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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)