DR. STEVEN POMARICO, INSTRUCTOR
AN INTRODUCTION TO LIFE ON EARTH
What is Biology?
--- The science of living organisms and life processes.
O.K., so what is science?
If biology is the science of “life,” what exactly is life?
We all recognize what life is, but it’s difficult to define.
The characteristics of life: 1) -Complex, organized structure
2) -Homeostasis - the ability to maintain the structure and regulate the internal environment.
3) -Response to stimuli - a change outside (or inside) leads to another change
4) -Ability to acquire material and energy >The material and energy are often transformed<
6) -Reproduction - either sexual or asexual >DNA is genetic information, the “blueprint” for the offspring<
7) -Ability to evolve - to change to fit the environment
Complex, organized structure The complexity of life is built in levels. (see fig 1-1)
Each level has ingredients or components which interact to make something greater than the sum of the parts.
-Organelles (not present in prokaryotes)
-Tissues (present only in multicellular eukaryotes)
-Organs (present only in multicellular eukaryotes)
-Organ systems (present only in multicellular eukaryotes)
-the ability to maintain the structure and regulate the internal environment.
Life is easier without a lot of changes to deal with.
Response to stimuli
Organisms react to external and internal stimuli.
Some reactions are slow and some reactions can’t be seen
Ability to acquire material and energy >The material and energy are often transformed<
Take in nutrient (food) for raw materials and energy (heterotrophs)
Use sunlight for energy (photosynthesis) and take in raw materials (autotrophs)
Metabolism changes the raw material and energy into the forms which are needed for maintenance, growth, reproduction, etc.
All organisms grow during their life
Individuals reproduce their own kind.
The genetic information for “How to build an offspring” is stored in the DNA of the parent(s) and that information is passed on to the offspring.
If the environment changes, then the population of organisms must change to fit the environment or possibly die out. This process of survival of the fittest is natural selection
The evolutionary changes are usually slow, taking several generations and occur by the accumulation of DNA changes known as mutations.
>>>>>All life forms have these characteristics in common, yet there is an amazing diversity in the forms of life on the planet.
All living organisms are organized into groups. Each of the major organizational groups called domains
There are two prokaryotic domains; Bacteria and Archaea and a eukaryotic domain; Eukarya.
Within the domains are at least 6 groups known as kingdoms (See fig. 1-1).
Each of the major organizational groups called kingdoms have different attributes which define them. (See table 1-1)
The first difference is cell type Prokaryotic versus Eukaryotic
|PROKARYOTES |EUKARYOTES |
|No nucleus or nuclear envelope |Nucleus with a nuclear envelope |
|Genetic material in a “nucleoid region” |Genetic material within the nucleus |
|No organelles or internal membranes |Contains cytosol with membrane-bound organelles |
Kingdom Cell Type