Name: _____________________________________________________ Date: ________________ Hour: ____________
Week of 2/7-3/11 Notes- Advance Biology
http://www.pbs.org/wgbh/nova/odyssey/clips/ Video clips of Chicken, Pig, and Human Embryos
In animals, ___________________________________________________________________
_______________________________________ is the first step in a complete series of events.
It is this series that finally gives rise to a full-grown organism. This is called development.
In the early stages of development, the organism is called an _______________
The study of the development of an embryo is called _________________________
Although embryos develop in many different ways, the basic processes are always the same in
animals. The three different processes of development include:
1. Cleavage
Main focus today
a. Gastrulation
2. Growth
3. Differentiation
a. Morphogenesis
__________________________________= First series of cells divisions after fertilization
-
Number of cells doubles during each division
Cells _________________________________
Each division _________________________________________
____________________= solid ball of cells resulting from early divisions of cleavage
____________________= hollow sphere formed as the cells continue to divideo A sphere only _________________________
o Filled with_______________________
o __________________________________= fluid filled inside
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Name: _____________________________________________________ Date: ________________ Hour: ____________
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Name: _____________________________________________________ Date: ________________ Hour: ____________
Activity: Examining early embryonic stages of the sea star
Introduction:
Echinoderms (sea stars, sea urchins, sea cucumbers) are useful for illustrating the stages of early development
for multicellular animals. Sea stars develop in an aquatic environment and develop quickly into a larva that is
capable of feeding itself. Explain why you might not expect a sea star’s egg to be heavily laden with yolk:
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
Directions:
Obtain a whole-mount microscope slides provided.
Identify the following components, structures, and stages of development listed below. Use the figure on the
next page (35. 1) for help.
Cleavage: Successive division of the embryo results in a two-cell, four-cell, and eight-cell stage. The next cell
stage is called ________________________________-cell stage. A many-cell stage occurs after that. Cleavage
occurs without an accompanying increase in size. Sketch this
_______x (power)
Blastula: The large number of embryonic cells of the morula arrange themselves into a blastula, a singlelayered ball with a fluid-filled cavity, called a blastocoel, in the middle. Sketch a blastula and label the
blastocoel.
_______x (power)
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Name: _____________________________________________________ Date: ________________ Hour: ____________
Early gastrula: The cells of the blastula fold inward
to form a two-layered gastrula. The cavity
produced by the infolded layer of cells is the
archenteron, or primitive gut, which has an
opening to the outside called blastopore. The outer
layer of cells is the exoderm, and the inner layer is
the endoderm. Sketch this stage and label the
exoderm and endoderm.
_______x
Late gastulation: As development continues, two
pouches form by out-pocketing from the endoderm
surrounding the gut. These pouches become part
of the coelom (body cavity), and the walls of these
lateral pouches become the third germ layer, the
mesoderm.
_______x
SCAN IN FIGURE 35.1 FROM PACKET!!!!!!!!!!!!!!!
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Name: _____________________________________________________ Date: ________________ Hour: ____________
Elaboration Questions:
SCAN IN FIGURE 35.2 from packet (Frog development stages)
1. Examine the above drawing of the developmental stages of a frog embryo. Specifically, look at the
blastula. Compare the frog blastula to that of the sea star: ____________________________________
____________________________________________________________________________________
____________________________________________________________________________________
2. Compare the formation of the mesoderm in the frog to that in the sea star: ______________________
____________________________________________________________________________________
____________________________________________________________________________________
3. Neurula: During neurulation in the frog, two folds of ectoderm appear. The flat layer of ectoderm
between the folds is the neural tube, which will become the nerve cord and brain. An examination of
the neurula in cross section shows that the nervous system develops directly above the notochord, a
structure that arises from the invagination cells in the middorsal region.
Do sea stars have a notochord? ________ Explain: ____________________________________
4. List the three germ layers and the major organs that develop from each in the frog. Use your book for
help:
Germ Layer
1
2
3
Organs/Organ Systems Associated with Germ Layer
5. Critical thinking: Use your book to look up the definition of induction. What is induction and how does
it relate to the above table?
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Name: _____________________________________________________ Date: ________________ Hour: ____________
- Arrangement of cells in the developing embryo depends on ___________________
_____________________________________________________________________
- Humans have little yolk. Why?
- Amphibians, bony fish, birds, and reptiles have a large amount of yolk at __________
______________________________________________________________
- Yolk tends to slow down ___________________________________________
o Cleavage tends to take place at end of _________________________________
o Relate this back to what you found out about frog and sea star cleavage:
Gastrulation= when the blastula reaches ___________________________________________
- Cells on one side of the blastula move inward and form a two-layered embryo called
the ______________________________________________________
- Opening is called the blastopore- later becomes opening of ____________________
_____________________________________
- Germ layers:
o __________________________________=outer layer
o __________________________________= inner layer
o __________________________________= layer between
As the gastrula develops, the number of cells continues to _________________________
Since the cells now grow before dividing, the embryo begins to ________________________
Cell growth alone would produce only a formless mass of cells
The cells in the embryo must be arranged into _________________________________, and
within these structures, the cells must be specialized to ______________________________
_______________________________________
Although the cells of the gastrula are organized into distinct layers, (which were…..) they look
very much alike
________________________________________________= The changing of unspecialized
embryonic cells into the specialized cells, tissues, and organs that make up the organism
First signs of differentiation are found on the upper surface of the __________________
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Name: _____________________________________________________ Date: ________________ Hour: ____________
- Ectoderm cells divide, forming a neural plate that has 2 raised edges called
______________________________________________
- These slowly come together over the center of the ______________________,
forming a ________________________________________________
- In the later stages of development, the neural tube forms the _____________
____________________________________________________________
Role of neighboring cells
As embryo grows, there must be coordination and communication between its tissues
By late blastula or early gastrula stage, the way in which groups of cells will develop has
already been determined
Cells in certain regions develop along certain lines
Ex: There is a particular place in frog gastrula that normally develops into
an eye
If this tissue is removed from the embryo and placed in a special nutrient
solution:
If transplanted into another frog embryo:
_________________________= influence the development of neighboring
cells
- This process is called ________________________________________
- Scientists still don’t know exactly how this process works
Check Point:
Compare differentiation and cleavage:
Which germ layer do you think gives rise to the human heart? Explain.
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Name: _____________________________________________________ Date: ________________ Hour: ____________
External and Internal Development
Just like fertilization, development can take place inside or outside the body.
Regardless of where the development occurs, the embryo needs proper nutrients,
temperatures, oxygen, protection, and means of getting rid of waste.
-External Development
Water or land
External, AquaticIn most aquatic animals, fertilization and development take _____________
__________________________________________________________________
Nourishment comes from _____________________________________________
Oxygen diffuses into ____________________________, and wastes diffuse from
the ____________________________________________________
Usually little or _________________________________________________
 “Mouth feeders”
External, landBirds and most reptiles
Large amount of _____________, and a protective ________________________
Waterproof and porous
% of reptile eggs that survive less than % of bird eggs that survive…why?
Do reptiles or birds lay more eggs?
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Name: _____________________________________________________ Date: ________________ Hour: ____________
Internal structure of a chicken eggAs chicken embryo develops, it forms 4 membranes that lie outside the embryo
itself but inside the shell= _____________________________________________
1. ________________________________- outer most membrane- lines inside of
shell and surrounds the embryo and other 3 membranes
- aids in exchange of gases between embryo and environment
2. ___________________________________- saclike structure that grows out of
the digestive tract of the embryo –
-where exchange of oxygen and carbon dioxide take place
-where metabolic wastes collect
3. ____________________________- surrounds embryo contains amniotic fluid
4. _________________________- surrounds the yolk- source of food for embryo
Chick development:
Unlike sea stars and frogs, chicks develop on land, and there is no larval stage. Therefore, chick development is
markedly different from that of sea stars and frogs because of 3 features:
1. Extraembryonic membranes
2. Large amount of yolk to sustain development
3. Hard outer shell
Materials:
Unfertilized chick egg
Dissection prods
Petri dishes
water
SAFETY:
Wash hands after handling the egg
Clean up:
All parts are to go in the waste container. Wash and dry all petri dishes and dissecting tools.
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Name: _____________________________________________________ Date: ________________ Hour: ____________
Directions:
Get with a partner and obtain the materials above.
1. Carefully crack the egg into the petri dish filled with enough water to keep the egg moist, but not too
much that the water will overflow.
2. Examine the contents of the raw egg. The egg white is called albumin. Is the albumen consistent in
density and thickness? _____________________________________________________
a. These thicker masses are called chalazae. They result from the passage of the egg through the
oviduct. This aids in keeping the developing embryo at the top of the yolk.
3. On the top of the yolk mass, the germinal vesicle, a small, white spot content the clear cytoplasm of
the egg cell and the egg nucleus. The yolk and the germinal vesicle is the ovum.
4. Peel some of the chorion off the inside of the shell. Note how it looks and feels: ___________________
____________________________________________________________________________________
INSERT FIGURE 35.5 FROM LAB PACKET
Elaboration questions:
1. What premature membrane holds the yolk together?
2. What would happen to a chick embryo of the chorioan was impermeable?
3. What would happen to the embryo of the amnion never formed?
4. Make a prediction about where the posterior and anterior end of the chick form based on the
placement of the structures in this premature, unfertilized egg. Explain your reasoning.
5. How would the membranes of a human differ than those of a chick?
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Name: _____________________________________________________ Date: ________________ Hour: ____________
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Name: _____________________________________________________ Date: ________________ Hour: ____________
Internal Development
Mammals and some reptiles and sharks
Placental mammals= blood vessels of the embryo’s circulatory system are in close
contact with the mother’s circulatory system placenta  umbilical cord
Non-placental mammals= egg-laying mammals and pouched mammals (monotremes
and marsuipials)
Polarity
Eggs and zygotes of sea urchins and other animals have definite polarity established as the egg
developed within the mother ________________________________________________
During cleavage, planes of division follow a _______________________________________
relative to the poles of the zygote
Polarity is defined by __________________________________________________ in the
cytoplasm and yolk
This distribution of yolk is the key factor ______________________________________
______________________________________________
Usually concentrated towards 1 side of the egg= _____________________________
Opposite pole= _____________________________
Animal-vegetal axis of egg determines the __________________________________ axis
of embryo
Organogenesis =
=more localized shape changes in both tissues and __________________________
_________________________ and ________________________________are the first organs
to take shape in the embryos of frogs
______________________________= skeletal rod characteristic of all chordate embryos
______________________________= runs along anterior-posterior axis of the embryo-will become animal’s CNS
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Name: _____________________________________________________ Date: ________________ Hour: ____________
As organogenesis progresses, morphogenesis and cell differentiation continue to refine the
organs that arise from the _________________________________
Mammalian development
In contrast with the large, yolky eggs of birds, other reptiles, and monotremes, mammalian
eggs are small and store little nutrients.
-No________________________________
-Despite lack of yolk, go through a similar pattern of ________________________and
_________________________________________________________________
- Ethical concerns preclude experimentation on human embryos, so knowledge about
human development has been based partly on what we can extrapolate from other
mammals and in vitro fertilization.
THIS LEADS US TO THE TOPIC OF ……
Bioethics & You:
What is bioethics?
Beneficence-
Nonmalefecence-
Autonomy-
Justice-
Veracity-
Fidelity13
Name: _____________________________________________________ Date: ________________ Hour: ____________
Stations- Go through the 6 stations and fill in the following blanks. Focus on the lines that
are bolded. These are the sections that you absolutely need to get done in class. The rest can
be filled out using your book or internet searching skills:
STATION 1Fertilization= less ambiguously referred to as ______________________________________
Process of ______________________________ fusing with a _________________________
Begins with _________________________________________________________
Ends with ___________________________________________________________
Draw a sperm and label the parts:
What is an acrosome:
STATION 2
Cleavage=
Blastomere=
Cleavage begins with a zygote, progresses through a ______________ stage and terminates at the
_________ ______________________________
-Cell divisions without cell enlargement
-Morula produced (
) Same size as single cell
- Cell divisions affected by ___________________________________________________________
Briefly describe the 2 cell and 4 cell stage:
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Name: _____________________________________________________ Date: ________________ Hour: ____________
In which stage does the division of blastomeres become asynchronous?
Blastulation
-
Morula secretes ____________________________________________________
Blastomeres surround ________________________________________________________
Human embryo differentiantes into _________________________________ with inner cell
mass
A morula is a __________________________________________________________________ within a zona
pellucid
A morula usually consists of _____________ blastomeres= ____________________________________
Outer blastomeres are destined to become ______________________________________________________
__________________________________________________________________________________________
Inner blastomeres are destined to become _______________________________________________________
__________________________________________________________________________________________
Blastula= ______________________________________________________________________________
_____________________ into an epithelial monolayer.
Look at the ball of cells under the microscope. This is a cross section of a frog embryo at an early stage of its
growth. It shows a mass of about 64 cells that developed by cleavage from a single cell. Sketch what you
see:
Notice the center of the mass of cells. This hallow ball stage is called the blastula. Label this. Notice that the
cells in the lower part are larger than those of the upper part. Why would this be? _____________________
__________________________________________________________________________________________
__________________________________________________________________________________________
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Name: _____________________________________________________ Date: ________________ Hour: ____________
STATION 3
Gastrulation=
Gastrulation creates 3 germ layers:
Morphogenesis=
Ectoderm and endoderm are made by:
Mesoderm develops:
Look at the slide under the microscope. This is what the ball of cells from station 2 would look like after a
few days. It has developed into a gastrula. Compare the size of the two slides: _________________________
You can clearly see the three germs layers here. Sketch what you see and label the 3 germ layers:
STATION 4
Architecture: 4 features of early development distinguish the Protostomes and Deuterostomes
B. Spiral v. radial cleavage
1. Radial (
): planes of division perpendicular to or
include _____________________
2. Spiral (
): planes of division become oblique to ______
_______________________; upper cells lie in cleavage grooves between lower
cells
C. The blastopore becomes the ______________ and _______________________
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Name: _____________________________________________________ Date: ________________ Hour: ____________
On the protostome side are these kind of critters:
On the deutrostome side are these kinds of critters:
Characteristic
Protostomes
Determinate
Deuterostomes
Indeterminate
Cleavages
Radial
Fate of blastopore
Anus
Splitting of mesoderm
STATION 5
Ectoderm becomes:
Endoderm becomes:
Mesoderm becomes: Notochord, muscle, excretory system, gonads, outer covering of internal organs, dermis,
bones and cartilage, and circulatory system
Coelom=
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Name: _____________________________________________________ Date: ________________ Hour: ____________
Sketch a cross section of a coelom showing the 3 germ layers
An ___________________________________ does not have a body cavity
A ___________________________________________ has a body cavity called a pseudocoelom located
between endoderm and mesoderm
Coelomate=
Symmetry
Gut
Coelom
Embryonic Germ
Layers
Sponges
Cnidarians
Flatworms
Roundworms
Mollusks
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