PCAT Exam: Biological Processes - General Biology - Biology Basics

Biology is the study of living organisms and the processes that are vital for life. Scientists who study biology are interested in the origin, evolution, structure, function, growth, and distribution of these living organisms. They study these organisms on a cellular level, individually or as populations, and look at the effects they have on their surrounding environment.

There are five foundations of modern biology: cell theory, evolution, genetics, homeostasis, and energy.

Cell theory is the idea that the cell is the fundamental unit of life. Living organisms are made up of one or more cells, and the products that are generated by those cells. Cells have processes that both produce and use energy, known as metabolism. They also contain deoxyribonucleic acid (DNA), which is hereditary information that gets passed on to subsequent generations.
 

Evolution is the theory that all living organisms descended from one common ancestor. Charles Darwin generated a viable scientific model of evolution based on the concept of natural selection. Natural selection is the idea that certain individuals of a species (or sometimes a species as a whole) with more advantageous phenotypes are more likely to survive than those individuals with less advantageous phenotypes. Over long periods of time, populations of species can develop phenotypes specialized for their environment.
 

Genetics is the study of genes. Genes are the primary unit of inheritance between generations or organisms. They are regions of DNA that encode ribonucleic acid (RNA) and proteins, all of which have specific forms and functions. DNA is present in all living cells and is important for the cell’s own functions, as well as for its ability to divide and pass on information to subsequent daughter cells.
 

Homeostasis is the ability of a system, such as a cell or organism, to regulate itself so that its internal conditions remain stable even when its external environment may be changing. By maintaining homeostasis, systems are able to function normally even in adverse conditions.

The constant flow of energy is important for the survival of living organisms. All organisms have vital functions that require the input of energy and other functions that release energy. These processes work together to drive all chemical reactions required for life.