4. Ecology

4. Ecology

4.1 Ecosystem Ecology

Concept of Ecology

• Definition: Ecology is the branch of biology that studies the interactions between organisms and their environment.
• Objectives: Understanding how living organisms interact with one another and with their physical surroundings.

Biotic and Abiotic Factors

• Biotic Factors: Living components of an ecosystem, including plants, animals, fungi, and microorganisms.
• Abiotic Factors: Non-living components, such as temperature, light, water, soil, and nutrients, that influence the distribution and behavior of organisms.

Species Interactions

• Types of Interactions:
  • Predation: One organism (predator) kills and consumes another (prey).
  • Competition: Species compete for limited resources (food, space).
  • Mutualism: Both species benefit from the interaction (e.g., pollinators and flowering plants).
  • Commensalism: One species benefits, and the other is neither helped nor harmed.
  • Parasitism: One organism benefits at the expense of another.

Concept of Ecosystem

• Definition: An ecosystem is a community of living organisms interacting with each other and their physical environment.
• Types: Terrestrial (e.g., forest, grassland) and aquatic (e.g., freshwater, marine) ecosystems.

Structural and Functional Aspects

• Pond Ecosystem:

  • Structure: Zones (littoral, limnetic, profundal) with varying light penetration and types of organisms (e.g., algae, fish).
  • Function: Nutrient cycling, energy flow, and habitat provision.

• Forest Ecosystem:

  • Structure: Layers (canopy, understory, forest floor) with diverse plant and animal species.
  • Function: Carbon storage, oxygen production, and habitat diversity.

Food Chain and Food Web

• Food Chain: A linear sequence showing how energy and nutrients flow from one organism to another (e.g., grass → rabbit → fox).
• Food Web: A complex network of interconnected food chains, illustrating the multiple feeding relationships in an ecosystem.

Trophic Level

• Definition: The hierarchical levels in an ecosystem, based on the flow of energy and nutrients.
• Levels:
  • Producers: Organisms (e.g., plants) that produce their own food through photosynthesis.
  • Primary Consumers: Herbivores that consume producers.
  • Secondary Consumers: Carnivores that eat primary consumers.
  • Tertiary Consumers: Higher-level carnivores that eat other carnivores.

Ecological Pyramids

• Pyramid of Numbers: Represents the number of organisms at each trophic level.
• Pyramid of Biomass: Illustrates the total mass of living matter at each trophic level.
• Pyramid of Energy: Shows the flow of energy through different trophic levels, typically decreasing at each level.

Productivity

• Primary Productivity: The rate at which producers convert sunlight into chemical energy (organic matter).
• Secondary Productivity: The generation of biomass by heterotrophic organisms (consumers).

Biogeochemical Cycles

• Carbon Cycle: Movement of carbon through the atmosphere, biosphere, hydrosphere, and geosphere, involving processes like photosynthesis, respiration, and decomposition.
• Nitrogen Cycle: The series of processes through which nitrogen is converted in the environment and in living organisms, including nitrogen fixation, nitrification, denitrification, and ammonification.

Concept of Succession

• Definition: The process of change in the species structure of an ecological community over time.
• Types:
  • Primary Succession: Occurs on previously uninhabited environments (e.g., after a volcanic eruption).
  • Secondary Succession: Follows disturbances that leave the soil intact (e.g., after a forest fire).

4.2 Ecological Adaptation

Concept of Adaptation

• Definition: Adaptation is the process by which organisms adjust to their environment to improve their chances of survival and reproduction.
• Types: Physiological, behavioral, and morphological adaptations.

Hydrophytes and Xerophytes

• Hydrophytes: Plants adapted to grow in water or very moist environments (e.g., lilies, cattails).
  • Characteristics: Floating leaves, air-filled cavities, and reduced root systems.
• Xerophytes: Plants adapted to dry environments (e.g., cacti, succulents).
  • Characteristics: Thick cuticles, deep root systems, and modified leaves (spines) to reduce water loss.

4.3 Ecological Imbalances

Greenhouse Effects and Climate Change

• Greenhouse Effect: The warming of Earth’s surface due to the trapping of heat by greenhouse gases (e.g., CO₂, methane).
• Climate Change: Long-term alteration in temperature and typical weather patterns; impacts include rising sea levels, extreme weather, and shifts in ecosystems.

Depletion of Ozone Layer

• Ozone Layer: A region of the Earth's stratosphere that absorbs most of the Sun's harmful ultraviolet radiation.
• Causes of Depletion: Release of ozone-depleting substances (e.g., chlorofluorocarbons or CFCs).
• Consequences: Increased UV radiation leads to higher rates of skin cancer, cataracts, and harm to ecosystems.

Acid Rain

• Definition: Precipitation with a pH lower than 5.6, caused by the release of sulfur dioxide and nitrogen oxides into the atmosphere.
• Effects: Damages aquatic ecosystems, soil, and vegetation; can lead to the degradation of buildings and historical monuments.

Biological Invasion

• Definition: The introduction of non-native species to an ecosystem, which can disrupt the local flora and fauna.
• Consequences: Competition with native species, loss of biodiversity, alteration of ecosystem functions, and potential economic impacts.