OD Unit 1: Taxonomy and Phylogeny of Life

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


1. must be able to reproduce with each other
2. 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)


1. occupation of a habitat in a particular place


1. Only if they have viable offspring, not sterile offspring

BSC Problem 2

Criterion of interbreeding cannot be applied to:


1. many plants self-pollinate (beans and peas)
2. asexual organisms (bacteria)
3. while most animals are sexually reproducing, MANY are NOT
4. 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