Basic Biological Principles

Characteristics of Life, Cells, Organization of Life

7 Characteristics of Life

• Living things MUST exhibit these 7 characteristics to be considered living:1. Order2. Metabolism3. Response to a Stimulus4. Reproduction5. Homeostasis6. Growth and Development7. Evolutionary Adaptation

7 Characteristics of Life

• Order– Organized arrangement of parts in a living thing or

group of living things• Smallest to largest

– Atom– Molecules– Cell – Tissue– Organ – Organ system– Organism

• Single-celled organisms stop at the cell level and most multi-celled organisms exhibit all levels

(1) Order

7 Characteristics of Life

• Metabolism – All of the chemical reactions that take place in an

organism– Chemical reactions either break down molecules

or build up molecules in the body– Organisms must be able to perform chemical

reactions

(4) Energy processing

• Response to a Stimulus– Must be able to react to the environment– Running away from a prey or a plant growing towards

light• Reproduction– Produce more of your own kind– Asexual-only ONE parent and make a genetically

identical clone to the parent– Sexual-usually more than one parent and make

genetically different offspring from the parents

7 Characteristics of Life

(5) Response to the environment

(6) Reproduction

• Homeostasis– Maintain stable internal conditions• Temperature, water, salts, gases and even cell number

– If our temperature increases, humans sweat– If water levels drop too low, we get thirsty and our

kidneys save water• Growth and development– Increase in size and mature/change from embryo

to adult

7 Characteristics of Life

(2) Regulation

(3) Growth and development

• Evolutionary Adaptation– Ability of an entire species to change genetically

over generations to survive in a changing environment

– Species that do not adapt will become extinct

7 Characteristics of Life

(7) Evolutionary adaptation

• Cells– Basic unit of structure and function in a living

thing (first level where life appears)– Two types of cells:• Prokaryotic cells-cells that do NOT have a nucleus or

membrane-bound organelles• Eukaryotic cells-cells that HAVE a nucleus and

membrane-bound organelles

Cells

• Cell Size– Cells are small to be efficient• Being small allows them to maximize their ability to

exchange nutrients and waste with the environment• Cells can become larger by:

– Increasing surface area (flat shape and folds in membranes)– Dividing up labor

• Prokaryotic cells remain small to maintain efficiency• Eukaryotic cells can be larger because labor is divided

into compartments

Cells

• Similarities between prokaryotic and eukaryotic cells (every cell has these structures):– Cell membranes– Genetic material (DNA)– Ribosomes– Cytoplasm

Cells

Eukaryotic Cells

• Nucleus• Membrane-bound

organelles• Larger in size• Linear chromosomes

Prokaryotic Cells

• No nucleus• No membrane-bound

organelles• Smaller in size• Circular chromosomes

Differences between Prokaryotic and Eukaryotic Cells

DNA(no nucleus)

Prokaryotic cell

Membrane

Eukaryotic cell

Nucleus(contains DNA)

Organelles

Prokaryotic Cell Structure

External Structures• Pili• Flagellum• Capsule• Cell wall• Cell membrane

Internal Structures• Ribosome• Cytoplasm• Nucleiod• Plasmid• Chromosome

Nucleoid

Ribosomes

Plasma membrane

Cell wall

Capsule

Flagella

Bacterialchromosome

Pili

Eukaryotic Cell Structure (found in both plant and animal cells)

• Flagellum• Cilia• Cell (plasma)

membrane• Cytoskeleton• Nucleus• Nucleolus

• Endoplasmic reticulum• Golgi apparatus• Lysosome• Mitochondrion• Centrosome• Food vacuole• Vesicle

Smooth endoplasmicreticulum

Roughendoplasmicreticulum

CYTOSKELETON:

NUCLEUS:

Nuclear envelope

Chromosomes

Nucleolus

Ribosomes

Golgiapparatus

Plasma membrane

Mitochondrion

Peroxisome

Centriole

Lysosome

Microtubule

Intermediatefilament

Microfilament

Eukaryotic Cell Structure

• Plant cells only– Cell wall– Central vacuole– Chloroplast

Smooth endoplasmicreticulum

Rough endoplasmicreticulum

CYTOSKELETON:

NUCLEUS:

Nuclear envelope

Chromosome

NucleolusRibosomes

Golgiapparatus

Plasma membrane

Mitochondrion

Peroxisome

Cell wall

Central vacuoleMicrotubule

Intermediatefilament

Microfilament

Cell wall ofadjacent cell

Chloroplast

Plasmodesmata