SPECIES

1
SPECIES

• What sort of Biological Entity is it?

2
What is a Species?

• Biological Species Concept
• 1 or more populations of individuals that can
  interbreed and produce fertile offspring, and are
  reproductively isolated form other such groups.
• Members of a species have a shared gene pool.
• Different populations can mate and produce
  fertile offspring.

3
What is a Species?

• Butwhat about asexual organisms?
• Morphological Species Concept
• Groups of organisms that share certain
  morphological or biochemical traits.
• This is rather subjective.
• Phylogenetic Species Concept
• Groups of organisms (or lineages) that share
  recent common ancestry.

4
Speciation

• How do species arise?
• Microevolution
• Pre-existing organisms (ancestors).
• Divergent Evolution
• Adaptation to specific environmental cues.
• (This contrasts Convergent Evolution)
• Similar adaptations in organisms from very
  different lineages.

5
Speciation

• Biological Species Concept
• 1 or more populations of individuals that can
  interbreed and produce fertile offspring, and are
  reproductively isolated form other such groups.
• Reproductive Isolation
• Prevents Gene Flow.
• If no gene flow, then populations can develop
  into more and more different sub-populationsperha
  ps eventually forming species.

6
Reproductive Isolating Mechanisms

• Pre-Zygotic Isolating Mechanisms
• Post-Zygotic Isolating Mechanisms

7
Pre-Zygotic Isolating Mechanisms

• Prevent Reproduction Attempts
• Habitat Isolation
• Isolated in space/habitat.
• Temporal Isolation
• Mating occurs at different times
• Behavioral Isolation
• Differences in mating displays, calls, chemicals
• Mechanical Isolation
• Incompatibility of reproductive organs (the
  key doesnt fit the lock)

8
Post-Zygotic Isolating Mechanisms

• Copulation occurs, but offspring are kept from
  developing breeding.
• Gamete Isolation sperm egg dont fuse.
• Zygote Mortality Zygote dies, unable to
  function.
• Hybrid Inviability Hybrid is produced, but does
  not survive to adulthood.
• Hybrid Sterility Hybrid is produced, but is
  unable to produce viable gametes.

9
Speciation

• Formation of new species via reproductive
  isolation.
• Allopatric Speciation
• 2 populations become reproductively- isolated
  while separated from each other (geographic
  barrier).

10
Speciation

• Sympatric Speciation
• 2 populations become reproductively-isolated
  while occupying the same geographic area.

11
How Fast?

• Gradualist Model
• Punctuated Equilibrium Model

12
Systematics

• Science of organizing the diversity of life.
• Taxonomy Identification Naming
• Phylogeny Analyzing evolutionary relationships
  among groups.
• Classification Placing organisms into an
  organized categorization scheme.

13
Taxonomy

• Identification Naming
• Taxon a group of organisms (Taxa)
• Species the most fundamental group.
• Group of interbreeding populations that are
  reproductively isolated from other such groups
  (and evolving independently of other such groups).

14
Taxonomy

• New species each given a Scientific Name
• Carolus Linnaeus
• Binomial Nomenclature
• 2-word Latin name.
• Pinus strobus
• Dictyostelium discoideum
• Bubo virginianus
• Common Names also
• Can be misleading

15
Taxonomy

• Pinus strobus
• 1st word Genus
• A generalized name
• 2nd word specific epithet
• A descriptive name
• Always in italics or underlined.
• Genus is capitalized, epithet is lower case.
• Specific epithet never used alone!

16
Phylogeny

• Grouping new species/taxa with closely-related
  taxa from an evolutionary perspective.
• Phylogenetic Trees

17
Phylogeny

• Outgroups

18
Classification

• Categorizing organisms into a hierarchy of names
  (hopefully) according to their relatedness.
• Historically based on convenience.
• Starting at Species (the most exclusive group),
  organisms are grouped into more and more broad
  inclusive Taxa.
• Species is the only level that really exists as
  an true single entity.

19
Classification

• Kingdom
• Phylum/Division
• Class
• Order
• Family
• Genus
• Species

Animalia Chordata Mammalia Primates Hominidae Ho
mo Homo sapiens
20
Classification
Animalia
Chordata
Aves
Mammalia
Strigiformes
Primates
Hominidae
Tytonidae
Tyto
Homo
Tyto alba
Homo sapiens
21
Systematics

• Tree of Life http//tolweb.org/tree/phylogeny.ht
  ml