Animal Growth and Development

What is the Different between Growth and Development??

Animal Development Introduction to animal development Development requires both cell growth and cell differentiation (different cells express different genes) How are new organisms produced?

Fertilization In mammals, sperm travel from the vagina to the fallopian tube Fertilization takes place in the fallopian tube to form Zygote

Once fertilization ends… What’s next? 5

How many step happen in animal growth and development?

TWO PHASES Embryonic Phase Pasca Embryonic Phase

Egg and Zygote Polarity Most animals have eggs and zygote with polarity: Animal pole: low concentration of yolk. Vegetal pole: yolk concentrated here 8

Morulation Blastulation Gastrulation Differentiation/ Organogenesis EMBRYONIC PHASE After fertilization…there are 3 major steps of embryonic phase: Morulation Blastulation Gastrulation Differentiation/ Organogenesis

Animal Embryonic Development Stages of development 1. Early Cleavage (Morulation) Cleavage begins within an hour of fertilization; series of mitotic divisions Zygote divides into 2, 4, 8, … smaller and smaller blastomeres without increasing size of embryo Cleavage involves about 12 divisions resulting in solid ball of blastomeres How are new organisms produced?

In Amphibians Completed in 24 hrs. 1st and 2nd plane is meriodional; 3rd is equatorial 16-64 cell stage – morula 128 – 15,000 cell stage – blastula

2. Cleavage - blastulation rapid cell divisions little cell growth packaging of cytoplasmic heterogeneity final product is a hollow ball of cells = blastula cells = blastomeres hollow cavity = blastocoel 13

Cont… yolky eggs alter pattern of divisions animal hemisphere divides normally vegetal (yolky) hemisphere divides less often produces larger cells amount of yolk affects cleavage pattern

3. Gastrulation Gastrulation - sorts all the cells into distinct cell layers (ectoderm, endoderm, and mesoderm) Blastula (hollow ball of cells) transformed into the Gastrula (three layered stage)

Gastrulation 1. Gastrulation begins- Blastopore formed Blastopore - midway opening on one side of the blastula -Site of cell migration from the surface into the interior (Invagination) - Future site of anus

Gastrulation 2. Cell migrating to form layers Archenteron – primitive gut formed (endoderm) future mouth

Gastrulation 3.Gastrulation complete - Gastrula formed Endoderm and archenteron -replace the blastocoel Mesoderm - forms a layer between the ectoderm and endoderm Ectoderm- forms the outer layer. Yolk plug- (endoderm) marks the site of the blastopore and of the future anus

Gastrulation in a sea urchin embryo Digestive tube (endoderm) Key Future ectoderm Future mesoderm Future endoderm Blastocoel Mesenchyme cells Vegetal plate Animal pole Vegetal pole Filopodia pulling archenteron tip Archenteron Blastopore 50 µm Mouth Ectoderm Mesenchyme: (mesoderm forms future skeleton) Anus (from blastopore) The blastula consists of a single layer of ciliated cells surrounding the blastocoel. Gastrulation begins with the migration of mesenchyme cells from the vegetal pole into the blastocoel. The vegetal plate invaginates (buckles inward). Mesenchyme cells migrate throughout the blastocoel. Endoderm cells form the archenteron (future digestive tube). New mesenchyme cells at the tip of the tube begin to send out thin extensions (filopodia) toward the ectoderm cells of the blastocoel wall Contraction of these filopodia then drags the archenteron across the blastocoel. Fusion of the archenteron with the blastocoel wall completes formation of the digestive tube with a mouth and an anus. The gastrula has three germ layers and is covered with cilia, which function in swimming and feeding. 5 1 2 3 4 19

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Differentiation/Organogenesis Changing process of structure and function become specific tissue. Formation of organ systems from germ layers 21

Ectoderm Makes up the outer covering of the gastrula Becomes: Nervous system Epidermis

Mesoderm Becomes: Muscles Heart Kidney Dermis Circulatory, urinary, reproductive system

Endoderm Becomes: Digestive system Respiratory System Liver Pancreas

There are two divisions Pasca Embryonic Phase Maturity and Completing become more perfect organism. There are two divisions Regeneration Metamorphosis

1. Regeneration Repairing damage/lost organ. Eg. High Animal Asexual Reproduction. Eg. Planaria

2. METAMORPHOSIS 1. Insect a. Ametabole NO metamorphosis - No Larva Stage - Increasing body size. Eg. Book Lice

b. Hemimetabola Unperfect Metamorphosis. Stage: Egg  Larvae  semi-imago  imago/adult. Eg. Grasshopper Cockroach

c. Holometabola Perfect Metamorphose Stage: Egg  Larvae (Instar) Pupae  Imago/Adult. Eg. Butterfly

2. Amphibi Premetamoprhosis Fertelized egg  Kecebong Prometamorphosis Hind Limb appear and grow slowly. Climax Metamorposis Front Limb appear and tail be lost

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