Test One Key Terms

Homology / Homologous Characteristics

Homology / Homologous Characteristics

Characteristics are similar in two or more species because they are inherited from a common ancestor

Synapomorphy

A trait that is shared by a group of related species (evolved in the immediate common ancestor group)

Phylogeny

A visual representation of the evolutionary history of populations, genes, or species

Exaptation

A trait that is initially carries out one function and is later co-opted for a new function. The OG function may or may not be retained

Clades

Single branches in the tree of life that represent an organism and all of its descendants (like a starting point for two related species)

Outgroups

Groups of organisms (species) that are outside of the monophyletic group being considered. Used to infer the ancestral states of characters (used as a point of comparison)

Homoplasy

Describes a character state similarity not due to shared descent (produced by convergent evolution or evolutionary reversal)

Horizontal Gene Transfer

The transfer of genetic material other than from parent to offspring to another organism without reproduction, then passed down to descendants

Coalescence

The process by which, by looking back through time, the genealogy of any pair of homologous alleles merges in a common ancestor

Paralogs

Homologous genes that arise by gene duplication. Paralogs together form a gene family

Maximum Parsimony

A statistical method for reconstructing phylogenies that IDs tree topology that minimizes the amount of change or number of steps required to fit the data

Bootstrapping

A statistical method for estimating the strength of evidence that a particular branch in a phylogeny exists

Neighbor Joining

A distance method for reconstructing phylogenies. IDs tree topology with the shortest possible branch lengths

“MRCA”

Most recent common ancestor

Evolution

Change in frequency of heritable traits over time

Epigenetics

Heritable changes in a gene function that aren’t related to genetic differences

Example of horizontal gene transfer

Eastern emerald slug takes genetic information from leaves to produce chlorophyll to mimic a leaf (needs to eat the algae once)

Convergent evolution

The independent evolution of similar traits (homoplasious) from DIFFERENT ancestral conditions (EPAS1 vascular and altitude differences)

Parallel evolution

The independent evolution of similar traits from the SAME ancestral conditions (Lactose)

Example of homoplasious traits through reversal

leg reduction and loss in snakes, glass lizards, and worm lizards

Definition of Deep homology

Convergence of complex traits based on homologous elements

Example of deep homology

The convergence of opsins and crystallins for use in complex eyes (co-opted as well)

Bottleneck definition

A sudden decrease in population size resulting in drift 

What restores diversity lost by drift?

Mutation and gene flow

Discrete / discontinuous genetics

Can be placed in categorial and distinct morphs of phenotypes (red, green, blue)

Discontinuous/discrete variation in a population often occur from a single gene with a few alleles. How can a complex system result in just two or three phenotypes?

Genetic or GxE threshold, variation in multiple genes interact but there is a tipping point.

V_G + V_E

V_G x V_E

V_E

V_E + V_G x V_E

Complex adaptations in mantis shrimp

Strong raptorial front “arms” and 16 photoreceptors which capture UV and polarized light

What is NOT an explanation for how convergent complex traits may be made more likely to occur?

Adaptive mutations

Describe how gene duplication may allow ability of novel, adaptive traits to evolve?

The original function is maintained by one paralog while the other is freed to accumulate mutations

How are h² and H² different?

 H² is more inclusive

What could result in a novel trait in a population?

Recombination or independent assortment (crossing of alleles), novel genetic - environment interaction, novel environment, gene flow

Carter, Goldizen & Heinsihn 2012 (our second paper) studied Namibian rock agamas and suggested that…

Behaviors were influenced by individual (likely genetic) differences, season, and plasticity (individuals’ different responses to season.)

Byrne & Corp 2004 (our first paper) found?

That evolutionary increases in neocortical size correlated with higher deception rates, suggesting that benefits of deception may have favored this brain growth.

DeWaal and Ferrari 2010 (our 3rd paper) argued that…

Focusing on deeply homologous neural elements like mirror neurons, can give us a better understanding of cognition than the “top-down” approach.

Why, in general, is the use of independent contrasts important?

Without them, we cant know if traits evolved together multiple times or if the tend to be paired together due to common decent.

What evolutionary processes best explain leglessness in snakes?

Changes in spatial and temporal expression of limb blocking and developmental genes

“Deep homology”, as seen in the evolution of complex eyes of vertebrates and cephalopods (like octopi), refers to…

Convergent complex traits whose similarities are due in part to the incorporation of homologous elements