Systematics

Distinguish between branches, tips and nodes on a phylogenetic tree, and understand what each represents.

Node: A root is the ancestral population from which all the other species originate. A node represents a branching point from the ancestral population

Tips: represent groups of descendent taxa (often species)

Explain what a 'phylogenetic tree' represents.

A phylogentic tree represents a hypothesis about evolutionary relationships. a diagram that depicts the lines of evolutionary descent of different species, organisms, or genes from a common ancestor.

List the levels of the Linnaean system of taxonomy in their proper, nested hierarchical format

Kingdom, Phylum, Class, Order, Family, Genus, and Species

Explain the difference between ancestral characters and derived characters.

Ancestral traits are what the ancestors of the species had, a derived trait is a trait that is seen in the species but not in its ancestor

Explain the difference between monophyletic, polyphyletic and paraphyletic taxons

monophyletic: a group that includes a single ancestral species and all its descendants.

polyphyletic: A group of organisms that belong to different evolutionary lineages and do not share a recent common ancestor.

paraphyletic taxons: A group of organisms that includes an ancestral species and some, but not all, of its descendants.

Explain what is meant by a "molecular clock" (and the underlying assumptions) and why how they are used when constructing phylogenies

molecular clocks are measures of changes in the gene sequence that occur over time. It is useful in obtaining evolutionary information when you have little or no fossil record

Explain the difference between homologous characters and homoplasious (analogous) characters.

Homologous: structures that are similar in related organisms because they share a common ancestor

homoplasious (analogous): structures that are similar in unrelated organisms due to function

Explain why 'phylogenetic trees' are considered hypotheses

Scientists consider phylogenetic trees to be a hypothesis of the evolutionary past since one cannot go back to confirm the proposed relationships.

Provide an adaptive explanation for why similar structures may have evolved in different species.

similar structures mar evolve due to similar environmental pressures which result in adaptation

Explain how characters that have evolved by parallel or convergent evolution complicate the construction of phylogenies

analogous structures appear similar and perform similar functions, making it seem that two species are closely related.

Parallel evolution implies that two or more lineages have changed in similar ways, so that the evolved descendants are as similar to each other as their ancestors were.

Describe the process that leads to parallel evolution and convergent evolution

The repeated and similar large-scale morphological evolutionary trends of distinct lineages suggest that adaptation by means of natural selection (functional constraints) is the major cause of parallel evolution

Convergent evolution is a process in biology. It occurs when two species from unrelated lines develop the same traits or features. This happens because they live in similar habitats, and have to develop solutions to the same kind of problems. ... Both species might have acquired the trait by descent from a common ancestor.

Explain what is meant by 'the assumption/principle of parsinomy' in the context of systematics.

The simplest explanation is most likely to be correct unless other data suggest a more complicated explanation.

Evolutionary change is an unlikely event. The evolution of a character twice is extremely unlikely. Evolutionary trees with derived characters appearing once are most parsimonious.

Explain how the fossil record be used when constructing phylogenies

The fossil record is often used to determine the phylogeny of groups containing hard body parts; it is also used to date divergence times of species in phylogenies that have been constructed on the basis of molecular evidence.

Explain why systematists use outgroup comparisons.

By comparing members of the ingroup with each other and with the outgroup, we can determine which characteristics were derived at various branch points of evolution.

Describe the potential advantages/disadvantages associated with using molecular characters when constructing a phylogenetic tree

Molecular characters allows the independent testing of evolutionary hypotheses based on fossils

Advantages

-abundant data

-Easier comparison of distant or very close relations

Disadvantages

-only 4 states of nucleotides, 20 in amino acids

-base change may have evolved independently