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BIOL 3012 > 47 Chapter > Flashcards

47 Chapter Flashcards

1
Q

Model organisms

A

Species chosen for the ease with which they can be studied in the laboratory.

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2
Q

Fertilization

A

The formation of a diploid zygote from a haploid egg and sperm.

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3
Q

General events that occur during fertilization

A

First, sperm dissolve or penetrate any protective layer surrounding the egg to reach the plasma membrane. Next, molecules on the sperm surface bind to receptors on the egg surface, helping ensure that fertilization involves a sperm and egg of the same species. Finally, changes at the surface of the egg prevent polyspermy, a condition in which multiple sperm nuclei enter the egg, fatally disrupting development.

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4
Q

The cell surface events that take place during fertilization have been studied most extensively in sea urchins.

A

True

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5
Q

Acrosome

A

A vesicle in the tip of a sperm containing hydrolytic enzymes and other proteins that help the sperm reach the egg.

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6
Q

Acrosomal reaction

A

The discharge of hydrolytic enzymes from the acrosome when the sperm approaches or contacts an egg.

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7
Q

Fast block to polyspermy

A

The depolarization of the egg in plasma membrane that begins within 1-3 seconds after a sperm binds to an egg membrane protein. The depolarization lasts about 1 minute and prevents additional sperm from fusing with the egg during that time.

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8
Q

Slow block to polyspermy

A

The formation of the fertilization envelope and other changes in an egg’s surface that prevent fusion of the egg with more than one sperm. The slow block begins about 1 minute after fertilization.

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9
Q

Cortical reaction

A

Cortical granules, in the cortex of the egg cytoplasm, lifts the vitelline layer away from the egg and hardens the layer into a protective fertilization envelope. Additional enzymes clip off and release the external portions of the remaining receptor proteins, along with any attached sperm.

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10
Q

Formation of the fertilization envelope requires a high concentration of Ca 2+ in the egg. Why?

A

First, the binding of the sperm to the egg activates a signal transduction pathway that triggers release of Ca2+ into the cytosol from the endoplasmic reticulum. The resulting increase in Ca2+ levels causes cortical granules to fuse with the plasma membrane.

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11
Q

Fertilization initiates and speeds up metabolic reactions that trigger the onset of embryonic development, “activating” the egg. There is, for example, a marked increase in the rates of cellular respiration and protein synthesis in the egg following fertilization.

A

True

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12
Q

What marks the end of the fertilization stage?

A

The first cell division

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13
Q

Zona pellucida

A

The extracellular matrix surrounding a mammalian egg.

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14
Q

No fast block to polyspermy has been identified in mammals.

A

True

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15
Q

Overall, the process of fertilization is much slower in mammals than in sea urchins: the first cell division occurs within 12-36 hours after sperm binding in mammals, compared with about 90 minutes in sea urchins. This cell division marks the end of fertilization and the beginning of the next stage of development, cleavage.

A

True

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16
Q

Cleavage

A

The succession of rapid cell divisions without significant growth during early embryonic development that converts the zygote to a ball of cells.

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17
Q

Blastomeres

A

An early embryonic cell arising during the cleavage stage of an early embryo.

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18
Q

Blastula

A

A hollow ball of cells that marks the end of the cleavage stage during early embryonic development in animals. Consists of the first five to seven cleavage divisions.

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19
Q

Blastocoel

A

The fluid-filled cavity that forms in the center of a blastula.

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20
Q

Yolk

A

Nutrients stored in an egg.

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21
Q

In frogs (and many other animals), cleavage is asymmetric, reflecting the asymmetric distribution of yolk across the egg.

A

True

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22
Q

Vegetal pole

A

The point at the end of an egg in the hemisphere where most yolk is concentrated; the opposite of animal pole.

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23
Q

Animal pole

A

The point at the end of an egg in the hemisphere where the least yolk is concentrated; opposite of vegetal pole.

24
Q

Cleavage furrow

A

An indentation that forms in the cell surface as cytokinesis divides the cell in half.

25
Q

Holoblastic

A

Referring to a type of cleavage in which there is complete division of the egg; occurs in eggs that have little yolk or a moderate amount of yolk (such as those of the frog)

26
Q

Meroblastic

A

Referring to a type of cleavage in which there is incomplete division of a yolk-rich egg, characteristic of avian development.

27
Q

Morphogensis

A

The development of the form of an organism and its structures.

28
Q

Gastrulation

A

In animal development, a series of cell and tissue movements in which the blastula-stage embryo folds inward, producing a three-layered embryo, the gastrula.

29
Q

Organogenesis

A

The formation of organs.

30
Q

Gastrula

A

An embryonic stage in animal development encompassing the formation of three layers: ectoderm, mesodermal, and endoderm.

31
Q

The cell layers produced in gastrulation are collectively called the ______________________.

A

Embryonic germ layers

32
Q

Ectoderm

A

The outermost of the three primary germ layers in animal embryos; gives rise to the outer covering and, in some phyla, the nervous system, inner ear, and lens of the eye.

33
Q

Endoderm

A

The innermost of the three primary germ layers in animal embryos; lines the archenteron and gives rise to the liver, pancreas, lungs, and the lining of the digestive tract in species that have these structures.

34
Q

Diploblasts

A

Are organisms that only develop an ectoderm and an endoderm during gastrulation.
-Include cnidarians

35
Q

Mesoderm

A

The middle primary germ layer in a triphoblastic animal embryo; develops into the notochord, the lining of the coelom, muscles, skeleton, gonads, kidneys, and most of the circulatory system in species that have these structures.

36
Q

Invagination

A

The infolding of a sheet of cells into the embryo.

37
Q

Archenteron

A

The endoderm-lined cavity, formed during gastrulation, that develops into the digestive tract of an animal.

38
Q

Blastospore

A

In a gastrula, the opening of the archenteron that typically develops into the anus in deuterostomes and the mouth in protostomes.

39
Q

Deuterostomes

A

Are animals in which the mouth develops from the second opening of the embryo, not the blastospore.

40
Q

Protostomes

A

Are animals in which the mouth develops from the first opening formed during gastrulation.

41
Q

Dorsal lip

A

The region above the blastospore on the dorsal side of the amphibian embryo.

42
Q

Primitive streak

A

A thickening along the future posterior-anterior axis on the surface of an early avian or mammalian embryo, caused by a piling up of cells as they congregate at the midline before moving into the embryo.

43
Q

The starting point for gastrulation in chicks is an embryo consisting of upper and lower layers— known as the ____________________—lying atop a yolk mass

A

Epiblast and hypoblast

44
Q

All the cells that will form the chick embryo come from the __________

A

Epiblast

45
Q

Blastocyst

A

The blastula stage of mammalian embryonic development, consisting of an inner cell mass, a cavity, and an outer layer, the trophoblast. In humans, blastocyst forms 1 week after fertilization.

46
Q

Inner cell mass

A

An inner cluster of cells at one end of a mammalian blastocyst that subsequently develops into the embryo proper and some of the extraembryonic membranes.

47
Q

Trophoblast

A

The outer epithelium of the blastocyst

48
Q

Embryo Implantation

A

The stage in embryo development when the fertilized egg attaches to the uterine wall.

49
Q

Embryo implantation is initiated by _______________. How?

A

The trophoblast secretes enzymes during implantation which breaks down molecules of the endometrium, allowing invasion by the blastocyst.

50
Q

Around the time the embryo undergoes implantation, the inner cell mass of the blastocyst…

A

Forms a flat disk with an inner layer of cells, the epiblast, and an outer layer, the hypoblast.

51
Q

As is true for a bird embryo, the human embryo develops almost entirely from epiblast cells.

A

True

52
Q

Extraembryonic membrane

A

One of four membranes located outside the embryo that support the developing embryo in reptiles and mammals.

53
Q

Four embryonic membranes

A

Yolk sac
Amnion
Chorion
Allantois

54
Q

As implantation is completed, gastrulation begins.

A

True

55
Q

Cells that contribute to the formation of the placenta

A

Cells of the invading trophoblast, the epiblast, and the adjacent endometrial tissue all contribute to the formation of the placenta.

56
Q

Amniote

A

A member of a clade of tetrapods named for a key derived character, the amniotic egg, which contains specialized membranes, including the fluid-filled amnion, that protects the embryo. Amniotes include mammals as well as birds and other reptiles.

BIOL 3012 (14 decks)

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