Campbell+Biology+Concepts+and+Connections+9th+Ed

The Chemical Basis of Life

Introduction to Coral Reefs

  • Coral reefs are diverse ecosystems formed from calcium carbonate skeletons of coral animals.

  • They serve as habitats for a variety of marine life, including numerous fish species.

  • Rising atmospheric CO2 is a threat to coral reefs due to its chemical reactions in seawater.

The Role of Chemistry in Life

  • Chemistry is foundational to biology, explaining how elements combine into compounds.

  • Chemical reactions are vital for cellular functions, emphasizing the importance of understanding chemistry in biological contexts.

Water: The Essence of Life

  • Life originated in water, and all organisms depend on it for survival.

  • Cells are composed of approximately 70% water, where essential chemical reactions take place.

  • The distinct properties of water highlighted in this chapter are crucial for sustaining life.

Hierarchy of Biological Organization

  • Biological systems are structured hierarchically, with new properties emerging at each level, starting from atoms to molecules and cells.

  • Understanding the elementary chemical concepts is crucial as they apply throughout the study of life.

Chemical Bonds (Sections 2.5-2.9)

Structure of Atoms

  • The atomic structure dictates the types of bonds possible between atoms.

  • Living organisms consist primarily of certain elements, combined into compounds.

Elements and Compounds

  • Elements: Substances that cannot be broken down into simpler substances (e.g., oxygen, carbon).

  • Compounds: Composed of two or more different elements in a fixed ratio (e.g., sodium chloride).

  • Pure substances can exhibit emergent properties that differ from their constituent elements.

Essential Elements for Life

  • Humans require 25 essential elements, with 99% of body mass made up of six key elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus.

  • Trace elements, while present in minor amounts, are crucial for various biological functions.

Trace Elements and Nutritional Health (Section 2.2-2.4)

Importance in Diet

  • Trace elements such as iodine and iron are essential in very small quantities but crucial for health.

  • Iodine deficiency can lead to health issues like goiter; sources include seafood and iodized salt.

  • Iron deficiency is prevalent globally, especially among women and children; fortification and diet improvement are key solutions.

Public Health Measures

  • Fluoride is added to drinking water for dental health, with a history of controversy demonstrating the intersection of science and public policy.

Atom Structure and Isotopes (Section 2.3-2.4)

Subatomic Particles

  • Atoms consist of protons (+), neutrons (no charge), and electrons (-).

  • Atomic number is defined by the number of protons, while mass number is the sum of protons and neutrons.

  • Isotopes differ in neutrons but have the same atomic number, affecting stability.

Radioactive Isotopes

  • Useful as tracers in biology and medicine; they help monitor processes within organisms despite posing some risks.

  • Examples include studies on photosynthesis and medical imaging.

Chemical Bonds (Sections 2.5-2.8)

Types of Bonds

  • The distribution of electrons affects chemical properties; atoms may interact to complete their outer electron shells through:

    • Ionic Bonds: Formed by electron transfer, creating charged ions that attract each other (e.g., NaCl).

    • Covalent Bonds: Involve sharing electrons, which can be polar (unequal sharing) or nonpolar (equal sharing).

  • Hydrogen Bonds: Weaker interactions crucial for life, especially in water.

Water's Properties (Sections 2.10-2.14)

Cohesion and Surface Tension

  • Cohesion among water molecules leads to surface tension, essential for water transport in plants.

Temperature Regulation

  • Water's high heat capacity allows it to absorb heat, stabilizing environmental temperatures.

Ice's Density

  • Ice's lower density compared to liquid water allows it to float, providing insulation for aquatic ecosystems.

Solvent Properties

  • Water's polarity makes it an excellent solvent, facilitating numerous biological reactions necessary for life.

Acidic and Basic Conditions

  • pH influences chemical reactivity; buffers in biological systems maintain stability within cells.

Impact of CO2 on Coral Reefs (Section 2.15)

Ocean Acidification

  • Increasing atmospheric CO2 levels lower ocean pH, impacting marine life, particularly coral reefs through calcification processes.

  • Studies show that diminished carbonate ion concentration slows coral growth, threatening ecosystem diversity.

Search for Extraterrestrial Life (Section 2.16)

Water as a Criterion

  • The search for life on distant planets centers on detecting water, which is essential for life as demonstrated on Earth.