Concept of an ecosystem as per my b pharm syllabus
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Based on the B.Pharm syllabus (BP206T β Environmental Sciences, Unit II), here is a comprehensive note on the Concept of an Ecosystem:
πΏ Ecosystem β B.Pharm Environmental Sciences (BP206T, Unit II)
1. Definition
An ecosystem is a natural, functional, ecological unit comprising living organisms (biotic components) and their non-living environment (abiotic components) that interact with each other to form a stable, self-sustaining system.
"Living organisms cannot be isolated from their non-living environment because the latter provides materials and energy for the survival of the former."
The term "Ecosystem" was first coined by A.G. Tansley in 1935.
2. Structure of an Ecosystem
The structure of an ecosystem consists of three main components:
A. Abiotic Components (Non-living / Physical)
These include:
- Climatic factors β sunlight, temperature, rainfall, wind, humidity
- Edaphic factors β soil type, mineral content, pH
- Inorganic substances β COβ, Oβ, Nβ, water, minerals
- Organic substances β proteins, carbohydrates, lipids (link biotic and abiotic)
B. Biotic Components (Living)
| Category | Role | Examples |
|---|---|---|
| Producers (Autotrophs) | Make food via photosynthesis | Green plants, algae, phytoplankton |
| Consumers (Heterotrophs) | Feed on other organisms | Animals, birds, insects |
| Decomposers (Saprotrophs) | Break down dead organic matter | Bacteria, fungi |
Classes of Consumers:
- Primary consumers (Herbivores) β eat plants (e.g., deer, rabbits, insects)
- Secondary consumers (Carnivores) β eat herbivores (e.g., frogs, snakes, foxes)
- Tertiary consumers β feed on carnivores (e.g., eagles, tigers)
- Omnivores β eat both plants and animals (e.g., humans, bears)
C. Energy Components
- Solar energy is the primary energy input.
- Energy flows unidirectionally from producers β consumers β decomposers.
3. Functions of an Ecosystem
The four key functions are:
- Energy flow β Unidirectional transfer of energy through the food chain
- Nutrient cycling (Biogeochemical cycles) β Cycling of nutrients (C, N, P, S) between biotic and abiotic components
- Productivity β Primary (by producers) and secondary (by consumers)
- Decomposition β Breakdown of dead organic matter by decomposers, returning nutrients to the soil
4. Energy Flow in an Ecosystem
- All organisms need energy and nutrients to survive.
- Energy transformations begin with the fixation of sunlight by producers (photosynthesis).
- Energy is transferred through trophic levels.
- At each trophic level, ~90% energy is lost as heat (10% Law by Lindemann, 1942).
Food Chain
A linear sequence showing the flow of energy from one organism to another:
Producers β Primary Consumers β Secondary Consumers β Tertiary Consumers
Example (Grassland):
Grass β Rabbit β Snake β Eagle
Example (Aquatic):
Phytoplankton β Zooplankton β Fish β Shark
Food Web
- A network of interconnected food chains in an ecosystem.
- More realistic representation of feeding relationships.
- Provides stability to the ecosystem β if one species is lost, others can compensate.
5. Ecological Pyramids
Graphical representation of the number, biomass, or energy at each trophic level:
| Type | What it shows | Shape |
|---|---|---|
| Pyramid of Numbers | Number of organisms at each trophic level | Upright (in most ecosystems) |
| Pyramid of Biomass | Total dry weight (biomass) at each level | Upright (terrestrial); Inverted (aquatic) |
| Pyramid of Energy | Energy at each trophic level | Always upright |
6. Nutrient Cycling
- Also called Biogeochemical Cycles.
- Nutrients are recycled between living organisms and the environment.
- Key cycles: Carbon cycle, Nitrogen cycle, Phosphorus cycle, Water (Hydrological) cycle.
7. Types of Ecosystems (as per B.Pharm Syllabus)
A. Terrestrial Ecosystems
| Type | Key Producers | Key Consumers |
|---|---|---|
| Forest Ecosystem | Trees (teak, bamboo, ferns) | Insects, birds, tigers, elephants |
| Grassland Ecosystem | Grasses, herbs, shrubs | Cows, deer, foxes, eagles |
| Desert Ecosystem | Cacti, succulents, dry shrubs | Camels, reptiles, insects |
B. Aquatic Ecosystems
| Type | Features |
|---|---|
| Pond | Small, shallow, self-sustaining |
| Lake | Large, stratified (littoral/limnetic/profundal zones) |
| Stream/River | Flowing water (lotic); seasonal variation |
| Ocean | Largest ecosystem; pelagic/benthic zones |
| Estuary | Where river meets sea; high productivity; nursery for marine life |
8. Characteristics of an Ecosystem
- It is a structural and functional unit of ecology.
- It is a dynamic (ever-changing) system.
- It is self-sustaining β has its own producers, consumers, and decomposers.
- Maintains homeostasis β ability to self-regulate.
- It has boundaries (though often not sharp).
9. Important Scientists / Terms
| Name | Contribution |
|---|---|
| A.G. Tansley (1935) | Coined the term "Ecosystem" |
| E.P. Odum | Father of modern ecology; detailed ecosystem functions |
| Lindemann (1942) | 10% Law of energy transfer |
| E.O. Wilson | Emphasized biodiversity in ecosystems; wrote Diversity of Life (1993) |
π Quick Revision Points (Exam-ready)
- Ecosystem = Biotic + Abiotic components interacting together
- Producers = Autotrophs; Consumers = Heterotrophs; Decomposers = Saprotrophs
- Energy flow = Unidirectional; Nutrient cycling = Cyclical
- 10% Law: Only 10% energy passes from one trophic level to the next
- Food web is more stable than food chain
- Pyramid of energy is always upright
- Forest ecosystem β services: nutrient cycling, biodiversity, rainfall regulation, soil erosion prevention
This covers the complete Concept of Ecosystem as per the B.Pharm 2nd Semester Environmental Sciences (BP206T) syllabus. Let me know if you want detailed notes on any specific type of ecosystem (forest, grassland, aquatic, etc.) or topics like nutrient cycles or ecological pyramids!
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