Properties of Living things
· Early Views of life
§ 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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Last updated; 03/11/2004