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)

Made of cells Cell Theory says that  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

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 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 = 30 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 Some have a cell wall

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 – CO 2, NH 4 and heat, sweat, urine/feces, even oxygen (plants) Energy is used to do WORK

Respond / Interact 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…..

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 die)

Highly Organized Adult human has +30 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.

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 Cal a day to stay alive of the need by an adult human.

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)

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)