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Food Chains and Ecological Pyramids

  • Food Chains

    • A linear sequence showing the transfer of energy from one organism to another as they consume each other.

    • Describes how energy and nutrients move through ecosystems.

  • Ecological Pyramids

    • Representation of the distribution of biomass, numbers, or energy among trophic levels in an ecosystem.

Material Cycles

  • Matter Cycling

    • Matter, such as carbon, nitrogen, and water, is never lost; it is recycled and shifts between the soil, air, living organisms, and back to the environment.

    • Processes include excretion, decomposition, and reuse by organisms.

  • Levels of Organization

    • Ecology studies organisms at various scales:

      • Organism: Individual survival mechanisms.

      • Population: Group of the same species in a specific area.

      • Community: Different species interacting within an area.

      • Ecosystem: Community plus the non-living components (like climate, water).

      • Biosphere: Global sum of all ecosystems, encompassing all life on Earth.

Atomic Structure

  • Atoms

    • The smallest units of an element retaining its chemical properties, often referred to as the "Lego bricks" of the universe.

  • Molecules

    • Formed when two or more atoms bond together chemically, such as in H₂O.

    • Molecules determine the properties of substances.

  • Matter Transformation

    • Matter cannot be destroyed in a closed system; it is transformed from one form to another.

    • The recycling of atoms means every atom on Earth is billions of years old and has existed in various forms (e.g., Carbon atoms from extinct species).

  • Ecological Impact

    • In ecosystems, decomposition by organisms returns matter back to the soil or atmosphere for reuse in new life forms.

Composition of Organisms

  • Major Elements

    • Four elements (oxygen, carbon, hydrogen, nitrogen) account for 96% of the mass of living organisms.

    • Each element is composed of atoms which share a defined number of protons in their nuclei.

Atomic Measurements

  • Mass Number

    • Total number of protons and neutrons in an atom's nucleus.

    • Isotope: Different forms of an element that vary in atomic mass due to differing numbers of neutrons.

  • Atomic Number

    • The total number of protons in an atom's nucleus; unique to each element (e.g., Carbon has an atomic number of 6).

  • Examples of Isotopes

    • Carbon-12 (6 protons, 6 neutrons) and Carbon-14 (6 protons, 8 neutrons): Carbon-14 is heavier and radioactive.

Types of Chemical Bonds

  • Covalent Bonds

    • Formed when atoms share electrons, often between nonmetals.

    • Example in water: Oxygen attracts electrons more strongly than hydrogen, creating polar covalent bonds with slight positive charges on hydrogen and slight negative on oxygen.

Energy and Chemical Reactions

  • Energy in Bonds

    • Forming bonds requires energy; breaking bonds releases energy.

    • Activation Energy: Energy required to initiate a chemical reaction (e.g., a match starting a fire).

  • Acid-Base Properties

    • Acids: Substances that readily donate hydrogen ions.

    • Bases: Substances that readily bond with hydrogen ions.

    • pH Scale: Logarithmic scale where each step represents a tenfold change in acidity: 0-7 (acidic), 7 (neutral), 8-14 (basic).

  • Examples of Acids and Bases:

    • Tomatoes: pH 4, Wine: pH 3, Vinegar: pH 2, Stomach Acid: pH 0.

Biological Macromolecules

  • Types of Macromolecules

    • Lipids: Fats and oils.

    • Carbohydrates: Sugars and starches.

    • Proteins: Polymers of amino acids with diverse functions.

    • Nucleic Acids: DNA and RNA, essential for genetic information storage and transfer.

Metabolism and Enzymes

  • Metabolism

    • A collection of enzymatic reactions within an organism, facilitating the conversion of substrates to energy and products.

    • Enzymes, usually proteins, lower the activation energy needed for reactions.

Water Cycle

  • Evaporation and Condensation

    • Evaporation: Water changes from liquid to gas, moving into the atmosphere.

    • Condensation: Gas transforms back to liquid, leading to precipitation as rain or snow.

  • Impact on Heat Distribution

    • The water cycle helps distribute heat globally by moving energy through evaporation and precipitation.

Energy Transfer in Ecosystems

  • Ecosystems and Energy Flow

    • The second law of thermodynamics indicates that energy transfer is inefficient; some energy is always lost, typically as heat.

    • Entropy: Measures the degree of disorder in a system, and it increases in isolated systems over time.

  • Food Webs and Trophic Levels

    • A food web is an interconnected network of food chains representing the complex feeding relationships in an ecosystem.

    • Primary Consumers: Herbivores that eat plants; Secondary Consumers: Carnivores that eat herbivores; Tertiary Consumers: Carnivores that eat other carnivores.

  • Decomposers: Organisms such as bacteria and fungi that breakdown dead organic material, recycling nutrients back into the ecosystem.

  • Efficiencies and Energy Transfer

    • Predator Efficiency: Less than 100%; energy transfer follows the 10% Rule which illustrates that only about 10% of energy becomes biomass in the next trophic level (e.g., 100 kg of clover can support about 10 kg of rabbits which can support about 1 kg of foxes).

Precipitation and Groundwater

  • Water Cycle Components

    • Precipitation: Water droplets in clouds become heavy and return to Earth.

    • Infiltration: Process by which water seeps into the ground, replenishing groundwater.

  • Quantifying Water Movement

    • Evaporation from oceans: 425,000 km³, runoff from streams: 30,000 km³.

    • Percolation through the soil and porous rocks to groundwater is crucial for maintaining water supplies.

Carbon Cycle and Human Impact

  • Cellular Respiration

    • Organisms respire, returning CO2 back into the atmosphere and breaking down organic molecules to release energy.

    • Decomposition: Bacteria and fungi decompose organic matter, releasing CO2 into the atmosphere and soil, effectively recycling carbon in ecosystems.

  • Oceanic Involvement in the Carbon Cycle

    • Oceans absorb CO2, storing it long-term while also impacting ocean acidity.

  • Anthropogenic Contributions

    • Human activities generate excess CO2, contributing to global warming due to the saturation of carbon sinks.

Nitrogen Cycle

  • Nitrogen Fixation

    • Carried out by nitrogen-fixing bacteria, some of which reside in leguminous plants' root nodules; converts N₂ into bioavailable forms (NO₃⁻).

    • Lightning also plays a role in nitrogen fixation.

  • Denitrification

    • Denitrifying bacteria convert nitrates back to N₂, occurring in anaerobic environments (e.g., waterlogged soils).

  • Nitrogen Cycle Stages

    • Includes fixation, ammonification, nitrification, and denitrification.

Phosphorus Cycle

  • Phosphorus Cycling

    • Decomposers release phosphate back into the soil from dead organic matter; this cycle is slower compared to carbon and nitrogen cycles.

  • Human Influence on Phosphorus

    • Large fertilizer application can disrupt natural phosphorus balance in ecosystems.

Sulfur Cycle

  • Sulfur Dynamics

    • Human activities, primarily fossil fuel combustion, lead to significant sulfur release affecting rainfall acidity.

    • Organic sulfur is cycled within food chains and returned to the environment as animals die and decompose.