Life is organized on many structural levels
Higher levels may exhibit emergent properties
Cells are the fundamental unit of life
Continuity of life is based on heritable information encoded in DNA
Organisms are open systems that continually interact with environment
Diversity and unity are dual facets of life
Evolution is the unifying principle of biology
Science is a process of inquiry
1. Cellular organization: all life consists of cells or cell products
2. Growth and development: based on information encoded in DNA
3. Reproduction: living organisms reproduce
4. Living organisms (populations) evolve and adapt to environment
5. Heredity is based on DNA molecules.
6. Living organisms maintain a steady state within internal environment despite large fluctuations in external environment
7. Living organisms respond to internal and external stimuli
8. Living organisms show metabolic activity. Energy is obtained from the environment. Metabolism is the totality of chemical processes in the organism.
Taxonomy is the science of classification. The need to classify is as old as language. A systematic scheme is necessary in order to identify, classify, and capture the unity of organisms.
Taxonomy began in the 4th century BCE with Aristotle who divided matter into three categories: animal, vegetable, and mineral. In the 18th century CE, Carolus Linneaus streamlined botanical classification and introduced the binomial system that is still in use today.
* scientific names contain two parts: the genus and the species
* genus is always capitalized and may be used alone, species is never capitalized and never used alone
* the scientific name must be italicized or underlined.
* once spelt out completely, the name may be abbreviated as shown below:
Some forms of Escherichia coli are pathogenic; however, there are several strains of E. coli that are beneficial.
The system most often encountered by students is the 6 kingdom system.
They are: Archaebacteria, Eubacteria, Protista, Fungi, Plantae, and Animalia. The kingdom is the most inclusive taxon based on type of cell and mode of energy acquisition. A new system treats the eukaryotes and the two prokaryotic kingdoms as three separate domains: a higher level classification than kingdom
The levels of classification following kingdom are based on evolutionary benchmarks and increasing exclusion. In all, there are 7 levels of classification.
Kingdom, Phylum (or Division in the plant kingdom), Class, Order, Family, Genus, and Species.
There are many different ways to define species, but the most useful one to most biologists is the following:
A species is comprised of populations of related organisms that interbreed freely in Nature to produce fertile offspring.