Topic 1 - Biological Diversity and Survival

Unit 1: Biological Diversity SCIENCE 9

INDEX

• Topic 1: Biological Diversity & Survival

• Topic 2: Habitat and Lifestyle

• Topic 3: Passing it On

• Topic 4: Wearing Your Genes

• Topic 5: DNA and Chromosomes

• Topic 6: Natural & Artificial Selection

• Topic 7: The Sixth Extinction

• Topic 8: Preserving Biodiversity

TOPIC 1: BIOLOGICAL DIVERSITY AND SURVIVAL

Learning Objectives

• Describe the importance of variation in living things & why variation occurs.

• Provide examples of variations among and between species.

• Identify the role of variation in strengthening ecosystems under changing environmental conditions.

Variations in Organisms

Definition of Variations

• Variations are visible differences in behavior or physical traits observed between organisms.

• These variations can occur across species (interspecific variations) and within species (intraspecific variations).

Interspecific Variations

• Over 8.7 million different species known globally, most being plants, insects, and microorganisms.

• Approximately 10,000 new species are discovered annually.

Intraspecific Variations

• A species is defined as a group of organisms that can interbreed and produce fertile offspring due to genetic similarities.

Biological Diversity

Definition and Importance

• Biological diversity refers to the variation of life on Earth, measured through interspecific and intraspecific variation within ecosystems.

• Increased variations correlate with greater biodiversity.

• Comparison Example: Coral reef ecosystems are generally more diverse than deserts.

Reasons for Variations

Benefits of Variations

• Variations may allow organisms to better survive in their specific environments.

• Example: Skin color variation helps humans adapt to varying exposure to sunlight, which is crucial for vitamin D absorption while minimizing UV damage.

Case Study: Human Skin Color Adaptation

• Origin of Homo sapiens: Initially in Africa, populations migrated north where sunlight was less abundant.

• Individuals with genetic mutations for dark skin are likely to survive and reproduce in sunny environments, while lighter-skinned individuals predominate in sunnier regions where protection from UV rays is essential.

Adaptations

Definition and Types

• Variations that enhance survival are termed adaptations.

• Types of Adaptations:

  • Structural: Observable differences in physical traits.

  • Behavioral: Differences in how organisms act.

Role in Natural Selection

• Adaptations arise from genetic variation, and those that promote survival increase reproductive success.

• Over time, advantageous adaptations become more common within populations, potentially leading to speciation when populations diverge significantly.

Evolution

Mechanism of Evolution

• Evolution, driven by natural selection, accounts for Earth’s biodiversity.

• It relies on genetic variation that can enhance survival and reproduction in changing environments.

The Value of Variation

• High biodiversity in species and ecosystems enhances resilience and adaptability to environmental changes.

Examples of Biodiversity in Action

• Example 1: Mountain Pine Beetles affect Lodgepole Pine trees; diverse forests withstand infestations better than uniform ones.

• Example 2: Illustrative case study titled "The Terrifying Truth About Bananas" emphasizes the importance of variations.

Measuring Diversity

Diversity Index

• The diversity index assesses ecosystem health by dividing the number of different species in an area by the total number of organisms.

• A high diversity index generally indicates a healthy ecosystem.

Geography and Diversity

• Ecosystems near the equator typically show a higher diversity index due to increased sunlight and rainfall, supporting more plant species.