Chapter 26

Domain System

Bacteria, archaea, eukarya

Kingdoms

Monera (prokaryotes), protista, plantae, fungi, animalia

Linnaean Classification

and phylogeny can differ from each other.

Homoplasies

are analogous structures or molecular sequences that evolved independently; molecules are identified by math tools.

Sister Taxa

are groups that share immediate common ancestor.

Phylogenies

are inferred from morphological and molecular data.

Speciation Product

are orthologous genes.

Shared Characters

are used to construct phylogenetic trees; along with different characteristics are in comparison for an organism with its ancestor; can be both ancestral and derived (depending on context).

Max Parismony

assumes that tree that requires fewest evolutionary events is most likely.

Branch Length

can reflect on number of genetic changes that have been taken place in certain DNA sequence in that lineage; can represent chronological time, can be determined from fossil record.

Basal Taxon

diverges early in history of group and originates near common ancestor of group.

Homologous

elements are more likely when they are similar in two complex structures; characters can be used to infer phylogeny once they have been identified.

mt-DNA

evolves rapidly and can be used to explore recent evolutionary events.

Taxonomic Groups

from broad to narrow include: 1)domain 2)kingdom 3)phylum 4)class 5)order 6)family 7)genus 8)species

Branch Points

from hundreds of millions of years ago can be useful when DNA that codes for r-RNA changes relatively slowly.

Cladistics

group organisms by common descent.

Systematists

have proposed classification system that would recognize only groups that include common ancestors and all its descendants; get information about morphologies, genes, biochemistry of living organisms; need to distinguish whether similarity is homology or analogy when making phylogeny; use computer programs, math tools when analyzing comparable DNA segments from different organisms; can never be sure of finding best tree in large data sheet; narrow options by applying max parismony and max likelihood.

Molecular Clocks

help track evolutionary time; uses constant rates of evolution in some genes to estimate absolute time of evolutionary change; are calibrated against branches whose dates are known from fossil record; does not run as smoothly as expected if mutations were neutral; application of HIV suggests that that strain spread to humans during 1930s; more advanced approach estimated first spread to humans around 1910.

Key Features in Linnaeus' system

include two part names for species and hierarchical classification that remain useful today.

Rooted Tree

includes branch to represent last common ancestor of all taxa in tree.

Gene Duplication

increases number of genes in genome (providing more opportunities for evolutionary changes); result in gene families; can be traced to common ancestor like homologous genes.

Polytomy

is branch which more than two groups emerge.

Shared Ancestral Character

is character that originated in an ancestor of taxon; are characters shared by out-group and in-group that predate divergence of both groups from common ancestor.

Systematics

is discipline that classifies organisms and determines their evolutionary relationships.

Phylogenetic Tree

is evolutionary history of group of organisms; represents hypothesis about evolutionary relationships; for best hypothesis fit most data (morphological, molecular, and fossil).

Phylogeny

is evolutionary history of species or group of related species; provides important information on similar characteristics in closely related species; was used to identify species of whale from which 'whale meat' originated; bracketing allows people to predict features of ancestor from features of its descendants; analysis shows HIV is descended from viruses that infect chimpanzees and other primates.

Shared Derived Character

is evolutionary novelty unique to particular clade.

Genus

is first part of name.

Paraphyletic

is grouping that consists of ancestral species and some descendants.

Polyphyletic

is grouping that has distantly related species but does not include their most recent common ancestor; groups are distinguished from paraphyletic groups since they do not include most recent common ancestor.

Orthologous Genes

is homology that results from speciation event and occurs between genes found in different species; are widespread and extend across many widely varied species (Ex: humans, mice diverged about 65 million years ago, 99% of human genes are orthologous); has nucleotides substitutions that are assumed to be proportional to time since they last shared common ancestor.

Molecular Similarities

is important when distinguishing homology from analogy.

Horizontal Gene Transfer

is movement from one genome to another; occurs by exchange of transposable elements, plasmids, viral infection, and organisms fusion; occurrence is result of disparities between gene trees; has played key role in evolution of both prokaryotes and eukaryotes; is argued by some biologists to be so common that early history of life should be represented as tangled network of connected branches.

Max Likelihood

is principle that states that tree can be found that reflects most likely sequence of evolutionary events given certain rules about how DNA changes overtime.

Taxonomy

is scientific discipline concerned with classifying and naming organisms.

Specific Epithet

is second part that is unique for each species within genus.

Analogy

is similarity due to convergent evolution. (Ex: bats and birds [functions of wings])

Homology

is similarity due to shared ancestry (Ex: bat and bird wings [fare limbs]).

Clade

is species group that includes ancestral species and all its descendants; a shared character first appeared in is useful to know when inferring to evolutionary relationships.

Out-group

is species or group of species that is closely related to in-group; is group diverged before in-group; are used by systematics to differentiate between shared derived, and shared ancestral characteristics.

Hierarchical Classification

is system Linnaeus introduced for grouping species in higher inclusive categories.

Taxon

is taxonomic unit at any level of hierarchy.

Binomal

is two part species scientific name.

Monophyletic

is valid clade signifying that is has ancestor species and all its descendants.

In-group

is various species being studied.

Genome

is where an organism's evolutionary history is documented

Carlos Linnaeus

published system of taxonomy based on resemblances in 18th century.

Branch Point

represents divergence of 2 species.

Paralogous Genes

result from gene duplication (multiple copies of these genes; can diverge within clade that carries them and often evolve new functions; has nucleotides substitutions that are proportional to time since genes became duplicated.

Polygenetic Trees

show patterns of descent (not phenotypic similarity); do not indicate when species evolved or how much change occurred in lineage.

Tree of Life

understanding continues to change based on new data; branches have had insight from people through molecular systematics lately; suggests eukaryotes and archaea are more closely related to each other than to bacteria; is based largely on r-RNA genes (some other genes reveal different relationships).