Lecture Unit 2-2 (2)

Unit 2: Biodiversity

Case Study: Will We Slice Through the Serengeti?

  • Wildebeest, zebras, and antelope migrate across Africa each year during seasonal changes.

  • The Maasai people are semi-nomadic herders coexisting sustainably with the ecosystem.

  • Two protected areas exist within Tanzania and Kenya but have isolated N. Tanzania communities, causing poverty.

  • Tanzania's president proposed a paved highway through the Serengeti to connect these communities to urban areas.

Impact of Building a New Road

  • Concerns raised by conservationists about:

    • Blocking migration routes

    • Increased traffic collisions leading to animal deaths

    • Easier access for poachers

    • Accelerated human development near reserves

  • The East Africa Court of Justice blocked the initial plan for a new route, proposing an alternative.

  • A new president in 2016 suggested an oil pipeline through the Serengeti, reigniting protests.

Biodiversity Overview

  • Definition: Variety of life across all biological organization levels.

  • Species: Organisms sharing unique characteristics capable of breeding fertile offspring.

  • Species Diversity: Assessment of the number or variety of species in a given area.

    • Species Richness (r): Total number of species.

    • Evenness/Relative Abundance: Variation in number of individuals among species.

Genetic and Ecosystem Diversity

  • Genetic Diversity: Variation in DNA among individuals; low diversity leads to vulnerability.

  • Ecosystem Diversity: Range of ecosystems and habitats; richer ecosystems recover better from disruptions.

  • A population bottleneck reduces genetic diversity, increasing vulnerability.

Bottleneck Events

  • Defined as drastic population reduction due to environmental disturbances.

  • Leads to smaller, less genetically diverse surviving populations, further hindering resilience to environmental changes.

Natural Disruptions to Ecosystems

  • Natural disruptions can have significant environmental consequences, comparable to human-made disturbances.

  • Types of disruptions:

    • Periodic: Occur regularly (e.g., dry-wet seasons).

    • Episodic: Occasional, irregular events (e.g., hurricanes).

    • Random: No regular occurrence (e.g., volcanic eruptions).

Climate Change Over Geological Time

  • Carbon dioxide and temperature levels have fluctuated over 800,000 years.

  • Rising sea levels impact coastal habitats, forcing species like mangroves to migrate inland.

Wildlife Migration

  • Wildlife migrates for temperature, food, mating, and disruptions.

  • Examples: Monarchs travel 3,000 miles to Mexico; Arctic Terns migrate from Arctic to Antarctic.

  • Climate change causes shifts in migration timing and patterns.

Ecological Tolerance

  • Ecological Tolerance: Range of environmental conditions that organisms can withstand.

  • Graphs define tolerable abiotic factors for species.

  • Adaptations: Changes over time in response to environmental pressures, enhancing survival.

Genetic Diversity Mechanisms

  • Genetic diversity arises from evolution, mutations, and gene recombination.

  • Adaptations lead to fitness disparities, where advantaged traits are passed through generations.

Evolutionary Drivers

  • Natural selection dictated by environmental conditions affects species survival.

  • Key observations of natural selection include reproduction struggles and genetic variation.

Rate of Evolution

  • Rapid environmental change can hinder species adaptation.

  • Species with short lifespans adapt faster (e.g., bacteria).

K-selected vs. r-selected Species

  • K-selected (Kings of Quality): Large, fewer offspring, high parental care, thrive in stable environments.

  • r-selected (Rodents of Quantity): Small, many offspring, rapid maturity, suited for volatile environments.

Endangered & Invasive Species

  • Species health is closely linked to ecosystem health; invasive species threaten native species.

  • Strategies to combat endangerment include habitat protection and legislation.

Human Threats to Biodiversity (HIPPCO)

  • Habitat Loss: Deforestation, urbanization, and habitat fragmentation.

  • Invasive Species: Outcompete natives, disrupting ecological balances.

  • Pollution and Climate Change: Affect species survival and ecosystem functionality.

Ecological Succession

  • Two types: Primary (starts from bare rock) and Secondary (uses existing soil post-disturbance).

  • Pioneer Species: First to colonize an area (e.g., moss, lichen).

  • Climax Community: Mature stage of succession with stable species.

Island Biogeography

  • Island size and proximity to mainland affect species diversity and richness.

  • Evolution on islands leads to adaptive radiation due to limited resources.

  • Larger islands support more species due to greater niches and lower extinction rates.