Life Science Module 4: Evolving Concept of Life

Module 4: Introduction to Life Science - Lesson 11: Evolving Concept of Life

• The cell is the basic unit of all organisms, distinguishing living from nonliving things.
• Cell understanding emerged with the invention of the microscope and has evolved with fields like Biology, Biochemistry, and Molecular Biology.
• 1658: Athanasius Kircher (Jesuit priest) observed maggots and other organisms arising from decaying animal bodies.
• 1658: Jan Swammerdam described oval-shaped red blood cells and noted globular particles in a frog embryo.
• 1665: Robert Hooke (English Physicist) described "cells" as microscopic compartments in cork (Latin word cella meaning small room).
• Hooke also summarized his microscopic observations in Micrographia.
• Hooke invented a compound microscope with a light illuminator.
• 1668: Antonie van Leeuwenhoek (Dutch scientist) learned to grind and study microscopic particles, organisms invisible to the naked eye (animalcules - protozoans, sperm cells, pond water, etc.).
• Leeuwenhoek was known for creating powerful microscopes (up to 300x magnification). He did not invent the microscope.

Needham's Test (1740)

• John Turberville Needham (English Biologist) believed microorganisms do not come from pre-existing ones.
• He heated infusions (nutrient broth) in an experiment.

Spallanzani's Experiment (1767)

• Lazzaro Spallanzani (Italian scholar) verified Needham's test.
• Spallanzani's experiment showed all life forms originate from pre-existing ones.

1831: Robert Brown

• Brown identified the nucleus as a crucial part of the cell.
• He found nuclei in various plant cells (epidermal, parenchymal, and internal), not just in leaves of orchids.

1838: Cell Theory

• Matthias Jacob Schleiden (botanist) proposed that all structural features of plants contain cells.
• Theodore Schwann (zoologist) stated all tissues are composed of cells.
• Schleiden's proposal (cytoblast) suggested cells originate from cellular components within, not external material.

1850: Cytoplasm

• Robert Remak, Rudolf Virchow, and Albert Kolliker refuted Schleiden's ideas and conducted experiments.
• Kolliker introduced the term "cytoplasm."

Discoveries of Other Cell Organelles (1890s)

• 1897: The endoplasmic reticulum (ergoplasm) was discovered.
• 1898: Carl Benda discovered the mitochondrion.
• 1898: Camilo Golgi discovered the Golgi Apparatus.

1882: Mitosis

• Walther Flemming coined the term "mitosis" and observed the splitting of chromosomes.

1888: Cell Cycle

• Wilhelm Waldeyer studied metaphase and other cell cycle phases in plants, animals, and microorganisms.

Lesson 12: Origin of First Life Forms

• Cell Theory: All cells originate from pre-existing cells.
• Theory of Special Creation: A theological doctrine that all life on Earth was created by divine intervention.
• Duane Tolbert Gish (Institute of Creation Research): Supported Special Creation, arguing that fossils don't support evolution.
• Cosmozoic theory (Panspermia): Life originated elsewhere in the universe and spread to Earth (e.g., as spores).
• Theory of Spontaneous Generation (Abiogenesis): Life arises from non-living components.
• 1668: Francesco Redi (Italian scientist): Conducted experiments to demonstrate maggots don't spontaneously arise but develop from fly eggs.

Lesson 13: Unifying Themes in Life

• Hierarchy of Organisms: A hierarchical organizational chart of organisms, from atoms to biomes.
  • Cell (basic unit of life)
  • Tissue (group of similar cells)
  • Organ
  • Organ System
  • Species
  • Community
  • Ecosystem
  • Biosphere
• Organism characteristics include adaptation to environment, homeostasis, energy use (ATP), development, nutrient utilization, and responses to environment (e.g., phototropism, geotropism).
• Relationships among organisms include symbiosis (mutualism, parasitism, commensalism, competition), predation (energy transfer), and perpetuation (reproduction).

Lesson 14: The Cell as the Basic Unit of Life

• Cell Organelles:
• Phospholipid bilayer: Protective barrier that controls substance entry/exit; Uniport, Symport, Antiport mechanisms describe protein-facilitated transport.
• Cell wall: Rigid structure maintaining plant cell shape, preventing bursting.
• Mitochondrion: Organelle responsible for ATP (energy) generation; also initiates programmed cell death (apoptosis).
• Golgi Apparatus: Organelle near the nucleus, linked to other organelles; involved in processing and transporting molecules.
• Vacuole: Stores water and wastes, larger in plant cells than animal cells.
• Peroxisome: Membrane-bound vesicles containing oxidative enzymes; involved in oxidation of long-chain fatty acids, and synthesis of plasmalogens.
• Lysosome: Organelle containing hydrolytic enzymes used for digestion and autophagy (self-destruction).
• Nucleus: Contains the nucleolus; the nuclear envelope includes the outer membrane (connected to the rough ER) and internal lamina for support.
• Nucleolus: Houses eukaryotic genetic material, involved in genome replication and transcription.
• Rough Endoplasmic Reticulum(RER): Network of membranes; responsible for protein folding (necessary for protein function).
• Smooth Endoplasmic Reticulum(SER): Extensive in liver; primarily involved in lipid processing, converting lipids into water-soluble products for excretion. This process takes place in the liver.
• Ribosomes: Composed of small and large subunits; assemble proteins on mRNA's (messenger RNA) code.
• Cytoplasm: Contains essential substances supporting the cell's metabolic activity.
• Flagellum: Filamentous protein structure powered by molecular motors using ATP energy for locomotion.
• Chloroplast: Organelle related to photosynthesis containing chlorophyll.

Assessment

• Seatworks and assignments (specific page numbers provided)