Themes and Foundations of General Biology: Study Notes

Ch 1 – Themes of Biology

What Characterizes Life?

Biologists define life by a set of common characteristics shared by all living organisms. These characteristics distinguish living things from non-living matter.

• Living things contain nucleic acids, proteins, carbohydrates, and lipids.

• Living things are composed of cells.

• Living things reproduce.

• Living things use energy and raw materials.

• Living things respond to their environment.

• Living things maintain homeostasis.

• Populations of living things evolve and have adaptive traits.

Homeostasis

Homeostasis is the process by which living organisms maintain a stable internal environment despite changes in the external environment.

• Examples: Regulation of body temperature, pH balance, and water content.

Natural Selection

Natural selection is the process by which beneficial genetic traits become more common in a population because they increase the chances of survival and reproduction.

• Members of a population possessing advantageous traits survive and reproduce more successfully.

Unifying Themes in Biology

Biology is organized around several unifying themes that help explain the diversity and complexity of life.

• Organization

• Information

• Energy and matter

• Interactions

• Evolution

Biological Organization

Biological organization uses reductionism, an approach that reduces complex systems to simpler components that are manageable to study.

Emergent Properties

Emergent properties result from the arrangement and interaction of parts within a system. The whole is greater than the sum of its parts.

• Emergent properties are characteristic of biological entities as a whole, not just their individual components.

• Example: Water's properties (cohesion, surface tension, ability to dissolve substances) emerge from the interaction of hydrogen and oxygen atoms.

Structure and Function in Biology

Structure and function are correlated at all levels of biological hierarchy. The shape and arrangement of biological structures enable their specific functions.

Cells: The Basic Unit of Life

Cell Theory

All living things are composed of cells, which are the basic units of structure and function in organisms.

• Two main types of cells: Prokaryotic and Eukaryotic

Comparison of Prokaryotic and Eukaryotic Cells

The following table summarizes the key differences between prokaryotic and eukaryotic cells:

Feature	Prokaryotic Cells	Eukaryotic Cells
Nucleus	No true nucleus; DNA in nucleoid region	Has a membrane-bound nucleus
Size	Generally small (1–5 μm)	Larger (10–100 μm)
DNA Structure	Circular DNA, usually a single chromosome	Linear DNA arranged in multiple chromosomes
Membrane-Bound Organelles	Absent	Present (mitochondria, ER, Golgi apparatus, etc.)
Cell Wall	Present (peptidoglycan in bacteria)	Present in plants (cellulose) and fungi (chitin); absent in animals
Ribosomes	Small (70S)	Larger (80S in cytosol, 70S in mitochondria/chloroplasts)
Cell Division	Binary fission	Mitosis or meiosis
Examples	Bacteria, Archaea	Plants, Animals, Fungi, Protists

Genetic Material: Chromosomes, DNA, and Genes

• Chromosomes: Thread-like structures made of DNA and proteins that carry genetic information in the form of genes.

• DNA: The molecule that stores genetic instructions for the development, functioning, growth, and reproduction of all living organisms.

• Genes: Segments of DNA that contain instructions to make specific proteins or functional RNA, determining traits and characteristics.

DNA Structure and Function

• DNA is a double helix composed of two strands.

• The four nucleotides in DNA are: Adenine, Guanine, Cytosine, and Thymine.

• Base pairing: Adenine pairs with Thymine (A-T) via 2 hydrogen bonds; Guanine pairs with Cytosine (G-C) via 3 hydrogen bonds.

Inheritance and Gene Expression

• Each parent contributes a gamete containing half of their DNA; offspring inherit a full set of genes from both parents.

• Gene expression: The process of converting information from a gene to a cellular product (usually a protein).

• Process: DNA → Transcription → mRNA → Translation → Protein

Genomics and Proteomics

• Genome: An organism's entire set of genetic instructions.

• Genomics: The study of sets of genes within and between species.

• Proteome: The entire set of proteins expressed by a cell or group of cells.

• Proteomics: The study of proteins and their properties.

Energy Flow and Chemical Cycling

• Energy flows through ecosystems, entering as light and exiting as heat.

• Chemical elements (e.g., carbon, nitrogen, oxygen) are recycled within ecosystems.

Interactions and Evolution

Interactions Between Organisms and Environment

• Both organisms and their environments are affected by their interactions.

• Types of interactions: Mutually beneficial (e.g., cleaner fish and host), One benefits/one harmed (e.g., lion kills zebra), Both harmed (e.g., plants compete for limited resources).

Patterns Explained by Evolution

• Unity: Similar traits among species explained by descent from a common ancestor.

• Diversity: Wide variety of species and adaptations explained by natural selection and evolutionary processes.

Domains and Kingdoms of Life

• Three domains: Bacteria, Archaea, Eukarya

• Kingdoms in Eukarya: Plantae, Fungi, Animalia

Universal Genetic Language

• DNA is the universal genetic language common to all organisms.

Evolution and Natural Selection

Evidence for Evolution

• Fossils document the evolution of life on Earth.

Natural Selection: Steps and Effects

• Population with varied inherited traits

• Elimination of individuals with certain traits

• Reproduction of survivors

• Increased frequency of traits that enhance survival and reproductive success

Phylogenetic Relationships

• Evolutionary relationships are presented in treelike diagrams (phylogenies).

The Scientific Method

Science and Inquiry

• Science: The search for information and explanation.

• Includes making observations, forming logical hypotheses, and testing hypotheses.

Data and Data Categories

• Data: Recorded or collected observations.

• Qualitative data: Descriptions.

• Quantitative data: Recorded measurements.

Reasoning in Science

• Inductive reasoning: Drawing generalizations from specific observations. Inductive = Small → Big

• Deductive reasoning: Using general premises to make specific predictions. Deductive = Big → Small

• Example of deductive reasoning: "All birds have wings. A sparrow is a bird. Therefore, a sparrow has wings."

Hypotheses and Experiments

• Scientific hypothesis: A testable and falsifiable explanation for a natural phenomenon.

• Scientific experiment: A controlled procedure to test a hypothesis and observe the effects of changing one or more variables.

• If the experiment does not support the hypothesis, revise the hypothesis and test again.

• If the experiment supports the hypothesis, repeat and test further.

Controlled Experiments and Variables

• Controlled experiments involve an experimental group and a control group.

• Experimental variable: The factor that is manipulated.

• Independent variable: The factor manipulated by researchers.

• Dependent variable: The effect of the manipulated factor.

Theory vs. Hypothesis

• A theory is broader in scope than a hypothesis and is supported by a large body of evidence.

Peer Review and Scientific Collaboration

• Scientists working in the same field check each other's claims by confirming observations or repeating experiments.

Science and Technology

• Science and technology are interdependent; advances in one often lead to advances in the other.