Characteristics of Living Things

Scientists say there might be up to 50 million different species of organisms on earth  What do all those have in common? –Made of cells  Also Made of matter-atoms and elements –Cells are made of atoms  All 50 million species are made mainly of carbon, hydrogen, nitrogen, and oxygen atoms.

Percentages of elements in all living things:  Oxygen: 65%  Carbon: 18.5%  Hydrogen: 9.5%  Nitrogen: 3.3  The rest are trace amounts of calcium, phosphorous, potassium, sulfer, chlorine, sodium, etc…

Fish salamander turtle chicken pig rat dog human

So where did life come from?  Until the 1600’s, most people believed in spontaneous generation. –Life can arise from non-living matter –Believed for 2,000 years.  For example: mice came from straw and frogs and turtles came from rotting wood and mud at the bottom of a mud puddle Spontaneous Generation

Francesco Redi (1668)  Disproved spontaneous generation  In his days, people thought maggots came from rotting meat.  This meant that flies (adult maggots) would have to come from dead animals (meat)

Redi’s experiment  In other words, they thought living things could arise from non living things.  Series of experiments using jars, lids, meat, and cloth netting… –Scientific method maybe????

Redi’s experiment Fly burgers

Characteristics that all life forms share…  Made of cells  Able to move: –ie(phototropism)  Perform complex chemical activities –Ie; digestion and photosynthesis  Grow and develop  Respond to stimulus  Reproduce

Ability to move…  Find food and shelter  Escape danger  What about plants? –Ever placed a plant near a window? Have you noticed how it leans towards the sunlight? Mimosa Plant

Perform Complex Chemical Activities  All life has to “break down” and “build up” substances (such as food)  Once broken down, they release energy.  How do our bodies do this? –By a process called metabolism

Metabolism   Metabolism generally involves the release or use of chemical energy. Nonliving things do not display metabolism.  Complete set of chemical reactions that occur in living organisms –1. Ingestion (eating)-getting food into your mouth. Now metabolism can begin… –2. digestion- process by which food is broken down into simpler substances (sugars, carbohydrates, etc) –3. Respiration-process by which living things take in oxygen and use it to produce energy

Metabolism…(cont) –4. Excretion- process of getting rid of waste materials.  If we didn’t get rid of the waste we would be literally poisoning your body

Respond to Stimuli  Living things respond to changes in light, heat, sound, and chemical and mechanical contact.  To detect stimuli, organisms have means for receiving information, such as eyes, ears, and taste buds.

Growth   Growth requires an organism to take in material from the environment and organize the material into its own structures. – –To accomplish growth, an organism expends some of the energy it acquires during metabolism. – –A person, for example, digests a meal of meat and vegetables and transforms the chemical material into more of himself or herself.

Reproduction  A living thing has the ability to produce copies of itself by the process known as reproduction. These copies are made while the organism is still living.  There are 2 types of reproduction: –Asexual reproduction –Sexual reproduction

Asexual Reproduction  Asexual reproduction involves only one parent, and the resulting cells are generally identical to the parent cell. –Bacteria reproduce asexually.

Sexual Reproduction  Involves more complex organisms (compared to bacteria). –2 parents contribute to the traits of the organism. –The new organism generally has a combination of the traits of both parents.  Not identical to either of the parents.