A3.2 Classification & Cladistics (HL) Flashcards
What is biological classification?
The process of organizing organisms into logical groups known as taxa
Taxa is the plural of taxon.
What is taxonomy based off ?
Observable characteristics and genome sequencing data
This combination allows for more accurate classification.
List the taxonomic groups in descending order of size.
- Domain
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
What is introgression?
The breeding of fertile offspring between two species that may only breed with one parent species afterward
This complicates species classification.
What is cladistics?
A newer classification system that uses unranked groups based on evolutionary relationships
Cladistics produces evolutionary trees.
What can occur when different species in distant taxa breed together?
They can produce fertile hybrids, creating new species that are difficult to classify
This complicates the hierarchical classification.
What is the basis for classifying organisms in modern taxonomy?
Evolutionary relationship
Classification is now based on DNA sequencing technology.
What are groups of organisms classified together based on common ancestry called?
Clades
Every member of a clade shares a recent common ancestor.
Define a common ancestor.
A shared ancestor of organisms
Example: The most recent common ancestor of siblings is their parents.
What is a monophyletic group?
A group that contains all descendants of a common ancestor.
List advantages of classification by evolutionary relationship.
- Ensures organisms are close evolutionary relatives
- Characteristics are likely shared due to common ancestry
- Helps avoid classification errors based on analogous characteristics
What is cladistics?
The branch of science that classifies organisms into clades.
What is a taxon?
A group of organisms given a name based on shared features.
What is the molecular clock?
A method to estimate the time since two species diverged based on mutation rates.
What does a node in a cladogram represent?
A common ancestor species.
What is the principle of parsimony?
The simplest explanation is preferred when constructing cladograms.
What led to the reclassification of the figwort family?
DNA sequence analysis showed that it was not a true clade.
What are the three domains of life?
- Archaea
- Eubacteria
- Eukaryotes
based on rRNA evidence
What distinguishes Archaea from other prokaryotes?
- Different cell wall composition
- Distinct lipid in cell membranes
- Ribosomes more similar to eukaryotic ribosomes
What is the significance of the number of differences in sequence data?
Indicates how closely related two species are and the time since divergence.
synapomorphis
shared derived trait that exists in 2 or more groups of organisms but not in ancestors
