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

1. Developed by Carl Linnaeus (1700s) and still widely used today.
2. Uses a hierarchical structure that groups organisms based on shared features.
3. The major taxonomic levels (from largest to smallest) are:

Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species

Binomial Nomenclature (Scientific Naming)

1. Each species has a two-part Latin name:
   1. Genus name: Capitalized (e.g., Homo)
   2. Species name: Lowercase (e.g., sapiens)
2. Both names are italicized when typed or underlined in writing.

Example

• Panthera leo → Lion
• Panthera tigris → Tiger

Why Use Scientific Names?

1. Clarity: Common names vary across languages and regions.
2. Precision: Scientific names are unique to each species.
3. Universality: They are used by scientists worldwide, ensuring consistent communication.

Identification of Organisms

1. Taxonomy is the science of classifying and identifying organisms.
2. Taxonomists use multiple tools to determine an organism’s identity and place it within the taxonomic hierarchy.
3. Correct identification ensures accuracy in ecological studies, biodiversity assessments, and conservation management.

1. Dichotomous Keys

1. Dichotomous keys are like a choose-your-own-adventure book for identifying organisms.
2. They consist of a series of paired statements or questions, each offering two choices.
3. By following the choices, you narrow down possibilities until you identify the organism.
4. Easy to use for known species but limited information for new or microscopic species.

2. Reference Collections and Specimen Comparison

1. Museums and herbaria store millions of preserved specimens for reference.
2. Taxonomists compare unknown specimens with known ones to confirm species identity.
3. Institutions like the Natural History Museum (London) maintain large collections used for global species identification and classification.

How It Works

1. Collect a Sample: Take a specimen or detailed photographs.
2. Compare with References: Match your sample to specimens in a collection or images in a field guide.
3. Consult Experts: Taxonomists or curators can provide insights based on their expertise.

3. DNA Analysis and Barcoding

1. Modern taxonomy uses DNA sequencing to identify species based on genetic codes.
2. The Barcode of Life Project (BOLD) maintains a global database of genetic sequences for species identification.
3. DNA analysis is particularly useful for:
   1. Cryptic species that look similar but are genetically distinct.
   2. Early developmental stages (e.g., larvae).
   3. Degraded or fragmentary samples.

Limitations of Traditional Methods

1. Physical characteristics may not reflect genetic differences.
2. Technical language in keys can confuse non-experts.
3. Some features (e.g., internal anatomy, physiology) are not easily observable in the field.
4. Sexual dimorphism or life-cycle changes (e.g., metamorphosis) can lead to misidentification.

Integration of Methods

1. Modern taxonomy combines morphological, genetic, and ecological data for more reliable identification.
2. Digital databases, AI-assisted identification tools, and online biodiversity portals are making taxonomy more accessible and efficient.