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**Refer to handout and make jot notes**. Unit 2 Reproduction: The Cell. The History of Cell Discovery :
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Unit 2 Reproduction: The Cell The History of Cell Discovery: Hans & Zacharias Janssen – 1590 – father and son Dutch spectacle-makers are sometimes credited for inventing the first truly compound microscope. However, the origin of the microscope - just like the origin of the telescope - is a matter of debate. Robert Hook - 1665 – improved on the compound microscope and illumination system - observed slices of cork through a microscope and compared cork’s tiny cavities to “small rooms” such as in a monastery and called them “cella”, which is Latin for cell - “Father of Microscopy" and published 'Micrographia' Anton van Leeuwenhoek - 1680's – produced over 500 single lens microscopes - discovered bacteria, protozoa, human blood cells & spermatozoa Matthias Schleiden - 1838 - proposed that all plants are made up of cells Theodor Schwann - 1839 - proposed that all animals are made up of cells Rudolph Virchow - 1855 - proposed that cells can come only from other cells - "Father of Pathology" cited as the first to recognize leukemia cells The last three scientists are cofounders of the Cell Theory.
Discovering the Origins of Cells: A TimelIne Redi Tested what theory: What was Redi’s experiment and conclusions? • What was Needham’s experiments & conclusions? What was Pasteur’s experiments & conclusions? Stated living cells come from other living cells Needham 4th C BC 1665 1668 1680 Mid 1700’s Mid 1800’s 1855 1838 1839 Hooke Redi A. van Leeuwenhoek Spallanzani Pasteur Virchow Aristotle Rejection to what hypothesis: His Theory is : - Observed living cells such as bacteria, protozoa, human blood cells & spermatozoa through a simple microscope What was Spallanzani’s experiment & conclusions? - First scientistto call spaces in cork “cells” Schwann Schleiden - Discovered that plants are made of cells - Discovered that animals are made of cells
What is a Cell? - the basic structural unit of life Technological advancements such as improved microscopes have helped to study living things in detail • Cell Theory: - the idea that cells are the fundamental units of life • All organisms are composed of one or more cells. • Cells are the basic units of structure and function in all organisms. 3. All cells come from the division of previously existing cells therefore they must contain genetic information. The activity of an entire organism depends on total activity of its independent cells.
Characteristics of Living Things • It is not always an easy thing to tell the difference between living, dead, and non-living things. Prior to the 1600's many people believed that nonliving things could spontaneously turn into living things. For example, it was believed that piles of straw could turn into mice. That is obviously not the case. There are some very general rules to follow when trying to decide if something is living, dead, or non-living. Listed here are the six rules used by scientists: • Living things: - are made of cells. • - obtain and use energy. - grow and develop. - reproduce. - respond to their environment. - adapt to their environment. • If something follows one or just a few of the rules listed above, it does not necessarily mean that it is living. To be considered alive, an object must exhibit all of the characteristics of living things. Sugar crystals growing on the bottom of a syrup container is a good example of a nonliving object that displays at least one criteria for living organisms. • Can you think of some other examples of nonliving objects displaying living characteristics?
III. Two Basic Cell Types: 1. Prokaryotic Cells - means “without nucleus” - single-celled organisms - lack internal membrane bound organelles (ie. no nucleus) - ex. bacteria - range in size from 1 to 10 micrometers (µm) 2. Eukaryotic Cells - means “true nucleus”` - multi-cellular organisms - contain many membrane-bound organelles (ie. nucleus) - all living organisms other than bacteria, ranging in size from 10 to 100 micrometers (µm) **Both prokaryotic and eukaryotic cells possess a cell membrane &/or cell wall, genetic material (DNA or RNA), ribosomes and cytoplasm.
Redi F. Redi (1626 – 1697)
