This week in 206

I. Sea urchin fertilization thru gastrulation.

II. Chick gastrulation thru organogenesis.

III. Fungi fertilization and sporangium development.

Dr. Lloyd

DevelopmentSea urchinDeuterostomeIsolecithalHoloblastic cleavage

ChickDeuterostomeTelolecithalMeroblastic cleavage

Fertilization

cleavage

Blastulation & gastrulation

Organogenesis & pattern formation

Why do cells move in specific ways at specific times?How, why, and when do cells become specialized?

Sea urchin body plan

© 1997 Chris Patton, Stanford University

Fertilization

Sea urchin fertilization

acrosome

Cortical granules

Fertilization membrane

© 1997 Chris Patton, Stanford University

Fertilization

Holoblastic--cleaves completely through cell Isolecithal--evenly dispursed yolk.

Sea Urchin Cleavage and blastulation1st div. 3 div.

8 cell

blastula Hatchedblastula

Three types of morphogenetic movements duringgastrulation.

Gastrulation -2 types of morphogeneticmovements.1. Ingression of ~40 cells to formPrimary mesenchyme cells (PMC)Formation of mesoderm.

Gastrulation2. Invagination of cells at vegetal poleForms blastopore and archenteron-primitive gut

3 germ layersectoderm-skin and nervous system.mesoderm-bone, muscle, circ. system, internal organs.endoderm-stomach and guts.

archenteron

2nd ingression of cells to formSecondary mesenchyme

Primary mesenchyme

Together=mesoderm

archenteron

2nd invagination at animal poleto form mouth

Complete gastrula

EctoMesoEndo

Germ layers

Sea urchin larval development.

Sea urchin larva

NucleusCytoplasmYolk

Telolecithal-asymmetric

shellShell membrane

albumen

Meroblastic cleavage-part cleavage

1st div. 2nd 3rd

4th

Chick

~100,000 cells when egg laid.Epiblast - 3 germ layers

ectodermmesodermendoderm

Delamination

Ingression-mesoderm

Chick gastrulation.

Primitive streak-cells ingress-induced by hypoblast~blastopore

Notochord-induced by Hansen’s nodeSomites-muscle, bone

Embryo lifts off surface-3 layers-ectodermmesodermendoderm

Becomes brain

Sacs form around embryo

Fresh laid egg-blastodisc 13 hour egg

24 hour chick sections

33 hour chick sections

33 hour whole mount

48 hour 72 hour