2.1A Organisms Notes

Biosphere

1. The biosphere represents the zone of life on Earth, extending from the deepest ocean trenches to the highest mountaintops where living organisms can survive.
2. It includes individuals, populations, communities, and ecosystems.

Structure of the Biosphere

1. Individual: A single living organism that carries out life processes independently (e.g., a single oak tree).
2. Population: A group of individuals of the same species living in the same area at the same time and capable of interbreeding (e.g., a herd of elephants).
3. Community: All the different populations interacting within a particular area (e.g., trees, insects, and birds in a rainforest).
4. Ecosystem: A biological community plus its physical environment interacting together (e.g., coral reef, desert, tundra).

Components of Biosphere

Atmosphere

1. The layer of gases surrounding Earth.
2. Provides CO₂ for photosynthesis, O₂ for respiration, and protects organisms from harmful radiation.

Hydrosphere

1. Includes all water bodies (oceans, rivers, lakes, groundwater, glaciers).
2. Essential for metabolic reactions, nutrient transport, and climate regulation.

Lithosphere

1. The solid outer layer of the Earth, composed of rocks and soils.
2. It provides essential nutrients (e.g., nitrogen, phosphorus, potassium) to plants and microorganisms.

Interactions Within the Biosphere

1. The biosphere is a self-regulating system that maintains balance through continuous energy flow (mainly from the Sun) and nutrient cycling.
2. Life depends on:
   1. Energy input: Solar radiation captured via photosynthesis.
   2. Nutrient cycling: Movement of carbon, nitrogen, phosphorus, and water through ecosystems.
   3. Stability of environmental conditions: Suitable temperature, pH, and moisture levels.

Human Impact on the Biosphere

1. Deforestation: Destroys habitats and reduces biodiversity.
2. Pollution: Contaminates air, water, and soil, harming organisms.
3. Climate Change: Alters temperature and weather patterns, affecting ecosystems.

Species

1. Members of a species share a gene pool, meaning they can exchange genetic material through reproduction.
2. This is known as the Biological Species Concept (BSC).
3. Based on the Biological Species Concept (BSC):
   1. Interbreeding: Members of the same species can reproduce with each other.
   2. Fertile Offspring: Their offspring must also be able to reproduce.
   3. Reproductive Isolation: Different species cannot naturally interbreed or produce viable, fertile offspring

Individuals and Species

1. Individual Organism: A single living being of a species
2. Species: A group of individuals capable of interbreeding

Limitations of the Biological Species Concept

1. Geographically isolated populations: May evolve separately but still belong to the same species (e.g., island vs. mainland populations).
2. Asexual organisms: Such as bacteria, reproduce without interbreeding, making the BSC inapplicable.
3. Extinct species: Cannot be tested for reproductive compatibility.
4. Incomplete reproductive barriers: Some species hybridize under specific conditions.

Classification of Organisms

1. Classification allows scientists to organize the immense diversity of life and predict shared characteristics among organisms.
2. It provides a universal system of naming, avoiding confusion caused by local or common names.
3. Helps scientists trace evolutionary relationships and understand the structure of ecosystems.

The Linnaean System of Classification