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Topic 4: Comparative Development
� What is development?
� What are the major stages of development?
� Gametogenesis to Cleavage
� Gastrulation & Neurulation
� Human development and extra-embryonic structures
� Organogenesis
� Growth & Maturation
� What are some examples of organogenesis?
� Eye Development
� Pharyngeal development
What is development?
� Transformations that an organism undergoes from
single cell to death (also ontogeny)
� Free living and embryonic parts of life cycle
� How we get from one cell to a complex organism
� Indirect versus direct development
Free Living Ontogeny
gametogenesis
What are the stages of development?
� ______________
� Oogenesis
� Spermatogenesis
� 2 parts
� Meiosis �
� Cellular
specialization
� Diploid to haploid
2N
4N
2N
1N
Pre-meiotic
duplication
Meiosis I
recombination
Meiosis II sister
chromatids
separate
Spermatogonium Oogonium
1o spermatocyte
Liem et al. 2001, Fig 4-6
1o oocyte
2o spermatocytes
2o oocyte
1st polar
body
4 spermatids
1 ovum + 3 polar bodies
4 spermatozoa
Spermiogenesis
Stages of Development –
Gametogenesis: Cellular Specialization
� ____________________
� Produces spermatozoa
� Acrosome with species
recognition molecules
� Nucleus
� Neck with mitochondria
� Tail for locomotion
� _______________
� Rather unspecialized
� Cortical cytoplasm
involved in fertilization
� Two genomes (nuclear &
mitochondrial)
Liem et al. 2001, Fig 4-7
Stages of Development - Fertilization
Newly Ovulated Ovum
Fertilized Ovum = Zygote
� Outer jelly coat swells in
amphibians
� Zygote formed
Liem et al. 2001, Fig 4-8
� _____________________
� Acrosome + Cortical Granules
� Sperm nucleus drawn in
� Primary egg cell membrane � fertilization
membrane
� Perivitelline space created
Stages of Development - _______
� Cell division to form a
blastula
� 1 cell to ball of cellsC
� Cto hollow ball of cells
� Cells are blastomeres
� Space inside is blastocoel
� __________ becomes an
__________
Liem et al. 2001, Fig 4-10A
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Stages of Development - Cleavage� Cleavage depends on
the amount of yolk in
the egg
� Little Yolk
� Cleavage equal &
holoblastic
� More Yolk
� Cleavege unequal &
holoblastic
� Lots of Yolk
� Cleavage meroblastic
Liem et al. 2001, Fig 4-10
Amphioxus Frog Chicken
Stages of Development - ____________
� Cells move to form
________________
� Ectoderm
� Epidermal
� Neural
� Mesoderm
� Chondramesoderm
� Endoderm
Liem et al. 2001, Fig 4-11A
This is a “fate map” of a blastula
Stages of Development - Gastrulation
� _____________
shrinks
� _____________
is formed
� Archenteron will
become gut
� Opening to
archenteron is
blastopore
� Blastopore will
become anus
Liem et al. 2001, Fig 4-12
Stages of Development - Gastrulation
� Gastrulation occurs by
different mechanisms
in different species
� _________________
(Cephalochordates)
� _________________
(Amphibians)
� _________________
(Birds)
� Related partly to
amount of yolk
Vertebrate Life Fig 3-1
Amphioxus Frog Chicken
Stages of Development - ___________
� Gastrula � neurula
� Neural plate forms
� Invagination to give
neural folds
� Fusion into neural
tube
� _________________
� Some nerves
� Pigment cells
� Some cranial bones
� Some endocrine
cells
Liem et al. 2001, Fig 4-15
Stages of Development
Zygote
Blastula
Gastrula
Neurula
Liem et al. 2001; Vertebrate Life Fig 3-1
Cleavage
Gastrulation
Neurulation
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Extraembryonic Membranes
� Extraembryonic
� Ectoderm
� ____________ mesoderm
� ____________ mesoderm
� Endoderm
� Produce extraembryonic structures
� Ectoderm + Somatic Mesoderm
� _______
� _______
� Endoderm + Splanchnic Mesoderm
� _____________ – Contains yolk
� _____________ – Receives waste
Protect embryo}
Liem et al. 2001, Fig 4-17
Early Stages of Human Development
� Why might mammals be different
from a chicken or frog?
� Cleavage produces a _________
� Outer __________________
� Homologous to extraembryonic
ectoderm
� Inner __________________
� Gives rise to the embryo, termed
the fetus
� ____________________
� Contains allantois & yolk sac
� Connects embryo to trophoblast
� Becomes umbilical cord
Liem et al. 2001, Fig 4-18A,B
Early Stages of Human Development
� _________________
� Close contact between
embryo and uterus
� Formation of a _________
� Made of both embryonic
and maternal tissue
� Very little yolk
� Gas Exchange, nutrient
delivery & waste removal
Photo © MA Hill
Stages of Development - _____________
� The formation of organs
and organ systems
� Much of development
� Very complicated
� A separate course!
� Germ layers subdivide and
give rise to other
structures
� Use a flow chart to learn
development
Liem et al. 2001, Fig 4-16B
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Vertebrate Life, fig 3-2See Liem et al. 2001, Table 4-1 for a similar table
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Stage of Development –
Growth & Maturation
� Postnatal stages of
development
� Scaling
� Increases in size
� Changes in proportions
� Next Lecture
� Sexual maturation
� Completion of gonadal
development
� Secondary sexual
characteristics
© Krempel; www.advancedaquarist.com
A Closer Look at Organogensis:
Eye Development and Induction
See Liem et al. Fig 4-20
1.Evagination of optic vesicle
2.Induction of lens placode by
optic vesicle
3.Invagination to optic cup
4.Invagination to lens cup
5.Pinching off of lens vesicle
6.Lens vesicle induces
cornea
7.Formation of pigmented
and neural retinas
8.Neural retina induces lens
1 2
3 4 5 6
7
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A Closer Look at Organogenesis:
Development of the Pharynx
A complex structure arising from all germ layers
Liem et al. 2001, Fig 4-36
Development of the Pharynx
� Epidermal ectoderm
� _____________
� Neural ectoderm
� ______________
� ______________
� Neural crest cells
� ______________ & ganglia
� Some bones
� Mesoderm
� Branchiomeric muscles
� ____________
� Skeletal parts of gill arches
� Endoderm
� Pharyngeal pouches
� ____________ gland
Liem et al. 2001, Fig 4-39
Development of the Pharynx
1. Invagination of epidermal ectoderm & pharyngeal endoderm forms 6
pharyngeal plates, clefts & pouches and 7 pharyngeal arches
2. Anterior 4 pharyngeal plates disappear to give pharyngeal/gill slits
3. Each pharyngeal arch has:
Liem et al. 2001, Fig 4-38B
Archenteron
- Ectroderm laterally
- Endoderm medially
- Internal aortic arch,
cranial nerve, skeletal
rod, and
branchiomeric muscle
Development of the Pharynx
Liem et al. 2001, Fig 4-37
� How many gill
slits does the
lamprey have?
� The shark?
� A bony fish?
� A human
embryo?
� A human adult?