Phylogeny Flashcards
taxon
- a named group of organisms
homologous structures (2)
- features that share a common ancestry: structures arise from the same structure in their MCRA
- structures that are homologous may also be similar in function and appearance, but this is not true for all homologous structures
how can embryonic origins support comparative morphology studies (2)
- can provide evidence for whether or not structures are homologous
- is a certain feature has the same precise embryonic origin, it is most likely homologous; due to broadness of differentiation in embryos, we cannot confirm that the are homologous
phylogeny
- evolutionary history of any group of organisms
phylogenetic tree (2)
- graphical representation of HYPOTHESIZED evolutionary relationships among taxa
- can use genetics, traits, behaviours, geography, etc to construct phylogenies
monophyletic group
- group consists of an ancestor and ALL of its descendants
node
- each node represents a common ancestor
- not an individual, but a population of organisms
common ancestor and homologous characters
- more recently two groups shared a common ancestor, the more homologous characters we would expect them to share
convergent evolution
- produces similar characters that are NOT the result of inheritance from a common ancestor
evolutionary divergence (2)
- can produce characters that no longer appear similar, even though they are homologous
- can lead to secondary loss of characters
ancestral character state
- pre-existing character state that is not new to a certain taxon
derived character state
- character state that has been changed and is new within that taxon
synapomorphy
- derived character state that is shared by 2+ taxa
how can deuterostome and protostome taxa be identified (2)
based on early embryonic development:
- protostomes (“first mouth”): blastopore at anterior end of embryo and gives rise to region of the mouth
- deuterostomes (“second mouth”): blastopore at posterior end of embryo and gives rise to region of the anus
what are the shared characters of all chordates (5)
all appear in at least one developmental stage, although it may not be retained into adulthood:
- dorsal hollow nerve chord
- notochord
- pharyngeal slits
- post-anal tail
- endostyle (homologous to thyroid gland in vertebrates)
dorsal hollow nerve chord (5)
- synapomorphy for….
- definition
- origins
- composition
- function
- synapomorphy for chordates
- hollow, fluid-filled structure dorsal to the digestive tract
- arises from neural tube/neural plate ectoderm
- composed of neurons and glial cells and forms central nervous system (the brain and spinal cord in vertebrates)
- transmit signals to rest of body
notochord (5)
- synapomorphy for….
- definition and structure
- function
- origins
- presence in vertebrates
- synapomorphy for all chordates
- slender rod with core of cells and fluid surrounded by tough fibrous sheath
- provides structural support: can bend from side to side, but cannot be axially compressed (length remains the same)
- arises from mesoderm
- functionally replaced by vertebral column during development in many vertebrates
pharyngeal slits (3)
- synapomorphy of…
- position
- formation
- most likely a synapomorphy of deuterostomes
- pharynx is anterior chamber of digestive tract (posterior to the mouth)
- during development, walls of pharynx penetrated by series of openings, but are closed before embryo is born/hatched in many terrestrial vertebrae
endostyle (5)
- synapomorphy for…
- position
- definition
- function
- homologous to…
- synapomorphy for chordates
- arises from ventral side of pharynx during development
- groove filled with glandular tissue
- produces mucus and processes iodine
- homologous to thyroid gland in chordates
post-anal tail (3)
- synapomorphy for…
- definition
- function
- synapomorphy for chordates
- posterior elongation of the body extending beyond the anus; notochord extends into structure
- functions to produce lateral undulation for movement
myomeres (2)
- definition
- function
- segmented blocks of skeletal muscle separate by layers of connective tissue; arranged in series from anterior to posterior
- pull notochord from side to side to create movement
notochord vs nerve cord (2)
- notochord provides structural support for body
- nerve cord used for rapid communication of signals within body
deuterostomes (3)
- echinodermata, hemichordata, chordata
chordata (3)
- cephalochordata, urochordata, vertebrata
echinodermata (2)
- sea stars, sea cucumbers, sea urchins, sand dollars, etc
- adults have pentaradial symmetry
hemichordata
- includes acorn worms and pterobranchs
cephalochordata
- amphioxus or sea lancelot
- have all 5 chordate characteristics
urochordata
- eg. sea squirts
- undergo metamorphosis; lose some chordate characteristics as adults
vertebral column
- series of separate bones or cartilage blocks located along the longitudinal axis of the body
cranium
- composed of cartilage/bone
muscular pharyngeal pump
- for feeding, likely replaced ciliary pump of chordata common ancestor
what characters differentiated ancestral vertebrates from ancestral urochordates (3)
- vertebral column
- cranium
- muscular pharyngeal pump
agnatha (2)
- vertebrates without jaws
- include myxinoidea (hagfish) and lampreys (petromyzontida)
myxinodea (5)
- characteristics (3)
- phylogeny (2)
- agnatha and vertebrata
- hagfish only found in marine environments
- often scavengers. feeding on dead fish, dying fish, or invertebrates; can also be predatory
- release huge volumes of slime if attacked
- lack vertebrae; likely secondarily lost
petromyzontida (4)
- phylogeny (1)
- characteristics (3)
- agnatha and vertebrata
- lamprey have a larval stage using muscular pharyngeal pump for suspension feeding
- have endostyle; during metamorphosis into adult, it transitions to thyroid gland
- some adults are parasitic and attach to prey using their round mouths to feed on blood and fluids; others do not feed at all as adults
what characters differentiated ancestral gnathostomata from ancestral agnatha (3)
- bone
- jaws
- pectoral and pelvic fins/girdles
jaw (2)
- biting device derived from splanchnocranium of the skull
- allowed for great increase in gnathostome diversity due to wider variety of food sources than available for filter-feeding ancestors
pectoral and pelvic fins
- gave ancestral gnathostomes stability and precise control of steering while swimming, allowing for increased maneuverability
gnathostomes (2)
give rise to:
- chondrichthyes
- teleostomi
chondrichthyes (4)
- elasmobranchii and holocephali
- cartilaginous fish: secondary loss of bone
- control their buoyancy by producing oils (using their liver) and by swimming
- negatively buoyant, so they will sink if they stop swimming
teleostomi
- actinopterygii, sarcopterygii, tetrapods
what characters differentiated ancestral teleostomi from ancestral gnathostomes (3)
gas bladder
gas bladder
- acts as a swim bladder that provides natural buoyancy
- act as lungs for gas exchange in other teleostomi
actinopterygii
- teleosts exist within actinopterygii and contain large number of extant species
tetrapoda
- amphibia, sauropsida, mammalia
what characters differentiated ancestral tetrapoda from ancestral lobe-finned fishes
- legs and digits
legs and digits (2)
- paired muscular appendages and well-defined joints
- evolved from fleshy fins
amphibia (3)
- salamanders, newts, frogs and toads, and caecilians
- most have thin, scaleless skin covered in mucous to allow for cutaneous respiration
- most have aquatic larval stage, then undergo metamorphosis into a semi-terrestrial or terrestrial adult stage
anamniotes (2)
- fish and amphibians
- do not produce amnion, chorion or allantois; many still produce yolk sacs
amniotes (4)
- embryos that produce amnion, chorion, allantois, and yolk sac
- two main lineages: sauropsida and mammalia
- in oviparous (egg-laying amniotes), the embryo is packaged within a tough shell
- waterproof membranes allowed for laying of eggs on land (transition to terrestrial environment) and prevent desiccation
sauropsida
- testudinata, lepidosauria, archosauria
archosauria
- crocodilia
- aves
testudinata (4)
- turtles
- have bony shell made up of dorsal carapace and a ventral plastron
- secondary loss of teeth
- beak composed of keratin
lepidosauria (2)
- snakes, lizards
- hemipenes are synapomorphy; pair or intromittent organs
crocodilia
- crocodiles, alligators, caiman
aves (2)
- birds
- can be distinguished by presence of feathers and endothermy
mammals (2)
- monotremata, metatheria, eutheria
- synapomorphies: endothermy, hair, mammary glands
monotremata (2)
- platypus, beaver
- lay eggs, oviparous
metatherians and eutherians
- give birth to free-living young (viviparous)
