Ecosystem class 12th|Echology |Lecture 1|By Rahulsirbio

The topic "Ecosystem" is a key part of the class 12 biology syllabus, focusing on the interrelationships between living organisms and their physical environment. Here's a detailed overview:

Definition

An ecosystem is a functional unit of nature, comprising living organisms (biotic components) and their physical environment (abiotic components), interacting with each other.

Types of Ecosystems

Natural Ecosystems

Terrestrial: Forest, desert, grassland.

Aquatic: Freshwater (ponds, lakes, rivers) and marine (oceans, seas).

Artificial Ecosystems

Managed or human-made ecosystems, such as gardens, aquariums, and crop fields.

Components of an Ecosystem

Abiotic Components

Non-living elements like sunlight, temperature, water, air, soil, and nutrients.

Biotic Components

Producers (Autotrophs): Green plants, algae, etc.

Consumers (Heterotrophs): Herbivores, carnivores, omnivores.

Decomposers (Saprotrophs): Bacteria and fungi, which break down organic matter.

Functions of an Ecosystem

Energy Flow:

Energy flows in a unidirectional manner through food chains and food webs.

Trophic Levels:

Producers → Primary consumers → Secondary consumers → Tertiary consumers.

Governed by the 10% law of energy transfer.

Nutrient Cycling:

Involves biogeochemical cycles like the carbon cycle, nitrogen cycle, and water cycle.

Ecological Pyramids:

Pyramid of Number: Number of organisms.

Pyramid of Biomass: Dry weight of organisms.

Pyramid of Energy: Energy content at each trophic level (always upright).

Homeostasis:

Ecosystems maintain balance through self-regulation mechanisms.

Productivity of an Ecosystem

Gross Primary Productivity (GPP): Total energy captured by producers through photosynthesis.

Net Primary Productivity (NPP): GPP minus energy used in respiration by producers.
NPP = GPP - R

Food Chain and Food Web

Food Chain: Linear sequence of organisms through which energy flows.

Grazing Food Chain (GFC): Begins with producers.

Detritus Food Chain (DFC): Begins with dead organic matter.

Food Web: Network of interconnected food chains showing complex feeding relationships.

Ecological Succession

The process of gradual change in the types of organisms in an ecosystem over time.

Primary Succession: Starts on bare, lifeless surfaces (e.g., lava).

Secondary Succession: Occurs in previously inhabited areas.

Significance of Ecosystem

Maintains the balance of energy and nutrients.

Supports biodiversity.

Regulates climate and cycles essential elements.

This comprehensive overview should help in understanding ecosystems for Class 12. Let me know if you need explanations of specific concepts!