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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?