Vertebrate Evolution & Diversity. Trends in Animal Evolution. Is there evidence that any of these trends have reversed over time?. Symmetry none radial bilateral Pattern of gastrulation no blastopore protostome deuterostome Digestive system
Is there evidence that any of these trends have reversed over time?
none radial bilateral
no blastopore protostome deuterostome
None gastrovascular cavity complete digestive system
acoelomate pseudocoelomate eucoelomate
none segmented fused segments
none hydrostatic exoskeleton endoskeleton
What are exoskeletons made of? …endoskeletons?
Consider animals with endoskeletons…Do they demonstrate evidence of segmentation? Describe the relationship.
What is this vascular system used for?
What features of embryonic development are shared by members of these two groups?
Do all chordates have a vertebral column?
Segmentation: muscles arranged in segmented blocks
Most with an internal and jointed skeleton, differing from that of echinoderms
Sessile marine animals, some are colonial
Filter-feed, using pharyngeal slits
Animal encased in a tunic of cellulose-like CHO
Larvae (c) presents all four chordate characteristics (“tail chordates”)
How have the slits been adapted for filter feeding?
Do you find evidence of segmentation in the larval form?
What is the term used to describe the change in body form here?
Small, burrowing animals, marine
Adults possess all four chordate traits (“head chordates”)
Muscles arranged in “chevron” (<<<<<) around notochord
Sensory tentacles around mouth
How is the mouth modified to support this method of feeding?
Cephalochordates are the closest living relatives of modern vertebrates.
Larval urochordate exhibiting paedogenesis*cephalochordate
* Early sexual maturity. Recall that genes that control development have played a major role in evolution (pg. 478)
Some fossils from the same period exhibit all of the vertebrate characteristics.
? ancestral vertebrates, @ 530 mya
Neural crest: Unique group of embryonic cells that develop into various structures, including skeletal elements like the skull.
Note that not all craniates have a vertebral column.
The endoskeletons of craniates are made of cartilage or a combination of cartilage and bone (mineralized tissue). How are these tissues related in embryonic development?
yellow = fibrous c.t.
blue = bone
green = notochord
Adapted from Tree of Life web site, available at http://tolweb.org/tree?group=Craniata
All marine. Mostly bottom-dwelling scavengers
Slime glands along the sides for defense
Cartilaginous skeleton; no jaws, no teeth, no appendages, no spine
Mostly blind, well-developed sense of smell
Why are hagfishes considered the most primitive of the craniates?
Rigid spine of cartilage or bone gives support and anchors muscles better than the notochord.
Marine and freshwater environments
Clamp round mouth onto flank of live fish, use rasping tongue to penetrate skin and ingest blood
Cartilaginous skeleton, including spine
No paired appendages, no jaws
Jaws and mineralized teeth: firmly grip and slice food items, eat prey that had been inaccessible
Paired appendages (fins): accurate maneuvering in aquatic environments
What are the respiratory organs in fish?
These diverse fish have a swim bladder; it permits neutral buoyancy
better locomotion in terrestrial and shallow water environments
What does “tetrapod” mean?
Does this adaptation mean a completely terrestrial lifestyle?
Do these animals demonstrate other adaptations to life on land?
an adaptation for thermal insulation and flight
Light and hollow skeleton; - other flight adaptations
Legs and wings, most species move by flying
Amniote egg with a shell
Mouth developed into a beak
A variety of feeding mechanisms
provides the ability to adequately nourish offspring
Mammary glands in the females to provide milk to young
Legs lost in some (marine mammals)
Amniote embryo, but does not develop a shell
Variety of feeding mechanisms
Which vertebrate characteristic is most responsible for their success in relatively dry environments?
Lungs and feathers were most important. That makes me best at taking advantage of the “dry” environment!
The amniote egg was the most important adaptation to life on land.
Nobody would have gotten anywhere without my cranium!
Wait a minute! I can fly…I think it’s the ability to provide milk to offspring.
General traits of reviewed phyla, subphyla and classes
Important evolutionary trends in body plan:
Notochord, nerve cord, tail, pharyngeal slits: Chordates
Cranium, brain development, neural crest cells: Craniates
Vertebral column: Vertebrates
Jaws, 2 sets of paired appendages, mineralized skeleton and teeth: Chondrichthyes (sharks and rays)
Lungs or lung-derivatives: Osteichthyes (bony fishes)
Amniote egg: Mammals, turtles, snakes and lizards, birds
These trends helped animals adapt to different environments or exploit the same environment in a different manner