Evolution and Phylogeny Flashcards

EVOLUTION

Evolution is the change in the inherited traits of populations of organisms over many generations.
It is descent with inherited modification.

Phylogeny refers to the evolutionary history of a species or group of organisms; it's essentially a family tree.

A clade is a grouping that includes a common ancestor and all the descendants (living or extinct) of that ancestor.

Archaea: Single-celled organisms lacking a nucleus and other membrane-bound organelles, similar to bacteria but with unique biochemical and genetic characteristics.
Bacteria: Single-celled prokaryotes lacking a nucleus and other membrane-bound organelles but with different genetic and biochemical traits than Archaea.
Eukarya: All organisms whose cells have a nucleus and other membrane-bound organelles, including plants, animals, fungi, and protists.

Phylogenetic trees are constructed by analyzing shared characteristics, primarily DNA and protein sequences, to determine how closely related organisms are.
Taxon: Represents the evolutionary relationships among a set of organisms or group of organisms (taxa).
The tips of the tree represent groups of descendant taxa, often species.
Nodes of the tree represent the common ancestors of descendants.
Two descendants that split from the same node are called sister groups.
Outgroup: A taxon outside the group of interest, used as a reference point.

Phylogeny: The actual evolutionary history/relationships among species or groups of organisms (a concept or hypothesis, not a diagram).
Evolutionary Tree: A general term for any branching diagram that represents evolutionary relationships.
Phylogenetic Tree: A diagram that represents a hypothesis about the evolutionary relationships among organisms.
Cladogram: A type of phylogenetic tree that shows only the branching order/relationships, not time or amount of change.

A common ancestor is an ancestral organism shared by two or more groups of organisms.

Phylogenies are like trees, not ladders; lineages may split and diverge.
Reading phylogenies from left to right has no correlation with the level of advancement. The order is arbitrary.
For any speciation event on a phylogeny, the choice of which lineage goes to the right and which goes to the left might be arbitrary; these phylogenies are equivalent.

Homologies: Traits with the same origin but potentially different functions.
Analogies: Traits that have similar functions but evolved independently due to convergent evolution.

Divergent Evolution: When two or more species evolve from a common ancestor, becoming more different over time.
Often involves structures similar in underlying anatomy but differing in function.
Convergent Evolution: When unrelated species evolve similar traits independently, often due to similar environmental pressures.

To group organisms into clades, use shared ancestry as the basis for classification.
Incorporate molecular and morphological evidence.

Time is generally represented by branch lengths, where longer branches often indicate a greater amount of time since the branch point.
Extinctions are usually represented by branches that end before the tip of the tree, indicating that the lineage represented by that branch is no longer extant.

Mutations are changes in an organism's DNA sequence.
They are the source of new genetic variation, providing the raw material for evolution.
Mutations can be harmful, but they can also lead to beneficial traits that are favored by natural selection.
Mutations occur spontaneously at a low rate, but they can be accelerated by environmental factors like radiation or certain chemicals.

Gene flow is the transfer of genetic information between populations.
It occurs when individuals move from one population to another and reproduce there, or when gametes (like pollen) are transported between populations.
Gene flow tends to make populations more similar to each other by introducing new alleles or increasing the frequency of existing ones.

Genetic drift is a random change in allele frequencies due to chance events, particularly in small populations.
It can lead to a loss of alleles or the fixation of alleles that are not necessarily adaptive.
For example, if a small number of individuals from a population start a new colony, the genetic makeup of the new population may not be representative of the original population due to chance.

Individuals with traits that make them better adapted to their environment are more likely to survive and reproduce.
These advantageous traits are passed on to the next generation, leading to an increase in the frequency of those traits in the population.
Natural selection acts on existing genetic variation, favoring traits that enhance survival and reproduction in a particular environment.