Transcript Figure 32.12 Comparing the molecular based and grade

Vertebrate Evolution &
Diversity
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Trends in Animal Evolution
Symmetry
none  radial  bilateral Is there evidence that any of these
trends have reversed over time?
Pattern of gastrulation
no blastopore  protostome  deuterostome
Digestive system
None  gastrovascular cavity  complete digestive system
Body cavities
acoelomate  pseudocoelomate  eucoelomate
Segmentation
none  segmented  fused segments
Skeletons
none  hydrostatic  exoskeleton  endoskeleton
What are exoskeletons made of? …endoskeletons?
Consider animals with endoskeletons…Do they demonstrate
evidence of segmentation? Describe the relationship.
Deuterostomia
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Phylum Echinodermata
• “spiny skinned”
• water vascular system
What is this vascular system
used for?
Phylum Chordata
• named for the notochord
What features of embryonic
development are shared by
members of these two
groups?
Do all chordates have a
vertebral column?
Phylum Chordata (chordates)
-evidence from anatomical comparisons
2.
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4.
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Segmentation:
muscles
arranged in
segmented
blocks
Most with an
internal and
jointed
skeleton,
differing from
that of
echinoderms
1. Where is the notochord located, relative to the digestive tube and
nerve cord? What is its function?
2. Where is the nerve cord located in most non-chordate animals?
3. What is the pharynx? How are these slits specialized in aquatic
organisms?
4. Describe the advantage of a muscular, post-anal tail.
Subphylum Urochordata – tunicates
 Sessile marine animals, some are colonialHow have the slits been
 Filter-feed, using pharyngeal slits
adapted for filter feeding?
 Animal encased in a tunic of cellulose-like CHO
 Larvae (c) presents all four chordate characteristics (“tail
chordates”)
Do you find evidence of segmentation in the larval form?
Fig 34.3
What is the term used to describe the change in body form here?
Subphylum Cephalochordata – “lancelets”
 Small, burrowing animals, marine
 Adults possess all four chordate traits (“head chordates”)
is the mouth modified to support this
 Suspension feeders How
method of feeding?
 Muscles arranged in “chevron” (<<<<<) around notochord
 Sensory tentacles around mouth
2 cm
Fig 34.4
The Origin of Vertebrates
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)
The fossil record suggests an
intermediate stage between
cephalochordates and
vertebrates, that lacks a
cranium, but has eyes.
Some fossils from the same
period exhibit all of the
vertebrate characteristics.
Haikouella
Myllokunmingia
? ancestral vertebrates, @ 530 mya
Fig 34.1
Fig 34.6
“Craniates”
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.
Fig 34.7
Phylogeny of
Craniates
Which adaptations enabled:
• better maneuvering in
the environment?
• more active lifestyle?
• larger size?
• terrestrial lifestyle?
• reproduction
independent of water?
Describe the blood
circulatory adaptations
that also support a more
vigorous lifestyle.
Craniates
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?
Hagfish
Jawless fishes
Lamprey
Gnathostome
“jaw”
KEY:
yellow = fibrous c.t.
blue = bone
green = notochord
Adapted from Tree of Life web site, available at http://tolweb.org/tree?group=Craniata
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Class Myxini – hagfish
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?
Fig 34.8
Fig 34.1
Vertebrates
Rigid spine of cartilage
or bone gives support and
anchors muscles better
than the notochord.
C. Cephalaspidomorphi – lampreys
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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
Fig 34.9
Jaws &
Appendicular
skeleton
Jaws and
mineralized teeth:
firmly grip and slice
food items, eat prey
that had been
inaccessible
Paired appendages
(fins): accurate
maneuvering in
aquatic
environments
Fig 34.10
Evolution of
vertebrate
jaws
Class Chondrichthyes: sharks and rays
Lungs
Lungs or lung
derivatives:
•in most fishes
developed into
swim bladder
(buoyancy)
What are the
respiratory organs
in fish?
•in other
organisms, lungs
function in
gas exchange
C. Actinopterygii - ray-finned fishes
These diverse fish have a
swim bladder; it permits
neutral buoyancy
Fig 34.12a
Legs
better locomotion
in terrestrial and
shallow water
environments
What does
“tetrapod” mean?
Does this adaptation
mean a completely
terrestrial lifestyle?
Amphibians – frogs, etc.
Fig 34.17
Amniotes
•extraembryonic
membranes (including
the amnion) bring the
aquatic environment
onto land!
•enables completion of
their life cycle on land
•first appeared in
mammal-like reptile
Do these animals
demonstrate other
adaptations to life
on land?
Amniotic egg
Fig 34.19
“Reptiles”
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Keratinized skin; lungs; internal fertilization
Fig 34.24
Feathers
an adaptation for
thermal insulation
and flight
Class Aves – birds
 Feathers
 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
Bird flight
Fig 34.26
Milk
provides the
ability to
adequately
nourish offspring
Mammalia – mammals
 Hair
 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!
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.
The amniote egg
was the most
important
adaptation to life
on land.
Summary
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General traits of reviewed phyla, subphyla and classes
Important evolutionary trends in body plan:
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Endoskeleton: Echinoderms
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)
Legs: Amphibians
Amniote egg: Mammals, turtles, snakes and lizards, birds
Feathers: Birds
Milk: Mammals
These trends helped animals adapt to different
environments or exploit the same environment in a
different manner