1. Ch.1.4: CHARACTERISTICS OF LIFE
In order to be considered LIVING an organism must meet
all 8 of the following criteria:
1. Made of cells, at least one
2. Take in and use energy, (do work, produce waste)
aka METABOLISM
3. Respond to their environment
4. Grow, develop and die
5. Be highly organized
6. Maintain homeostasis
7. CONTAIN DNA to Reproduce more cells and more organisms
8. CONTAIN DNA so have a means to evolve (“adapt” too easy to confuse with “respond)

2. Made of cells Cell Theory says that Cells must have at least
Cells are the basic structural and functional units of life
All organisms have at least one cell
Cells only come from pre-existing cells
Cells must have at least
1. cell membrane (defining boundary; keep things inside)
2. cytoplasm (material inside cell)
3. genetic material (DNA in the form of a chromosome)
4. free ribosomes ( to make proteins for the cell)
Viruses are “less than” a cell
Multicellular organisms vs. unicellular organisms
Prokaryotic cells vs. Eukaryotic cells
Plant cells vs. Animal cells vs. Bacteria cells

3. Cell Types PROKARYOTIC CELLS Pro/pre/ before
‘karyo’ = center or kernel
CM, cytoplasm, DNA and free ribosomes
Bacteria
Must be single cell
No nucleus made with nuclear membrane to keep in the 1 chromosome
No organelles that are made of membranes; no internal membrane structures or compartments …. Still MUST have a cell membrane
May have cell wall
EUKARYOTIC CELLS
‘eu’ = true
‘karyo’ = center or kernel
CM, cytoplasm, DNA and free ribosomes
Plants, Animals, Fungi and Protista
Can be single cell (mildew and algae) can be multicellular (people = 300 trillion)
Nucleus made of nuclear membrane to keep in the many chromosomes
Lots of membrane bound organelles that make compartments like endoplasmic reticulum and vacuoles and mitochondria … In addition to a cell membrane
Some have a cell wall

4. Take in energy METABOLISM Maintaining life requires constant energy
Photosynthesis provides energy for food web (solar energy becomes chemical energy when trapped and stored as sugar)
Autotrophic plants make their own “food”
Heterotrophic organisms must eat
Waste is given off – CO2, NH4 and heat , sweat, urine/feces, even oxygen (plants)
Energy is used to do WORK

5. Respond / Interact (don’t confuse with Adapt)
Respond means react
Respond to internal environment (low blood sugar, tired and hungry)
Respond to external environment (predator/ prey)
Immediate and short term compared to adaptations
Senses
Stimuli – something that an organism respond to
Examples: groan when alarm clock rings, stomach growls when hungry, dog growls when upset, hibernate when cold, grow toward the sunlight, shiver when cold, laugh, sweat during a test, make adrenaline when afraid…..

6. Grow, Develop and Die
Growth indicates an increase in size, bigger organisms and/or bigger cells – could be more cells
Development refers to changes in structure and function.
Baby -> toddler -> teen -> adult -> elderly.
Also changes such as metamorphosis
Senescence means to age.
Living = mortal, won’t live forever. Even things with long life spans (redwood tree years, still eventually age/ wear out/ die)

7. Highly Organized Adult human has +300 trillion cells
They aren’t just in a pile, and you wouldn’t work well as one big 120 pound cell!
Cells are highly organized internally by cell membrane, organelles, DNA , etc.
Organisms are also highly organized with cells  tissues  organs  organ systems and then organisms
Unicellular organisms are also highly organized.

8. Homeostasis
Process of maintaining a steady internal state while the external environment changes
Body temp, blood glucose level, hydration, etc.
Requires a constant input of energy.
1000 Cal a day to stay alive of the need by an adult human.

9. Have DNA for Reproduction
Cells wear out and need to be replaced
Skin cells reproduce, asexually, to make more skin cells
Asexual means one source of DNA (one parent); one skin cell divides and there are 2 new skin cells
Organisms will grow develop and die – have to make next generation or their species will be extinct
Reproduce more individuals by asexual reproduction or make reproductive cells to be used in sexual reproduction (potential new organisms… not every acorn will be a tree)

10. Have DNA to Evolve (sometimes called Adapt)
The gene pool of a population changes over long periods of time. (7-10 generations)
This is genetic, not nervous, endocrine, etc.
This is much slower and longer lasting than ‘responses’
Incorporated into the structure of DNA is its amazing ability to be replicated accurately AND the ability to change and to pass on the new version to the next generation.
Process driven by Natural Selection
(if you have genes for more successful traits – at that time, in that setting, then you will have offspring that will be successful at leaving offspring. If environment changes then “successful” traits will also change)