Biodiversity:

NCERT Reference: NCERT Biology Class 12, Chapter 13

Detailed Notes:

• Species Diversity:

  • Number of different species in a given area
  • Measured by species richness (total number of species) and species evenness (relative abundance of each species)
  • Higher species diversity increases ecosystem stability and resilience

• Ecosystem Diversity:

  • Variety of ecosystems in a given region
  • Includes terrestrial, aquatic, and transitional ecosystems
  • Each ecosystem has unique species composition and ecological interactions

• Genetic Diversity:

  • Variety of genes within a species
  • Important for adaptation to changing environmental conditions
  • Loss of genetic diversity can lead to inbreeding depression and increased susceptibility to disease

• Importance of Biodiversity:

  • Ecological: Provides essential ecosystem services such as climate regulation, water purification, and pollination
  • Genetic: Source of genes for crop improvement, medicine, and other biotechnology applications
  • Economic: Supports industries such as agriculture, forestry, and tourism
  • Ethical: All species have intrinsic value and deserve to be protected

Threats to Biodiversity:

• Habitat Loss: Conversion of natural habitats to urban, agricultural, or industrial areas
• Overexploitation: Unsustainable harvesting of species for food, fur, or other resources
• Pollution: Discharge of toxic chemicals into the environment
• Invasive Species: Non-native species that outcompete native species and disrupt ecosystem dynamics
• Climate Change: Alterations in temperature, precipitation, and sea level can lead to habitat loss and species extinction

Species Interactions:

NCERT Reference: NCERT Biology Class 12, Chapter 13

Detailed Notes:

• Populations:

  • Group of individuals of the same species living in the same area

  • Characteristics: Size, Density, Dispersion pattern (clumped, uniform, or random)

  • Population Growth Curves:

    • Exponential growth: Unrestricted growth under ideal conditions
    • Logistic growth: Growth slows down as resources become limited

  • Population Regulation Factors:

    • Density-dependent factors: Food availability, predation, competition, disease
    • Density-independent factors: Natural disasters, climate change

  • Life History Strategies:

    • Trade-offs between reproduction and survival: “R” vs “K” strategies

• Predation and Symbiosis:

  • Predation: Interaction between predator and prey species
    • Mechanisms: Pursuit predation, ambush predation, parasitism
  • Symbiosis: Close relationship between two different species
    • Types:
      • Mutualism: Benefits both species (e.g. pollinator-plant relationships)
      • Commensalism: Benefits one species, neutral to the other (e.g. epiphytes on trees)
      • Parasitism: Benefits one species (parasite), harms the other (host)

• Competition:

  • Occurs when two or more species require the same limited resource
  • Types:
    • Intraspecific Competition: Competition between individuals of the same species.
    • Interspecific Competition: Competition between individuals of different species

Ecosystems and Ecological Services:

NCERT Reference: NCERT Biology Class 12, Chapter 15

Detailed Notes:

• Ecosystem Structure:

  • Abiotic Components: Non-living physical and chemical factors (e.g. temperature, water, soil)
  • Biotic Components: Living organisms in the ecosystem (e.g. plants, animals, microorganisms)
  • Trophic Levels: Hierarchical organization of organisms based on feeding relationships (e.g. producers, consumers, decomposers)
  • Energy Flow: Transfer of energy from producers to consumers through food chains and webs
  • Biogeochemical Cycles: Movement of essential nutrients through the ecosystem (e.g. carbon cycle, nitrogen cycle)

• Ecosystem Services:

  • Benefits that humans derive from ecosystems
  • Provisioning Services: Provide essential resources (e.g. food, water, timber)
  • Regulating Services: Regulate environmental conditions (e.g. climate regulation, pollination, waste decomposition)
  • Supporting Services: Maintain the conditions for life (e.g. soil formation, nutrient cycling)

• Human Impacts on Ecosystems:

  • Deforestation: Clearance of forests for agriculture, logging, or development
  • Urbanization: Conversion of natural areas to urban settlements
  • Pollution: Discharge of toxic substances into the environment (e.g. air pollution, water pollution)
  • Climate Change: Alterations in temperature, precipitation, and sea level

Biomes and Adaptations:

NCERT Reference: NCERT Biology Class 12, Chapter 14

Detailed Notes:

• Major Biomes: Large regions characterized by distinct climate and vegetation types

  • Forest Biome: Temperate forests, Tropical rainforests, Boreal forests
  • Grassland Biome: Temperate grasslands, Savannas
  • Desert Biome: Hot deserts, Cold deserts
  • Tundra Biome: Arctic tundra, Alpine tundra
  • Aquatic Biomes: Oceans, Lakes, Rivers, Wetlands

• Adaptations: Inherited traits that enhance survival and reproduction in a particular environment

  • Structural Adaptations: Physical features (e.g. body shape, coloration, camouflage)
  • Physiological Adaptations: Internal mechanisms (e.g. metabolism, water regulation, hibernation)
  • Behavioral Adaptations: Learned or instinctive behaviors (e.g. migration, territoriality, communication)

Population Genetics:

NCERT Reference: NCERT Biology Class 12, Chapter 7

Detailed Notes:

• Genetic Variation:

  • Differences in DNA sequences among individuals in a population
  • Sources:
    • Mutation: Random changes in DNA sequence
    • Gene Flow: Transfer of alleles between populations
    • Genetic Drift: Random fluctuation of allele frequencies in small populations
    • Non-random Mating: Assortative mating, Disassortative mating

• Maintenance of Genetic Variation:

  • Balancing Selection: Natural selection maintains multiple alleles in a population
  • Heterozygote Advantage: Heterozygous individuals have higher fitness than homozygous individuals

• Hardy-Weinberg Equilibrium:

  • Model that describes the genetic structure of a population that is not evolving
  • Conditions for Equilibrium:
    • No mutation
    • No gene flow
    • No genetic drift
    • No non-random mating
  • Deviations from Equilibrium: Any of the above conditions are violated
  • Significance: Provides a baseline for comparing populations undergoing evolution

• Inbreeding and Outbreeding:

  • Inbreeding: Mating between closely related individuals

    • Consequences: Increased homozygosity, Inbreeding depression (reduced fitness)
    • Measures to prevent: Outcrossing, introduction of unrelated individuals

  • Outbreeding: Mating between unrelated individuals

    • Advantages: Increased heterozygosity, Hybrid vigor (increased fitness)

Community Ecology:

NCERT Reference: NCERT Biology Class 12, Chapter 13

Detailed Notes:

• Community Structure:

  • Species Composition: Types and relative abundance of species in community
  • Species Richness: Number of different species in a community
  • Abundance: Number of individuals of each species in a community
  • Diversity Indices: Measure species diversity and evenness in community (e.g. Simpson’s index, Shannon-Wiener index)

• Community Dynamics:

  • Succession: Gradual change in species composition and structure of community over time
  • Climax Communities: Stable, self-sustaining communities at the end of succession
  • Disturbance: Natural events (e.g. fires, storms, droughts) or human activities that disrupt community structure
  • Resilience: Capacity of community to recover after a disturbance

• Keystone Species and Indicator Species:

  • Keystone Species: Species that have a disproportionate impact on the structure and function of community relative to its abundance
  • Indicator Species: Species that respond sensitively to environmental changes, often used as indicators of ecosystem health or environmental degradation

Ecological Niches and Resource Utilization:

NCERT Reference: NCERT Biology Class 12, Chapter 13

Detailed Notes:

• Ecological Niche: The full range of conditions and resources that allow a species to survive and reproduce in an ecosystem

  • Fundamental Niche: The entire set of conditions and resources that a species can potentially occupy
  • Realized Niche: The subset of the fundamental niche that a species actually occupies due to competition and other ecological interactions

• Resource Utilization:

  • Competition for Resources: occurs when two or more species require the same limited resource
  • Niche Overlap: The degree to which two species use the same resources in the same environment
  • Resource Partitioning: Strategies that reduce niche overlap and competition between species (e.g. differences in habitat use, feeding times, or food preferences)
  • Character Displacement: evolutionary divergence in traits (size, morphology, behaviour) between species that exploit similar resources

Case Studies of Environmental Issues:

NCERT Reference: NCERT Biology Class 12, Chapter 16

Detailed Notes:

• Deforestation and its impacts:
  • Causes: Logging, agriculture, urbanization, mining