Biology: Levels of Biological Organization

Study Notes

Biology: The study of life and organisms and their interactions with one another and their environments.
Cell Theory: A foundational principle in biology consisting of three main postulates:
- All living things are composed of one or more cells.
- The cell is the basic unit of life.
- All cells arise from pre-existing cells.

Atoms: Basic unit of matter; bonds form molecules.
Molecules: Groups of atoms; smallest unit of chemical compounds; molecular structures compose cells.
Cells: Smallest living units; they group into tissues.
Tissues: Groups of similar cells working together; organize into organs.
Organs: Comprised of multiple tissue types; specialized for specific tasks.
Organ Systems: Groups of organs that function together.
Organism/Individual: A single living entity with all necessary organ systems.
Population: Multiple individuals of the same species in a defined area and specific time.
Community: Interactions among different populations in a specific area.
Ecosystem: A community and its non-living environmental factors.
Biosphere: The global sum of all ecosystems; areas of the Earth that support life.

Zacharias Janssen (1595): Invented the first compound microscope; introduced the concept of using two glass lenses to magnify objects.
Robert Hooke (1665): Utilized a compound microscope to examine cork slices; discovered and named "cells," referring to their resemblance to monastery rooms; identified dead cells in cork tissue.
Anton van Leeuwenhoek (1674): Enhanced microscope design; first to document live microorganisms from diverse samples; termed “animalcules” for motile organisms; recognized motility as a sign of life; known as the "Father of Microbiology."
Robert Brown (1831): Discovered the nucleus as a central structure in plant cells, contributing to the understanding of cellular organization.

Microscope: A scientific instrument designed to view very small objects by enlarging the image. Different types enhance observational capabilities in biology, leading to significant discoveries in cell structure and function.