Ch 1.2 Course Overview Evolution as a Unifying Theme
III. Evolution- the unifying theme of biology A. Evolution is used to unify biology at different scales of size through out the history of life on Earth. 1. Roughly 1.8 million of the 10 to 100 million species thought to live on Earth are identified. Thousands are discovered yearly. a. Taxonomy is the science that names and groups (classifies) species into increasingly broad categories. b. The categories, going from broadest (largest) to narrowest (smallest) are: Domain Order Kingdom Family Phylum Genus Species name Class species
B. Organizing Diversity- Domains & Kingdoms 1. Placement into a category depends on similarities in structure, function, embryo development and DNA 2. A three domain, six kingdom system is currently used. 3. Two domains contain only prokaryotes. (bacteria.) 4. The domains are: a) Archaebacteria- bacteria adapted to extreme conditions, possibly the oldest organisms on Earth b) Eubacteria- most bacteria c) Eukarya- contains only eukaryotes; everything other than bacteria & viruses
4. Four kingdoms are found in Domain Eukarya. They are: a) Protista- protozoans & algae b) Fungi c) Animalia d) Plantae The other two kingdoms are Archaebacteria and Eubacteria- also known as Domains The Kingdoms
C. Unity in Diversity • Life is diverse, but unity can be found in all life on a cellular level. a. The structure & function of DNA is the same for all cells. b. DNA is the universal genetic language of all organisms c. Organelle structure & function is the same in eukaryotic cells.
D. Charles Darwin & the theory of Natural Selection • Darwin published On the Origin of Species by means of Natural Selection in 1859. • His 2 main points were a. Species show evidence of “descent with modification” from common ancestors b. Natural selection is the means by which “descent with modification” occurs. • Fossils and other evidence of how life on Earth has changed over billions of years is used to support his theory. • Darwin’s theory can be used to explain both the unity & diversity of life.
E. Darwin’s Observations • Individuals in a population have traits that vary. • Many of these traits are heritable. • More offspring are produced than survive. • Competition is inevitable • Organisms usually suit their environments • Darwin’s Inferences • The individuals best suited to their environment will most likely survive & reproduce. • Eventually, most of the population will have the helpful traits. • Thus, the environment “selects” for the beneficial traits. • Also, by selection, an ancestral species canbecome two or more descendant species.
G. Phylogenetic trees • Phylogenetic tree- a diagram used to illustrate possible evolutionary relationships between ancestor & their descendant species.
Questions: • Choose a plant, fungus, or animal familiar to you and classify it from Domain to species. Use the internet to look it up. Do not use the one in the book or the notes! • What are the criteria used to place organisms into groups? Name the all the domains and kingdoms • When did Darwin publish On the Origin of Species? What were his two main premises? • What 4 inferences did Darwin draw from his observations?