Animal Reproduction Development...Oogenesis Meiosis 1 completed during egg maturation Meiosis 2 completed triggered by fertilization ovulation • Unequal meiotic divisions – unequal

2007-2008

Animal Reproduction

&

Development

28 Oct. 2010 Embryology.ppt 2

What IS an Animal?

• Petunia is a plant and

• Wolf spider is an

animal.

• No trouble.


What IS an Animal?

• Coral

– sessile (“rooted”?)

– stem, branches,

– greenish.

– Resembles plant;

– but this IS an

animal! Why?

What Am I?

– Of some 1.5 million species of organisms known to

science

• Over two-thirds are animals

– Humans have a long history of studying animal

diversity

• But classifying an animal isn’t always easy

– Imagine you were the first person to encounter the

animal pictured here

• With all of its varying characteristics, what would you

think it is?

– Biologists often encounter classification problems

• When evolution creates organisms with similar

characteristics

A Tasmanian tiger, 1928

http://www.parks.tas.gov.au/wildlife/mammals/devil.mov

http://www.parks.tas.gov.au/index.aspx?base=387

2007-2008

Domain

Bacteria

Domain

Archaea

Domain

Eukarya

Common ancestor

Kingdom: Animals

Domain Eukarya

Animal Characteristics • Heterotrophs

– must ingest others for nutrients

• Multicellular

– complex bodies

• No cell walls

– allows active movement

• Sexual reproduction

– no alternation of generations

– no haploid gametophyte

Porifera

Cnidaria

Platyhelminthes

sponges Sea jellies flatworms roundworms

Nematoda

Mollusca Arthropoda Chordata

Annelida Echinoderm

mollusks

multicellularity

Ancestral Protist

tissues

bilateral symmetry

body cavity

segmentation

Animal Evolution

coelom

Sea stars vertebrates

endoskeleton

segmented worms

insects spiders

backbone

WHAT is an ANIMAL?

1. Animals are multicellular, heterotrophic eukaryotes that

get energy through ingestion.

2. Animals lack cell walls but have proteins for structural

components such as collagen and have unique cellular

junctions.

3. Animals have nervous and muscle tissues for movement.

4. Most animals reproduce sexually with a dominant diploid

stage, flagellated sperm, nonmotile egg, zygote, cleavage,

blastula, gastrula, larval stages, and metamorphosis.

5. Animals have special regulatory genes called Hox. Only

animals have homeobox genes found in homeotic genes.


What IS an Animal?

• Basic structure (not definition) = Tube-in-tube

– Body wall = outer tube

– gut (GI tract) = inside tube

• mouth

• anus

THE ORIGINS of ANIMAL

DIVERSITY

There are 35 Phyla of animals

• The Cambrian Explosion – Lot’s of fossil

evidence of most extant animal Phyla.

• Ediacaran Period (used to be part of

Precambrian) 600 to 542 MYA.

• Evidence suggests that multicellular

animals were around 1.1 BYA that matches

the Molecular evidence.

Why?

• Ecological causes- The emergence predator

prey relationships caused diversity.

• Geological Causes- The increase in oxygen

would allow multicellular animals

• Genetic Causes – Changes in the Hox gene

at this time lead to a variety of body plans

• Animals can be organized by the following

categories:

Type of symmetry

Type of gastrulation

Type of coeloem

Symmetry Animals show 3 types of symmetry

• 1. Asymmetrical

• No apparent structure around any axis

• 2 . Radial Symmetry

• Has top and bottom, but no front, rear, left or right

Bilateral symmetry

Has Dorsal (top), Ventral (bottom),

Anterior (front), Posterior (rear), left

& right

Often show cephalization, the

concentration of sensory and feeding

parts to the anterior


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


Sequence of Events:

1. Fertilization

2. Cleavage

4. Gastrulation

5. Mesoderm formation

6. Organogenesis

7. Neurulation

Oogenesis

Meiosis 1 completed during egg maturation

Meiosis 2 completed triggered by fertilization

ovulation

• Unequal meiotic divisions

– unequal distribution

of cytoplasm

– 1 egg

– 2 polar bodies

What is the advantage of this development system?

Put all your egg in one basket!

Fertilization

• fertilization

• cleavage

• gastrulation

• neurulation

• organogenesis

Fertilization • Joining of sperm & egg

– sperm head (nucleus) enters egg

Cleavage • Repeated mitotic divisions of zygote

– 1st step to becoming multicellular

– unequal divisions establishes body plan

• different cells receive different portions of egg cytoplasm &

therefore different regulatory signals

Cleavage

• zygote morula blastula

– establishes future development

zygote

blastula morula

gastrulation

Embryology & Animal

Classification

• Animals differ in the way they develop

embryologically

• Two ways they can differ

1.Fate of the blastopore

2.Type of cleavage in gastrula formation

Cleavage – 2 types 1. Radial cleavage The cellular divisions occur in

perpendicular axes to each other. (Echinoderms & Chordates)

2. Spiral Cleavage (Annelid, Arthropods & Molluscs)

In spiral cleavage the cellular divisions occur diagonally, in a twisting pattern.


Sequence of Events:

4. Gastrulation = formation of a gut;

– Major MORPHOGENIC event !!!

– Location of cells after GASTRULATION determines

further development


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."

Archenteron (primitive gut) deep cavity

which will form gut


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.

• Establish 3 cell layers

– ectoderm

• outer body tissues

– skin, nails, teeth

– nerves, eyes, lining of mouth

– mesoderm

• middle tissues

– blood & lymph, bone & notochord, muscle

– excretory & reproductive systems

– endoderm

• inner lining

– digestive system

– lining of respiratory, excretory & reproductive systems

Gastrulation

ectoderm

mesoderm

endoderm

protostome vs. deuterostome

gastrulation in primitive chordates

http://learningobjects.wesleyan.edu/gastrulation/animations.php?ani=3D

Protostomes

– animals in which blastopore forms mouth (1st mouth) worms, mollusks, arthropods

Deuterostomes – (second mouth)

animals in which the blastopore forms anus. Echinoderms chordates

Coelomes

A Coeloem refers to the body cavity of an animal

These form from the 3 derm layers

Three types of coelomes

1. Acoelomates have no internal body cavity

2. Pseudocoelomates have an incompletely formed

body cavity

3. Coelomates have a fully developed body cavity

completely lined by mesoderm

Testing… All of the following correctly describe the fate of the embryonic

layers of a vertebrate EXCEPT

A. neural tube and epidermis develop from ectoderm

B. linings of digestive organs and lungs develop from

endoderm

C. notochord and kidneys develop from endoderm

D. skeletal muscles and heart develop from mesoderm

E. reproductive organs and blood vessels develop from

mesoderm

Testing… In a study of the development of frogs, groups of cells in the germ layers of several embryos in the early gastrula stage were stained with five different dyes that do not harm living tissue. After organogenesis (organ formation), the location of the dyes was noted, as shown in the table below.

Tissue Stain

Brain Red

Notochord Yellow

Liver Green

Lens of the eye Blue

Lining of the digestive tract Purple


Sequence of Events:

6. Organogenesis

– Formation of organs from three germ layers

– Differentiation & continued Morphogenesis


Organogenesis

• Ectoderm

– Epidermis

– Lining of mouth & rectum

– Cornea of eye

– Lens of eye

– Nervous system

Embryology.ppt 52

Organogenesis

• Endoderm forms thin linings (mostly)

– linings of gut & branches

– lining of excretory ducts, bladder

– " " lungs, trachea

– " " reproductive ducts,

• uterus, vas deferens

– liver

– pancreas


Organogenesis

• Mesoderm

– Skeleton,

– Muscles (skeletal, smooth, cardiac)

– Dermis of skin

– Heart, blood, blood vessels

– Kidneys,

– Ovaries/testes, etc.


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

Differentiation-specialization

the changing of unspecialized embryonic cells

(STEM) into the specialized cells, tissues and

organs which perform different functions.

Neurulation • Formation of notochord & neural tube

– develop into nervous system

Notochord

Neural tube

develops into vertebral column

develops into CNS (brain & spinal cord)

Neurolation The process that initiates the

formation of the nervous system.

Organogenesis

Umbilical blood vessels

Chorion

Amnion

Yolk sac

Allantois Fetal blood vessels

Maternal blood vessels

Bird embryo

Mammalian embryo

Placenta

Placenta • Materials exchange across membranes

Human fetal development

7 weeks 4 weeks


10 weeks


12 weeks 20 weeks


• The fetus just spends much of the 2nd & 3rd trimesters just growing

…and doing various flip-turns & kicks inside amniotic fluid

Week 20


• 24 weeks (6 months; 2nd trimester)

fetus is covered

with fine, downy

hair called lanugo.

Its skin is

protected by a

waxy material

called vernix


• 30 weeks (7.5 months)

umbilical cord

Getting crowded in there!!

• 32 weeks (8 months)

The fetus sleeps

90-95% of the

day & sometimes

experiences REM

sleep, an

indication of

dreaming

Birth

positive feedback

Intestine

Placenta

Umbilical cord

Wall of uterus

Vagina

Cervix

Birth (36 weeks)

Bladder

Gestation

is the period of development of an embryo/ fetus

human 40 weeks

whale 12 months

elephant 18 months

medaka 10 days

chicken 21 days

The end of the journey!

And you think 9 months of AP Bio is hard!

Reproductive

cells

Somatic

cells

Digestive

cavity

1 Colonial protist,

an aggregate

of identical cells

2 Hollow sphere

of unspecialized

cells (shown in

cross section)

3 Beginning of cell

specialization

(cross section)

4 Infolding

(cross section)

5 Gastrula-like

“proto-animal”

(cross section)

The ancestor of animals was probably a colonial,

flagellated protist

– Cells in these protists

• Gradually became more specialized and layered

Figure 18.2A

3 body layers

ectoderm

mesoderm

endoderm

Body Cavity

How much is the

digestive tract

separated from

the rest of the

body?

ectoderm

ectoderm

mesoderm

endoderm

ectoderm

mesoderm

endoderm

mesoderm

endoderm

acoelomate

pseudocoelomate

coelomate

coelom cavity

pseudocoel

Documents

Animal Reproduction Development...Oogenesis Meiosis 1 completed during egg maturation Meiosis 2 completed triggered by fertilization ovulation • Unequal meiotic divisions – unequal