Reading Assignment: POHS Chapter 40 - Animal Development - pp. 883- 902

Self Quiz: 1-10

Applying Concepts: optional

Reading Assignment: POHS Chapter 15 - Differential Gene Expression - pp. 330-350

Self Quiz: 1-10

Applying Concepts: optional

Overview

Development - development is the only mechanism by which changes in the genome 
(genotype) come to be expressed (phenotype) and thus subject to natural selection
	development not simply cascade of gene expression but cascade of interactions 
		between genome and environment
	epigenetics - branch of biology dealing with the interaction between genome and
		 environment during developing
	examples of epigenetic development
		dermatoglyphs
		teratogens
		temperature dependent sex determination

Problem in multicellular development is how to go from unicellular zygote to an 
	adult organism consisting of a multiple number of cells of differing types 
	arranged into functional tissues and organs; hence 3 major processes 
	1)	necessary to increase # of cells = cell growth
	2)	necessary to provide diversity of cells types = cell differentiation
	3)	necessary to arrange tissues into functional organs and organ 
			systems = morphogenesis (= organogenesis)

Major steps in animal development

1.	Development begins with the activation of an ovum by a sperm 
		(fertilization in sexual reproduction) or by other means 
		(parthenogenesis).
2.	The activated ovum divides repeatedly, and comparatively rapidly, about 
		8 to 12 times by mitosis.  The result is a ball of cells, the blastula, 		with a cavity, the blastocoel (blastulation) 
3.	There then ensues a rearrangement of cells; the rearrangement of cells 
		results in the formation of the embryonic layers:  an outer 
		ectoderm and an inner endoderm, these being separated. by a 
		middle mesoderm (gastrulation)
4.	As development continues there is an increase in cell number, the cells 
		become visibly differentiated, and there are structural 
		rearrangements of the cells leading to the formation of organs 
		and tissue layers (organogenesis)
5.	Throughout the metazoans there is considerable uniformity in the 
	structures developing from each embryonic layer.  Typically the skin, 
	nervous system, and some types of excretory organs (glands) are 
	derived from the ectoderm; the lining of the alimentary canal and the 
	associated organs are derived from endoderm; the circulatory system, 
	muscles, connective tissue, and some types of excretory organs are 
	derived from the mesoderm.

Lecture Outline - Animal Development (Ch. 40)

Fertilization - union of sperm and egg
	complex process
	sperm activation 
		external fertilization - associated with species isolating 
			mechanisms
		internal fertilization
	egg activation - mechanisms to avoid polyspermy (polyploidy)
	differential contributions of egg and sperm

Embryogeneis
	cytoplasmic rearrangement
	cleavage - pattern influenced by amount and distribution of yolk
		onset of cell fate (cell determination)
		mosaic vs. regulated development
	gastrulation - formation of primary embryonic ("germ") layers
		protostomes vs deuterostomes
		amphibians vs amniotes
	neuralation - an example of organogenesis

Extraembryonic membranes

Topics not covered in lecture for which you will be responsible:

	amniocentesis and chorionic villus sampling	p. 899

Lecture Outline - Differential Gene Expression (Ch. 15)

Important concepts and definitions
	development
	growth - cell division (hyperplasia) vs cell expansion (hypertrophy)
	differentiation vs determination
	totipotent vs pleuripotent

Differentiation 
	Briggs & King/Gurdon experiments > differentiation does not result from
		 loss of genetic material
	MyoD1 as an example of a developmental transcription factor

Factors involved in cell determination
	cytoplasmic segregation
		sea urchins
		C. elegans
	induction
		vertebrate lens
		neural tube

Pattern formation
	apoptosis (programmed cell death)
	morphogens

Segmentation - important innovation in development/evolution
	segmentation genes in Drosophila
	segment identification (homeotic) genes
	homeobox genes

Topics not covered in lecture for which you will be responsible:

	mammalian cloning (Dolly)	pp. 334-5
	imaginal discs in insects	pp. 335-6
	plant development		pp. 336, 342-343