Objectives Identify Starfish Development using the models and microscope slides Understand when sperm penetrates the egg it creates a membrane barrier Understand purpose of umbilical cord and placenta in mammals ID: 186864
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Slide1
Plant and Animal Development - Exercise 10
Objectives
Identify Starfish Development using the models and microscope slides.
Understand when sperm penetrates the egg, it creates a membrane barrier.
-Understand purpose
of umbilical
cord and placenta in mammals.
-Know primary germ layers.Slide2
Pages 1 - 4 is skipped unless your instructor
wants you to know this stuff, you have to
do this on your own. You will learn more
about this in BI108, if you take the class.Slide3
All multicultural, sexually reproducing animals utilize gametes to transmit genetic information to their offspring.
The contribution to the offspring is limited to their nuclear contends - I.e., a haploid set of chromosomes. Egg cells are typically much larger than sperm cells. They, too, contribute a haploid set of chromosomes to the offspring; however, they may also provide nutrients (for energy and growth)
, in the form of yolk, to sustain the development of the offspring to the point that it can obtain its own food.
There are several different types of eggs with respect to the amount and distribution of yolk
.Slide4
Those organisms that live independently will usually pass through one or more immature larval stages before reaching their final mature form
. The more yolk that an egg possess, the more time the embryo has to develop tissues and organs that will enable it to live indecently. Organisms that develop on land must be protected from desiccation (drying out) by remaining in mother’s body or have a protective barrier. Also, there must be enough yolk to support a considerable amount of development, as occurs in bird and reptile eggs, for example.Slide5
The fusion of the haploid sperm nucleus with the haploid egg nucleus at fertilization produces a diploid
zygote
,
which is the beginning of new organism.
The first stage of development is
cleavage
,
during which the cells rapidly dividing by mitotic cell division without increase their mass
.
Each of the cells is called a
blastomere
. The embryo, therefore, increases its cell number, but it does not grow in overall size.
As cleavage progresses, the
blastomeres
tend to become peripherally located, leaving a space or cavity (the
blastocoel
)
in the center of the embryo. Cleavage ends with the formation of a hollow ball of cells called a
blastula
. Slide6
The next process is called
morphogenesis
.
During this, the shape and body form of the organism will be produced and the embryo will begin to grow an enlarge.
Some cells will migrate to other locations in the embryo. This movement of embryonic cells is referred to as
morphogenesis movements
. The movements coupled with the continued multiplication of cells will produce three layers of cells.
The three specialized cell layers are called the
primary germ layers
.Slide7
Ectoderm
: Outermost layer. It gives rise to the
skin
and associated structure and the
nervous system
.
Mesoderm
: Middle layer. It gives ruse to muscle, bone, tendons, blood, and other
connective tissues
. The
kidney, gonads and the heart
.
Endoderm
: Inner layer. It gives rise to the lining of the organs of the
digestive system
, the
lining of the lungs, liver, cell of the pancreas
and produce digestive enzymes.Slide8
Morphogenesis is initiated by the inward migration of a group of cells towards the interior of the embryo into the
blastocoel
.
The particular morphogenesis movement is referred to as an
invagination
,
and during this time the embryo is called a
gastrula
.
The
invagination
(aka
gastrulation
)
creates an opening to the outside of the embryo which is called the
blastopore
. As
gastrulation
progresses, the inward moving cells from an internal cavity called the
archenteron
,
which is continuous with the
blastopore
.
Once the primary germ layers have formed,
differentiation
of these cells into mature tissues begin to occur.Slide9
Starfish Development ModelsSlide10Slide11
Cleavage
Early cleavage stage embryos (2,4, and 8 cell stages)
Early cleavage stage embryos (2,4, and 8 cell stages)Slide12Slide13
CleavageSlide14Slide15Slide16Slide17
GastrulaSlide18
Development in placental mammals
Nearly unique to most mammals in the animal kingdom is the protection and nourishment of the embryo (fetus) within the uterus of the mother by assistance of a complex organ called the placenta.
There is no active, feeding larval stage in mammals, because the mother and the placenta provide food for embryonic growth through the umbilical cord.
Embryos are attached to the umbilical cord with the placenta.Slide19
Various mammals in their placenta.
-What’s the thing cord that attaches the placenta to the animal for nutrients?Slide20
The
Umbilical cord…Slide21
Chicken Embryonic StagesSlide22
Sperm
Identify: Sperm head & flagellumSlide23
Starfish embryos, various stages Fig 110a - Rust
Early Starfish Development
Females and males shed their gametes into water where fertilization occurs. These
slides contain a mixture of all of the various embryonic stages in whole mounts.Slide24
Single Egg cell – Unfertilized egg
Before sperm penetration of the egg occurs, the nucleus and a single nucleolus are clearly visible in the unfertilized egg cell.
Label: nucleus, nucleolus, nuclear membrane, cytoplasmSlide25
Zygote
Fertilized egg:
Once the sperm penetrate the egg, the egg cell (which was actually a secondary
oocyte
) completes meiosis. The nucleus will no longer be visible. A
fertilization membrane
is formed,
which prevents any other sperm cells from entering the egg.
Label: Fertilization membraneSlide26
Two Cell Stage Fig. 110C - RUST
When a sperm has
gotten into the egg,
the egg will create a
membrane barrier to
prevent other sperm
from entering.Slide27
Cleavage
Early cleavage stage embryo
(2,4, and 8 cell stages)Slide28
Early Blastula Figure 110g - RUSTSlide29
Late Blastula Figure 110h - RUSTSlide30
Cleavage Figures 110i – 110k - RUST
Label:
Blastopore
&
BlastocoelSlide31
Gastrula Figure 110l - RUST
Label:
Blastocoel
, archenteron,
blastopore
, ectoderm, endoderm, & mesoderm..
Late gastrulaSlide32
Larva of Starfish Figure 110m - RUST
Label mouth, esophagus, stomach, intestine, and anusSlide33
ChickSlide34
Page 10 – Lab Book - Questions
1. What stage of development is characterized by an increase in the number of cells but no overall increase in the mass of the embryo?
2. Which of the starfish stages that you drew marks the beginning of morphogenesis?Slide35
Page 10 – Lab Book - Questions
1. What stage of development is characterized by an increase in the number of cells but no overall increase in the mass of the embryo?
Cleavage
2. Which of the starfish stages that you drew marks the beginning of morphogenesis?
GastrulaSlide36
Page 11 – Lab Book - Questions
Yolk in animal eggs is used for food energy for
growth of the embryo until the embryo hatches or
becomes a large larva. The starfish egg has almost no
yolk and develops into a larva with a complete digestive
tract fort eight hours after fertilization. A frog egg has a
moderate amount of yolk and develops into a larva
(tadpole) 10 days after fertilization. A bird egg has a very
large amount of yolk and doesn’t hatch for three weeks.
Does there seen to be any connection between the
amount of yolk present in a starfish egg and the rate at
which the larval stage and its digestive system develops in
the starfish embryo? Explain.Slide37
Page 11 – Lab Book - Questions
Yolk in animal eggs is used for food energy for growth of the
embryo until the embryo hatches or becomes a large larva. The
starfish egg has almost no yolk and develops into a larva with a
complete digestive tract fort eight hours after fertilization. A frog egg
has a moderate amount of yolk and develops into a larva (tadpole) 10
days after fertilization. A bird egg has a very large amount of yolk
and doesn’t hatch for three weeks. Does there seen to be any
connection between the amount of yolk present in a starfish egg and
the rate at which the larval stage and its digestive system develops in
the starfish embryo? Explain.
The more yolk, the longer it takes
to develop into a larva and your digestive system isn’t fully
developed.Slide38
Page 12 – Lab Book - Questions
7. Name several functions of the placenta.
9. Compare how the sperm is transported to the egg in a flowering plant and how the sperm travels to the egg of a starfish. Slide39
Page 12 – Lab Book - Questions
7. Name several functions of the placenta.
Provides protection, nutrients (food & oxygen). It
helps to remove carbon dioxide and wastes from
fetus.
9. Compare how the sperm is transported to the egg in a flowering plant and how the sperm travels to the egg of a starfish.
In starfish the sperm is just thrown to the water and it swims towards the egg to fertilize it.