Overview
This lecture introduces core biological terms, characteristics of living things, and the hierarchical organization of biology from particles to the biosphere.
Introduction to Biology
- Biology is the study of living organisms and their interactions with non-living factors.
- "Biotic" means living; "abiotic" means non-living (often "a-" indicates absence).
- Ecology studies how biotic and abiotic factors interact.
Characteristics of Living Organisms
- Living things are composed of one or more cells (unicellular or multicellular).
- Ability to reproduce: asexual (identical offspring) or sexual (genetically unique offspring via gametes).
- Growth and development occur in both unicellular and multicellular organisms.
- Must obtain and use energy; key processes include photosynthesis and cellular respiration.
- Metabolism is the sum of all chemical reactions in an organism (distinct from metabolic rate).
- Respond to internal and external stimuli (e.g., blood glucose, heat, light).
- Maintain homeostasis (stable internal conditions like pH, temperature, glucose).
- Contain DNA as genetic material.
- Evolve and adapt over generations (basis for natural selection).
Viruses vs. Living Organisms
- Viruses lack most characteristics of life (not made of cells, no independent reproduction, no metabolism, don’t respond to stimuli, no homeostasis, do not grow/develop).
- Viruses can have DNA or RNA as genetic material (living things have only DNA).
- Viruses can evolve and adapt, which is their only life-like trait.
Levels of Biological Organization
- Subatomic Particles: Protons, neutrons, and electrons make up atoms.
- Atoms: Smallest unit of matter with element properties; matter has mass and occupies space.
- Molecules: Two or more atoms chemically bonded; macromolecules are key in living things.
- Cell Organelles: Functional structures within cells (e.g., mitochondria).
- Cells: Basic unit of life; can be prokaryotic or eukaryotic.
- Tissues: Groups of similar cells with a shared function (only in multicellular organisms).
- Organs: Structures made of several tissue types for specific tasks.
- Organ Systems: Groups of organs performing related functions.
- Organism: An individual living thing; defined at the species level (can produce fertile offspring).
- Population: Group of the same species living and interacting in an area; evolution acts at this level.
- Community: All populations of different species in an area, interacting.
- Ecosystem: The community plus abiotic (non-living) factors.
- Biosphere: All of Earth's ecosystems combined.
Key Terms & Definitions
- Biology — study of living things.
- Biotic — living factors.
- Abiotic — non-living factors.
- Homeostasis — maintaining stable internal conditions.
- Metabolism — all chemical reactions in an organism.
- Species — group able to produce fertile offspring.
- Population — same species in an area.
- Community — all living populations in one area.
- Ecosystem — living + non-living in one area.
- Biosphere — all ecosystems on Earth.
Action Items / Next Steps
- Review the characteristics of life and levels of biological organization.
- Prepare for the next lecture on organism classification and microevolution.