Chapter 26 Textbook Flashcards
What two methods do scientists use to determine and categorize evolutionary relationships?
- morphological characteristics
- molecular characteristics
Morphological characteristics meaning
Relating to the outward appearance of structural features of an organism or its parts. Includes a description of characteristics such as size, shape, colour, number, and arrangement of any other visible feature.
Molecular characteristics meaning
Features based on the macromolecular composition of an organism, most notably the content and sequence of DNA and proteins.
What are these characteristics used to create?
Phylogenetic trees
Phylogenetic Trees meaning
A branching diagram that represents a hypothesis about the evolutionary history of a group of organisms
How can phylogenies be used?
As a hypothesis; We can make and test predictions based on the assumption that a phylogeny— our hypothesis—is correct. This is particularly valuable when looking at extinct groups, such as the dinosaurs.
Phylogenetic bracketing
Phylogenetic bracketing is a method of inference used in biological sciences. It is used to infer the likelihood of unknown traits in organisms based on their position in a phylogenetic tree.
Phylogeny meaning
The evolutionary history of a species or group of related species.
Systematics meaning
A scientific discipline focused on classifying organisms and determining their evolutionary relationships.
How is ancestry important when studying about organisms today?
Organisms share many characteristics because of common ancestry. As a result, we can learn a great deal about a species if we know its evolutionary history. For example, an organism is likely to share many of its genes, metabolic pathways, and structural proteins with its close relatives.
Taxonomy
A scientific discipline concerned with naming and classifying the diverse forms of life.
Why is using the common names for organisms confusing?
Common names used in everyday language can often cause confusion because they are too general (refer to more than one species), like a finch for example. Or they do not accurately reflect the organism to the fullest degree. For example a jellyfish isn’t a fish.
What system was made to thus avoid confusion when naming organisms?
Binomial Nomenclature
How does the Binomial Nomenclature system work?
The first part of a binomial is the name of the genus (plural, genera) to which the species belongs. The second part, called the specific epithet, is unique for each species within the genus. The names are all in Latin additionally.
What species are grouped together?
Ones that are closely related are grouped into the same genus.
What are the levels of Linnaean Classification?
From broadest to most specific
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
What is an analogy for the Linnaean Classification?
The resulting biological classification of a particular organism is some- what like a postal address identifying a person in a particular apartment, in a building with many apartments, on a street with many apartment buildings, in a city with many streets, and so on.
Taxon meaning
A named taxonomic unit at any given level of classification.
Relationship between taxonomy and phylogenetic trees?
The branching pattern often matches how taxonomists have classified groups of organisms nested within more inclusive groups. Sometimes however, there are differences.
- Taxonomists occasionally place a species into a genus or some other group that it is not closely related to. This could be because over time the organism lost key traits shared by relatives, and could get reclassified after examining DNA.
- Linnaean Classification doesn’t expand on the interconnected relationships between groups like mammals, birds, reptiles etc
Branch points on phylogenetic trees
The relationships are often are depicted as a series of dichotomies, or two-way branch points. Each branch point (or internal node) represents common ances- tor of the two evolutionary lineages diverging from it.
Tree Topology definition
In biology, tree topology is the branching structure of a phylogenetic tree, or evolutionary tree, that shows the evolutionary relationships between organisms. It’s a diagrammatic representation that summarizes the patterns of relatedness between species, independent of the branch lengths.
Rooted definition
A branch point within the
tree (often drawn farthest to the left) represents the most recent common ancestor of all taxa in the tree.
Basal taxon
In a specified group of organisms, a taxon whose evolutionary lineage diverged early in the history of the group.
How is phylogeny inferred?
Systematists must gather as much infor- mation as possible about the morphology, genes, and bio- chemistry of the relevant organisms. It is important to focus on features that result from common ancestry, because only such features reflect evolutionary relationships.
Homology definition
Similarityin characteristics resulting from a shared ancestry.
What is it called when there is similarity between organisms because of convergent evolution rather than shared ancestry?
Analogy
Analogy definition
Similarity between two species that is due to convergent evolution rather than to descent from a common ancestor with the same trait.
When does convergent evolution occur?
Convergent evolution occurs when similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionary lineages
Two clues to distinguish between homology and analogy
- Comparing internal anatomy, physiology and reproductive systems: Animals with similar evolutionary pasts will have a degree of similarity in anatomy
- The complexity of the characteristics compared: If two organisms have a similarly complex structure (physical, genetic etc) is likely they have an evolutionary past.
What is commonly used for comparing complexity?
Skulls
Homoplasy definition
A similar (analogous) structure or molecular sequence that has evolved independently in two species.
Molecular systematics
A scientific discipline that uses nucleic acids or other molecules to infer evolutionary relationships between different species.
Cladistics definition
A scientific discipline that uses nucleic acids or other molecules to infer evolutionary relationships between different species.
Clades definition
A group of species that includes an ancestral species and all of its descendants.
When is a taxon equivalent to a clade?
Only if it is monophyletic (from the Greek, meaning “single tribe”), signifying that
it consists of an ancestral species and all of its descendants
Monophyletic defintion
Pertaining to a group of taxa that consists of a common ancestor and all of its descendants. A monophyletic taxon is equivalent to a clade.
Paraphyletic definition
Pertaining to a group of taxa that consists of a common ancestor and some, but not all, of its descendants.
Polyphyletic defintion
Pertaining to a group of taxa derived from two or more different ancestors.
Shared ancestral character
A character, shared by members of a particular clade, that originated in an ancestor that is not a member of that clade.
Shared derived character
An evolutionary novelty that is unique to a particular clade.
Outgroup
A species or group of species from an evolutionary lineage that is known to have diverged before the lineage that contains the group of species being studied. An outgroup is selected so that its members are closely related to the group of species being studied, but not as closely related as any study-group members are to each other.
Ingroup
A species or group of species whose evolutionary relationships we seek to determine.
