321 Flashcards
Monophyletic
A taxon in which all species share a common ancestor, & all species derived from that common ancestor
Polyphyletic
Derivation of a taxon from two or more ancestral sources
Paraphyletic
A taxon in which all species share a common ancestor, but not all species derived from that common ancestor are included
Taxonomy vs systematics
» Taxonomy: The science of naming, describing and classifying organisms and includes all plants, animals and microorganisms of the world.
» Systematics: The science that studies the distinctive characteristics of species and how they are related to other species through time. Field of biology that studies and tries to establish phylogenies (= evolutionary histories)
Plesiomorphy
Near ancestral type
Symplesiomorphy
Shared ancestral type
Apomorphy
Away from ancestral
Process (microevolution)
to do with how the process occurs
History (macroevolution)
process created history with many unique events
hutton
- Uniformitarianism
– Present is the key to the past - Gradualism
– Features of the earth result from slow accumulation of events
such as those we see occurring now
Thomas Malthus
populations grow
exponentially while agriculture grows
linearly; therefore, populations will always
outstrip their resource base.
Lamarck
Theory of Evolution (1809)
* Organisms continually change to become better
adapted to their environment
* A feature acquired during an individual’s lifetime could be passed on to offspring
Cuvier
Strongly opposed the idea of evolution
* Catastrophism
* Only natural catastrophes, such as the “Great
Flood”, could account for the form and nature of
a 6,000-year-old Earth
Lyell
The earth is very old
* Made Hutton’s ideas accessible to a wide
audience, including Darwin
* Advocated uniformitarianism and
gradualism
darwin observations
Similarity (unity) & dissimilarity (diversity)
* Redundant forms from place to place
* common ancestry
* Variation on a basic form within a region
* Due to descent with modification
wallace
‘Father of biogeography’
* Independently proposed theory of
evolution due to natural selection
clade
A clade is a grouping that
includes a common ancestor
and all the descendants (living
and extinct) of that ancestor.
homology
Similarities due to shared ancestry
» Do not necessarily have the same function
» Sharing of homologies among species indicates that
they have evolved from a common ancestor that
possessed the same feature
analogy
Similarity between structures that is NOT the result of
a common evolutionary origin
» Phenotypic similarity that is due NOT to common
descent but to similarity of function
Convergence
Similar appearance NOT due to common ancestry
* Could be analogous but not homologous
Parallelism
Independent evolution of similar structure from common
ancestor
* Raptorial feet from perching feet in owls and falcons
parallelism example
thorny devil vs horned lizard
ancestral
plesiomorphic
derived
apomorphic
Homoplasy
describes a character state similarity not due to shared
descent (for example, produced by convergent evolution or
evolutionary reversal). Closely related to the idea of analogy but more
general because it does not include similarity in function.
Maximum parsimony
The preferred tree is the one with the least homoplasies
(fewest reversals + convergences)
Often called the shortest tree: it is the tree with the fewest changes
of character state
Cladogenesis
Branching of a lineage
into two or more
descendant lines
* Evolution that results in
the splitting of a lineage
Anagenesis
Evolutionary change of
various characteristics in
each descendant
* Evolution within a lineage
Pseudoextinction:
A phenomenon in which a
taxon changes by anagenesis over evolutionary time,
until it is so different from the ancestor that it is
reclassified as a new taxon.
dating phylogenic trees
-Radiometric dating
-Molecular clock
Radiometric Dating
“Absolute” ages of geological events: based mostly on radioactive decay
that changes unstable radioactive atoms to stable daughter atoms;
occurs at a constant rate; hence each element has a specific half life.Only igneous rocks can be dated; hence, fossilbearing sedimentary rocks must be bracketed
between younger & older igneous rocks
molecular clock
Most DNA consists of non-coding parts of the molecule
* Even within coding regions, changes at 3rd base positions of
each codon are mostly silent substitutions (they don’t change
the amino acid)
* If non-coding and silent changes predominate, then most
mutations are not expressed in the phenotype
* Not being expressed, they are not subject to selection
* They, thus, may accumulate at a stochastic (=non-deterministic)
rate
Rates of Molecular Evolution
D = 2rt
Evidence for evolution
- Homology
- Embryological similarities
- Vestigial characters
- Convergence
- Suboptimal design
- Geographic distribution
- Intermediate forms
Types of evidence:
- Phylogenetic – DNA sequences
- Morphological – shared
homologies - Geographic – where and when
traits evolve
mosaic evolution
Different phenotypic characters evolve at different rates
Allometry
How physical
traits change with body size
(scaling relationship
between traits and boody
size).
Allometric growth
– differential rate of growth of
different parts of an organism during its ontogeny
Heterochrony
To describe cases in which an ontogenetic sequence of events did not
recapitulate the phylogenetic sequence
Evolutionary change in phenotype caused by an alteration of
timing of developmental events (Futuyma, 2013)
* Change in the relative timing of developmental events in one
species relative to an ancestral species
PAEDOMORPHOSIS
: conditions in which a
larva becomes sexually mature without
attaining adult body form.
NEOTENY
May result from a slowing of somatic
development relative to sexual development
PROGENESIS
Less commonly from an acceleration of
sexual development relative to somatic
development
Paedomorph Advantage Hypothesis
Neoteny may have
been favoured to remain in relatively safe aquatic habitat,
rather than undergoing metamorphosis & facing a new suite
of terrestrial predators.
Adaptive radiation
diversification of a group of organisms into forms filling
different ecological niches; diversification of a species or single ancestral
type into several forms that are each adaptively specialized to a specific
environmental niche.
- Species flock
A group of closely related species all living in the same
ecosystem
* Should be applied to species assemblage of monophyletic
origin
* Evolved within the same ecosystem from a single ancestral
species by repeated speciation events
* One or more synapomorphies in all members of the
assemblage which is/are absent in relatives outside the flock
adaptive radiation
evolutionary lineage that has undergone exceptionally rapid
diversification into a variety of lifestyles or ecological niches.
