23 Oct. 2014 Embryology.ppt 1

ANIMAL EMBRYOLOGY

A brief essay on relationships of major animal groups.

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What IS an Animal?

• Petunia is a plant and• Wolf spider is an

animal.

• No trouble.

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What IS an Animal?

• Coral• sessile (“rooted”?)

• stem, branches,

• greenish.

• Resembles plant;but this IS an

animal! Why?

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What IS an Animal?

• Definition of "Animal"• Multicellular (so are plants, fungi)

• Eukaryotic (so are plants, fungi)

• Diploid (usually) (sporophytes are, too)

Meiosis produces gametes • Sperm, egg are the only haploid cells

Heterotrophic by ingestionCells lack cell walls.

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What IS an Animal?

• Basic structure (not definition) = Tube-in-tube Body wall = outer tube gut (GI tract) = inside tube

• mouth

• anus

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Embryological Development in Animals

• Every animal begins as ZYGOTE

• How do animals develop tube-in-tube body form?

• Important in understanding relationships, classification of Phyla.

Quiz question 49

• 49. Animals can be distinguished from members of other Kingdoms, because animalsa. have cell walls

b. have haploid gametes

c. are heterotrophic by ingestion

d. are prokaryotic

e. are eukaryotic

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Three fundamental processes:

1. Morphogenesis• (morph- = shape, + genesis = origin)

• Origin of shape, form

2. Differentiation• Process of cells becoming different, and

specializing for different functions

3. Growth• Increase in size, requires input of matter, food

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Sequence of Events:

1. Fertilization

2. Activation

3. Cleavage

4. Gastrulation

5. Mesoderm formation

6. Organogenesis

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Sequence of Events:(frog or sea urchin model)

1. Fertilization• Fusion of sperm nucleus with egg nucleusProduces zygote (diploid)

2. Activation• Increase in metabolism

• Egg metabolically inert, zygote active

• Movement of cytoplasm• Synthesis of materials needed for cleavage

Quiz question 50

• 50. One of the Fundamental Processes in embryonic development is a. gastrulation

b. cell division by mitosis

c. differentiation of cells

d. increase in size of cells

e. organogenesis

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Sequence of Events:

3. Cleavage• from Zygote• Division by mitosis

• 2 blastomeres 4 blastomeres 8 blastomeres 16 32 64 128 256 512

Blastula

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Sequence of Events:

4. Gastrulation = formation of a gut; • Major MORPHOGENIC event !!!

• Location of cells after GASTRULATION determines further development

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Sequence of Events:

• 4. Gastrulation• Invagination &

movement of cells to inside • yields 2 tissue layers

• Ectoderm

• Endoderm

• yields Archenteron• “ancient gut” = first

formation of "inside tube."

Quiz question 51

• 51. Cleavage results in a hollow sphere of 500—1000 cells called a(n) a. archenteron

b. blastula

c. clavicle

d. dendrite

e. gastrula

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Sequence of Events:

• 5. Mesoderm Formation• 3rd "germ layer"Ectoderm = “outside skin”Mesoderm = "middle skin"Endoderm = “inside skin”

Details of mesoderm formation vary among phyla !!

• to be studied with those phyla.

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Sequence of Events:

6. Organogenesis• Formation of organs from three germ layers

• Differentiation & continued Morphogenesis

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Organogenesis

• Ectoderm• Epidermis

• Lining of mouth & rectum

• Cornea of eye

• Lens of eye

• Nervous system

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Organogenesis

• Endoderm forms thin linings (mostly)• linings of gut & branches

• lining of excretory ducts, bladder

• " " lungs, trachea

• " " reproductive ducts, • uterus, vas deferens

• liver

• pancreas

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Organogenesis

• Mesoderm• Skeleton,

• Muscles (skeletal, smooth, cardiac)

• Dermis of skin

• Heart, blood, blood vessels

• Kidneys,

• Ovaries/testes, etc.

Quiz question 52

• 52. Which of the following is the earliest in the sequence of events in embryonic development of animals? a. cleavage

b. organogenesis

c. meiosis

d. gastrulation

e. heterotrophy

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Organogenesis

• Ectoderm How Nervous system gets

inside• Dorsal surface of embryo

forms Neural plate

• Plate sinks inward forming Neural groove

• Edges of groove fuse to separate Neural tube from epidermis