Biology Lecture Notes: Characteristics of Life, Levels of Organization, Cells, Interactions, and DNA to Proteins

Characteristics of Life

  • Organization: Life ranges from single cells to multicellular organisms; cells are the fundamental building blocks.

  • Evolutionary Adaptation: Traits change over generations to better suit the environment.

  • Regulation: Internal control of processes to maintain stability (homeostasis) in changing environments.

  • Energy Processing: Obtaining and using energy (e.g., metabolism).

  • Growth and Development: Increase in size and maturation guided by DNA.

  • Response to Environment: Ability to detect and respond to stimuli.

  • Reproduction: Producing offspring to ensure the continuation of the species.

Themes of Biology

  • Organization

  • Information (e.g., DNA)

  • Energy and Matter (flow and cycling)

  • Interactions (among organisms and with the environment)

  • Evolution (descent with modification)

  • Structure and Function: The form of a biological structure is closely related to its function (example: hummingbird beak shape is suited for feeding on nectar).

Levels of Organization

From smallest to largest:

  • Molecule

  • Organelle

  • Cell

  • Tissue

  • Organ

  • Organism

  • Population

  • Community

  • Ecosystem

  • Biome

  • Biosphere

The Cell: Basic Unit of Life

  • Eukaryotic cells:

    • Defined nucleus enclosed by a membrane.

    • Contain membrane-bound organelles (e.g., mitochondria, endoplasmic reticulum).

    • Include plants, animals, fungi, and protists.

  • Prokaryotic cells:

    • No nucleus; genetic material (DNA) is in a region called the nucleoid.

    • Lack membrane-bound organelles.

    • Include Bacteria and Archaea.

  • Key distinction: The primary difference is the location of DNA and the presence/absence of membrane-bound compartments.

Taxonomy and Domains of Life

  • Three Domains:

  1. \text{Bacteria}

  2. \text{Archaea}

  3. \text{Eukarya}

  • Within Eukarya, major kingdoms include:

    • Plantae

    • Fungi

    • Protista (a very diverse group that doesn't fit neatly into other kingdoms)

    • Animalia

  • Taxonomy: The science of classifying organisms. Organisms are typically named by their genus and species.

Making a Protein (Gene Expression)

  1. DNA (a gene) contains the genetic information for building a specific protein.

  2. Transcription: Messenger RNA (mRNA) is synthesized from the DNA template in the nucleus.

  3. mRNA leaves the nucleus and travels to a ribosome (the protein synthesis factory).

  4. Translation: Amino acids are assembled in a specific sequence according to the mRNA codons, forming a polypeptide chain.

  5. The polypeptide folds into its unique three-dimensional functional protein structure, which then carries out a specific trait or behavior.

Energy and Matter in Living Systems

  • Producers: Organisms that make their own energy, usually through photosynthesis (e.g., photosynthetic plants, algae, some bacteria).

  • Consumers: Organisms that obtain energy by consuming other organisms.

  • Energy Flow:

    • Energy typically originates from sunlight.

    • Sunlight is converted into chemical energy by producers.

    • Chemical energy is transferred through food webs.

    • Energy is used for work in organisms.

    • Some energy is inevitably lost as heat at each transfer.

  • Matter Cycling:

    • Chemical nutrients (e.g., carbon, nitrogen) are recycled within an ecosystem.

    • Producers absorb nutrients from the environment.

    • Consumers obtain nutrients by eating producers or other consumers.

    • Decomposers (e.g., fungi, bacteria) break down dead organic matter, returning nutrients to the soil and atmosphere for reuse by producers.

Interactions and Regulation (Feedback Mechanisms)

  • Feedback regulation: Biological processes are controlled by their output.

  • Negative feedback: Stabilizes systems by reducing the initial stimulus or change. This is the most common type of regulation (e.g., regulation of body temperature, blood sugar levels).

  • Positive feedback: Amplifies the initial stimulus or change, often leading to a rapid end point or snowball effect (e.g., childbirth contractions, blood clotting).

Information and Protein Synthesis (DNA, RNA, Proteins)

  • DNA (Deoxyribonucleic Acid):

    • The "recipe book" containing all genetic information for an organism's traits and behaviors.

    • Structure: double helix, composed of nucleotide building blocks.

    • Location: primarily in the nucleus of eukaryotic cells.

  • Genes: Specific segments of DNA that contain the instructions for coding a particular protein.

  • RNA (Ribonucleic Acid):

    • Ribonucleic acid; typically single-stranded.

    • Contains ribose sugar (instead of deoxyribose in DNA).

    • mRNA (messenger RNA): Carries genetic instructions from DNA in the nucleus to the ribosomes in the cytoplasm to make proteins.

  • Proteins: The workhorse molecules that perform most cellular functions, executing traits and behaviors.

  • Genome: The complete set of DNA (all genes) within an organism.

  • Gene expression: The process where gene intrustructions are used to make a protein