Ch.1.4: CHARACTERISTICS OF LIFE

In order to be considered LIVING an organism must meetall 8 of the following criteria: 1. Made of cells, at least one 2. Take in and use energy, do work, produce waste 3. Respond to their environment 4. Grow, develop and die 5. Be highly organized 6. Maintain homeostasis 7. Heredity; contain DNA

Be able to reproduce; at least cells, and eventually organisms using the directions in the DNA

DNA is able to change and these changes allow populations to evolve

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 ; • 1 chromosome• No nuclear membrane around chromosome• No organelles that are made of membranes;

no internal membrane structures or compartments; including no nucleus/nuclear 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 found in single celled

organisms (mildew and algae) can be found in multicellular organisms (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

Maintaining life requires constant energyPhotosynthesis 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 eatWaste is given off – CO2, NH4 and heat ,

sweat, urine/feces, even oxygen (plants)Energy is used to do WORK

Respond

Respond means react 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 800 -2000 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 Homeo = same Stasis = steady; together = the same, steady state

Body temp, blood glucose level, hydration, etc. Requires a constant input of energy. 1000 Cal a day to stay alive of the 2000-2500

need by an adult human.

Heredity (Heritable Information )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 (egg/ sperm/pollen/spores) to be used in sexual reproduction (potential new organisms… not every acorn will be a tree)

Heredity (Heritable Information)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’ Impacts populations (genes available) NOT individuals

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)