9. Animal DevelopmentAnimal Development
How do each of these contribute to the studyHow do each of these contribute to the study
of development?of development?
comparative embryologycomparative embryology
evolutionary embryologyevolutionary embryology
teratologyteratology
mathematical modelingmathematical modeling
11. Comparative EmbryologyComparative Embryology
How does the concept of germ layers support epigenesis?How does the concept of germ layers support epigenesis?
How does the concept of induction fit in here?How does the concept of induction fit in here?
12. Comparative EmbryologyComparative Embryology
What principles didWhat principles did
von Baer articulatevon Baer articulate
with respect to vertebratewith respect to vertebrate
development?development?
13. Comparative EmbryologyComparative Embryology
General features of large group of animalsGeneral features of large group of animals
appear earlier than specialized features ofappear earlier than specialized features of
smaller groupsmaller group
Less general characteristics develop from moreLess general characteristics develop from more
generalgeneral
14. Comparative EmbryologyComparative Embryology
A particular type of embryo, instead of passingA particular type of embryo, instead of passing
through adult stages of a lower form, departsthrough adult stages of a lower form, departs
more and more from it.more and more from it.
Embryo of higher animal is only like earlyEmbryo of higher animal is only like early
embryo of lower animal.embryo of lower animal.
16. Evolutionary EmbryologyEvolutionary Embryology
How have observations of embryos contributed to ourHow have observations of embryos contributed to our
understanding of evolutionary relationships?understanding of evolutionary relationships?
17. Evolutionary EmbryologyEvolutionary Embryology
Why is the distinction between analogous andWhy is the distinction between analogous and
homologous structures important?homologous structures important?
20. Figure 1.20(1)Figure 1.20(1) Reaction-diffusionReaction-diffusion
System of Pattern GenerationSystem of Pattern Generation
21. Figure 1.22Figure 1.22 Pigment patterns of zebrafishPigment patterns of zebrafish
homozygous for the wild-type allele (A) and for threehomozygous for the wild-type allele (A) and for three
different mutant alleles (B–D) of the leopard genedifferent mutant alleles (B–D) of the leopard gene
Editor's Notes
purely descriptive focus only on embryo to experimental to integrative with respect to genetics, biochemistry, and at different levels of biology.
considers more than just embryo, entire life cycle
How does one cell generate many different cell types?
How do cells form ordered structures – morphogenesis?
How is cell division tightly regulated?
How are sperm and egg set apart to form next generation?
How do changes in development create new body forms and which heritable changes are possible?
How is development of organism integrated into context of its habitat and how do chemicals alter development?
epigenesis – Aristotle & Harvey
organs are formed from scratch
in embryonic chick parts develop from tissues that have counterpart in adult
weakness – hard to explain how this happens
preformation – Malpighi
growth of preformed structures going back to sperm or egg; is there a lower limit to size?
germ layers show progression of development
shows how each layer gives rise to different types of cells
tissue formation requires cooperation among different types of cells
All vertebrate embryos have similar structures: gill arches, notocords, spinal cords which develop early
Feathers and scales both develop from skin
in fish visceral clefts develop into gills, in mammals they develop into eustacian tubes
Can trace the movement and positioning of cells
dyes, fluorescent tags, radioactive labels used
formation of chimeric embryos
picture is zebrafish embryo with fluorescent label showing formation of neural tube, especial forebrain and midbrain
See similarities in larval stages that don’t exist later on
analogous – have similar function and therefore similar structure but not necessarily related
homologous – have similar structure because of common ancestry
malformations – genetic anomalies seen on left
disruptions – come from environmental influences like use of thalidomide
isometric – proportional growth – follows a predictable formula as in equiangular spiral growth
allometric – different rates of growth of different parts at different stages
Turing Model – two different solutions interact to produce stable patterns during morphogenesis
alternating areas of high and low concentrations of solutions
evidence to support model comes from mutations in leopard gene in zebrafish
can generate models via computer to predict patterns
Figures\Chapter01\DevBio7e01201.jpg
Leopard gene codes for an enzyme catalyzing one of the reactions of reaction-diffusion system.
Mutations change kinetics of synthesis or degradation leading to change in patterns.
Figures\Chapter01\DevBio7e01220.jpg
