Chapter 22: Phylogenies

Flashcards covering key concepts from the lecture notes on phylogenies, classification, evolutionary history, fossil evidence, molecular data, and major extinction events.

What is allopatric speciation?

Speciation by geographic separation.

Differentiate vicariance and peripatric speciation.

Vicariance: population splits due to a geographic barrier. Peripatric: dispersal with a small peripheral population that diverges.

In peripatric speciation, what happens to the ancestral population and the pattern of divergence?

The ancestral population seeds a small peripheral population; most genetic divergence occurs in the small peripheral population.

What is the Biological Species Concept (BSC)?

Species are groups whose members can interbreed and produce fertile offspring; example: horse and donkey produce an infertile mule.

What issue arises with common names for species (e.g., Alces alces being called moose or elk)?

Common names vary by culture/region, so the same species can have different names.

Who developed binomial nomenclature and when?

Carolus Linnaeus, in 1758 (Systema Naturae).

What are the two parts of a binomial name and its purpose?

Genus and species; provides a universal naming system within a hierarchical classification.

What is the mnemonic used to remember Linnaean ranks and what do the initials stand for?

King Phillip Came Over For Great Spaghetti; Kingdom, Phylum, Class, Order, Family, Genus, Species.

What did Darwin recognize about the origin of species in 1859?

Distinct populations of an ancestral species separate and diverge over time, giving rise to multiple descendant species with nested similarities.

What is the Phylogenetic Species Concept (PSC) definition?

All members have descended from a single common ancestor and share a common fate.

In a phylogenetic tree, what is a node?

The point where a branch splits, representing a common ancestor.

What is the root of a phylogenetic tree?

The most ancient common ancestor from which all taxa in the tree descend.

What is a sister group in a phylogenetic tree?

Groups that are more closely related to each other than to any other groups on the tree.

Phylogenetic trees are reconstructions of what data?

Molecular and fossil data used to look at lineages.

Do rotating around nodes change the relationships in a phylogenetic tree?

No — rotating around nodes does not change relationships.

Define monophyletic group.

A group that includes a common ancestor and all of its descendants.

Define paraphyletic group.

A group that includes a common ancestor and some, but not all, descendants.

Define polyphyletic group.

A group that does not include the most recent common ancestor of its members.

What is a synapomorphy?

A shared derived character that defines a monophyletic group.

How are synapomorphies used in constructing phylogenetic trees?

Presence/absence of synapomorphies helps define groups descended from a common ancestor.

Differentiate homologous and analogous characters.

Homologous: shared due to common ancestry. Analogous: similar due to convergent evolution.

What is a molecular clock?

The idea that genetic differences accumulate at a relatively constant rate over time, allowing estimates of divergence times.

How can molecular data be used to build phylogenies?

Variation in DNA/RNA serves as character states to construct distance matrices and trees.

What is a distance-based phylogeny?

A method that uses pairwise genetic distances to infer relationships and build a tree.

How is the total distance between two taxa calculated in a distance matrix?

The sum of the differences along all branches connecting the taxa.

What is the practical use of phylogenetic trees in biology and medicine?

To trace relationships among sequences or pathogens and infer common ancestry.

What are synapomorphies and why are they important?

Shared derived characters that define clades and help infer evolutionary relationships.

What is the fossil record useful for in studying evolution?

Providing a time dimension and environmental context; older fossils are in lower layers, newer on top.

What does radiometric dating rely on?

The decay of isotopes (e.g., carbon-14) with a known half-life to determine age.

What role did cyanobacteria and microbial mats play in Earth's history?

Cyanobacteria in microbial mats contributed to O2 production and the appearance of stromatolites in the fossil record.

What is Archaeopteryx and why is it significant?

A transitional fossil showing both dinosaur and bird features (e.g., flight-related traits) reinforcing dinosaur-bird evolutionary link.

What were the Permian and Cretaceous extinctions, and why are they important?

Permian extinction (about 252 mya) was the most severe mass extinction; Cretaceous extinction led to the demise of non-avian dinosaurs and allowed mammals to diversify.

On a 24-hour clock of Earth's history, when did humans appear?

11:59 PM