Chapter 2 Flashcards
What is systematics?
study of biological diversity and origin
What is the four main goals of systematics?
- document and understand Earth’s biological diversity
- reconstruct history of biodiversity
- develop natural/ evolutionary classification of living and extinct organisms
- identify and reclassify polyphyletic taxa
What are 5 other roles of systematics?
- identify and distinguish species
- describe and name new taxa
- provide tools to aid others in identifying specimens
- infer evolutionary relationship among species and higher taxa
- undertake biogeographic analyses
What is a phylogenetic tree?
diagrams of branches and nodes depicting flow of genetic information over time; shows how organisms are related
How is a phylogenetic tree made? (2)
- one tree from one common ancestor
- traces of pattern through anatomy and genome in all organisms
What are characters?
homologous anatomical or genetic traits
What are five examples of characters?
morphology,
anatomy,
development,
karyotype (chromosomal makeup),
behavior
What are character states?
variation in form of character
What is a clade?
a monophyletic group of a common ancestor and all descendants
What are 4 examples of paraphyletic groups?
- Reptilia excluding birds
- Crustacea excluding Hexapoda
- Invertebrata excluding vertebrates
- Prokaryota excluding Eukaryota
How does polyphyletic groups arise (2)?
- insufficient knowledge on how taxons are related
- often grouped due to convergent evolution
What are three examples of polyphyletic groups?
- Radiata (Radial Symmetry)- Cnidaria, Ctenophora, and Echinodermata
- Articulata- Annelida and Arthropoda
- Yeast classified in Protists
What are homologous characters?
shared ancestry present in two or more taxa
How is homologous characters identified (2)?
- embryological evidence
- position and structure of nucleotide or amino acids sequences
What are the levels for homology?
genes, anotomical structures, and developmental processes
What is an example of homology at one but not at another level?
Distal-less- gene is homologous, but appendage produced is not
How is similarity of function not a valid way to determine homology?
nonhomologous genes can converge
What are orthologues?
genes evolved from speciation
What are paralogues?
Genes separated by duplciation events
What is molecular phylogenetics?
trees built from DNA sequences
What is an apomorphy?
shared, derived character state
What is a plesiomorphy?
older state of a character
How is a trait identified in a tree as apomorphic or plesiomorphic?
apomorphy when a new transformation takes place, and the pre-transformed trait is a plesiomorphy
What is an example of a trait being both apomorphic and plesiomorphic?
having three segments in Arthropods is apomorphic in hexapods, but those stemming from hexapods are plesiomorphic
What is a primitive character state?
attributes of lineages that are relatively older and have been retained from some distant ancestor
What is convergent evolution?
similar structures evolve in distant groups differently
What are 2 examples of convergent evolution?
- example- vertebrate and cephalopod eye
- example- voice and vocal learning of mammals and birds
What is a parallel character?
similar features that has arisen more than once in different species but share common genetic or developmental basis
What is another word for parallel characters?
distant homology/ evolutionary repeatedness
What are parallel characters commonly seen in, and an example?
morphological reduction
loss of vision or pigmentation
What is evolutionary reversal?
a feature reverts back to a previous ancestral condition
What is a homoplasy?
recurrence of similarity in evolution
What kind of events are homoplasies?
includes convergence, parallelism, and reversal
How does convergence differ from parallelism and reversal?
parallelism and evolutionary reversals have underlying homologies, unlike convergence
How are phylogenies constructed?
identify homologous characters and monophyletic groups
What does a phylogeny do?
represent evolutionary hypotheses of relationships
How is a phylogeny represented (3)?
tree
classification
narrative discussions
What does a tree do?
depict pattern of relatedness
What does classification do?
dynamic representation of history of life
What is a flaw of classification?
do not always reflect precise arrangement of natural groups
protists are paraphyletic
How is paraphyly in classifications solved?
indicate their paraphyletic status using a notation
What is phylogenetic systematics/ cladistics?
infers patterns of evolutionary relationships to produce explicitly and testable hypotheses of genealogical relationships among monophyletic groups
What is cladistics based on?
one common ancestor
How is the optimal tree selected?
parsimony/ Ockham’s razor
model-based methods of nucleotide evolution
What is parsimony?
explains data in the simplest way, with the least amount of changes
What kind of models is used to make trees?
maximum likelihood, distance methods, and Bayesian analyses
What is cladogenesis?
splitting one species into two or more
What is the explicit phylogenetic hypothesis?
tree with precise points where apomorphies occur
What is sister taxa?
groups with the same immediate common ancestor
What is polytomy?
when more than two species emerge from a common ancestor
Why does polytomy arise?
uncertainty among precise evolutionary relationships
What is classification important? (2)
- efficiently cataloging all species
- serves as a descriptive function
What taxonomic rankings am I forgetting?
- class > cohort; family > Tribe
- super, sub, and infra-
What are two problems with creating classifications?
- traditional Linnean ranks are too few
- legacy names- names redefined to represent monophyletic groups
Two examples of legacy names
Protostomia and Deuterostomia
non-monophyletic groups like heteropods and crustacea
What are solutions to creating classification? (3)
unranked classification
phylogenetic sequencing convention
imprecise classification
What is unranked classification, and an example?
- use groups that reflect phylogeny
- example- Annelida and Mollusca
What is phylogenetic sequencing convention?
using molecular data to identify relationship
What is imprecise classification?
have readers refer to a tree to understand precise relationship
What are two goals of nomenclature?
- any single kind of organism has one and only one correct name
- no two kinds of organisms bears the same name
Four reasons to avoid common names?
- misleading
- some have no common name
- some, like Spanish dancers, refer to multiple species
- example- bugs are not all true bugs
What is binomial nomenclature?
binomen of generic/genus and specific epithet
Two rules of binomial nomenclature
- never use specific epithet alone
- latin because scientific papers were in Latin
What are synonyms?
different names for the same species
What is the strickland code, and by who?
- code for uniformity of nomenclature
- British Association for the Advancement of Science
What is the revised strickland code, and by who?
International Code of Zoological Nomenclature
International Commission on Zoological Nomenclature
What do plants and bacteria use for nomenclature?
- plants use the International code of Nomenclature for Algae, Fungi, and Plants
- bacteria uses International Code of Nomenclature of Bacteria
What did the ICZN do>
changed names of two parts to names of two names
rules on legal matters, not the interpretation
Why is changing to two names important?
system is binary; both genus and species names can only be one word each
What is a trinomen?
scientific name with subspecies
What are the five codes for biological nomenclature principles?
- botanical, bacterial, and zoological codes are independent of each other
- taxon can bear one and only one correct name
- no two genera within a given code can bear the same names; no two species within one gneus can bear the same name
- correct or valid name of a taxon is based on priority of publication
- for superfamily in animals and order in plants, and all levels lower, taxon names must be based on type specimens, type species, or type genera
What is an exception to principle 1?
permissible , but not recommended for plant and animal to share the same genus
What is an exception for principle 4?
exceptions for very old names that has not been used
What is a type specimen, and what does it do?
- typical representative of a new species that is stored
- allows others to compare to see if they have the same species
Fun species names
- Agra vation
- Thetys vagina
- Humbert Humberti
- Sayonara
- Batman
- Zeus
What is the biological species definition, and why is it flawed?
- defines species as groups of interbreeding natural populations that are reproductively isolated from others
- fails to accommodate nonsexual species
What is the evolutionary species concept?
species is a single lineage or ancestor-descendant population that maintains indeity from others with its own evolutionary tendencies
What is the only rule in classification?
it be a natural group
