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Properties of Living things

 

 

·        Early Views of life

o       Vitalism:

§        Life was generated by a objects acquisition of “Ethers” which would manifest animate it.

§        Led to idea of spontaneous generation

·        Flies came from dead animals

·        Mice came from Hay

§        Idea was challenged by scientist Francesco Redi in 1698.

·        Designed an experiment where 3 jars contained meat.

o       One Jar contained meat and had an open top which would allow the passage of “ethers” and flies. (maggots would appear on the meat)

 

o       The second jar was covered with an airtight lid allowing the passage of neither “ethers” or flies. (no maggots would appear on the meat)

 

o       The third was covered by a screen allowing passage of “ethers”, but not flies. (no maggots would appear on meat)

     Setup 1              Setup 2           Setup 3

 

o       Since the third setup would theoretically allow the passage of “ethers”, but no maggots appeared, it was implied that flies were the source of the maggots.

 

·        Led to the theory of Biogenesis

o       All life comes from preexisting life

 

PROPERTIES of LIFE

 

1. Be made of Cells.

·        The Cell is the basic unit of life

·        Is self contained and possesses a barrier (membrane) which separates itself from the environment.

·        Two types of organisms.

·        Unicellular - One celled organism (Uni=1)

·        Multicellular - Many cells (Multi=”many”)

 

2. Living Things must Reproduce.

·        Must be able to create more of it’s own kind

·        Two types of reproduction:

·        Sexual - Two parent organisms combine genetic material to produce the offspring.

·        Asexual - When a single organism can divide or “bud” to create it’s offspring without another of it’s species.

 

3. Living things must Have DNA.

·        (Universal Genetic Code?)

 

4. Living things must Grow & Develop.

·        Growth refers to two processes.

·        Increase in the number of cells.

·        Increase in the size of cells.

·        Development refers to changes in the organism which occur through it’s life-span.

·        Includes cell differentiation.

·        Includes organ development

·        Includes aging & death.


 

5. Living things obtain & use energy.

·        Energy is used by all living things for growth, development & reproduction.

·        Life processes which result in “building” the organism ia known as Anabolism.

·        Life process where energy is extracted by “breaking-down” substances is called Catabolism.

 

6.  Living things must Respond (or react) to their environment in some way.

·        Something which causes an organism to react is known as a Stimulus (stimuli).

·        The ability of an organism to react is called Irritability.

·        Most responses are geared for maintaining Homeostasis.

·        Homeostasis is a process where an organism maintains a stable internal environment so life can continue.

·        Some examples include temperature, pH, and water content of the cell.

 

7. Must Maintain homeostasis.

·        Internal stable set of internal conditions allowing the chemical reactions of life to occur.

 


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Mike Stanley

Last updated; 03/11/2004