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APn 20 Classification of Living Things, Part I
Taxonomy
Defined
The branch of biology concerned with identifying,
Phylogenetic Trees
Terms
1. Systematics: study of the diversity of organisms using information from
Binomial System
2. Phylogeny: the
1. Developed by Carolus Linnaeus (1707-1778)
2. Uses two-part name:
a. first part:
3. Primitive character: a trait that is present in a common ancestor and
4. Derived character: present only in a
b. second part: specific epithet....species name
c. Both names:
d. Genus name:
3. More to do...
5. Related: share a
Tracing Phylogeny
Fossil Record
1. Because fossils can be dated,
Identification of Species
1. Can be difficult because there are variations among species:
2. Biological definition of species states:
3. Species definition can be problematic:
4. Subspecies: when a species has a wide geographic range,
variant types may tend to
Example: Elaphe obsoleta obsoleta and
Elaphe obsoleta bairdi: rat snakes
5. Taxon (taxa pl.) group of organisms in a
2. Might be difficult to associate fossils with currently living groups
3. Fossil record is incomplete:
Homology
1. Homology: character similarity that stems from having a common ancestor;
homology helps indicate when species belong to a related group.
2. Homologous structures: are related to each other through common descent but
may differ
3. Convergent evolution: acquisition of similar traits in distantly related organisms
as a result of adapting to
4. Analogous structures: same function, but do not have common ancestry.
5. Parallel evolution: produces similar characters in related lineages without
occurring in a
Classification Categories
Molecular Data
1. Taxonomists use ___ categories:
2. Domain: higher category
3. The higher the category, the
4. Members of a Kingdom share general characters; members
of a species share quite
5. Character:
Basics
1. Speciation occurs when mutations bring about
2. Each lineage accumulates changes in their DNA/proteins over
Protein Comparisons
1. Early studies used:
2. Amino acid sequences are now used to determine the differences in
proteins between two species: fewer differences = more
3. Few universal proteins, so limited
6. Additional levels of classification can be added by adding
super-, sub-, or infra- thus, there are more than
RNA/DNA Comparisons
1. DNA-DNA hybridization: separates the DNA strands of two species and combines the
strands, the more
2. DNA hybridization shows chimpanzees closer to humans than to
Humans are markedly different in adaptation to
3. Mitochondria DNA (mtDNA) mutates 10x faster than nuclear DNA, use it for
Molecular Clocks
Idea that the rate at which mutational changes accumulate in certain genes is constant
over time and is not involved in adaptation to the environment. Best when backed-up by
the