midterm studying Flashcards
taxonomy
science of naming and classifying organisms
two approaches to taxonomy
- group according to phenotypic similarity (=Linnaeus’ method)
- group according to evolutionary relationships: Phylogenetic systematics
linnaeus’ method
grouping according to phenotypic similarities
phylogenetic systematics
grouping according to evolutionary relationships
- uses phenotypic traits, according to maximum parsimony/fewest changes
- molecular phylogenetics/DNA analysis
cladistics
- taxonomic groups must correspond to monophyletic groups aka CLADES
- based on shared derived characters, aka synapomorphies
synapomorphies
shared deriived characters
homologous traits
-similarities inherited from common ancestors
analogous traits
similarities not due to homolgy, but convergent evolution, aka homoplasies
ie. flight in bats and birds
modern approach to taxonomy uses…
fossils, traits of extant species, DNA and other molecular markers
living tetrapods
- herps: amphibians and reptiles
- birds
- mammals
linnean system
kingdom phylum class order family genus species
are herps monophyletic?
NO: tetrapods branched off from amphibians way before birds and reptiles even formed
tetrapods by phylogenetics
- amphibia
- mammalia
- testudomorpha/turtles
- crocodylia/ crocodiles
- aves/birds
- lepidosauria/lizards, snakes, tuatara
reptilia monophyletic?
NO: its polyphyiletic, containing turles, crocodiles, and lizards/snakes
selective forces leading to terrestrial activity
- movement between bodies of water for new food, escaping drought or predators, or juvenile dispersal
- use lands for new egolocial niche, new food, no predators, competition free
adaptions required for land
- gas exchange outside of water
- locomotion
- stronger skeleton
- distinct larval and adult forms, since reproduction was still water dependent
what were the first animals to breathe air
- fish! ie. the long=nosed gar, breathed air possibly in low oxygen water, or shallows
- air breathing fish have evolved at least two separate times
sarcopterygian: ancestor of tetrapods
- lobe-finned fishes, air breathers, could breathe to survive in mud holes
- lobed fins for ‘“walking”
early aquatic tetrapod: acanthostega gunnari
-could walk, sister group to amphibians
Tiktaalik roseae
- another species linking fish and land vertebrates
- has hand bones/wrists that are intemediates between lobe-finned fish and land tetrapods
Temnospondyls
- most speciose amphibians of paleozoic and ancestors of modern amphibians
- ie. branchiosaurus, a sister group to modern amphibians
paedomorphosis
-evolutionary change in which juvenile characteristics are retained in adult form
class amphibia orders
- gymnophiona (caecilians)
- cauudata (salamanders)
- anura (frogs and toads)
common traits of amphibians
- moist, permeable skin with mucous glands
- poison glands in skin
- ears, eyes, and teeth
- carnivorous
- repro tied to water
- undergo metamorphosis
amniotic egg
- egg has 3 extra membranes: amnion, chorion, allantois, facilitates reproduction away from water, egg is self-containted, surrounded by protective shell
- this is a synopomorphy of ‘reptiles’, birds, and mammals
group following amphibians…
reptiles, replaced amphibioans on land because
- they could more successfully reproduce away from water
- have stronger jaws and teeth, due to being diapsid, two pairs of holes in skull
the permian was a time of…
diversification of jaws and food sources
-saw rise of herbivorous amphibians, fin-backed mammal like reptiles, and THERAPSIDS
therapsids
mammal-like reptiles
amniote skulls
mammals=synapsid
non-turtle reptiles, birds= diapsid
- turtles=anapsid
permian extinction, who survived?
-only temnospondyls, and some amniotes survived
