\di-ve-ləp-\di-ve-ləp-mənt\mənt\

By By James KwanJames Kwan, , Kai Kai OransOrans, ,

and and Amy WAAHNAmy WAAHN

Different Forms of DevelopmentDifferent Forms of Development

Tadpoles and caterpillars are larval forms Tadpoles and caterpillars are larval forms of adult formsof adult forms

Larval form of sea urchin drifts in ocean Larval form of sea urchin drifts in ocean surface waters until it develops into an surface waters until it develops into an adultadult

The zygotes of some animals (humans) The zygotes of some animals (humans) develop into an infant that is much like the develop into an infant that is much like the adult form.adult form.

Stages of DevelopmentStages of Development

FertilizationFertilizationCleavageCleavageGastrulationGastrulationOrganogenesisOrganogenesis

FertilizationFertilization

Internal and external fertilizationInternal and external fertilizationGonads of the parents produces sperm Gonads of the parents produces sperm

and eggsand eggsContact of sperm with egg surface initiates Contact of sperm with egg surface initiates

metabolic reactions, activating eggmetabolic reactions, activating eggMain function: combining haploid sets of Main function: combining haploid sets of

chromosomes into a single diploid zygotechromosomes into a single diploid zygote

The Acrosomal ReactionThe Acrosomal Reaction

Acrosomal reaction: specialized vesicle at Acrosomal reaction: specialized vesicle at tip of sperm (acrosome) discharges tip of sperm (acrosome) discharges enzymes that digest the jelly coat enzymes that digest the jelly coat surrounding the eggsurrounding the egg

Contact of the tip of acrosomal process Contact of the tip of acrosomal process (sperm structure) with egg membrane (sperm structure) with egg membrane leads to fusion of plasma membranesleads to fusion of plasma membranes

Fast block to polyspermyFast block to polyspermy

The Corsical Reaction and The Corsical Reaction and Activation of EggActivation of Egg

Vesicules fuse with egg plasma Vesicules fuse with egg plasma membranemembrane

Formation of fertilization envelope, Formation of fertilization envelope, resisting entry of additional spermresisting entry of additional sperm

Slow block to polyspermySlow block to polyspermyActivation of egg: substantial increase in Activation of egg: substantial increase in

the rates of cell respiration and protein the rates of cell respiration and protein synthesis synthesis

Acrosomal and Cortical ReactionsAcrosomal and Cortical Reactions

Fertilization shares many features in Fertilization shares many features in common with that of sea urchins.common with that of sea urchins.

Differences in timing among speciesDifferences in timing among speciesExample: in sea urchins, eggs have Example: in sea urchins, eggs have

completed meiosis when released from completed meiosis when released from femalefemaleHuman eggs are arrested at metaphase of Human eggs are arrested at metaphase of

meiosis IImeiosis II

Mammalian FertilizationMammalian Fertilization

Zona pellucida: extracellular matrix of the Zona pellucida: extracellular matrix of the eggegg

Ensures moist environment for spermEnsures moist environment for spermNo fast block to polyspermyNo fast block to polyspermyFunctions as sperm receptor: binding Functions as sperm receptor: binding

initiates acrosomal reaction and cortical initiates acrosomal reaction and cortical reactionreaction

Example: increase in sperm motilityExample: increase in sperm motility

Fertilization in MammalsFertilization in Mammals

CleavageCleavage Succession of rapid cell Succession of rapid cell

divisiondivision Cells carry out S and M Cells carry out S and M

phasesphases Blastomeres: smaller cells that Blastomeres: smaller cells that

result from the partition of the result from the partition of the zygotezygote

Zygotes of sea urchins and Zygotes of sea urchins and other animals have definite other animals have definite polaritypolarity Planes of division follow a Planes of division follow a

pattern relative to poles of pattern relative to poles of zygotezygote

Establishment of three body Establishment of three body axesaxes

Cleavage cont’dCleavage cont’d

Polarity defined by uneven distribution of Polarity defined by uneven distribution of substances in cytoplasmsubstances in cytoplasm

Yolk: stored nutrientsYolk: stored nutrients Vegetal pole (pole of egg where yolk is Vegetal pole (pole of egg where yolk is

concentrated) and animal pole (pole where yolk concentrated) and animal pole (pole where yolk concentration decreases)concentration decreases)

Animal-vegetal axis of egg determines head-tail Animal-vegetal axis of egg determines head-tail axis of embryo (ex: sea urchin eggs have a-v axis of embryo (ex: sea urchin eggs have a-v axis due to uneven distribution of substancesaxis due to uneven distribution of substances

Cleavage cont’dCleavage cont’d Holoblastic cleavage: Holoblastic cleavage:

blastocoel (fluid-filled cavity) blastocoel (fluid-filled cavity) centrally located, cleavage centrally located, cleavage furrow passes all the way furrow passes all the way through the cellsthrough the cells

Examples: animals whose Examples: animals whose eggs contain relatively little eggs contain relatively little yolk, such as frogs, sea yolk, such as frogs, sea urchins, echinoderms, most urchins, echinoderms, most chordates and deuterostomeschordates and deuterostomes

Meroblastic cleavage: Meroblastic cleavage: incomplete division of eggincomplete division of egg

Example: bird eggsExample: bird eggs

GastrulationGastrulation Morphogenetic process: Morphogenetic process:

groups of cells take up groups of cells take up new locations that allow new locations that allow the formation of tissues the formation of tissues and organsand organs

For most animals, it is a For most animals, it is a rearrangement of blastula rearrangement of blastula cells, producing 3-layered cells, producing 3-layered embryo with primitive embryo with primitive digestive tubedigestive tube

Positioning allows cells to Positioning allows cells to interact with each other, interact with each other, generating organsgenerating organs

Gastrulation cont’dGastrulation cont’d

Three layers produced collectively called Three layers produced collectively called embryonic germ layers:embryonic germ layers:

Ectoderm: outer layerEctoderm: outer layerEndoderm: lines embryonic digestive tractEndoderm: lines embryonic digestive tractMesoderm: fills space between ectoderm Mesoderm: fills space between ectoderm

and endodermand endoderm

Gastrulation cont’dGastrulation cont’d Shallow invagination Shallow invagination

(cells buckle inward) (cells buckle inward) transforms into transforms into archenteronarchenteron

Blastopore: open end of Blastopore: open end of archenteronarchenteron

Gastrulation in sea Gastrulation in sea urchins and frogs urchins and frogs produces three-layered produces three-layered embryo (characteristic of embryo (characteristic of most animal phyla, most animal phyla, established early in established early in development)development)

Gastrulation (chicken)Gastrulation (chicken)

OrganogenesisOrganogenesis Regions of the three embryonic Regions of the three embryonic

germ layers develop into germ layers develop into rudimentary organs during rudimentary organs during organogenesisorganogenesis

Cell migration, cell condensations, Cell migration, cell condensations, cell signaling, cell shape changes cell signaling, cell shape changes (similar mechanisms for vertebrates (similar mechanisms for vertebrates and invertebrates, but still and invertebrates, but still differences because of different differences because of different body plans)body plans)

Condensation of dorsal mesoderm Condensation of dorsal mesoderm forms notochordforms notochord

Infolding of ectodermal neural plate Infolding of ectodermal neural plate forms neural tube, becomes central forms neural tube, becomes central nervous systemnervous system

Neural Crest formed, a collection of Neural Crest formed, a collection of cells that disperse throughout the cells that disperse throughout the body giving rise to teeth, bones, body giving rise to teeth, bones, cartilage cartilage

Cell Differentiation Cell Differentiation

Cells become specialized in structure and functionCells become specialized in structure and functionOrganized into tissues and organs in a 3-D arrangementOrganized into tissues and organs in a 3-D arrangementCytoplasm contains both RNA and proteins encoded by Cytoplasm contains both RNA and proteins encoded by mother’s DNAmother’s DNAMaternal substances in the egg that influence the courses of Maternal substances in the egg that influence the courses of development are called cytoplasmic determinantsdevelopment are called cytoplasmic determinantsCombination of these helps determine developmental fate by Combination of these helps determine developmental fate by regulating expression of cell’s genesregulating expression of cell’s genesAnother source of developmental info is the environment around Another source of developmental info is the environment around a cell (induction)-signaling pathwaysa cell (induction)-signaling pathwaysTranscription regulates gene expressionTranscription regulates gene expression

MorphogenesisMorphogenesis Major aspect of development, Major aspect of development,

involve movement of cellsinvolve movement of cells Changes in cell shape involve Changes in cell shape involve

reorganization of the cytoskeleton reorganization of the cytoskeleton (ex. cells of neural plate into (ex. cells of neural plate into neural tube)neural tube)

Also drives cell migrationAlso drives cell migration Convergent extension, cells of a Convergent extension, cells of a

tissue become narrower while tissue become narrower while becoming longer, changes becoming longer, changes spherical shape of gastrula to spherical shape of gastrula to rectangular shape of embryorectangular shape of embryo

Extracellular Matrix (ECM)Extracellular Matrix (ECM)

ECM= glycoproteins and macromolecules ECM= glycoproteins and macromolecules outside cell plasma membraneoutside cell plasma membrane

Cell membrane receptors bind to ECMCell membrane receptors bind to ECMSubstances to inhibit migrationSubstances to inhibit migrationDialogue between cells as move on ECMDialogue between cells as move on ECM

Fate MappingFate Mapping Territorial diagrams of Territorial diagrams of

embryonic developmentembryonic development Combined with Combined with

manipulation of test subject manipulation of test subject developmentdevelopment

Discoveries:Discoveries: 1) specific tissue of older 1) specific tissue of older

embryo are of founder cells embryo are of founder cells with unique factors b/c of with unique factors b/c of asymmetrical divisionasymmetrical division

2) older cells have less 2) older cells have less development potentialdevelopment potential

Pattern FormationPattern Formation

Cells influence fates through induction, Cells influence fates through induction, switch on special genes to differentiate cell switch on special genes to differentiate cell tissuetissue

Dorsal lip of blastopore = “organizer”Dorsal lip of blastopore = “organizer” Pattern formationPattern formation Positional information (molecular cues)Positional information (molecular cues) Apical ectodermal ridge (AER) – promote Apical ectodermal ridge (AER) – promote

limb-bud outgrowthlimb-bud outgrowth Zone of polarizing activity (ZPR) – limb bud Zone of polarizing activity (ZPR) – limb bud

organizerorganizer

Axes of the Body PlanAxes of the Body PlanNonamniote vertebrates instructions for forming Nonamniote vertebrates instructions for forming

the body axes are established early (oogenesis the body axes are established early (oogenesis or fertilization)or fertilization)

Amniote body axes aren’t established until laterAmniote body axes aren’t established until laterPositional information is provided by Positional information is provided by

cytoplasmic determinants and inductive signalscytoplasmic determinants and inductive signalsAxes genes are encoded by genes from the Axes genes are encoded by genes from the

mother, fittingly called maternal effect genesmother, fittingly called maternal effect genes

Cell MovementCell Movement

Cell adhesion molecules (CAMs) –proteins Cell adhesion molecules (CAMs) –proteins that guide cell migration and stabilize that guide cell migration and stabilize tissue by binding to CAMs of other cellstissue by binding to CAMs of other cells

Cadherins (important group of CAMs) Cadherins (important group of CAMs)

Body Plan OverviewBody Plan Overview Body plan is a set of morphological and developmental traits Body plan is a set of morphological and developmental traits

integrated into a wholeintegrated into a whole Animals can be classified based on symmetry (radial, top and Animals can be classified based on symmetry (radial, top and

bottom, or bilateral)bottom, or bilateral) Bilateral animals have four sides and a central nervous system Bilateral animals have four sides and a central nervous system

(brain) in the anterior end(brain) in the anterior end Symmetry fits lifestyleSymmetry fits lifestyle Number of germ layers can differentiate as wellNumber of germ layers can differentiate as well Cnidarians and comb jellies have only two: ectoderm and Cnidarians and comb jellies have only two: ectoderm and

endoderm (diploblastic) while bilaterally symmetrical animals endoderm (diploblastic) while bilaterally symmetrical animals have three (triploblastic)have three (triploblastic)

Most triploblastic animals possess a body cavity, called coelom, Most triploblastic animals possess a body cavity, called coelom, which forms from tissue derived from mesoderm which forms from tissue derived from mesoderm

Coelom contains fluid that cushions suspended organs and Coelom contains fluid that cushions suspended organs and enables organs to grow independently of outer body wallenables organs to grow independently of outer body wall

Body Plan IllustratedBody Plan Illustrated

Hox GenesHox Genes Specify anterior-posterior segment Specify anterior-posterior segment

identity during embryonic identity during embryonic developmentdevelopment

Play a role in limb pattern formationPlay a role in limb pattern formation Mutations in regulatory sequences Mutations in regulatory sequences

cause major changes in body form cause major changes in body form (Drosiphila growing legs in place of (Drosiphila growing legs in place of antennae) antennae)

Differing patterns in insects and Differing patterns in insects and crustaceans can explain variation in crustaceans can explain variation in number of leg bearing segmentsnumber of leg bearing segments

In arthropods changes in the In arthropods changes in the sequence of existing Hox genes sequence of existing Hox genes influenced increased body segment influenced increased body segment diversity, a hard exoskeleton, and diversity, a hard exoskeleton, and jointed appendagesjointed appendages

Control development of the major Control development of the major regions of the vertebrate brain regions of the vertebrate brain (similarities between anterior-posterior (similarities between anterior-posterior order in lancelets and vertebrates)order in lancelets and vertebrates)

Protostome vs. DeuterostomeProtostome vs. Deuterostome

Three differences: cleavage, Three differences: cleavage, coelom formation, fate of coelom formation, fate of blastoporeblastopore

Protostomes undergo spiral Protostomes undergo spiral determinate cleavage, determinate cleavage, mesoderm splits and forms mesoderm splits and forms coelomcoelom

Deuterostomes have radial Deuterostomes have radial indeterminate cleavage, folds indeterminate cleavage, folds of archenteron become of archenteron become coelomcoelom

In protostomes, blastopore In protostomes, blastopore becomes head while in becomes head while in deuterostomes it becomes deuterostomes it becomes anusanus

Invertebrate AdaptationsInvertebrate Adaptations Cnidarians have diploblastic Cnidarians have diploblastic

radial body, gastrovascular radial body, gastrovascular cavity, polyp and medusa formcavity, polyp and medusa form

Cephalopods (octopus) feet Cephalopods (octopus) feet evolved into a muscular siphon evolved into a muscular siphon and part of the tenticle, well and part of the tenticle, well developed sense organs and developed sense organs and complex brain, lost shell from complex brain, lost shell from mollusk ancestors mollusk ancestors

Arthropods have a rigid Arthropods have a rigid exoskeleton, a variety of gas exoskeleton, a variety of gas exchange organs, special exchange organs, special appendages for specific tasksappendages for specific tasks

Crustaceans and Echinoderms Crustaceans and Echinoderms (starfish) can regrow lost arms (starfish) can regrow lost arms and legsand legs

Chordate-Vertebrate AdaptationsChordate-Vertebrate Adaptations

Simple chordates Lancelets and Simple chordates Lancelets and tunicates show that ancestral tunicates show that ancestral chordates had genes related to chordates had genes related to the mammalian heart, thyroid the mammalian heart, thyroid gland, and braingland, and brain

Aquatic vertebrates developed Aquatic vertebrates developed fins, vertebrae, and a more fins, vertebrae, and a more extensive skullextensive skull

Mineralization allowed animals to Mineralization allowed animals to become predators (started in the become predators (started in the mouth and skull)mouth and skull)

Gnathostomes developed gills for Gnathostomes developed gills for gas exchange and jaws also gas exchange and jaws also underwent duplication of Hox underwent duplication of Hox genesgenes

Tetrapods developed legs in Tetrapods developed legs in place of fins to walk on landplace of fins to walk on land

Amniote AdaptationsAmniote Adaptations Vertebrate embryos require an aqueous environment to Vertebrate embryos require an aqueous environment to

developdevelop Movement of vertebrates onto land required shell and Movement of vertebrates onto land required shell and

uteral adaptations, increased embryonic contact with fluid uteral adaptations, increased embryonic contact with fluid Amniotes include birds and mammals (amnions)Amniotes include birds and mammals (amnions) Extraembryonic membranes include (chorion, amnion, Extraembryonic membranes include (chorion, amnion,

yolk sac, allantois) provide life support systemyolk sac, allantois) provide life support system

Mammalian DevelopmentMammalian Development Small eggs, store few nutrients, holoblastic cleavageSmall eggs, store few nutrients, holoblastic cleavage Fertilization takes place in the oviductFertilization takes place in the oviduct Despite lack of yolk, mammalian gastrulation and organogenesis are Despite lack of yolk, mammalian gastrulation and organogenesis are

similar to that of birds and other reptilessimilar to that of birds and other reptiles At completion of cleavage, embryo is in blastocyst stageAt completion of cleavage, embryo is in blastocyst stage Trophoblast initiates implantation and provides supportTrophoblast initiates implantation and provides support Inner cell mass forms epiblast and hypoblast, homologous to those of Inner cell mass forms epiblast and hypoblast, homologous to those of

birdsbirds When implantation is completed, gastrulation begins, invading When implantation is completed, gastrulation begins, invading

trophoblast, mesodermal cells, and endometrial tissue contribute to trophoblast, mesodermal cells, and endometrial tissue contribute to forming a placentaforming a placenta

By the end of gastrulation, embryonic germ layers have formed, as By the end of gastrulation, embryonic germ layers have formed, as well as extraembryonic mesoderm and membraneswell as extraembryonic mesoderm and membranes

Extra-embryonic membranes in mammals are homologous to those Extra-embryonic membranes in mammals are homologous to those of birds and other reptilesof birds and other reptiles

Developmental DisordersDevelopmental Disorders

Mental RetardationMental Retardation Top 3 causes: Down syndrome, fetal alcohol syndrome Top 3 causes: Down syndrome, fetal alcohol syndrome

and Fragile X syndrome and Fragile X syndrome Include: epilepsy, autism, cerebral palsy and other Include: epilepsy, autism, cerebral palsy and other

disordersdisorders

Fetal Alcohol SyndromeFetal Alcohol Syndrome

When the female ingests alcohol, it When the female ingests alcohol, it crosses the placental barrier and can stunt crosses the placental barrier and can stunt or modify growth, damage neurons and or modify growth, damage neurons and brain structure, and cause other physical brain structure, and cause other physical or mental disordersor mental disorders

Amount, frequency, and timing of ingestion Amount, frequency, and timing of ingestion is currently not known. So when you get is currently not known. So when you get pregnant, do not drink alcohol.pregnant, do not drink alcohol.

Down SyndromeDown Syndrome

Caused by an extra whole or part of the Caused by an extra whole or part of the 2121stst chromosome chromosome

Inhibits cognitive ability, physical growth, Inhibits cognitive ability, physical growth, and can cause facial anomaliesand can cause facial anomalies

Lower than average mental capabilityLower than average mental capabilityFamily environment and vocal lessons can Family environment and vocal lessons can

lesson the disadvantages, but currently, a lesson the disadvantages, but currently, a cure is unknowncure is unknown

Cerebral PalsyCerebral Palsy

cerebral palsy often includes limitations of cerebral palsy often includes limitations of sensation, perception, cognition, communication, sensation, perception, cognition, communication, and behaviour, by epilepsy, and by secondary and behaviour, by epilepsy, and by secondary musculoskeletal problemsmusculoskeletal problems

Occurs during pregnancy, birth, or rarely, after Occurs during pregnancy, birth, or rarely, after birthbirth

Disturbance of the cerebrum is the area of Disturbance of the cerebrum is the area of cause, but specific cause is still debatedcause, but specific cause is still debated

There is currently no known cureThere is currently no known cure

Congenital Physical AnomaliesCongenital Physical Anomalies Did you know, most people have a congenital physical Did you know, most people have a congenital physical

anomaly if examined enough?anomaly if examined enough? Some Examples of these include…Some Examples of these include…

Curved pinky (clinodactyly )Curved pinky (clinodactyly ) Triple nipples (supernumerary nipples)Triple nipples (supernumerary nipples) Short fourth toe Short fourth toe Sacral Dimples (dimple over the spine)Sacral Dimples (dimple over the spine) Extra fingers (polydactyly)Extra fingers (polydactyly) Indentations near the ear (preauricular pits )Indentations near the ear (preauricular pits ) Webbed toesWebbed toes Extremely long fingers (Arachnodactyly ) and can bend back 180 Extremely long fingers (Arachnodactyly ) and can bend back 180

degreesdegrees Genu Valgum (knees bend inwards and hit each other)Genu Valgum (knees bend inwards and hit each other) Flat feetFlat feet Genu Varum (knees bend outwards – bowlegged people)Genu Varum (knees bend outwards – bowlegged people) Pectus Excavatum (caved in or sunken chest)Pectus Excavatum (caved in or sunken chest)

What Causes these Physical What Causes these Physical Anomalies?Anomalies?

Well, in general, we don’t know. They’re Well, in general, we don’t know. They’re called “Sporadic” disorderscalled “Sporadic” disorders

What can be some causes?What can be some causes?Some are genetic (polydactyly)Some are genetic (polydactyly)Some are environmental (mom drinks alcohol Some are environmental (mom drinks alcohol

or mercury or other harmful substance during or mercury or other harmful substance during pregnancy)pregnancy)

Many are multifactorial (combination of Many are multifactorial (combination of genetic and environmental disorders)genetic and environmental disorders)

What are some cures?What are some cures?

We don’t cure most of the Congenital We don’t cure most of the Congenital Physical Anomalies.Physical Anomalies.

For the ones that make us stick out in For the ones that make us stick out in society, we sometimes chop them off society, we sometimes chop them off (amputation) to hide them(amputation) to hide them

ReferencesReferences "Fertilization." "Fertilization." Gale Encyclopedia of ScienceGale Encyclopedia of Science. Ed. K. . Ed. K.

Lee Lerner and Brenda Wilmoth Lerner. 4th ed. Lee Lerner and Brenda Wilmoth Lerner. 4th ed. Detroit: Gale Group, 2008. Detroit: Gale Group, 2008. Student Resource Center - Student Resource Center - BronzeBronze. Gale. PIEDMONT HIGH SCHOOL. 10 Apr. . Gale. PIEDMONT HIGH SCHOOL. 10 Apr. 2009 <http://find.galegroup.com/srcx/infomark.do?2009 <http://find.galegroup.com/srcx/infomark.do?&co>. &co>.

Cobb, Bryan H., PhD. "Embryo and embryonic Cobb, Bryan H., PhD. "Embryo and embryonic development." development." Gale Encyclopedia of ScienceGale Encyclopedia of Science. Ed. K. . Ed. K. Lee Lerner and Brenda Wilmoth Lerner. 4th ed. Lee Lerner and Brenda Wilmoth Lerner. 4th ed. Detroit: Gale Group, 2008. Detroit: Gale Group, 2008. Student Resource Center - Student Resource Center - BronzeBronze. Gale. PIEDMONT HIGH SCHOOL. 10 Apr. . Gale. PIEDMONT HIGH SCHOOL. 10 Apr. 2009 <http://find.galegroup.com/srcx/infomark.do>.2009 <http://find.galegroup.com/srcx/infomark.do>.

Campbell, Neil A., and Jane B. Reece. Campbell, Neil A., and Jane B. Reece. BiologyBiology. San . San Francisco: Pearson Education, Inc., 2008.Francisco: Pearson Education, Inc., 2008.