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Evolution
The process by which the genetic structure of populations changes over time.
Divergent evolution is the
accumulation of differences
between groups which can
lead to the formation of
new species.
Goldfields and Ahinahina (silversword) a highly evolved member of the
composite family.
Evolution
In convergent evolution,
unrelated species become similar
in appearance as they adapt to the
same kind of environment.
Euphorbia and Astrophytum are only distantly
related, but have independently converged
on a very similar body form.
Evolution
Characteristics derived from a common ancestor are
termed homologous.
• similar in structure and embryonic
• not necessarily similar in function.
Analogous or homoplasy includes convergent
evolution.
Similar evolutionary pathways under similar
environmental conditions = Similarity of structure in
unrelated or distantly-related organisms
A. Equisetum (Division Sphenophyta). B. Casuarina (Division Anthophyta). One
is a flowering tree and the other is a non-flowering plant with an apical sporebearing cone (strobilus).
Evolution
Coevolution:
describe cases where two (or more) species
reciprocally affect each other’s evolution.
Happen when species have close
ecological interactions with one another.
• Predator/prey and parasite/host
• Competitive species
• Mutualistic species
Exclusive “matches” between plants and
insects
Species concept
Species = “Kind”
Biological species concept (genetic isolation):
A group of organisms capable of interbreeding and producing fertile offspring of both
genders, and separated from other such groups with which interbreeding does not
normally happen
Morphology is important
Some problems with the species concept
Morphological species
A population or group of populations that differs morphologically from other
populations
Heteromorphyc generations
Sterile hybrids may become
widespread if they are able to
reproduce asexually Equisetum x
ferressii
Some problems with the species concept
Iris
Platanus x hybrida
A fertile hybrid from
2 species isolated for
at least 50 million
years
Some problems with the species concept
Developmental plasticity.
However, through artificial selection Brasica oleracea has proven to be highly
flexible and has been bred for its leaves, inflorescence, stalks, leaf buds and
roots.
Artificial
selection
Broccoli, kohlrabi, cabbage, collard greens, cauliflower, brussel sprouts and kale
Diversity and its order
Systematics: the study of biological diversity in an
evolutionary context, including taxonomy and
phylogenetics.
Taxonomy uses a hierarchical classification system
Linnaean (binomial) system of classification:
genus and specific epithet = species name.
Pinus flexilis –Limber pine
P. lambertiana – Sugar pine
P. morrisonicola – Taiwan white pine
P. monticola –Western white pine
- A named taxonomic unit at any level is called a taxon.
*
Diversity and its order
Members of different taxon may be grouped into subgroups
Subkingdoms
Subphylums or Subdivisions
Subclass
Suborder
Subfamily
Subgenus
Subspecies
Varieties*
Binomila name + var.
Pinus elliottii var. elliottii
Pinus elliottii var. densa
Diversity and its order
The International Code of Botanical
Nomenclature (ICBN) is the set of
rules and recommendations dealing
with the formal botanical names that
are given to plants.
• Only one correct name that is
accepted worldwide
• The value of a scientific name is
that it is an identifier
• Not necessarily of descriptive
value
• Not necessarily accurate
Diversity and its order
The ICBN
• Plants
• Blue-green algae
• Fungi
• Photosynthetic protistas and
taxonomically
• Related non-photosynthetic groups.
Different rules and codes for
Fossils
Cultivated plants (International Code of
Nomenclature for Cultivated Plants)
Diversity and its order
A botanical name is fixed to a taxon by a
"type” usually deposited and preserved in
a herbarium.
Names in Latin (or Greek)
Navicula tripunctata (O.F. Müller)
Bory 1822
Authority
Navicula tripunctata (O.F. Müller) Bory
1822
Nomen conservandum, to avoid
disadvantageous nomenclatural changes
• Family
• Genus
• Species
Phacelia nashiana = P. campanularia
Systematics and cladistics
A B
C
D
E F
G
H
I
Modern phylogenetic systematics are based on cladistic
analysis.
A phylogenetic diagram (tree) is also called a cladogram.
A clade is a group of organisms which consist of
1)  all the descendants of an ancestral organism
2)  the ancestor itself.
Systematics and cladistics
Monophyletic pertains to a taxon that is derived from a single ancestral
species.  only legitimate cladogram type!
Polyphyletic pertains to a taxon whose members were derived from two or
more ancestors not common to all members.
Paraphyletic pertains to a taxon that excludes some members that share a
common ancestor with members included in the taxon.
Systematics and cladistics
Possession of unique features
that reflect a common
evolutionary origin vs.
widespread features present in
the common ancestor and lost
over the time in some of the
members of the group.
Principle of parsimony
Adoption of the simplest assumption
in the formulation of a theory or in
the interpretation of data, especially
in accordance with the rule of
Ockham's razor.
Homology is preferred over analogy
or homoplasy
A universal evolutionary tree. Ribosomal RNA
Nucleic acids:
• Data for understanding
evolutionary relationships
• Genes with different rates of
change in different lineages
• Non-coding sequence used as
neutral markers that reflect past
evolutionary events
Serial endosymbiotic theory
Systematics and cladistics
Molecular data alone may not provide the most accurate account of
phylogenetic relationships
Systematics uses diverse approaches:
Morphology
Anatomy
Palynology
Microscopy
Biochemistry
Molecular Biology
Genetics
Physiology
Ecology
Evolution
Bioinformatics