Assignments and Term Paper. Grading altered 10% for assignments – once a week, presentations twice a week. 5% for term paper – groups of 4 25% quizzes 25% mid-term 35% final exam. Lecture 2 Variety of Life. Classification of living organisms Methods of classification
1. Taxonomy works out for us a vivid picture of the existing organic diversity of the earth.
2. Taxonomy provides much of the information permitting a reconstruction of the phylogeny of life.
3. Taxonomy reveals numerous interesting evolutionary phenomena.
Arranged as a hierarchy, with largest group at the top:
Family-category including 1 genus or a group of genera of common phylogenetic origin, which is separated from other families.
Genus-category containing a single species, which is separated from other taxa by behaviour, morphology, or some other characteristics.
Species-group of closely related organisms capable of interbreeding to produce fertile offspring.
How similar is the DNA?
What type of cell is it?
Example : Hemoglobins
Human beta chain 0 Mouse 27
Gorilla 1 Gray kangaroo 38
Gibbon 2 Chicken 45
Rhesus monkey 8 Frog 67 Lamprey 125
Dog 15 Sea slug (a mollusk) 127
Horse, cow 25 Soybean (leghemoglobin) 124
Number of amino acid differences between the beta chain of humans and the
hemoglobins of the other species. In general, the number is inversely
proportional to the closeness of kinship.
Most bacteria may be placed into one of three groups in response to oxygen:
Aerobic bacteria thrive in the presence of oxygen and require it for their continued growth.
Anaerobic bacteria cannot tolerate gaseous oxygen, such as those bacteria which live in deep underwater sediments, or those which cause bacterial food poisoning.
Facultative anaerobes, which prefer growing in the presence of oxygen, but can continue to grow without it.
Most bacteria may be placed into one of two groups depending on what they use as a source of energy:
Heterotrophs derive energy from organic compounds that they must take in from the environment -- this includes saprobic bacteria found in decaying material.
Auxotrophs fix carbon dioxide to make their own food source light energy (photoautotrophic), e.g the cyanobacteria, green sulfur bacteria, purple sulfur bacteria, and purple nonsulfur bacteria or by oxidation of nitrogen, sulfur, or other elements (chemoautotrophic). The sulfur bacteria use hydrogen sulfide as hydrogen donor, instead of water like most other photosynthetic organisms.Classification of Bacteria