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Chapter 3: Matter, Energy, and Life

  • Copyright © McGraw-Hill Education.

Introduction to Ecology

  • Ecology is the scientific study of relationships between organisms and their environment.

  • Core question: How do matter and energy exchange between organisms and their surroundings?

  • Focus of chapter: Matter and energy.

Elements of Life

  • Matter: Everything with mass and volume.

    • States of Matter: Solid, Liquid, Gas, Plasma.

  • Conservation of Matter: Matter is recycled; it is neither created nor destroyed.

  • The principle states that atoms in our body may have been part of different organisms, even dinosaurs.

Elements

  • Elements: Cannot be broken down into simpler forms through ordinary chemical reactions.

    • Total of 122 elements, but only 4 (C, H, O, N) make up 96% of mass of living organisms.

  • Atoms: Smallest units exhibiting characteristics of the element.

    • Composed of:

      • Protons (+)

      • Neutrons (neutral)

      • Electrons (-) (orbiting the nucleus)

  • Structure: Protons and neutrons form the nucleus; electrons orbit around it.

Chemical Bonds

  • Compounds: Substances made of different kinds of atoms.

    • Molecules: Two or more atoms bonded together.

    • Chemical Bonds: Forces holding atoms in molecules together.

      • Ionic Bonds: Formed between oppositely charged ions (e.g., Na<sup>+</sup> and Cl<sup>-</sup>).

      • Covalent Bonds: Atoms share electrons (e.g., water has unequal sharing leading to slight charges).

Common Molecules

  • Basic examples include:

    • Water (H<sub>2</sub>O)

    • Carbon Dioxide (CO<sub>2</sub>)

    • Methane (CH<sub>4</sub>)

    • Nitrogen (N<sub>2</sub>)

pH Scale

  • Measures concentration of H<sup>+</sup> ions in solution.

  • Scale of acidity:

    • 1 - Battery Acid

    • 7 - Pure Water (Neutral)

    • 14 - Soapy Water (Basic)

Organic Compounds

  • Organic Compounds: Comprised of biomolecules crucial for living things containing carbon.

  • Major Categories:

    • Lipids

    • Carbohydrates

    • Proteins

    • Nucleic Acids

Cells

  • Cells: Microscopic compartments that conduct life processes.

    • Surrounded by lipid membranes regulating material flow in/out.

    • Interior divided into organelles.

  • Enzymes: Proteins that act as molecular catalysts in chemical reactions.

  • Metabolism: Enzymatic reactions performed within an organism.

Energy

  • Energy: Capacity to perform work.

    • Types:

      • Kinetic - Energy in motion.

      • Potential - Stored energy.

      • Chemical - Energy within food or fuels.

  • Heat: Energy transferred between objects at different temperatures.

Thermodynamics

  • Energy supply is essential for biological processes.

  • First Law: Energy cannot be created or destroyed.

  • Second Law: Energy transfer leads to increased entropy (disorder).

Energy for Life

  • Most organisms rely on the sun for energy.

  • Exceptions include archaea that derive energy from inorganic compounds (chemosynthesis).

Energy from the Sun

  • Importance of solar energy:

    • Warmth: Narrow temperature range for organism viability.

    • Photosynthesis: Transformation of radiant energy into chemical energy in plants.

Photosynthesis

  • Occurs in chloroplasts:

    • Equation: 6 H<sub>2</sub>O + 6 CO<sub>2</sub> + Solar Energy → C<sub>6</sub>H<sub>12</sub>O<sub>6</sub> + 6 O<sub>2</sub>

  • Produces glucose as primary fuel for metabolic processes.

Cellular Respiration

  • Reaction: Splitting carbon and hydrogen atoms to form CO<sub>2</sub> and H<sub>2</sub>O.

    • Equation: C<sub>6</sub>H<sub>12</sub>O<sub>6</sub> + 6 O<sub>2</sub> → 6 H<sub>2</sub>O + 6 CO<sub>2</sub> + Energy

Energy Exchange in Ecosystems

  • Explains interaction between producers (photosynthesis) and consumers (respiration).

From Species to Ecosystems

  • Ecology: Studies organisms and their environment.

  • Species: Genetically similar organisms that can breed and produce fertile offspring.

  • Populations: Members of the same species in a given area.

  • Biological Community: Interacting populations in an area.

Ecosystem Definition

  • Ecosystem: Biological community plus its physical environment.

    • Includes climate, water, minerals, sunlight, and more.

Food Chains and Food Webs

  • Producers: Photosynthesizers that form the base of ecosystems (plants).

  • Productivity: Biomass produced over time.

    • Primary Productivity: Basis of growth in ecosystems.

  • Food Chain: Series demonstrating feeding relationships; Food Web: Interconnected food chains with multiple sources.

Trophic Levels

  • Classification of organisms based on diet:

    • Herbivores (Primary Consumers)

    • Carnivores (Secondary and Tertiary Consumers)

    • Omnivores (Eat plants and meat)

    • Scavengers/Detritivores (Recycle bodies and waste)

    • Decomposers (Break down organic matter)

Ecological Pyramids

  • Pyramids represent energy loss at each trophic level, where energy decreases moving up the pyramid.

    • 10% Rule: Only 10% of energy is passed from one trophic level to the next.

Material Cycles

  • Hydrologic Cycle: Path of water through the environment; evaporation, condensation, precipitation.

  • Carbon Cycle: Incorporation of carbon into living organisms through photosynthesis and respiration.

    • Carbon sinks and carbon sources balance CO<sub>2</sub> in the atmosphere.

  • Nitrogen Cycle: Vital for proteins and nucleic acids; nitrogen-fixing bacteria convert nitrogen into usable forms for plants.

  • Phosphorus Cycle: Needed for DNA and ATP; longest cycle without atmospheric presence.