Lecture 3 Flashcards
what is bilateral symmetry?
-2 sided symmetry (right + left sides) (2 planes)
is bilateral symmetry an ancestral or derived characteristic?
-derived characteristic
how do you refer to top and bottom sides?
-dorsal (top)
-ventral (bottom)
how do you refer to front and back sides?
-anterior (front)
-posterior (back)
what is cephalization?
-development of a head region where sensory cells begin to concentrate at the anterior end
how are sensory cells distributed in radial symmetrical animals? are they cephalized? how do these animals move?
-networks of individual neurons
-scattered + evenly distributed
-not cephalized
-immobile/weakly swim (drifting)
how are sensory cells distributed in bilateral symmetrical animals? are they cephalized? how do these animals move?
-clustering of neurons (ganglia)
-concentrated in specific areas (head/anterior)
-considered cephalized
-active movement due to concentration
what does cephalization build?
-the central nervous system
what is the purpose/advantages of the central nervous system?
-complex integration (info processing)
-complex behaviour
what is segmentation?
-the division of an organism’s body plan into identical repeating body units
what type of symmetry is segmentation typically found?
-bilateral
is segmentation an ancestral or derived character?
-derived character
what type of evolution does segmentation come from?
-convergent evolution
in which of the 10 main phyla is segmentation present?
-chordata
-annelida
-arthropoda
what type of gut evolution is an ancestral character?
-gastrovascular cavity in the Cnidarians
what type of gut evolution is a derived character?
-complete gut (mouth + anus)
what does gut evolution depend on? how many possibilites are there?
-the fate of the blastopore
-2 possibilities
what are the 2 possibilities of gut evolution?
-mouth forms first, anus forms later
-anus forms first, mouth forms later
what is an organism whose mouth forms first called? what is an example?
-protostome (protostomia clade)
-ex: snail
what is an organism whose mouth forms later called? what is an example?
-deuterostome (deuterostomia clade)
-ex: echinoderms + chordates
what are the key features of the echinoderm phylum?
-water vascular system
-tube feet
-ampulla
what makes up the water vascular system? what is it used for?
-hydraulic canals
-locomotion
what is the purpose of tube feet?
-locomotion
-sensing
what are ampulla?
-small bulbs on the end of tube feet
how does the ampulla enable movement?
-water pressure
what are the 2 forms of echinoderms?
-larvae and adult forms
what type of symmetry is present in larval echinoderms?
-bilateral
what type of symmetry is present in adult echinoderms?
-radial symmetry in multiples of 5
what are examples of adult echinoderms that have pentaradial symmetry (5 planes)
-sea stars
-sea urchins
what symmetry clade would we place echinoderms under?
-bilateria (despite radial symmetry in adult forms)
what are examples of organisms in the echinoderm phylum?
-sea stars
-sea urchins
-sand dollars
-sea cucumbers
what are the key features of the chordata phylum?
-bilaterians
-deuterostomes
-notochord
-dorsal hollow nerve cord
-pharyngeal gill arches/slits
-post-anal tail
-contains 3 major clades
what is the notochord’s purpose?
-provide strength + support
-adds flexibility (made of cartilage)
what does the dorsal hollow nerve cord develop into?
-the central nervous system
what do the pharyngeal gill arches/slits allow for? what can they develop into?
-water movement
-lungs
what is filtered out by the pharyngeal gill arches/slits? what does this make them?
-food particles
-suspension feeding device
what is contained within the post-anal tail?
-skeletal elements
-muscles
what feature of the chordates is typically reduced during embryonic development?
-post-anal tail
what are the 3 major clades found within the chordates?
-cephalochordata (lancelets)
-urochordata (tunicates)
-vertebrata
what are the key aspects of the cephalochordata clade?
-also called ‘lancelets’
-maintain chordate characteristics through entire lifespan
-most basal group for the living chordates
-outgroup for all chordates
what are the key aspects of the urochordata clade?
-also called ‘tunicates’
-loses chordate characteristics after larvae stage
-undergoes metamorphosis
-cilia captures food particles
-water exits through the ex-current siphon
what features are lost in the urochordata?
-dorsal hollow nerve cord
-notochord
-post-anal tail
why is the dorsal hollow nerve cord lost?
-reduced to ganglion
why is the post-anal tail lost?
-does not need to swim after larvae stage
what are the key aspects of the vertebrata clade?
-animals with vertebrae and a skull
-skeletal + nervous systems present
what are the derived characters within the vertebrata clade?
-vertebrae enclosing a spinal cord
-elaborate skull
-fin rays in aquatic forms
what are the basal vertebrates?
-jawless fish
-hagfish + lampreys
what are the key aspects of hagfish?
-bottom dwelling (floor) scavengers
-skull is made of cartilage
-notochord is kept within the adult stage
-produce slime for speed (defense mechanism)
what are the key aspects of lampreys?
-most are parasitic
-skeleton is made of cartilage
-clamp their mouth onto live fish
what are jaws suspected to have evolved from?
-skeletal support rods of the pharyngeal slits
-the rods fuse together
-these modified rods are stronger + provide a larger opening
what is the importance of having a larger mouth opening?
-can catch larger prey
where did the evolution of jaws present itself?
-in the gnathostoma clade
-ex: sharks, ray finned fishes, lobe finned fishes, amphibians, reptiles, birds, and mammals
where did the evolution of lungs and bone begin?
-the osteichyan clade
how did ray-finned fishes develop? what are some examples?
-bony fins
-flexible rays modified for maneuvering + defense
-ex: trout, salmon, cod, and seahorses
what do lobe-finned fishes have? what are some examples?
-muscle on their fins
-ex: lungfishes and tetrapods
where did limbs likely develop from?
-tetrapod organisms in the gnathostoma clade
-amphibians
how did limbs likely develop? what are features of these organism?
-fins replaced with limbs
-head is separated with a neck
-pelvis bones are fused to the backbone
what are tetrapods?
-gnathostoma organisms with 4 limbs
do adult tetrapods have gills?
-NO
what are examples of amphibians that have limbs?
-salamanders
-frogs
what are key aspects of salamanders?
-either fully aquatic or can live on land
-external fertilization
-often retain juvenile characteristics as adults
what are key aspects of frogs?
-mostly on land (have an aquatic larval stage with gills)
-variety of adaptations (to avoid predation)
where did the amnion develop?
-the amniota clade
-ex: reptiles, birds, and some mammals
is the amnion (amniotic egg) a derived or ancestral character?
-derived character
what are the parts of the amniotic egg?
-4 extra embryonic membranes
-amnion
-chorion
-yolk sac
-allantois
what is the purpose of the amnion?
-shock absorber
what is the purpose of the chorion?
-gas exchange
what is the purpose of the yolk sac?
-provide nutrients
what is the purpose of the allantois?
-waste storage
what are the advantages of having the 4 extra embryonic membranes?
-eggs can be laid on land
-does not require water
where did the evolution of milk production and hair develop?
-mammalia
-3 clades within
what is the purpose of producing milk?
-used by mothers to nourish babies
what is the purpose of having hair?
-hair helps to retain heat
what are the 3 clades within the mammalia?
-monotremata
-marsupials
-eutherials
what is an example of an organism within the monotremata clade? what do they do?
-ex: platypus
-lay eggs
what is an example of an organism within the marsupial clade? what is a key feature of them?
-ex: kangaroo
-babies are underdeveloped
-short gestation (time in womb)
what is an example of an organism within the eutherials clade? what is a key feature of them?
-ex: elephants or humans
-better development
-longer gestation (time in womb)
