Studied by 2 people
Taxonomy
Formal system for naming and grouping species
Systematics (newer: 1980s)
Broader science of classifying organisms based on how they
re related
Carolus Linnaeus
Designed current classification system
Used morphology to develop a classification system for plants and animals
Given distinct names to divide animals kingdom into species
Morphology
Study of shape
Hierarchy of Taxonomic ranks
Kingdom, Phylum, Class, Order, Family, Genus, Species
Human Taxonomy
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Mammalia
Order: Primates
Family: Homonidae
Genus: Homo
Species: Homo sapiens
Dogs
Animalia, Chordata, Mammalia, Carnivora, Canidae, Canus, Canus familiaris
Classification
denotes the construction of classes
Systematization
Recognition of individual groups based on relationships
ID natural groups
traits that show family resemblances
Autapomorphy
a trait that is unique to that group, evolving at the same time, derived trait
3 Main Domains
Bacteria, Archaea, Eukarea
Homology/Homologous Characters
Character similarity resulting from common ancestry, but similarity doesn’t always means common ancestry
Convergence (Homoplays/analogy)
Character similarity that misrepresents common descent
Reflects natural selection, not relatedness
MEANING: they look alike, but aren’t related
Homologous
the bird wing and a bat wing
Analagous
the insect wing and a bird wing
Species
specific traits in common, share habitat, similar physiology, fertile offspring, share ancestors, smallest group
Typological Species Concept (TSC)
focuses solely on morphology similarity/type
OLD IDEA
Linnaeus’ time: a species was considered a distinct and immutable entity (before Darwin)
A type specimen was labeled and deposited in a museum (ideal form of a specimen)
Species are no longer defined solely by possession of certain morphological features
Synapomorphy
SHARED derived characteristic
Symplesiomorphy
SHARED ancestral characteristics
Tetrapods: Lizards, horses, monkies
Synapomorphy: 4 legs, amniotic eggs
Symplesiomorphy: vertebrae, jaws
Not shared: hair, mammary glands (only horses and monkies)
Biological Species Concept (BSC)
to be a member of a species
must be able to reproduce with each other
not reproducing with members of other species
“a species is a reproductive community of populations (reproductively isolated from others) that occupies a specific niche in nature.”
Sometimes species status can be evaluated directly by conducting breeding experiments
BSC Problem 1
Two good species that can make hybrids
Ad hoc criterion (after the fact criterion)
occupation of a habitat in a particular place
Only if they have viable offspring, not sterile offspring
BSC Problem 2
Criterion of interbreeding cannot be applied to:
many plants self-pollinate (beans and peas)
asexual organisms (bacteria)
while most animals are sexually reproducing, MANY are NOT
a lot of life doesn’t use sexual reproduction
Why evolution has said no to sex
If you are finally perfect and mate with someone not perfect, you will get imperfect offspring.
BSC Problem 3
Lacks an explicit temporal dimension (TIME)
can only asses reproductive compatibility on organisms alive today
a species has limits in space and time
Ring Species
Where you have a geographic barrier and a species goes around it because they can’t live in those conditions
Greenish Warblers
Evolutionary Species Concept (ESP)
A single lineage of ancestor-descendant populations that maintains its identity from other such lineages and that has its own evolutionary tendencies and historical fate
Trilobite lineage
Anagenesis
Gradual (slow) change in the same universal lineage
Cladogenesis
Branching event with 2 lineages forming 2 species at the same time
A new branch forming
Definition accommodates both sexual and asexual forms, as well as fossils
Phylogenetic Species Concept (PSC)
Smallest grouping of organisms that are distinct from other such groups and within which there is a parental pattern of ancestry and descent
Works with ESC
Trying to provide an answer
Why there are many concepts
disagreement; a sign of dynamic research
cannot predict which species concepts will remain useful in the future
possible that disagreements regarding species can lead to breakthroughs
Unity from diverse scientific concepts
Observation : most SC recognize the same species as species
“Good species” = agreement
During the process of forming new species - much disagreement
Speciation was once though to take millions/thousands of years
Today, many examples of speciation in action
Note 
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