animal reproduction development...oogenesis meiosis 1 completed during egg maturation meiosis 2...
TRANSCRIPT
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.
28 Oct. 2010 Embryology.ppt 3
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
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.
28 Oct. 2010 Embryology.ppt 11
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
28 Oct. 2010 Embryology.ppt 22
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
28 Oct. 2010 Embryology.ppt 23
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.
28 Oct. 2010 Embryology.ppt 32
Sequence of Events:
4. Gastrulation = formation of a gut;
– Major MORPHOGENIC event !!!
– Location of cells after GASTRULATION determines
further development
28 Oct. 2010 Embryology.ppt 33
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
28 Oct. 2010 Embryology.ppt 35
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
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
28 Oct. 2010 Embryology.ppt 50
Sequence of Events:
6. Organogenesis
– Formation of organs from three germ layers
– Differentiation & continued Morphogenesis
28 Oct. 2010 Embryology.ppt 51
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
28 Oct. 2010 Embryology.ppt 53
Organogenesis
• Mesoderm
– Skeleton,
– Muscles (skeletal, smooth, cardiac)
– Dermis of skin
– Heart, blood, blood vessels
– Kidneys,
– Ovaries/testes, etc.
28 Oct. 2010 Embryology.ppt 54
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
Human fetal development
10 weeks
Human fetal development
12 weeks 20 weeks
Human fetal development
• The fetus just spends much of the 2nd & 3rd trimesters just growing
…and doing various flip-turns & kicks inside amniotic fluid
Week 20
Human fetal development
• 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
Human fetal development
• 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