pigment, sensory nerves, special sensory nerves, component of skeleton, jaw, middle ear, skull
(mesenchyme from neural ectoderm)
What enduces overlying ectoderm to form neural tubes (raised lateral edges> turn in toward one another)?
2. dorsal hollow nerve chord
3. notochord (important earlier in development to lay down spine/ frame)
failure of nerve tube closure
-b/c folic acid deficiency (b-vitamin)
5. tail bud
What is segmented, what is not segmented, and where is the head derived from?
Where is segmentation first evident in?
1. vertebra, ribs, trunk muscles, spinal nerves,
3. segmented anterior tip of our ancestor
4. development of somites
1. dermatome (outer)
2. sclaratome (inner)
3. myotome (core)
5. somatic hypomere
6. splanchnic hypomere
7. lateral plates
-what does this become
2. axial skeleton
3. skeletal muscles
4. What do mesomeres become?
5. what do somatic hypomeres become?
6. visceral musculature
What do splanchnic hypomeres become?
1. dorsal lip inducing mesoderm to differentiate into notochord
2. notochord inducing neurectoderm to become dorsal, hollow nerve chord
comparative development of limbs- _____ early
Why are embryonic vertebrates so similar?
1. embryos are protected in eggs or inside their mothers
2. early development is constrained +variation is likely to be deleterious
-there are other developmental features suggest evolution transitions
Why does development so often seem to trace evolution?
give an example
Evolution often involves recycling old parts for new functions
"nature is prodigal of diversity but stingy in innovation"-Von Baer
ie. gill arches + their derivatives
-neural crest visceral skeleton
respiration-jaw fish tetrapods
-jaws sound transmission
evolutionary transformation of vertebrae, limb
change in the rate of development of one part of the body relative to others
forelimb of oppossum=accelerated as an adaptation to mursupial reproduction
primitive state in the evolution of bone
endochondral bone>cartilage precursor replaced by bone
1. fertilized egg
4. gonad maturation
7. metamorphosis is deleted
1.ancestral species-> descendant species
adult is a mixture of embryonic +adult features of ancestor
2.retention of embryonic/juvenille characters into adulthood
3. acceleration of adult trait so that its expressed earilier
4. neotonic + retain larval train of a tunicate ancestor
5. _____=_____ or adults that are morphologically similar to larvae
4. larvae vertebrates
5. salamanders, neotony
similarity of human and chimps ____
-composed of _____
largely in ____ which are the product of relative rates of growth
evolution of adult body form is attained via __________
all the same parts
changes in development
Why do they have the form they do?
Their life style
1. fusiform body of fish/birds
2. unguligrade leg of horses/ artiodactyls/ litzpterna
How do they get the form that they do?
Evolution by natural selection
-modification of development
List the 4 arguments for evolution
1. paleontological record
-fossils sometimes revealed shared ancestry amoung living vertebrates