a particular type of food to survive. They have narrow niches and are highly sensitive to environmental change.
  • Generalist Species: Organisms that can thrive in many different habitats and consume a wide variety of foods. They possess broad niches, which enable them to adapt readily to environmental changes.

• Classification of Species by Geographic Origin:

  • Native Species: Organisms that naturally evolved within a specific ecosystem. They are well-adapted and fully integrated into local food webs.
  • Endemic Species: Native species that can be found in one specific geographical place and nowhere else on Earth.
  • Indigenous Species: Native species that have a wider geographic range and naturally occur in several regions simultaneously.
  • Non-Native / Exotic Species: Organisms introduced—either intentionally or accidentally through human activities—into an area where they do not naturally occur.
  • Prominent local examples of introduced non-native species include:
    • Janitor Fish
    • Golden Apple Snail
    • Tilapia

Claim, Evidence, and Reasoning (CER) Framework

• Definition of CER: CER is a formal scientific method for answering questions and solving problems. It facilitates clear scientific explanations grounded in facts and logical thinking.

• Formula:   $\text{CER} = \text{Answer (Claim)} + \text{Proof (Evidence)} + \text{Explanation (Reasoning)}$

• Structural Components of CER:

  • Claim: The primary answer or solution proposed for a scientific question or problem.
  • Evidence: Specific facts, empirical observations, or scientific data that directly support the claim.
  • Reasoning: Scientific justification explaining how and why the provided evidence supports the claim.

• Case Study Scenario: The Disappearing Bees:

  • Context: A farming community observed a major decline in bee populations resulting from excessive pesticide application. Over subsequent months, fewer flowers produced fruits and vegetables, leading to smaller crop yields and a decline in animal populations dependent on those plants.
  • Problem Question: Should the community reduce pesticide use to protect the bee population? Why or why not?
  • Application of CER:
  • Claim: Bees are essential for maintaining healthy ecosystems.
  • Evidence: Bees act as key pollinators for flowers, facilitating plant reproduction and the formation of fruits and seeds.
  • Reasoning: Because bees enable plant reproduction, a reduction in bee populations directly reduces fruit and seed production, disrupting food availability across the entire ecosystem.

Classification of Threatened Species and IUCN Red List

• International Union for Conservation of Nature (IUCN):

  • The global authority on the status of the natural world and measures needed to safeguard it.
  • 2025 Global Assessment Statistics:
  • Total species assessed: $169\,420$ species.
  • Total threatened species facing potential extinction: $47\,000$ species.

• IUCN Red List Categories:

  • Extinct (EX): Assigned when there is no reasonable doubt that the last individual of the species has died.
  • Historical Examples: Passenger Pigeon, Dodo.
  • Extinct in the Wild (EW): Categorizes species known only to survive in captivity, cultivation, or as a naturalized population well outside their historical natural range.
  • Examples: Père David's deer, Franklin Tree.
  • Threatened Categories:
  • Critically Endangered (CR): Species facing an extremely high risk of extinction in the wild in the immediate future. Primary drivers include extreme habitat loss and severe hunting pressure.
  • Endangered (EN): Species facing a very high risk of extinction in the wild in the near future, largely driven by habitat destruction and overhunting.
  • Vulnerable (VU): Species facing a high risk of extinction in the wild if existing threat conditions continue unmitigated.
  • Near Threatened (NT): Species that do not currently qualify for a threatened status but are close to qualifying or are likely to qualify for a threatened category in the near future.
  • Least Concern (LC): Species with populations that are stable and abundant enough that they are unlikely to face extinction in the foreseeable future.
  • Data Deficient (DD): Species for which there is inadequate information on abundance or spatial distribution to make a direct or indirect assessment of extinction risk.

• Threatened Species in the Philippines: Comparative Assessment (2021 vs. 2025 IUCN Data):

  • Birds: $98$ species (2021) $\rightarrow$ $87$ species (2025)
  • Mammals: $42$ species (2021) $\rightarrow$ $44$ species (2025)
  • Reptiles: $40$ species (2021) $\rightarrow$ $36$ species (2025)
  • Amphibians: $27$ species (2021) $\rightarrow$ $27$ species (2025)
  • Fishes: $131$ species (2021) $\rightarrow$ $153$ species (2025)
  • Mollusks: $3$ species (2021) $\rightarrow$ $5$ species (2025)
  • Other Invertebrates: $336$ species (2021) $\rightarrow$ $402$ species (2025)
  • Plants: $652$ species (2021) $\rightarrow$ $1162$ species (2025)
  • Fungi and Protists: $1$ species (2021) $\rightarrow$ $1$ species (2025)
  • Total Threatened Philippine Species: $1330$ species (2021) $\rightarrow$ $1917$ species (2025) (representing a overall increase in threatened status across taxa).

• Major Threats to Biodiversity:

  • Habitat Destruction: Occurs when natural environments are altered, fragmented, or removed entirely, leaving native flora and fauna without adequate shelter or resources.
  • Primary Drivers: Deforestation, Urbanization, Mining operations, Agricultural expansion, Road construction.
  • Invasive Species: Non-native organisms introduced into new environments that spread rapidly, causing ecological or economic harm.
  • Impact Mechanisms: Outcompeting native organisms for food, spreading novel diseases, preying directly on native species, and physically altering ecosystems.
  • Pollution: The direct or indirect introduction of harmful substances or pollutants into the ecosystem.
  • Major Forms: Plastic pollution, Air pollution, Water pollution, Chemical pollution.
  • Human Population Growth: Rapid expansion of the human population increases demand for land, infrastructure, and raw materials, requiring more housing, industrial facilities, agricultural land, and transportation networks.
  • Climate Change: Long-term changes in global temperatures, weather patterns, and ocean chemistry.
  • Primary Causes: Combustion of fossil fuels, greenhouse gas emissions, widespread deforestation.
  • Overexploitation: The harvesting of renewable natural resources at a rate faster than they can naturally replenish.
  • Examples: Overfishing, illegal logging, wildlife trafficking, excessive trophy or subsistence hunting.

Ecosystem Components and Major Ecosystem Types

• Definition of Ecosystem: A structural and functional community of living organisms interacting continuously with one another and with their nonliving physical environment.

• Core Components of an Ecosystem:

  • Biotic Components (Living): All biological organisms within the system, including plants, animals, fungi, bacteria, and algae.
  • Abiotic Components (Nonliving): The physical and chemical elements of the environment, including sunlight, water, air, soil, temperature, salinity, rocks, rainfall, and tides.

• Detailed Ecosystem Profiles:

  • Tropical Rainforest:
  • Description: A warm, humid terrestrial ecosystem characterized by heavy rainfall, dense multi-layered vegetation, and rich biodiversity.
  • Key Biotic Components: Canopy trees, diverse animal taxa, fungi, epiphytes.
  • Key Abiotic Components: High rainfall levels, intense sunlight, soil nutrients.
  • Swamp:
  • Description: A wetland ecosystem where soil remains permanently or seasonally saturated or submerged under water, supporting woody vegetation.
  • Key Biotic Components: Water-tolerant trees, fish, amphibians (such as frogs).
  • Key Abiotic Components: Standing water, organic mud, ambient temperature.
  • Mangrove Forest:
  • Description: A specialized coastal marine/estuarine ecosystem dominated by salt-tolerant (halophytic) shrubs and trees with specialized root systems.
  • Key Biotic Components: Mangrove trees, fish nursery species, crabs, mollusks.
  • Key Abiotic Components: Brackish or saltwater, fine mud substrate, tidal oscillations.
  • Estuary:
  • Description: A partially enclosed coastal body of water where freshwater flowing from rivers meets and mixes with saltwater from the open sea.
  • Key Biotic Components: Estuarine fish species, crabs, algae, phytoplankton.
  • Key Abiotic Components: Fluctuating salinity levels, tidal flow, water volume.
  • Coral Reef:
  • Description: A massive biological marine structure constructed from calcium carbonate skeletons secreted by colonies of tiny animals called coral polyps.
  • Key Biotic Components: Coral polyps, reef fish, macroalgae, invertebrates.
  • Key Abiotic Components: Clear seawater, direct sunlight penetration, water temperature.

• Ecosystem Feature Matrix:

Interactive Learning, Activities, and Review Questions

• Activity: Endangered Species Prioritization ("Who's in the Greatest Danger?"):

  • Priority ranking exercise involving six key endemic/native Philippine species:
  1. Philippine Eagle
  2. Tamaraw
  3. Philippine Crocodile
  4. Giant Golden-crowned Flying Fox
  5. Philippine Brown Deer
  6. Philippine Warty Pig

• Classroom Game: "Keep the Box or Give the Box":

  • Rules and Mechanics:
  1. Divide the class into participating groups.
  2. The teacher reads a conceptual question aloud.
  3. The first group to raise their hand earns the right to answer.
  4. If answered correctly, the group chooses whether to KEEP THE BOX or GIVE THE BOX to a competing group.
  5. If answered incorrectly, the question passes to another group.
  6. The secondary group must answer; if correct, they decide whether to KEEP or GIVE the box.
  7. At the game's conclusion, boxes are opened to reveal point rewards or deductions.
  • Question Set and Point Values:
  • Question 1: Is sunlight a biotic or abiotic factor?
    • Answer: Abiotic
    • Box Value: $+10$ points
  • Question 2: Which of the following is a biotic feature of a mangrove forest? (A. Salinity, B. Mud, C. Mangrove tree, D. Temperature)
    • Answer: C. Mangrove tree
    • Box Value: $+8$ points
  • Question 3: Where does freshwater mix with seawater?
    • Answer: Estuary
    • Box Value: $-5$ points
  • Question 4: Which of the following is an abiotic factor found in a coral reef? (A. Coral, B. Fish, C. Sunlight, D. Algae)
    • Answer: C. Sunlight
    • Box Value: $+7$ points
  • Question 5: A warm and wet ecosystem characterized by dense vegetation and high biodiversity.
    • Answer: Tropical Rainforest
    • Box Value: $-3$ points
  • Question 6: The variety of living organisms found in an ecosystem.
    • Answer: Biodiversity
    • Box Value: $+5$ points
  • Question 7: The amount of water that falls from the atmosphere as rain in a particular area.
    • Answer: Rainfall
    • Box Value: $-2$ points
  • Question 8: A marine ecosystem built largely by corals and inhabited by many marine organisms.
    • Answer: Coral Reef
    • Box Value: $+15$ points

• Quick Recall Exercise: Biotic vs. Abiotic Categorization:

  1. Mangrove tree $\rightarrow$ Biotic
  2. Sunlight $\rightarrow$ Abiotic
  3. Crab $\rightarrow$ Biotic
  4. Salinity $\rightarrow$ Abiotic
  5. Coral $\rightarrow$ Biotic
  6. Mud $\rightarrow$ Abiotic
  7. Fish $\rightarrow$ Biotic
  8. Temperature $\rightarrow$ Abiotic
  9. Algae $\rightarrow$ Biotic
  10. Water $\rightarrow$ Abiotic

• Exit Ticket Review Prompts:

  1. Define biotic factors.
  2. Define abiotic factors.
  3. Identify one specific biotic feature of a mangrove forest.
  4. Provide a full definition of an estuary.
  5. Identify one specific abiotic feature of a coral reef.