JV

Biodiversity and Evolution – Comprehensive Study Notes

Biodiversity: Definitions and Scope

  • Biodiversity (Biological Diversity)

    • Term describing the number & variety of life on Earth.

    • Three nested levels:

    • Genetic diversity – variation within a species (alleles, gene pools).

    • Species diversity – variety & abundance of species in a region.

    • Ecosystem diversity – variation among communities & physical settings (forests, reefs, deserts, etc.).

  • Interdependence

    • All ecosystem components interact; change in one ↔ impacts the rest.

    • Failure to adapt → population decline or death, disturbing balance.

Populations, Communities & Carrying Capacity

  • Population – number of organisms of the same species in the same region.

  • Community – different populations co-existing in one region.

  • Carrying capacity (K)

    • Maximum population size an environment can sustain with available resources.

    • If N \rightarrow K → resources strained → mortality ↑.

  • Limiting factors (restrict growth/distribution)

    • Biotic: food, water, space, predation, disease, migration.

    • Abiotic: light, temperature, soil nutrients.

Quantitative Indices

  • Biodiversity Index \text{Biodiversity Index}= \frac{\text{Total # of different Species}}{\text{Total # of Living Items}}

    • High value → complex, stable & healthy ecosystem.

  • Population Density \text{Density}= \frac{\text{Number of Individuals}}{\text{Size of Area}}

    • Five common spatial patterns (as shown in module’s Figure 1):

    1. Random

    2. Uniform

    3. Clumped/Patchy

    4. Gradient/Edge-biased

    5. Central aggregation

    • Differences arise from resource distribution, social behaviour, predation, micro-climate, etc.

Status Categories of Species

  • Threatened – numbers declining rapidly; vulnerable to endangerment.

  • Endangered – population already very low; high risk of extinction.

  • Extinct – last individual has died (e.g., dinosaurs).

  • Philippine examples

    • Endangered: Philippine eagle, tarsier, tamaraw, Philippine crocodile, naked-backed fruit bat.

Causes of Species Decline & Extinction

Natural Causes

  1. Climate change – abrupt temperature shifts.

  2. Land development (natural events) – tectonics, uplift, etc.

  3. Acid precipitation – from volcanic or natural gas emissions.

  4. Diseases/Epidemics – virulent pathogens.

  5. Meteoric impact / Cosmic radiation – asteroid strikes.

  6. Spread of invasive species – out-compete natives, alter food webs.

Man-Made (Anthropogenic) Causes

  1. Deforestation – illegal logging, kaingin farming.

  2. Pollution

    • \text{Air}: CO(2), NO(x), hydrocarbons → smog, greenhouse effect.

    • \text{Water}: nutrient loading → algal blooms, fish kills.

  3. Destruction of coastal resources – dynamite fishing, muro-ami, mangrove conversion, overharvesting.

  4. Wildlife depletion / Over-exploitation – hunting, pet trade.

  5. Acid precipitation (industrial emissions + water vapour

Ethical / Practical Implications

  • Loss of biodiversity ⇒ diminished ecosystem services (food, medicine, climate regulation).

  • Cultural & aesthetic loss; inter-generational equity concerns.

Evolution & Geologic Time Scale

  • Evolution – gradual transformation of organisms over time; explains first appearance, adaptation & diversification.

  • Geologic Timescale – chronological model of Earth history, divided into eras:

    • Paleozoic ("ancient life") – marine invertebrates dominant; rise of fish, amphibians; first forests (ferns, cycads); ends with Permian mass extinction.

    • Mesozoic ("middle life") – "Age of Reptiles"; dinosaurs, conifers; ends with Cretaceous–Paleogene extinction.

    • Cenozoic ("recent life") – mammals, birds diversify; appearance of humans.

Connections to Previous Genetics Module

  • Genetic diversity underpins resilience; Non-Mendelian inheritance contributes to phenotypic variation affecting adaptability.

Key Terms & Formulas (Cheat-Sheet)

  • Biodiversity Index: \frac{S}{N} where S = species count, N = total individuals.

  • Population Density: \frac{N}{A} where A = area.

  • Carrying Capacity (K) – theoretical upper bound of N.

  • Endangered vs. Threatened vs. Extinct – descending order of remaining numbers.

Reflection Questions (Self-Check)

  • How do human activities tip the balance between carrying capacity & population size?

  • In what ways can evolutionary adaptation mitigate (or fail to mitigate) rapid environmental change?

  • Which local conservation efforts can you support to maintain Philippine biodiversity?