Lab -- echinoderm/frog/chicken development lab Flashcards
fertilization is thought to be the….
the start of development
fertilization is a necessary trigger for
for the continued development o fan oocyte into a complete organism
fertilization accomplishes two things:
1
1) activates the oocyte (or sometimes egg) so that it goes on to complete its development
fertilization accomplishes two things:
2
2) provides the means by which the haploid set of chromosomes of the sperm joins the haploid set of chromosomes of the egg –>
restores the diploid condition –>
makes a brand new, unique combination of genes in the individual that develops from the zygote that is created
examples of echinoderms
starfish, sea urchin, sea cucumber
fertilization in echinoderms
fertilization membrane lifts off surface of egg soon after the first sperm makes contact
membrane is 1 mechanism that prevents polyspermy
polyspermy
entrance of more than 1 sperm into the egg
fertilization membrane
long-term mechanical barrier that helps to ensure that the zygote will be diploid and not triploid, tetraploid, or whatever
while the membrane is being constructed…
a rapid and short-term electrical block to polyspermy protects the just-fertilized egg
nature’s role in preventing polyspermy in echinoderm fertilization
wild echinoderms release gametes into water –> water dilute egg and sperm –> lowers chance that more than 1 sperm will fertilize a single egg
echinoderm development:
flagella
allow sperm to move
echinoderm development:
what causes beginning of lifting of the fertilization membrane off the surface of the egg?
sperm makes contact on surface of egg –> blister forms and encompasses the whole egg
echinoderm development:
when completely raised off, the fertilization membrane will be ___ with the egg’s surface
concentric
echinoderm development:
when completely raised off, the fertilization membrane will be concentric with the ___
egg’s surface
echinoderm development:
what happens after sperm head migrates into egg’s cytoplasm?
sperm head enters egg’s cytoplasm ands begins to swell –> becomes male pronucleus
male pronucleus migrates toward female pronucleus
echinoderm development:
egg nucleus is called…
female pronucleus
echinoderm development:
what happens as male pronucleus migrates toward female pronucleus?
synthesis of DNA –> results in formation of a new chromatid for each of the chromosomes in the male and female pronuclei
echinoderm development:
male pronucleus fuses w/ female pronucleus…
forms zygote nucleus that contains a diploid # of chromosomes
echinoderm development:
as zygote forms and becomes embryo
tremendous increase in rate of biosynthetic activity in zygote
DNA synthesis
burst of RNA synthesis and protein synthesis
first cleavage in zygote
echinoderm development:
cleavage in the sea urchin is ___. This means….
holoblastic –> cleavage furrows cut completely and quickly thru the embryo
echinoderm development:
echinoderm egg characteristics
little or no you
has polarity
nucleus is offset towards animal pole and away from vegetal pole
echinoderm development:
after fertilization…
because there is so little yolk –> the cleavage of echinoderm zygotes is fairly rapid and complete
echinoderm development:
first cleavage in echinoderms is ___, beginning at the ___ and progressing to the ____
vertical
animal pole
vegetal pole
echinoderm development:
blastomere
side-by-side units
echinoderm development:
morula
what the embryo is called after formation of 16 blastomeres
echinoderm development:
what is produced after 1st cleavage?
2 blastomeres
echinoderm development:
what is produced after 2nd cleavage?
4 blastomeres
echinoderm development:
what is produced after 3rd cleavage?
8 blastomeres
echinoderm development:
what is produced after 4th cleavage?
16 blastomeres
echinoderm development:
cell division in cleavage vs. ordinary cell division
normal cell division – cells grow as they divide
cleavage – there is no cell growth w/ division –> that cell size decreases as cleavage progresses
echinoderm development:
large volume of the zygote is progressively cut up –> produces a ball of cells of ___ size
fairly normal
echinoderm development:
large volume of the zygote is progressively ___ –> produces a ball of cells of fairly normal size
cut up
echinoderm development:
eventually, the ball of cells forms a cavity, the ___, thereby becoming a ___
blastocoel
blastula
echinoderm development:
gastrulation (beginning stage)
a few cells of the vegetal plate (mesenchyme cells) detach and migrate into the interior of the embryo
echinoderm development:
primary mesenchyme cells are….
mesoderm cells that will form the skeleton of the larva that ultimately develops
echinoderm development:
gastrulation (later stage)
vegetal plate buckles inwards and extends itself into the interior of the embryo –> forms the endoderm that becomes the primitive gut (archenteron)
ectoderm is left on the outside to develop into the outer regions of the larva that is developing
echinoderm development:
echinoderm archenteron makes its way into the interior of the embryo –> curves to contact the sidewall of the gastrula and ultimately breaks thru at that point to form the ___
oral opening (mouth)
echinoderm development:
echinoderm archenteron makes its way into the interior of the embryo –> curves to contact the sidewall of the ___ and ultimately breaks thru at that point to form the oral opening (mouth)
gastrula
echinoderm development:
the ___, the original opening of the gastrula, becomes the anus of the larva that now is developing
blastopore
echinoderm development:
the blastopore, the ____ of the gastrula, becomes the anus of the larva that now is developing
original opening
echinoderm development:
echinoderms are classified as ___
deuterostomes
echinoderm development:
what is the difference b/n an oocyte and an egg?
an oocyte becomes an egg when meiosis is complete
echinoderm development:
what is the difference b/n an egg and a zygote?
an egg becomes a zygote when fertilization is complete (that is, when the haploid sperm and egg nuclei fuse to become 1 diploid nucleus)
frog/chicken development:
echinoderms develop from eggs that have ___ yolk
very little
frog/chicken development:
amphibians develop from eggs that have ___ yolk
a moderate amount of
frog/chicken development:
birds develop from eggs that have ___ yolk
huge amounts of yolk
frog/chicken development:
amount of yolk in an egg influences considerably the way….
early development progresses, particularly w/ respect to cleavage patterns and to morphogenesis
amphibian development:
amphibian eggs have considerably more yolk than ___ eggs
echinoderm
amphibian development:
yolk in amphibian eggs are ___ and ___ in the ___ than in the ___
more dense and more concentrated in the vegetal hemisphere than in the animal hemisphere
amphibian development:
in amphibians, there is an ___ of yolk
animal-vegetal polarization
amphibian development:
externally, most amphibian eggs also have a pigmented animal half and a non-pigmented vegetal half, a further manifestation of the egg’s ___
animal-vegetal polarity
amphibian development:
externally, most ___ eggs also have a ___ half and a ___ half, a further manifestation of the egg’s animal-vegetal polarity
amphibian
pigmented animal
non-pigmented vegetal
amphibian development:
after fertilization, there is a shift in the animal hemisphere pigment so that a crescent of grayish hue, the ___, is formed at what will ultimately be the dorsal region of the embryo
gray crescent
