69 terms

Organic Evolution Exam 2


Terms in this set (...)

Cope's rule
an evolutionary tendency to increase in size over time
Crown group
the "derived group" that evolved from the stem group
Stem Group
Early stage ancestors
Absolute dating
done by radiometric dating, measures decay of radioactive elements each type decays at a specific rate (1/2 life) U-235 = 0.7bya
Relative dating
A method used to determine the age of rocks by comparing them with those in other layers
Phyletic gradualism
slow steady change in a phylum with a steady accumulation of small changes
Punctuated equilibrium
short periods of rapid change and macroevolutionary events during which new taxa arise (speciation) interrupt long periods of little change (stasis). *requires speciation

Hypothesis applies to the abrupt appearance of closely related species, not the appearance of higher taxa.

The theory that species evolve during short periods of rapid change
Punctuated gradualism
-characters may evolve in between long-stable states in populations that do not undergo speciation.

-Random fluctuation in a character may result in a gradual net change over time.

-Consistent directional change is seldom recorded, perhaps because it often occurs too quickly to be preserved in a coarse fossil record
Geologic Time Scale
scale used by paleontologists to represent evolutionary time
similar stages of related organisms
Dollo's law
complex characters once lost, are not regained. This law is not universal and depends upon changes in the genetic code controlling development.
largest scale of biogeographic division of the earth's surface; based on historic distribution patterns of plants and animals.

represent large areas of the earth's surface where plants and animals developed in relative isolation over long periods of time, and are separated from one another by geologic barriers to migration
Disjunct distribution
two or more groups that are related but widely separated from each other geographically
the one-way movement of a species from the site of origin to new habitats. This expands the range of the species.
evolutionary separation of species by barriers such as those formed by continental drift
may account for the presence of related taxa in disjunct areas
species formation without branching of the evolutionary line of descent.
can cause disjunct distributions.
Ecological biogeography
uses present ecological factors (climate, soil, etc.) to explain distributions of animals
Historical biogeography
studies past geological events to understand present distributions, e.g. connection between South America and Africa explains the distribution of some taxa in those two continents
fundamental Ecological niche
the set of environmental conditions in which a species can maintain a stable population size.
realized ecological niche
the actual niche occupied by the species due to the influence of competitors, predators, etc.
Phylogenetic niche conservatism
Related species often have similar ecological requirements presumably due to their common ancestry.
Species tend to retain their ancestral niche characteristics.
Native or confined to a particular region
studies the processes and principles that control the geographic distribution of lineages of genes especially within species and closely related species

relies strongly on phylogenetic analysis of variant genes within species (gene trees, Ch. 2) to infer population history.

provides insights into the past movements of species
different forms of the same gene.
unequal crossing over
can occur between two homologous sequences or chromosomes not perfectly aligned resulting in tandem duplication in one chromosome and deletion in the other.
polyploidy formed between two related, but separate species
an individual with more than two chromosome sets, derived from one species
Back mutation
Occurs when a gene that has undergone a mutation reverses to its original
Crossing over
Process in which homologous chromosomes exchange portions of their chromatids during meiosis.
point mutation
gene mutation in which a single base pair in DNA has been changed
base-pair substitution
replaces one nucleotide and its partner with another pair of nucleotides
silent/synonymous mutation
result in no changes in the amino acid sequence.
missense/non-synonymous mutation
result in the wrong amino acid; They may or may not have consequences in the phenotype
Gene family
groups of genes that have similar sequences and related functions
Having too many or too few copies of a particular chromosome
condition in which an organism has extra sets of chromosomes
Genetic marker
Alleles that produce detectable phenotypic differences useful in genetic analysis
Intragenic recombination
An exchange of material between homologous sequences that differ at two or more base pairs can form new combinations in the DNA
A single gene having multiple effects on an individuals phenotype
A short, highly repeated, untranslated DNA sequence.
Tandem repeat
Two or more DNA sequences of base pairs that are repeated
substitutions of purine to purine or pyrimidine to pyrimidine
substitutions of a purine to a pyrimidine or vice versa
when a piece of DNA is relocated to a different locus
transposon/transposable element
genetic element that moves from one location to another in a genome
always include genes that code for the enzyme that accomplishes the transposition
3 types:
insertion sequences, transposons, retroelements
Wild type
An individual with the normal (most common) phenotype.
Lower jaw dentary only, single jaw joint, enlargement of brain
Hadrocodium Mammals
Late Triassic
Morganucodon (first mammals during Triassic, a gradual transition not a distinct point)
Teeth like mammals, more developed dentary squamosal joint, beginning of hammer and anvil
mid-late triassic
More tooth cusps, two jaw articulations
late permian
Dentary enlarged, teeth cusps, secondary palate, reduced quadrate
Large canines, center of palate recessed, hind legs more vertical
Temporal fenestra=Synapsida

Amniotic egg, other adaptations for life on land= amniotes
Archean era
2.6 bya - Photosynthetic bacteria
3.5 bya - First fossil evidence of life 3.5bya;
Proterozoic era
640 mya - Fossils of animals
1 bya - Trace fossils of animals
1.9bya - First eukaryotes
Paleozoic era
Cambrian, ordovician, silurian, devonian, carboniferous, permian periods
cambrian period
First appearance of most animal phyla
Earliest agnathans
ordovician period
Diversification of many inverterate phyla and agnathans
Mass extinction at end
silurian period
First jawed fish
Earliest terrestrial vascular plants and arthropods
devonian period
Age of Fishes
First tetrapods and insects
Mass extinction at end
carboniferous period
Forests of vascular plants
Diverse amphibians
First Reptiles
permian period
Pangaea formed
Mass extinction at the end
triassic period
Continents begin to separate
First dinosaurs and mammals
Mass extinction at the end
jurassic period
Continents separating
First birds
cretaceous period
Most land masses separated
Radiation of many groups
Mass extinction at the end
tertiary period
Continents nearing current positions
Radiation of mammals, birds, snakes, flowering plants, bony fish
First hominins
Quaternary period
Continents in modern positions
Repeated glaciation
First members of Genus Homo
mesozoic era
triassic, jurassic, cretaceous periods
cenzoic era
tertiary and quarternary periods