phylogeny and classification Flashcards
cladistics
the way we use the characteristics of plants and animals ot figure out how relationships and characteristics evolve throughout time
molecular phylogeny
gene sequences and characteristics that are used to make tree
what is studied in the evolution of diveristy of life
history oc change
mechanisms of change (comparitve embryology and developmental genetics)
what is developmental biolgoy
development from a singular fertilize cell to a full adult and the genes/processes involved
phylogenetic tree
tree of relationships
monophyletic clade
a single common ancestor included in the group; all descedenets of a common ancestor
(humans and chimps form a clade)
paraphyletic clade
groups that do not include all, but some descdenenats of the last common ancestor (reptiles; e.g. birds not included despite sharing common ancestor to crocodiles)
polyphyletic clade
groups that have more than one origin
e.g. birds, bats and pterodactysla re groupted together as ‘flying vertebrates’
cladogram
only represents the branching pattern and branch order;
but doesnt tell us the time of brancing/evolution information
is more of a hypothesis of evolitionary theory
phylogram
shows the information about branch lengths (quantity of evolution) AND branch order
hence the real rerpesentation of evolutionary history and time (of character development)
in groups
mammals and frogs are outgroups relative to the ingroup of dinorsaurs but dinosaurs and frogs are outrgorups relative to the ingroup of dinosaurs
what do two sistergrousp form
a monophyletic group
what methods can we use to recontruct the tree of life
cladistics
molecular phylogeny
phylogenic rescontruction
what do changing trees imply
changing evolutionary scenarios
why is it important to understand the evolution of characers
as there are continous changes of interpresetations of evolution
principle of parismony
choosing the simplest explanation, which requires the fewest assumptions, from a set of equivalent models that depic evolutionary scenarios
preferred hypothesis is the simples
characteristcs shared with a more primitive animal is the primitive state
origin of the principle of parsimony
medivieal philosopher william of occam; logical principle
symplesiomoprhies
are uniformative; as they are the primitive character
bad characater for defining a gorup
they do not prefer a tree
synanomorphies
are informative
shared derived characateristics
they prefer trees
how are new groups formed
discovered by characters only presesent in monophyletic group
why are shared primitive characterics bad
they dont define groups adn are uninformative
example of groups badly defined by shared primitive characterics
- Reptiles; defined by symplesiomorpheis such as scales and cold blooded; but birds have lost these traits in the archosauria; birds and cocodiles have shared derived characteristics (Extra hole in skull) implying birds are reptiles
- apes: defined by sympesiomorphies such as hairiness; but hairiness is too broad to define mamals relationsips; instead humans and chimps clsoely related but humans lost traditional ape features
aim of phylogentic trees and the principle of parsimony
to find lots of characteristics to find overlaps in overcomming the lack of informationg conercning parsimonous cost
why do we use molecular phylogeny
more accurate and sometimes morphological characterstics disagree
principle of pasrimony can also be applied to nucleoid genes
how does gene inheritance help in constructing trees
dna provides information
example of molecular data revealing information between groups
choanoflagellates are the closest relative to animals:
- gene fusion supports their close relationshio
- EGF and TK genes exist across all life but only metazoans and choanoflagalltes have a fused version of this gene that places them in a clade
example of where gene expression matters
HRP antibody (the horse radish peroxidase gene) only binds to a gene product in the nervous system of ecdysozoa
molecular phylenies determien other genetic characters like
- Elongation factor one alpha gene is preserved in all life; the gene has slowly evolve and varies in animals, plants, fungi and bacteria which allows for out groups and ingrousp to be eaily located
for example: both animals and fungi have extra amino acids in this gene; shows a molecular synacromorphy
examples of reclassification
spiral cleavage + bilateraly symmetry
ecihnodrms have gained and lost bilateral symmetry
the annelids have gained spiral cleaves in the the mesoderm
what do changes in minctonrdial gene order tlel us
supports insect and crustacean relationships
classification mneonimic
kindly put candy out for good students
classification linnear system
life domain kingdom phylum class order family genus species
classification order of humans
life domain : eukarya kingdom : animalia phylum : chordata; vertebrata class : mammalia order: primate family: hominidae genus: homo species: sapiens
legs evolution
- legs evolved in a transition between fish and tetrapods
we know jaws evolved before legs
fish and bird limb evolution
fish and bird limbs start similary in early embryos but end up differnet in adults
both have similar limb buds:
gene Tbx 5 switched on in the forelimbs/hindlimbs of tetrapods and in the pectoral and pelvin fin of sih
early in development genes guided in later development manipulated stem cells in fish and bird differently
embryonic development
process of change between first cell ana dult;
animals different due to different modes of embryonic developmen
embryogenesis
new morphologies evolve by changes in embryogenesis
- all animals start as undifferetiated unfertiilziied egg cells
- cell divisionc auses changes in animals apperances and properties
- final produce resutls in a differed state of development
so while embryos might be similar; different adults result
hence another mechanism and history of change
what do nonmorphological characteristics evolve to
behaviour
example of behavioural evolution
snails tentacles pulsate similar to a capterpillar
hence the Drigenia Flatworm Parasite has develoepd a dual life cycle that they infect a snail and mgirate to its tentacle to make it pulsate like a caterpillar
this results in a bird eating the snail thinking its a caterpillar and consumign the flatworm
shows evolution of behaviour change
