Chapter 39 Flashcards
What is a zygote?
The first cell of a new individual formed by the fusion of one gamete from each parent.
Give a short description of the genetic basis of sexual reproduction.
Meiosis and the formation of gametes typically occur in two prospective parents. At fertilization, a gamete from one parent fuses with a gamete from the other and forms the first cell of the new individual—the zygote.
Give a short description of asexual reproduction.
A single organism produces its own offspring. In asexual reproduction, one parents has all its genes represented in its offspring.
Is sexual or asexual reproduction better for an environment that does not vary over time?
Asexual reproduction is better, as the gene combinations that allowed the parent to reproduce can be expected to do the same for their offspring.
Why is sexual reproduction good for environments that change over time?
Every individual inherits a different combination of parental genes, increasing the odds that some offspring will have a gene combination that suits the changing environment.
Why is sexual reproduction costly?
Only half of a parent’s genes end up in the offspring; resources and energy must be allocated to forming gametes. Timing of gamete formation must be synchronized between partners, and there has to be a partner.
Why does sexual reproduction require timing?
Sperm in one individual must mature at the same time as eggs of another individual.
What is internal fertilization?
The union of sperm and egg within the female body.
What is yolk?
A thick fluid that contains proteins and lipids that nourishes the embryo until it can feed.
How are humans nourished in embryo?
Through a nearly yolk-less, fertilized egg and through physical changes in the mother’s bloodstream.
True or False: Separation into male and female sexes requires special reproductive cells and structures, and neural and hormonal control mechanisms.
True. They also require “forms of behaviour”, whatever the heck that means.
What are the six stages of animal reproduction and development?
- Gamete Formation2. Fertilization3. Cleavage4. Gastrulation5. Organ Formation6. Growth, Tissue Specialization
Describe the stage Gamete Formation.
Eggs form and mature in female reproductive organs. Sperm form and mature in male reproductive organs.
Describe the stage Fertilization.
A sperm penetrates an egg. Their nuclei fuse, and a zygote is formed.
Describe the stage Cleavage.
Mitotic cell divisions form a ball of cells called a blastula. Each cell gets regionally different parts of the egg cytoplasm.
Define Blastula.
A ball of cells that enclose a cavity (blastocoel) filled with their own secretions.
Describe the stage Gastrulation.
Cells self-organize as an early embryo (a gastrula) that has two or three primary tissue layers, which make the germ layers of a new individual.
Define Gastrula.
An early embryo.
What are Germ Layers?
The forerunners of the adult animals’s tissues and organs.
What are the Germ Layers of the Gastrula?
The Ectoderm, Endoderm, and Mesoderm.
What is the Ectoderm?
The outer germ layer. It forms first, and gives rise to nervous tissue and to the outer layer of skin or other body covering.
What is the Endoderm?
The inner germ layer, it is the tart of the respiratory tract and gut linings.
What is the Mesoderm?
In most kinds of animals, the mesoderm forms between the ectoderm and the endoderm. This layer is the source of all muscles, connective tissues, and the circulatory system.
Describe the stage Organ Formation.
Details of the body plan fill in as different cell types interact and form tissues and organs in predictable patterns.
Describe the stage Growth, Tissue Specialization.
The final stage of animal development, the tissues and organs grow in size and slowly begin to take on their final sizes, shapes, proportions, and functions.
What does sperm consist of?
Parental DNA and a bit of equipment that helps in swim to and penetrate an egg.
What is an oocyte?
An immature egg that has far more cytoplasm compared to the sperm. The cytoplasm has yolk proteins that will nourish a new embryo, mRNA transcripts for proteins that will by translated in early development, tRNAs and ribosomes to translate the mRNA transcripts, and proteins required to build mitotic spindles.
What is cytoplasmic localization?
When certain components are not distributed all through the egg cytoplasm, they are localized in one particular region or another. It helps guide development.
What is cytoplasmic localization a feature in all of?
Oocytes (immature egg).
What does cytoplasmic localization give rise to?
It gives rise to the polarity that characterizes all animal eggs.
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?
200.
Define Genome.
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.
Define Morphogenesis.
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?
- 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?
- 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.
Define Puberty.
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.
Where is mature sperm propelled in a sexually aroused male?
Into the Vasa Deferentia, a pair of thick-walled ducts. It continues into paired ejaculatory ducts and then into the urethra, through the penis and out at the tip.
What is Semen?
A thickened fluid that gets expelled from the penis during sexual activity, made by sperm mixing with glandular secretions while travelling to the urethra.
What does sperm use as an energy source?
Fructose, making most of semen a fructose-rich fluid.
What are prostaglandins?
Local signalling molecules that can increase the growth rate of cervical and uterine cancers that is secreted into semen.
What are the reproductive organs in males? (5)
- Testes (2) - sperm, sex hormone production2. Epididymis (2) - sperm maturation site and subsequent storage3. Vas Deferens (2) - rapid transport of sperm4. Ejaculatory Ducts (2) - conduction of sperm to penis5. Penis - organ of sexual intercourse
What are the accessory glands in males? (3)
- Seminal Vesicle (2) - secretion of large part of semen2. Prostate gland - secretion of part of semen3. Bulbourethral gland (2) - production of mucus that function in lubrication
What is the pH of vaginal fluid and at what pH does sperm swim most efficiently?
The pH of vaginal fluid is about 3.5-4.0. Sperm swims more efficiently at 6.0
Does prostate cancer have a genetic factor?
Yes, having a father of brother with prostate cancer doubles the risk.
What “increase of” do doctors look for in blood tests for prostate cancer?
They look for increases of prostate-specific antigen (PSA).