Biology: Exploring Life – Chapter 1 Study Notes

Biology: Exploring Life

The Scientific Study of Life

Biology is the scientific study of life, aiming to understand the living world and its processes. Biologists investigate what defines life and the characteristics that distinguish living organisms from non-living matter.

• Definition: Biology is the branch of science concerned with the study of living organisms and their interactions with one another and their environments.

• Key Properties of Life:

  • Order: Living things exhibit complex but ordered organization.

  • Reproduction: Organisms reproduce their own kind.

  • Growth and Development: Inherited information carried by genes controls the pattern of growth and development.

  • Energy Processing: Organisms take in energy and use it to power all their activities.

  • Regulation: Organisms have regulatory mechanisms that maintain a beneficial internal environment (homeostasis).

  • Response to the Environment: Organisms respond to environmental stimuli.

  • Evolutionary Adaptation: Over generations, traits that enhance survival and reproductive success become more common.

• Cell: The cell is the structural and functional unit of life. All living things are composed of one or more cells.

Classifying Life: The Three Domains

Biological Classification and Domains

Biologists classify species into broader groups to organize the diversity of life. The most widely accepted system divides life into three domains, based on cellular organization and genetic differences.

• Domain Bacteria: Consists of prokaryotic organisms with simple cells lacking a nucleus. Bacteria are found in many environments and play key roles in ecosystems.

• Domain Archaea: Also prokaryotic, but genetically and biochemically distinct from bacteria. Many archaea live in extreme environments.

• Domain Eukarya: Includes all eukaryotic organisms, which have cells with a nucleus. This domain encompasses:

  • Protists (a diverse group of mostly unicellular organisms)

  • Kingdom Plantae (plants)

  • Kingdom Fungi (fungi)

  • Kingdom Animalia (animals)

Example: Humans belong to Domain Eukarya, Kingdom Animalia.

Hierarchy of Organization

Levels of Biological Organization

Biologists study life at many levels, from the smallest molecules to the entire planet. This hierarchy helps organize the complexity of life into manageable levels.

• Molecule: A chemical structure consisting of two or more atoms.

• Organelle: A membrane-bound structure that performs a specific function in a cell.

• Cell: The fundamental unit of life.

• Tissue: A group of similar cells performing a specific function.

• Organ: A structure composed of several tissue types that perform a specific function.

• Organ System: A group of organs that work together to perform a major function.

• Organism: An individual living thing.

• Population: All individuals of a species living in a specific area.

• Community: All organisms in an ecosystem.

• Ecosystem: All living and nonliving components of a particular area.

• Biosphere: All environments on Earth that support life.

Emergent Properties: New properties that arise at each level of organization, resulting from the arrangement and interactions of parts as complexity increases.

Example: A single nerve cell cannot think, but networks of nerve cells in the brain can produce consciousness.