Phylogeny, Taxonomy, and Systematics Flashcards
Taxonomy
people?
pre-dates what?
The science of naming, describing, and classifying organisms
-well developed in native peoples who live on the land
pre-dates the science of evolutionary biology
Aristotle was the first greek biologist and historical figure to classify organisms
Taxonomy’s importance
-new species? many species?
-relevent to what?
New species being discovered all the time
-relevant to studies of biodiversity and conservation
-many species become extinct before they are described
Why is biodiversity being lost?
what does taxonomy provide?
Human activities cost an unprecedented amount of biodiversity
Taxonomy provides a basic understanding about the components of biodiversity
Carl Linnaeus did what?
What was his world view?
Published Species plantarum and System Naturae, describing and classifying plants and animals
-pre-evolutionary
believed he was cataloguing the plan of the Creator,
believed in the fixity of species
Linnaeus’ popularized what?
Popularized binomial nomenclature - where each species has a unique scientific name formed by the combination of the genus name and a specific epithet (e.g. Homo sapiens)
Linnaeus created what system?
Taxonomic classification system
-classification of all life within a hierarchy
-based on morphological characteristics
Life -> Domain -> Kingdom -> Phylum -> Class -> Order -> Family -> Genus ->Species
Taxonomic conventions
What is capitalized?
Phylum, subphylum, and class names are all capitalized
Genus name is capitalized, species name is lowercase (both are italicized or underlined)
Charles Darwin
year?
What did he do?
Proposed species changed over time (evolution)
In 1859
Hypothesized a mechanism for evolutionary change was natural selection
Believed all life was related on the basis of genealogical descent from a common ancestor
Taxonomy
The science of naming, describing, and classifying organisms
Systematics
The study of evolutionary relationships between organisms
Phylogeny
The evolutionary history of a group
Phylogenetics =
Systematics
What is phylogeny?
A phylogeny is a hypothesis of evolutionary relationships among species
Phylogenetic tree
Is called a cladogram, and is a graphical representation of a phylogenetic hypotheses
Understanding phylogenetic tree
Root of the tree represents ancestral lineage
Tips represent descendants
As you move from the root to the tips, you move forward in time
speciation event
It is represented as branching on a phylogeny and is called a speciation event
Phylogenetics
Allows us to study how certain traits evolve over time
Applications of phylogenetics (look at slide 22 and save photo for conservation point)
Tests hypotheses about long-extinct organisms
Uncovering the origins of Covid
Making conservation decisions by saving more, rather than less
Phylogenies made because?
In the absence of a perfect fossil record, we can never be certain of evolutionary history
Systematists have developed methods for inferring evolutionary relationships
These methods result in hypotheses of ancestor-descendent relationships
Character
Any feature that is used to examine variation with and among groups (taxa)
Types of features
Anatomical, cellular, biochemical, developmental characters (gene expression)
Protostomes vs Deuterostomes
Developmental characters can be used for generating phylogenetic hypotheses
Homology vs Homoplasy
Homology : Similarity due to common ancestry. Reveals a phylogenetic relationship
Homoplasy : Similarity that is not due to common ancestry (convergence or reversal) Does not reveal a phylogenetic relationship
Convergence
Adaptations that formed independently due to similar environmental conditions by distantly related organisms
This is not due to common ancestry, rather adaptation and evolution AND HOMOPLASY
Myrmecophagy
Animals that specialize in eating ants
Reversal
Loss of a derived feature with the reestablishment of an ancestral feature
Because homoplasies do not…. only ….
Reflect evolutionary history, only homologies should be used for reconstructing phylogenies
Synapomorphy
Inherited from most recent common ancestor
Shared derived homology
Symplesiomorphy
Shared ancestral homology
Inherited from more distant common ancestor
Symplesiomorphies aren’t useful for…
Inferring relationships between members of a group, rather characters that vary need to be examined across lineages in the clade
Cladists only use…
Synapomorphies to infer phylogeny
Outgroup
A group that is phylogenetically close to, but is not contained in the study group of interest
Order -> Species
Order ->
Suborder ->
Family ->
Genus ->
Species
Monophyletic, para, poly
Mono is the whole group
Para is some of the group
Poly is some of two groups (convergent evolution describes polyphyletic relationships)
Other fish and lungfish are…
Paraphyletic, with respect to amphibians
Inclusion of homo makes…
Pongidae and Homo monophyletic
Why do phylogenies and taxonomies change over time?
New data becomes available
-new tech, basic info becomes available, data on new species
Different types of data yield different phylogenies
-molecular vs morphological
Somewhat different techniques may be used to analyze data
Mono, para, poly phyletic
Mono - Includes an ancestor and all its descendants
Para - Includes an ancestor and some but not all of its descendants
Poly - Includes two distant relatives but not their common ancestor
Phylogenies, at the end of the day, are…
HYPOTHESES, THAT ARE SUBJECT TO CHANGE WHEN NEW DATA IS AVAILABLE
Define/Relate
taxonomy, systematics
monophyletic, synapomorphy
paraphyletic, symplesiomorphy
polyphyletic, homoplasy
convergence, reversal
Taxonomy - the science of naming, describing, and classifying organisms
Systematics - The study of evolutionary relationships
Taxonomy gives us methods to describe evolutionary relationships with linnaean hierarchies. Systematics seeks to describe evolutionary relationships that can be described used taxonomy. I.E. Class -> order -> family -> genus -> species can describe evolutionary relationships.
Monophyletic - a group that has all the descendants of a common ancestor
Synapomorphy - A trait that is inherited from a most recent common ancestor of a group cladistic group
Synapomorphies are the most recent state of a character that all monophyletic groups evolved from.
Paraphyletic - Not all descendants of a recent common ancestor are grouped together - leaving some out
Symplesiomorphy - A shared ancestral homology of a group that is not inherited from a most recent common ancestor, rather a more ancient ancestor.
Paraphyletic groupings can have ancestrally derived characters in the form of symplesiomorphies and this can be helpful in inferring evolutionary relationships between members of a group.
Polyphyletic- When a relationship is made between two distantly related groupsoui but not a common ancestor
Homoplasy - Similarity that is not due to a phylogenetic relationship. For example, convergent traits or reversal to an ancestral character state
Polyphyletic groupings can have identical derived character states that groups did not evolve from a recent common ancestor, rather it would evolve from similar environmental pressures. Homoplasies do not reveal a phylogenetic relationship nor do polyphyletic groups because they do not focus on similarities due to common ancestry and focus solely on the character state.
Convergence - When the same character evolves independently in groups that have distantly related ancestors
Reversal - When a derived character state reverts back to the ancestral character state
Both of these are homoplasies and cannot be used to infer phylogenetic relationships.
We are currently in the midst of a taxonomic revolution, whereby many previous-recognized taxonomic groupings (e.g., reptiles, fishes) have either been discarded or reclassified. In your own words, describe the main reasons for this taxonomic revolution.
New means of acquiring data on how evolutionary relationships is changing the game. It is revealing that there may be more members of a group than initially thought. Taxonomic groupings sought to group similar things together for the sake of clarity; however, some of these groupings were based solely in character state and not actual derivation. Genetic studies are showing that some other things may also be included in a taxonomic group. Monophyletic groups paint a clearer picture for evolutionary relationships as well, so previously-recognized taxonomic groupings have to be thought of as subject to change based on new scientific findings and not hard truths.
Review multiple choice
