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Topic 1: Cell Theory (1.1 Introduction to Cells (Cell Theory…
Topic 1: Cell Theory
1.1 Introduction to Cells
Cell Theory
Understanding: According to the cell theory, living organisms are composed of cells
Principles of the Cell Theory:
Cells are the smallest units of life
All living organisms are composed of cells
All cells comes from pre-existing cells
Application: Questioning the cell theory using examples of exceptions
Exceptions to the cell theory:
Striated Muscle Fibres: (Skeletal Muscle)
Very Long (>300 mm)
Contain hundreds of Nuclei
Challenges the idea that cells always function as autonomous units
Giant Algae: Ex. Acetabularia
Some unicellulars can grow into large sizes
Only contain 1 nucleus
Challenges the idea that larger organisms are always made of many microscopic cells
Aseptate Fungi:
Hyphae not divided up into sub-units containing a single nucleus
Long undivided sections of hypha which contain many nuclei
Challenges the idea that living structures are composed of discrete cells
Functions of Life
Understanding: Organisms consisting of only one cell carry out all functions of life in that cell
Unicellular = Smallest organisms capable of independent life
Characteristics of Life:
Metabolism (undertake essential chemical reactions)
Response (responsive to internal and external stimuli)
Homeostasis (maintain a stable internal environment)
Growth (move and change shape or size)
Reproduction (produce offspring, either sexually or asexually)
Excretion (exhibit the removal of waste products)
Nutrition (exchange materials and gases with the environment)
Application: Investigate the functions of life in Paramecium and one named photosynthetic unicellular organism
Unicellular = One cell must carry out all the characteristics of life
Paramecium (heterotroph):