Flashcards in [Chapter 39] Reproduction Deck (172)
What pole has most of the yolk in a yolk-rich egg?
The vegetal pole has most of the yolk and the animal pole has little.
In amphibian eggs, at what pole is pigment most concentrated?
Close to the animal pole.
True or False: Cleavage puts different parts of the egg cytoplasm into the same blastomeres.
False, cleavage puts different parts of the egg cytoplasm into different blastomeres.
True or False: The amount of yolk influences the pattern of cleavage division.
True, large volumes of yolk can slow or block the cuts that lead to division while in nearly yolk-less eggs the cuts slice straight through.
At what stage do cells start to migrate around and rearrange themselves?
They start to move at gastrulation. A portion at the embryo's surface will move inward.
What initiates gastrulation?
Signals from the cell of the dorsal lip.
True or False: Cleavage divides a fertilized egg into a number of small cells, increasing the original volume.
False. The division into multiple cells does not increase the original volume.
Define Selective Gene Expression.
When different cell lineage express different subsets of genes.
Define Cell Differentiation.
The process by which cell lineage becomes specialized in composition, structure, and function.
About how many differentiated cell types does an adult human body have?
The complete genetic material of an organism.
Does a differentiated cell still retain the entire genome?
Yes, making it possible to make a genetic copy (a clone) of an adult animal from one of its differentiated cells.
What are Morphogens?
Molecular signals that are encoded by master genes.
What is Embryonic Induction?
When embryonic cells produce signals that alter the behaviour of neighbouring cells.
True or False: Intercellular signals can encourage differentiation.
True. Example: secretion of morphogens in embryonic cells.
The process by which the tissues and organs form.
What happens to the body during morphogenesis?
The body begins to take shape as cells migrate, with entire sheets of tissue folding and bending, and with specific cells dying on cue.
What three main steps occur during morphogenesis?
1. Cells migrate to specific locations.2. Sheets of cells expand and fold as cells change in shape. This is caused by the controlled assembly and disassembly of microtubules and microfilaments.3. Programmed cell death helps sculpt body parts.
What is the process Apoptosis?
The programmed cell death hat helps sculpt body parts. Signals from certain cells activate the tools of self-destruction in target cells.
What is Pattern Formation?
The process by which certain body parts form in a specific place.
What does the tissue Apical Ectodermal Ridge (AER) stimulate to develop?
AER stimulates the mesoderm to develop, but earlier positional cues have already determined what the mesoderm will become.
What are Homeotic Genes?
Genes that regulate development of specific body parts. All animals have similar homeotic genes.
What three constraints influence body plans?
1. Physical constraints (ex. surface-to-volume ratio)2. Architectural constraints (as imposed by the body axes)3. Phyletic (evolutionary) constraints
What imposes the constraints on the body plan?
The constraints are imposed by interactions among genes that regulate development in a lineage.
True or False: Mutations led to a variety of forms among animal lineages by creating new genetic trails.
False. Mutations led to a variation of animal forms by modifying existing developmental pathways.
Human gametes form in primary reproductive organs (gonads). What are theres in males and what do they produce and secrete?
There are a pair of gonads in males called testes that produce sperm and secrete the sex hormone testosterone.
The stage of development when reproductive organs mature.
What is the first pair of coiled ducts that immature sperm travels through?
The epididymis, where secretions from glands in the walls will trigger events that put the finishing touches on sperm cells. The last part of the epididymis stores mature sperm.
How much sperm is matured per day and where do the unused sperm go?
100 million sperm is matured everyday, and unused sperm is resorbed or passed in urine.