Study guide vocab Flashcards
Phenotype
phenotype represents an interplay of the underlying genetic architecture of an organism and
the environment
What can be done with phenotypic traits?
Phenotypic traits can be observed and quantitated.
The majority of phenotypic
traits (which can be behaviors, morphological features, etc.) are influenced by more than one gene (polygenic) and can be multifactorial (polygenic + environmental). In other words traits are quantitative.
Phenotypic plasticity
Phenotypic plasticity is defined as a single genotype that may produce different phenotypes in
different environments.
Canalization
defined as a phenotype that is robust to changes in the genotype and the
environment
Describe the factors that go into patterns and rates in the fossil record
formation of new species and extinctions. These are reflected in the fossil record and represent changes over many generations (macroevolution).
Tempo and Mode of evolution can vary. Gradualism vs. Punctuated. Both examples are observed in the fossil record. Unfortunately the fossil record isn’t nearly as complete as we’d like.
Transitional forms rare in fossil record
Transitional forms
transitional fossils
very rare in the fossil record.They are so informative, however, because these fossils have characteristics that are intermediate between two distinct taxonomic groups, i.e. fish and tetrapods.
Phyletic gradulism
This is the traditional hypothesis that proposes a gradual change over a long period of time.
Gradual transition from one form to another is not always found in the fossil record.
Intermediate stages in the evolution of higher taxa are often unknown.
these gaps are usually explained by the incompleteness of the fossil record.
Punctuated equilibrium
Eldredge and Gould proposed in 1972 a new explanation:
Punctuated equilibrium: short periods of rapid change and macroevolutionary events
during which new taxa arise (speciation) interrupt long periods of little change called
stasis.
Describe what the Eldredge and Gould explanation was based on
based on the model known as
“founder effect speciation” or “peripatric speciation” proposed by Ernst Mayr in 1954
A new species appears suddenly in the fossil record because they evolved in small
populations separated from the ancestral species and then, fully formed, migrated in the region where the fossil samples were taken.
Macroevolution
evolution above the species level. This is something we can observe in the
natural world and is recorded in the fossil record. The pattern we see is descent (from a common ancestor) with modification.
Remember phylogenetic trees depict a “picture” or “hypothesis” of
macroevolution. d.
We can investigate the process of macroevolution using modern tools including
evolutionary
developmental biology (evo-devo).
How can we observe macroevolution patterns?
We can observe different macroevolutionary patterns including parallel and/or convergent
evolution, adaptive radiations, phenotypic plasticity, morphological stasis, and Dollo’s Law (of irreversibility).
What is the genetic toolkit?
The genetic toolkit is defined as genes in the genome that are used to form and pattern the body.
Their action occurs very early in ontogeny, typically during embryonic life.
Toolkit genes are deeply evolutionarily conserved and fall into two broad categories
name the two categories of genetic toolkit genes
transcription factors and signaling factors
transcription factors
(e.g. Hox) that regulate the expression of other genes (including themselves in autoregulation)
Signaling factors
(e.g. sonic hedgehog) that mediate short and long-range interactions between cells
Describe Von Baer’s Hourglass model
each organism has in its embryonic or larval
period of development, a ‘constriction time period’ which is under very high evolutionary
constraint
The developmental genes that are expressed during this ‘constriction’ are very
evolutionarily conserved at the sequence level and the expression patterns are also conserved
Hox genes and other toolkit genes are actively expressed (transcribed) and translated during this constriction period of embryonic life.
Describe assembly and evolution of the toolkit
comparisons of gene sets between phyla indicates the toolkit was assembled and
expanded early in animal evolution
Toolkit genes represent only a very small fraction of the genome
Toolkit genes are conserved among phyla. They are conserved in function and amino acid sequence across phyla.
What gene is associated with Pax-6?
eyes/eyeless
what gene in the toolkit is associated with appendages?
Distal-less/Dll
What gene in the toolkit is associated with Heart?
Tinman/NKX 2-5
What gene in the toolkit is associated with segmentation?
hairy/HER1 engrailed
What gene in the toolkit is associated with AP Axis Pattern?
Hox genes
Where are the majority of the toolkit gene families found, inferring their prescence later on?
choanoflagellates
Describe the major themes of EDB/evo-devo
shared developmental processes
The gene toolkit is small and conserved across phyla. E.g. Pax6 for eyes; Distal-less for
outgrowths.
Toolkit loci exhibit module CREs; this promotes diversity of body plans with a small number of toolkit loci
The origin of toolkit loci predates the body plan structures that they are responsible for. This is called deep homology. The deep homology refers to the same toolkit genes and developmental pathways. Importantly, the structures that are patterned by toolkit genes do not show structural homology (e.g insect vs. tetrapod appendages). Deep homology does not equal
structural homology.
