Chapter 1: evolution and foundations of biology

Course Announcements and Communication

  • Announcements and changes will be communicated through Blackboard.

Phylogenetic Tree of Organisms

  • A phylogenetic tree represents how organisms are related, exemplified by a child's drawing by Carolyn.

Evolutionary Theory

  • Key Contributors:

    • Charles Darwin and Alfred Wallace.

    • Darwin is primarily credited for formulating natural selection as the process of evolution.

  • Common Ancestry:

    • All living organisms descend from a common ancestor.

    • Genetic Evidence:

    • All organisms share the same genetic code for amino acids.

    • Shared codons evidence supports the common ancestry theory.

  • Importance of Evolution:

    • Evolution serves as a principal supporting idea in biology, and the textbook identifies five themes, with evolution being the first.

Definition of Biology

  • Biology is defined as the study of life, encompassing various sub-disciplines:

    • Immunology

    • Microbiology

    • Physiology

Defining Life

  • Difficult to provide a precise definition of life due to its diverse forms.

  • Key Characteristics of Life (according to the acronym "DOG RACER"):

    • DNA: All living organisms possess DNA for genetic information transmission between generations.

    • Organization: Levels of organization from molecules to cells to tissues to organs to systems.

    • Growth and Development: Organisms undergo growth and development stages.

    • Reproduction: Organisms reproduce asexually or sexually.

    • Adaptation: Evolution acts on populations, leading to adaptations.

    • Cells: Fundamental unit of all living organisms is the cell.

    • Energy Needs: All organisms require energy for metabolic processes.

    • Response to Environment: Organisms interact and respond to their surroundings.

Unifying Themes in Biology

  • Five unifying themes assist in understanding biological diversity:

    • Organization: Levels range from molecules to ecosystems.

    • Levels: Molecules, organelles, cells, tissues, organs, organ systems, organisms, populations, communities, ecosystems, and biospheres.

    • Hereditary Information: Encoded in DNA, determining traits and behaviors.

    • Energy Requirement: All organisms require energy (e.g., ATP) to maintain homeostasis and metabolic processes.

    • Interaction: Continuous interaction between organisms and their environment.

    • Evolution: Populations evolve, leading to diversity over time.

Emergent Properties

  • Emergent properties result from the organization of life:

    • As complexity increases from molecules to organelles, new functions emerge (e.g., photosynthesis in chloroplasts).

  • Example: Chlorophyll's role in photosynthesis requires the chlorophyll molecule to be part of a chloroplast.

Anatomy and Physiology

  • Anatomy: Study of form.

  • Physiology: Study of function; structure influences function (e.g., bird bone structure aiding flight).

Cellular Structure and Function

  • Common Features of All Cells:

    • DNA: Genetic information.

    • Plasma Membrane: Protective boundary around cells.

    • Ribosomes: Machinery for protein synthesis.

  • Two Basic Cell Types:

    • Prokaryotic Cells:

    • Generally smaller, lack membrane-bound organelles, no nucleus (e.g., bacteria).

    • Eukaryotic Cells:

    • Larger, contain membrane-bound organelles, including a nucleus (e.g., plants, animals, fungi).

Cell Theory

  • Cell Theory:

    • All organisms are comprised of one or more cells.

    • All cells arise from pre-existing cells through cell division.

  • Proposed in the 1800s; a cornerstone of biological understanding.

Information in Biology

  • DNA functions as hereditary material, composed of genes (discrete units of DNA).

  • Structure of DNA:

    • Double-stranded molecule with a phosphate backbone and complementary base pairs (adenine with thymine, cytosine with guanine).

  • Central Dogma of Molecular Biology:

    • Genetic information flows from DNA to RNA to protein:

    • Transcription: DNA to messenger RNA.

    • Translation: RNA to protein.

Energy and Matter in Life

  • Living organisms require energy derived ultimately from the sun, captured by photosynthetic organisms as chemical energy (e.g., carbohydrates).

  • Different forms of energy exist:

    • Kinetic energy: Motion.

    • Heat energy: Thermal energy.

Interaction in Biology

  • Here, organisms interact within their ecosystems:

    • Example: Turtles and fish benefit mutually by exchanging services (fish eat parasites off turtles).

Evolution

  • Developed by Darwin and Wallace; Darwin focused on natural selection as a mechanism for evolution.

  • Key Concepts of Evolution:

    • Common Ancestry: All species are related.

    • Descent with Modification: Species evolve over time through modifications.

    • Natural Selection: Acts upon individuals, but evolution occurs at the population level.

  • Population Definition: A group of individuals of the same species living in a specific area and able to interbreed.

  • Mechanism of Natural Selection:

    • Requires variation among individuals with heritable traits.

    • Favors traits that enhance reproductive success in a given environment.

    • Over time, advantageous traits increase in frequency within the population (e.g., dark vs. light beetles on a dark background).