Bio 20 IB Unit A Notes KEY 2024_25

Unit A: Energy and Matter Exchange in the Biosphere

Gaia Hypothesis: Proposed by James Lovelock (1979).
- Suggests that all living things on Earth function as one SUPERorganism.
- This organism changes its environment to create ideal conditions for life and self-regulates critical systems needed to maintain life.
Biosphere:
- The narrow zone around the Earth that supports life, acting as a closed system.
- Composed of three layers:
  - Lithosphere: Earth's land masses.
  - Hydrosphere: All water on Earth.
  - Atmosphere: The layer of gases surrounding the planet.
- Characterized by dynamic equilibrium, where changes in components can happen without disturbing the entire system.

Source of Energy:
- All energy on Earth originates from the Sun.
- Transferred via conduction, convection, and radiation.
Photosynthesis:
- The primary process that stores solar energy as carbohydrates.
- Early Earth was anoxic; some species used chemosynthesis as an early form of energy production.
Energy Transfer:
- Energy flows one way through the biosphere, primarily from the sun to producers and then to various consumer levels.
- Photosynthesis, chemosynthesis, and cellular respiration balance energy within ecosystems.
Chemosynthesis:
- Used by organisms that depend on chemical reactions to produce energy (e.g., iron-oxidizing bacteria).
Biotic vs. Abiotic Components:
- Biotic: Living components of the biosphere.
- Abiotic: Non-living components (temperature, water, light, etc.).

Species: Group of organisms capable of interbreeding and producing viable offspring.
Population: A group of the same species living in a defined area at the same time.
Community: Different populations living together and interacting in a given area.
Habitat: The environment where a species normally lives.
Ecosystem: A community of living organisms and their interactions with the abiotic environment.
Biodiversity: The variety and variability of life forms within an ecosystem, impacted by species removal.

Abiotic Variables affecting distribution include:
- Temperature, water availability, light intensity, soil pH, soil salinity, and mineral nutrient availability.
Plant Adaptations:
- Plants in extreme environments have adaptations like thick waxy cuticles to reduce water loss. Examples include:
  - Sand Dunes: Adaptations include rolling leaves and deep root systems for water uptake.
  - Mangrove Swamps: Adaptations include salt secretion mechanisms and cable roots for improved water absorption.

Different species possess ranges of tolerance for abiotic factors, determining where they can live and reproduce.
Adaptations are essential for survival in varying temperatures and water availability.

Energy is lost at each trophic level through respiration and heat, generally following a 10% rule of energy transfer efficiency.
Trophic Levels:
- Producers (autotrophs) ➔ Primary Consumers (herbivores) ➔ Secondary Consumers (carnivores).

Keystone Species: Play a crucial role in maintaining ecosystem structure, affecting the populations of other species.
Biogeochemical Cycles: Essential for recycling nutrients through various processes like photosynthesis and decomposition, influencing habitat health.

Conservation efforts include ex situ (outside natural habitats) and in situ (within natural habitats) measures.
The E.U. EDGE Program focuses on protecting species with fewer relatives and those at risk of extinction.

Eutrophication and pollution have drastic effects on aquatic systems, leading to loss of biodiversity and ecosystem services.
Ocean Acidification threatens species like corals by decreasing the availability of carbonate ions necessary for shell formation.

Transects and Quadrat Sampling are used to assess species distributions and population sizes, aiding in ecological studies.
Capture-mark-release techniques provide estimates of animal populations while accounting for movement and survival rates.

Human activities such as pollution, deforestation, and urbanization significantly influence biodiversity and ecosystem integrity, leading to crises in some species populations.