WHAT IS LIFE? Pages Organisms: living things, like the ones shown here are very different, but they all share 6 of the same characteristics

SIX Characteristics of Life Made up of cells Made up of similar chemicals Uses energy Grows and develops Responds to the world around them Reproduces

All living things are made of cells Cell: the basic unit of structure and function in an organism. An organism can be made up of one cell (unicellular) or many cells working together (multi-cellular). We study cells with a microscope, WHY?

All living things contain similar chemicals Water – Most abundant chemical in cells Carbohydrates - Energy Proteins – Building material of cells Lipids (fats) – Building material of cells Nucleic Acids – DNA and RNA

All living things use energy. An organisms cells are always hard at work.

All living things grow and develop. Growth: the process of becoming larger Ex. This blue crab is molting b/c it grew too large for its old shell. Development: the process of change during life to become a more complex org. Ex. Metamorphosis from an egg, larva, pupa, to finally an adult butterfly.

All living things respond to their surroundings. Stimulus: a change in an organism’s surroundings that causes the organism to react. Response: an action or change in behavior

All living things reproduce. Reproduce: to produce offspring that are similar to the parents

Life ONLY arises from Life Years ago it was believed that living things could come from non-living things –Ex. Flies came from rotting meat –Frogs came from mud puddles Spontaneous generation: the mistaken idea that living things can arise from non-living sources.Spontaneous generation

Two Scientists Worked Hard to DISPROVE this Mistaken Theory Francisco Redi’s Experiment –People believed flies came from rotting meat –Redi hypothesized that they came from microscopic EGGS that were laid on the meat. –Redi performed a controlled experiment in which put meat in two jars….one he left uncovered. –The flies got into one jar and not the other.

Louis Pasteur’s Experiment –People believed bacteria came from chicken soup –Pasteur hypothesized that the bacteria was carried in the air and reproduced in the warm broth. –Pasteur performed a controlled experiment in which put soup in two flasks –He boiled both flasks of soup to kill any pre- existing bacteria, then topped one flask while the other was left open. –After a few days, soup got cloudy with bacteria, in the open flask, the closed remained clear.

The Needs of Living Things Energy –Autotroph (gets energy from the sun) vs. Heterotroph (gets energy from eating) Water Living Space Stable Internal Conditions –Homeostasis: maintaining stable internal conditions