life

Characteristics of Life

  • Life can be identified by specific characteristics that differentiate living organisms from non-living entities.

Section 1.1: Identifying Life

  • Main Question: How do we know this cockroach is alive, and this rock is not?
  • Five Characteristics of Life:
    • Cellular Organization: All living things are composed of one or more cells. Examples include unicellular organisms (like bacteria) and multicellular organisms (like humans).
    • Use Energy: Living organisms obtain and utilize energy for growth, reproduction, and maintenance of their biological functions.
    • Maintain Homeostasis: The ability of an organism to regulate its internal environment to maintain stable, constant conditions conducive to life.
    • Reproduce and Grow: Living beings have the capability to reproduce, leading to the propagation of their species. This process involves growth, which can occur through cell division.
    • Evolve: Over time, populations of living organisms adapt to their environments through changes that are inherited across generations.

Life Organization

  • Life is structured in a hierarchical manner, starting from atoms up to complex biological structures.

Atomic and Molecular Level

  • Atom: The smallest chemical unit of a pure substance (element).
    • Example: Carbon atom.
Molecules
  • Chemical Molecule: Formed when two or more atoms bond together.
    • Example: DNA and proteins.
Cellular Components
  • Organelle: Specialized structures within a cell that perform distinct functions.
    • Examples: Chloroplasts (in plants), Mitochondria (powerhouse of cells).
  • Cell: The fundamental unit of life. Examples include leaf cells and skin cells.
    • Structure includes:
    • Plasmid
    • Nucleoid (composed of chromosomal DNA)
    • Pilus
    • Cytoplasm
    • Ribosome
    • Cell membrane
    • Cell wall
    • Glycocalyx
    • Flagellum
Developmental Biology
  • Development progresses from a single cell to a complete organism:
    • Stages: Zygote → Two-cell stage → Blastocyst → Fetus → Extraembryonic tissues.

Energy in Life

  • Life requires energy to sustain its organized structure and functions.
  • Energy allows organisms to maintain homeostasis, grow, and reproduce.
  • Example: It takes effort to maintain organization in a living system.

Homeostasis

  • Definition: Homeostasis is the regulation of an internal balance or equilibrium within organisms.
    • Factors that are maintained include:
    • Temperature
    • Water content
    • pH levels
    • Sugar levels
    • Waste management

Investigative Methods in Biology

Polling Example

  • Activity: A poll to assess understanding of what constitutes life.

Experimentation with CO2 Levels

  • A study presenting various test materials (corn kernels vs. glass beads) based on carbon dioxide production over time.
    • Independent Variable: Type of material (alive vs. non-alive).
    • Dependent Variable: CO2 production levels.
    • Results are expressed for both materials' CO2 outputs.

Molecular Interactions

Water and Chemical Bonds

  • Water molecule (H2O): Key for biological systems. Comprised of:
    • Polar covalent bonds due to unequal sharing of electrons between hydrogen and oxygen.
    • Partial charges: Hydrogen atoms have a slightly positive charge (δ+) while oxygen has a slightly negative charge (δ-).
  • Types of Bonds:
    • Covalent Bonds: Intra-molecular bond formed by the sharing of electrons between atoms.
    • Hydrogen Bonds: Inter-molecular attraction due to partial charges between molecules, weaker than covalent bonds.
    • Ionic Bonds: Formed by the complete transfer of electrons from one atom to another, resulting in charged ions.
Properties of Water
  • Polarity: Allows water to be an effective solvent, dissolving other polar or charged molecules (hydrophilic).
  • Cohesive and adhesive properties facilitate processes such as transpiration in plants:
    1. Water evaporates through leaf pores.
    2. Evaporating water molecules pull up additional water from below.
    3. Water continues to be pulled from the roots.

Hydrophilicity and Hydrophobicity

  • Hydrophilic Solutes: Substances that dissolve in water, primarily polar molecules and ions.
  • Hydrophobic Solutes: Substances that do not dissolve in water, typically nonpolar molecules like fats and oils.

Conclusion on Water’s Role in Life

  • Water is vital for biological functions due to its unique properties, including its ability to dissolve a wide range of substances, enabling vital biochemical reactions in all living organisms.