Cell Theory 2.1

Carissa Fletcher

Inter Community School Zurich

http://upload.wikimedia.org/wikipedia/commons/3/37/Wilson1900Fig2.jpg

What is a scientific theory?

A scientific theory is "a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment.“ (http://www.nap.edu/openbook.php?record_id=6024&page=2)

2.1.1 Outline Cell Theory (L2 Give a brief outline or summary)

Cell theory is a scientific theory that describes the properties of cells, it is one of the foundations of Cell Biology.

The cell theory states:• All living things or organisms are made of cells and their products.• New cells are created by old cells dividing into two.• Cells are the basic building units of life.

Credit for the theory is usually given to the scientists Schwann, Schleiden (1839) and Virchow (1855) (Virchow plagiarised from Remak).

http://www.biology.arizona.edu/cell_bio/tutorials/cells/cells3.html

C.Elegans

http://www.google.ch/imgres?imgurl=http://

http://lensonleeuwenhoek.net/overview.htm

2.1.2 Discuss the evidence for cell theory (L3 Give an account including, where

possible, a range of arguments for and against the relative importance of various factors, or comparisons of alternative hypotheses.)

1. When living things are observed under the microscope they consistently appear to be composed of cells.

http://labs.bio.unc.edu/Salmon/mitosis/newnewtdic.mov

2. Cells carry out a form of cell division to form new cells. This process of cell replication in eukaryotes is called mitosis and in prokaryotes is called binary fission.

The parental cell divides to produce identical daughter cells.

3. The cell is the smallestunit of organisation that can show all the characteristics of living processes. As organellesoften need other organelles for successful function.

http://www.chemgapedia.de/vsengine/vlu/vsc/en/ch/8/bc/vlu/zellbio/zellaufbau.vlu/Page/vsc/en/ch/8/bc/zellbio/eukaryont2.vscml.html

2.1.3 State that unicellular organisms carry out all the functions of life. (L1 answer without explanation)

Movement Respiration Sensitivity Growth Reproduction Excretion Nutrition Cells Homeostasis

http://www.buzzle.com/articles/euglena-facts.html

Euglena