Copy of IB ESS SL Notes

2.1 Species and Populations

  • Ecology: The study of living (biotic) and non-living (abiotic) components that interact within an ecosystem.

  • Abiotic factors: Non-living factors influencing organisms/system.

    • Example: Sunlight affects temperature and evaporation rates.

  • Levels of organization: Species → Population → Community → Ecosystem → Biome → Biosphere.

  • Ecosystem: A community of interdependent organisms and their physical environment.

  • Species: A group of organisms capable of reproducing and producing fertile offspring.

  • Scientific Names: Used to identify species scientifically (Genus species); always italicized or underlined.

  • Keystone Species: Crucial species for ecosystem maintenance, influencing structure and nature of ecosystems.

    • Example: Wolves in Yellowstone, beavers in rivers.

  • Niche: Specific role of an organism encompassing where, when, what, and how it lives.

    • Associated with trophic levels in ecosystems.

    • Example: Plants as primary producers, tigers in herbivore population control.

  • Niche Theory: No two species can occupy identical niches simultaneously to avoid competition.

    • Fundamental Niche: Range of conditions a species can live under.

    • Realized Niche: Actual conditions an organism lives under, often affected by competition.

    • Case Study: Joseph Connell's barnacles - comparing fundamental and realized niches.

  • Intraspecific competition: Competition between the same species, stabilizing population size and influencing phases of growth.

Interactions Between Organisms

  • Predation: The act of hunting.

  • Herbivory: Consumption of plants.

    • Example: Rabbits eating grass.

  • Parasitism: One organism relies on another for nutrition, often harming the host.

  • Mutualism: Interaction where both species benefit.

  • Competition: Struggle for resources; can be intra-specific or inter-specific.

  • Amensalism: One species is harmed while another is unaffected.

    • Example: Cows and sheep in pasture; cows starve due to competition from sheep.

  • Neutralism: No significant relationship exists between organisms.

  • Competitive exclusion principle: No two species can occupy the same niche indefinitely in limiting resource conditions.

  • American Alligator: A keystone species that creates gator holes for refuge of aquatic species during dry seasons.

Bioaccumulation vs Biomagnification

  • Pesticides: Man-made pollutants including herbicides, fungicides, and bactericides, designed to manage pests.

  • Bioaccumulation: Accumulation of substances (toxins) in an organism over time; organisms cannot eliminate them effectively.

    • Examples: DDT, Methyl Mercury; associated effects include cancer and birth defects.

  • DDT:

    • Benefits: Low toxicity for humans, effective against insects, inexpensive to produce.

    • Problems: Long environmental activity, causes shell thinning in birds.

    • Status: Banned in North America since the 1970s but still used in the Third World.

  • Biomagnification: Increasing concentration of toxins in organisms at higher trophic levels.

Ecological Pyramids

  • Ecological Pyramids: Represent numerical relationships between trophic levels in a community.

    • Choice of pyramid depends on data type/quantity collected.

  • The Second Law of Thermodynamics states energy decreases along food webs; thus, pyramids narrow as one ascends trophic levels.

    • Energy Loss: Approximately 90% lost at each level due to homeostasis, heat, and movement.

  • Pyramid of Biomass: Represents standing stock of each trophic level.

  • Pyramid of Productivity: Represents energy flow through trophic levels, always decreases as it ascends due to energy loss.

2.2 Communities and Ecosystems

  • Solar Energy Fate: Measured in joules per second per square meter (J s -1 m-2).

  • Solar Constant: The rate of solar energy reaching the top of Earth’s atmosphere.

  • Productivity: Conversion of solar energy into biomass over time, measured per unit area.

2.3 Flows of Energy and Matter: Biomes

  • Biomes: Collections of ecosystems sharing similar climatic conditions.

  • Biosphere: Portions of Earth inhabited by living organisms.

    • Aquatic Biomes: Freshwater and Marine; include swamps, rivers, coral reefs, and deep oceans.

    • Deserts: Characterized by hot and cold variations.

    • Forests: Tropical, Temperate, Boreal (Taiga).

    • Grasslands: Tropical, Temperate, Savanna.

    • Tundra: Arctic and Alpine types.

  • Climate: Major influencing factor regarding growth patterns, with geography also significant.

    • Factors: Temperature, precipitation, latitude, and altitude.

Biome Specific Characteristics

Tropical Rainforest

  • Characteristics: Hot and wet, high biodiversity.

  • Climate: Rainfall 2000-5000 mm/yr, average temperature 26-28 degrees Celsius.

  • Productivity: High net productivity; continuous growing season.

Deserts

  • Characteristics: Dry, high daily temperature variation.

  • Climate: Less than 250 mm/yr precipitation.

  • Adaptations: Drought-resistant plants, small mammals.

Temperate Grasslands

  • Characteristics: Dominated by grasses, ideal for agriculture.

  • Climate Factors: Precipitation equals evaporation.

  • Biodiversity: Low compared to forests.

Temperate Forests

  • Characteristics: Mild climate, often deciduous.

  • Climate Factors: Rainfall 500-1500 mm/yr.

Arctic Tundra

  • Characteristics: Cold, low biodiversity, thin soil.

  • Climate Factors: Low precipitation, permafrost present.

Deep Ocean

  • Characteristics: Covers 65% of Earth's surface, diverse environments from shallow to deep.

  • Light Limitation: Nutrient levels are low, leading to low primary productivity.

Succession and Zonation

  • Succession: Ecosystem evolution over time.

  • Zonation: Ecosystem changes along gradients (e.g., altitude).

  • Primary Succession: Colonization of barren land; starts with pioneer species.

    • Stages: Colonization, Establishment, Competition, Stabilization.

  • Secondary Succession: Recovery of complex ecosystems after disturbance.

K and R Strategists’ Reproductive Strategies

  • K-Strategists: Stable environments; longer-lived, fewer offspring.

  • R-Strategists: Unstable environments; short life cycles, rapid reproduction.

  • Survivorship Curves: Illustrates lifespan and mortality at various life stages.

robot