An embryonic mass of cells is used to study the stages of mitosis because, unlike most adult cells, embryonic cells are always dividing. Telophase is often associated with the beginning of cytokinesis. The cell cycle has a beginning and end, proceeding through gap 1, synthesis, gap 2, and mitosis stages, with gaps 1, 2, and synthesis making up interphase.
The science of synchronization of estrus and ovulation in females has made great strides.
Several protocols that allow producers to precisely schedule insemination of groups of females are available for fixed-time insemination in females.
Andrology lecture 16 Semen collection from male animals and its evaluationDrGovindNarayanPuroh
This lecture describes the techniques of semen collection and its evaluation. The lecture is useful for veterinary students, practitioners, semen labs, and aspirants of IAS
The science of synchronization of estrus and ovulation in females has made great strides.
Several protocols that allow producers to precisely schedule insemination of groups of females are available for fixed-time insemination in females.
Andrology lecture 16 Semen collection from male animals and its evaluationDrGovindNarayanPuroh
This lecture describes the techniques of semen collection and its evaluation. The lecture is useful for veterinary students, practitioners, semen labs, and aspirants of IAS
The biological process via which the testes, the male reproductive organs, produce sperm cells is known as spermatogenesis. It begins with the development of immature germ cells from stem cells in the seminiferous tubule walls, which grow into mature sperm cells featuring a condensed nucleus, a head, and a tail.
Meiosis is a double division which occurs in the diploid cells and give rise to four haploid cells ,each having half the number of chromosomes as compared to the parent cell.
Meiosis is the process in which a single cell divides twice to form four haploid daughter cells.
These cells are the gametes – sperms in males and egg in females.
For more details, visit @biOlOgy BINGE-insight learning
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
Key Trends Shaping the Future of Infrastructure.pdfCheryl Hung
Keynote at DIGIT West Expo, Glasgow on 29 May 2024.
Cheryl Hung, ochery.com
Sr Director, Infrastructure Ecosystem, Arm.
The key trends across hardware, cloud and open-source; exploring how these areas are likely to mature and develop over the short and long-term, and then considering how organisations can position themselves to adapt and thrive.
DevOps and Testing slides at DASA ConnectKari Kakkonen
My and Rik Marselis slides at 30.5.2024 DASA Connect conference. We discuss about what is testing, then what is agile testing and finally what is Testing in DevOps. Finally we had lovely workshop with the participants trying to find out different ways to think about quality and testing in different parts of the DevOps infinity loop.
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdfPaige Cruz
Monitoring and observability aren’t traditionally found in software curriculums and many of us cobble this knowledge together from whatever vendor or ecosystem we were first introduced to and whatever is a part of your current company’s observability stack.
While the dev and ops silo continues to crumble….many organizations still relegate monitoring & observability as the purview of ops, infra and SRE teams. This is a mistake - achieving a highly observable system requires collaboration up and down the stack.
I, a former op, would like to extend an invitation to all application developers to join the observability party will share these foundational concepts to build on:
Generative AI Deep Dive: Advancing from Proof of Concept to ProductionAggregage
Join Maher Hanafi, VP of Engineering at Betterworks, in this new session where he'll share a practical framework to transform Gen AI prototypes into impactful products! He'll delve into the complexities of data collection and management, model selection and optimization, and ensuring security, scalability, and responsible use.
Dev Dives: Train smarter, not harder – active learning and UiPath LLMs for do...UiPathCommunity
💥 Speed, accuracy, and scaling – discover the superpowers of GenAI in action with UiPath Document Understanding and Communications Mining™:
See how to accelerate model training and optimize model performance with active learning
Learn about the latest enhancements to out-of-the-box document processing – with little to no training required
Get an exclusive demo of the new family of UiPath LLMs – GenAI models specialized for processing different types of documents and messages
This is a hands-on session specifically designed for automation developers and AI enthusiasts seeking to enhance their knowledge in leveraging the latest intelligent document processing capabilities offered by UiPath.
Speakers:
👨🏫 Andras Palfi, Senior Product Manager, UiPath
👩🏫 Lenka Dulovicova, Product Program Manager, UiPath
UiPath Test Automation using UiPath Test Suite series, part 4DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 4. In this session, we will cover Test Manager overview along with SAP heatmap.
The UiPath Test Manager overview with SAP heatmap webinar offers a concise yet comprehensive exploration of the role of a Test Manager within SAP environments, coupled with the utilization of heatmaps for effective testing strategies.
Participants will gain insights into the responsibilities, challenges, and best practices associated with test management in SAP projects. Additionally, the webinar delves into the significance of heatmaps as a visual aid for identifying testing priorities, areas of risk, and resource allocation within SAP landscapes. Through this session, attendees can expect to enhance their understanding of test management principles while learning practical approaches to optimize testing processes in SAP environments using heatmap visualization techniques
What will you get from this session?
1. Insights into SAP testing best practices
2. Heatmap utilization for testing
3. Optimization of testing processes
4. Demo
Topics covered:
Execution from the test manager
Orchestrator execution result
Defect reporting
SAP heatmap example with demo
Speaker:
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
2. Why choose an embryonic
mass of cells to study the
stages of mitosis
• Unlike most cells in an
adult body, an embryonic
mass of cells is always
dividing. Most cells in the
adult body is quiescent and
will not divide unless
signals have been given to
them to divide, and many
cells such as muscle and
nerve cells have even lost
the ability to divide.
3. What stage of mitosis of
often associated with the
beginning of cytokinesis?
telophase
4. Does the cell cycle have a
beginning and an end?
• cell cycle, the ordered sequence of
events that occur in a cell in
preparation for cell division. The
cell cycle is a four-stage process in
which the cell increases in size (gap
1, or G1, stage), copies its DNA
(synthesis, or S, stage), prepares to
divide (gap 2, or G2, stage), and
divides (mitosis, or M, stage). The
stages G1, S, and G2 make up
interphase, which accounts for the
span between cell divisions. On the
basis of the stimulatory and
inhibitory messages a cell receives,
it “decides” whether or not it
should enter the cell cycle and
divide
5. •
spermatogenesis
•
•
The seminiferous tubules, in which the sperm are produced,
constitute about 90 percent of the testicular mass. In the young
male the tubules are simple and composed of undeveloped spermproducing cells (spermatogonia) and the Sertoli cells. In the older
male the tubules become branched, and spermatogonia are
changed into the fertile sperm cells after a series of transformations
called spermatogenesis. The Sertoli cells found in both young and
adult males mechanically support and protect the spermatogonia.
Each seminiferous tubule of the adult testis has a central lumen, or
cavity, which is connected to the epididymis and spermatic duct
(ductus deferens). Sperm cells originate as spermatogonia along the
walls of the seminiferous tubules. The spermatogonia mature into
spermatocytes, which mature into spermatids that mature into
spermatozoa as they move into the central lumen of the
seminiferous tubule. The spermatozoa migrate, by short
contractions of the tubule, to the mediastinum testis; they are then
transported through a complex network of canals (rete testis and
efferent ductules) to the epididymis for temporary storage. The
spermatozoa move through the epididymis and the spermatic duct
to be stored in the seminal vesicles for eventual ejaculation with
the seminal fluid. Normal men produce about one million
spermatozoa daily.
In animals that breed seasonally, such as sheep and goats, the
testes regress completely during the nonbreeding season and the
spermatogonia return to the state found in the young, sexually
immature males. Frequently in these animals the testes are drawn
back into the body cavity except in the breeding season, when they
again descend and mature; this process is known as recrudescence.
6. Spermatogenesis
• Spermatogenesis: the
process by which stem cells
develop into mature
spermatozoa. There are
three phases: (1)
Spermatocytogenesis
(Mitosis), (2) Meiosis, and
(3) Spermiogenesis
7. Spermatogenesis in the
Sexually Mature Male
• A. The gametogenic function of the
testes is to produce the male gametes
or spermatozoa. This process is termed,
spermatogenesis. The sites of
spermatozoa production are the
seminiferous tubules. The spermatozoa
originate from precursor cells that are
called spermatogonia, and these cells
line the basement membrane of the
seminiferous tubule. Spermatogenesis
can be divided into three portions:
• spermatocytogenesis -- proliferative
phase
• meiosis -- production of the haploid
gamete
• spermiogenesis -- "metamorphosis" of
spermatids into spermatozoa
8. oogenesis
• in the human female
reproductive system,
growth process in which
the primary egg cell (or
ovum) becomes a mature
ovum.
9. oogenesis
• The egg cell remains as a primary
ovum until the time for its release
from the ovary arrives. The egg
then undergoes a cell division. The
nucleus splits so that half of its
chromosomes go to one cell and
half to another. One of these two
new cells is usually larger than the
other and is known as the
secondary ovum; the smaller cell is
known as a polar body. The
secondary ovum grows in the ovary
until it reaches maturation; it then
breaks loose and is carried into the
fallopian tubes. Once in the
fallopian tubes, the secondary egg
cell is suitable for fertilization by
the male sperm cells
11. •
Stages of mitosis
•
Prior to the onset of mitosis, the chromosomes
have replicated and the proteins that will form
the mitotic spindle have been synthesized.
Mitosis begins at prophase with the thickening
and coiling of the chromosomes. The nucleolus,
a rounded structure, shrinks and disappears. The
end of prophase is marked by the beginning of
the organization of a group of fibres to form a
spindle and the disintegration of the nuclear
membrane.
The chromosomes, each of which is a double
structure consisting of duplicate chromatids, line
up along the midline of the cell at metaphase. In
anaphase each chromatid pair separates into two
identical chromosomes that are pulled to
opposite ends of the cell by the spindle fibres.
During telophase, the chromosomes begin to
decondense, the spindle breaks down, and the
nuclear membranes and nucleoli re-form. The
cytoplasm of the mother cell divides to form two
daughter cells, each containing the same number
and kind of chromosomes as the mother cell.
The stage, or phase, after the completion of
mitosis is called interphase
12. •
meiosis
•
Prior to meiosis, each of the chromosomes in the diploid
germ cell has replicated and thus consists of a joined pair
of duplicate chromatids. Meiosis begins with the
contraction of the chromosomes in the nucleus of the
diploid cell. Homologous paternal and maternal
chromosomes pair up along the midline of the cell. Each
pair of chromosomes—called a tetrad, or a bivalent—
consists of four chromatids. At this point, the homologous
chromosomes exchange genetic material by the process of
crossing over (see linkage group). The homologous pairs
then separate, each pair being pulled to opposite ends of
the cell, which then pinches in half to form two daughter
cells. Each daughter cell of this first meiotic division
contains a haploid set of chromosomes. The chromosomes
at this point still consist of duplicate chromatids.
In the second meiotic division, each haploid daughter cell
divides. There is no further reduction in chromosome
number during this division, as it involves the separation of
each chromatid pair into two chromosomes, which are
pulled to the opposite ends of the daughter cells. Each
daughter cell then divides in half, thereby producing a total
of four different haploid gametes. When two gametes
unite during fertilization, each contributes its haploid set of
chromosomes to the new individual, restoring the diploid
number
13. Rhizobium and legumes
• Rhizobium organisms in the soil
recognize and invade the root hairs
of their specific plant host, enter
the plant tissues, and form a root
nodule. This process causes the
bacteria to lose many of their freeliving characteristics. They become
dependent upon the carbon
supplied by the plant, and, in
exchange for carbon, they convert
nitrogen gas to ammonia, which is
used by the plant for its protein
synthesis and growth. In addition,
many bacteria can convert nitrate
to amines for purposes of
synthesizing cellular materials or to
ammonia when nitrate is used as
electron acceptor
14. rhizobidium
• Nitrogen Fixation by Legumes
• Legume nitrogen fixation starts with the
formation of a nodule. A common soil
bacterium, Rhizobium, invades the root
and multiplies within the cortex cells.
The plant supplies all the necessary
nutrients and energy for the bacteria.
Within a week after infection, small
nodules are visible with the naked eye.
In the field, small nodules can be seen
2-3 weeks after planting, depending on
legume species and germination
conditions. When nodules are young
and not yet fixing nitrogen, they are
usually white or grey inside. As nodules
grow in size they gradually turn pink or
reddish in color, indicating nitrogen
fixation has started. The pink or red
color is caused by leghemoglobin
(similar to hemoglobin in blood) that
controls oxygen flow to the bacteria.
15. •
•
Steps of Gram stain
•
•
•
Lab 6: Gram Stain
1. The bacteria are first stained with the basic
dye crystal violet. Both Gram-positive and Gramnegative bacteria become directly stained and
appear purple after this step.
2. The bacteria are then treated with Gram's
iodine solution. This allows the stain to be
retained better by forming an insoluble crystal
violet-iodine complex. Both Gram-positive and
Gram-negative bacteria remain purple after this
step.
3. Gram's decolorizer, a mixture of ethyl alcohol
and acetone, is then added. This is the
differential step. Gram-positive bacteria retain
the crystal violet-iodine complex while Gramnegative are decolorized.
4. Finally, the counterstain safranin (also a basic
dye) is applied. Since the Gram-positive bacteria
are already stained purple, they are not affected
by the counterstain. Gram-negative bacteria,
which are now colorless, become directly stained
by th e safranin. Thus, Gram-positive appear
purple, and Gram-negative appear pink.
16. What happens when milk
is pasteurized?
• heat-treatment process that
destroys pathogenic
microorganisms in certain foods
and be
• The times and temperatures are
those determined to be
necessary to destroy the
Mycobacterium tuberculosis and
other more heat-resistant of the
non-spore-forming, diseasecausing microorganisms found in
milk. The treatment also
destroys most of the
microorganisms that cause
spoilage and so prolongs the
storage time of food.verages.
17. • Pasteurization
• Pasteurization is most important
in all dairy processing. It is the
biological safeguard which
ensures that all potential
pathogens are destroyed.
Extensive studies have
determined that heating milk to
63° C (145° F) for 30 minutes or
72° C (161° F) for 15 seconds kills
the most resistant harmful
bacteria. In actual practice these
temperatures and times are
exceeded, thereby not only
ensuring safety but also
extending shelf life.
18. antibiotics
• chemical substance produced by a living
organism, generally a microorganism, that is
detrimental to other microorganisms.
• Antibiotics produce their effects through a
variety of mechanisms of action. A large
number work by inhibiting bacterial cell wall
synthesis; these agents are referred to
generally as β-lactam antibiotics. Production
of the bacterial cell wall involves the partial
assembly of wall components inside the
cell, transport of these structures through
the cell membrane to the growing wall,
assembly into the wall, and finally crosslinking of the strands of wall material.
Antibiotics that inhibit the synthesis of the
cell wall have a specific effect on one or
another phase. The result is an alteration in
the cell wall and shape of the organism and
eventually the death of the bacterium.
19. antibiotics
• Unlike bacteria, viruses
mimic the metabolic
functions of their host cells.
Antibiotics are not effective
against viruses.
22. How can you tell whether
Rhizopus is reproducing
sexually or asexually?
Fungi - Biology
• Rhizopus stolonifer (bread
mold) is a zygomycete.
• Asexual reproduction in
Rhizopus: Sporangia – note
the root like hyphae
(rhizoids) and horizontallygrowing hyphae (stolons)
at the base
• Sexual reproduction in
Rhizopus: hyphae meeting
(far left) and making a
zygospore (far right).
23. Rhizopus:
Asexual reproduction in Rhizopus:
Sporangia – note the root like hyphae
(rhizoids) and horizontally-growing
hyphae (stolons) at the base
24. Describe the relationship
found in lichen.
Lichens
• lichen is not a single
organism the way most
other living things are, but
rather it is a combination of
two organisms which live
together intimately.
25. Describe the relationship
found in lichen.
Lichens
• Most of the lichen is
composed of fungal
filaments, but living among
the filaments are algal cells,
usually from a green alga or
a cyanobacterium
26. Describe the relationship
found in lichen.
Life History and Ecology of Lichens
• Lichens are formed from a
combination of a fungal
partner (mycobiont) and an
algal partner (phycobiont).
• A lichen may absorb certain
mineral nutrients from any of
these substrates on which it
grows, but is generally selfreliant in feeding itself
through photosynthesis in
the algal cells.
27. Describe the relationship
found in lichen.
Life History and Ecology of Lichens
• Lichens growing in trees
are simply using the tree
as a home. Lichens growing
on rocks, though, may
release chemicals which
speed the degradation of
the rock into soil, and thus
promote production of new
soils.
28. Fungi: Benefits
Symbiotic Fungi
• Lichens are symbioses
involving fungi and
unicellular algae
• Mycorrhizae are symbioses
involving fungi and the
roots of plants
Multiclavula mucida, a lichenized basidiomycete (left) and Parmelia sp., a lichenized ascomycete (right)
29. The only distinction
between a fungi spore and
gamete is function
• Following a period of intensive growth,
fungi enter a reproductive phase by
forming and releasing vast quantities of
spores. Spores are usually single cells
produced by fragmentation of the
mycelium or within specialized
structures (sporangia, gametangia,
sporophores, etc.). Spores may be
produced either directly by asexual
methods or indirectly by sexual
reproduction. Sexual reproduction in
fungi, as in other living organisms,
involves the fusion of two nuclei that
are brought together when two sex
cells (gametes) unite. Asexual
reproduction, which is simpler and
more direct, may be accomplished by
various methods.
Editor's Notes
cell cycle, the ordered sequence of events that occur in a cell in preparation for cell division. The cell cycle is a four-stage process in which the cell increases in size (gap 1, or G1, stage), copies its DNA (synthesis, or S, stage), prepares to divide (gap 2, or G2, stage), and divides (mitosis, or M, stage). The stages G1, S, and G2 make up interphase, which accounts for the span between cell divisions. On the basis of the stimulatory and inhibitory messages a cell receives, it “decides” whether or not it should enter the cell cycle and divide
The seminiferous tubules, in which the sperm are produced, constitute about 90 percent of the testicular mass. In the young male the tubules are simple and composed of undeveloped sperm-producing cells (spermatogonia) and the Sertoli cells. In the older male the tubules become branched, and spermatogonia are changed into the fertile sperm cells after a series of transformations called spermatogenesis. The Sertoli cells found in both young and adult males mechanically support and protect the spermatogonia. Each seminiferous tubule of the adult testis has a central lumen, or cavity, which is connected to the epididymis and spermatic duct (ductus deferens). Sperm cells originate as spermatogonia along the walls of the seminiferous tubules. The spermatogonia mature into spermatocytes, which mature into spermatids that mature into spermatozoa as they move into the central lumen of the seminiferous tubule. The spermatozoa migrate, by short contractions of the tubule, to the mediastinum testis; they are then transported through a complex network of canals (rete testis and efferent ductules) to the epididymis for temporary storage. The spermatozoa move through the epididymis and the spermatic duct to be stored in the seminal vesicles for eventual ejaculation with the seminal fluid. Normal men produce about one million spermatozoa daily. In animals that breed seasonally, such as sheep and goats, the testes regress completely during the nonbreeding season and the spermatogonia return to the state found in the young, sexually immature males. Frequently in these animals the testes are drawn back into the body cavity except in the breeding season, when they again descend and mature; this process is known as recrudescence.
Spermatocytogenesis(also called Mitosis): Stem cells (Type A spermatogonia; singular = spermatogonium) divide mitotically to replace themselves and to produce cells that begin differentiation (Type B spermatogonia). Spermatogonia have spherical or oval nuclei, and rest on the basement membrane. (You are not responsible for distinguishing between Type A and Type B spermatogonia in lab.) Meiosis: Cells in prophase of the first meiotic division are primary spermatocytes. They are characterized by highly condensed chromosomes giving the nucleus a coarse chromatin pattern and an intermediate position in the seminiferous epithelium. This is a long stage, so many primary spermatocytes can be seen. Primary spermatocytes go through the first meiotic division and become secondary spermatocytes. The cells quickly proceed through this stage and complete the second meiotic division. Because this stage is short there are few secondary spermatocytes to be seen in sections. You are not responsible for identifying secondary spermatocytes in lab. Meiosis is the process by which the diploid number of chromosomes present in spermatogonia (the stem cells) is reduced to the haploid number present in mature spermatozoa.The products of the second meiotic division are called spermatids. They are spherical cells with interphase nuclei, positioned high in the epithelium. Since spermatids go through a metamorphosis into spermatozoa, they occur in early through late stages. You are not responsible for distinguishing the different stages of spermatids, but you are required to identify a spermatid.All of these progeny cells remain attached to each other by cytoplasmic bridges. The bridges remain until sperm are fully differentiated.Spermiogenesis: This is the metamorphosis of spherical spermatids into elongated spermatozoa. No further mitosis or meiosis occurs. During spermiogenesis, the acrosome forms, the flagellar apparatus forms, and most excess cytoplasm (the residual body) is separated and left in the Sertoli cell. Spermatozoa are released into the lumen of the seminiferous tubule. A small amount of excess cytoplasm (the cytoplasmic droplet) is shed later in the epididymis. Spermiogenesis: a process of metamorphosis from a round cell with typical organelles to a highly specialized, elongated cell well adapted for traversing the male and female reproductive tracts and achieving fertilization of an egg.Sertoli Cell & Developing Sperm Cells: an interactionThe Interaction At all stages of differentiation, the spermatogenic cells are in close contact with Sertoli cells which are thought to provide structural and metabolic support to the developing sperm cells. A single Sertoli cell extends from the basement membrane to the lumen of the seminiferous tubule although its cytoplasm is difficult to distinguish at the light microscopic level. They are characterized by the presence of a vesicular, oval, basally positioned nucleus which contains a prominent nucleolus. The nuclear envelope often contains a definite fold. The significance of the very close association of the two types of cells is unknown. Sertoli cells are endocrine cells - they secrete the polypeptide hormone, inhibin. Inhibin acts at the level of the pituitary to reduce the secretion of follicle stimulating hormone.
A. The gametogenic function of the testes is to produce the male gametes or spermatozoa. This process is termed, spermatogenesis. The sites of spermatozoa production are the seminiferous tubules. The spermatozoa originate from precursor cells that are called spermatogonia, and these cells line the basement membrane of the seminiferous tubule. Spermatogenesis can be divided into three portions:spermatocytogenesis -- proliferative phase meiosis -- production of the haploid gamete spermiogenesis -- "metamorphosis" of spermatids into spermatozoaDiscussion of spermatogenesis will be based on the adult male mammal that is a continuous breeder. The stages are outlined in Figure 2. B. Spermatocytogenesis and Meiosis This phase begins with the division of the spermatogonia, that line the seminiferous tubule, near the basement membrane. Spermatogonia originate at puberty by the proliferation of the gonocytesand are the descendants of the primordial germ cells. One or two divisions of spermatogonia occur to maintain their population in a stem cell pool. Of the cells resulting from these mitotic divisions, some spermatogonia stay in the "resting" pool, while the remaining type A spermatogonia proliferate several times and undergo 1 to 5 stages of division and differentiation. After the last division, the resulting cells are termed primary spermatocytes and this ends spermatocytogenesis. The primary spermatocytes then undergo the first of the two division that constitute meiosis. The first meiotic division produces two secondary spermatocytes. Division of the secondary spermatocytes completes meiosis and produces the spermatids (Figure 2). 2. The "resting" or stem cell spermatogonia remain dormant for a time and then join a new proliferation of spermatogonia. Since this new wave of spermatogonial divisions does not wait for the previous generation of cells to complete spermatogenesis, the result are an overlapping of generations in any one area of the seminiferous tubules. The purpose of this phenomena is to ensure a residual population of spermatogonia, without which the testis would exhaust its ability to produce sperm. The time required for one spermatogonium to divide and form spermatozoa requires about 4.5 to 5 times that time span between divisions of the stem cell spermatogonial. C. SpermiogenesisThis part of spermatogenesis is defined as the nuclear and cytoplasmic changes in the spermatid that results in the spermatozoa. Some aspects of the restructuring of the cell are: condensation of nuclear material formation of the acrosome formation of tail structures mitochondrial spiral formation removal of extraneous cytoplasm. The process of spermiogenesis ends in the testis with release of the spermatozoa from the Sertoli cell. The spermatozoa has been embedded up until now in the Sertoli cell. The process by which spermatozoa are shed into the lumen of the seminiferous tubule for transport out of the testis is spermiation. The overall results of spermatogenesis is: cell proliferation maintenance of a reserve germ cell population reduction in chromosome number genetic variation through meiosis shaping of the spermatid into the spermatozoa
1. Early in embryogenesis, primordial germ cells migrate from the yolk sac endoderm to the genital ridge (developing ovary) where they take up residence and are called oogonia. 2.These diploid oogonia undergo several mitotic divisions prior to or shortly after parturition, thus providing the developing ovary with a large supply of future ova (eggs). 3. When oogonia begin the first meiotic division, they are called primary oocytes.4. Primary oocytes are arrested in prophase of Meiosis I until the female reaches sexual maturity. They grow in size during this arrested phase, but do not divide. A human female is born with about 2 million primary oocytes in her ovaries, but by the time of puberty only about 400,000 are left due to atresia (degeneration).. When the female reaches sexual maturity and under the influence of follicle stimulating hormone (FSH), a small number of primary oocytes are stimulated to continue through Meiosis I.6.During this process the number of chromosomes is reduced from the diploid number (2N) to the haploid number (1N). 7. This division is uneven in that although the chromosomes are divided equally, most of the cytoplasm stays with the oocyte. The smaller polar body contains half the chromosomes but only a small amount of cytoplasm and will eventually degenerate. 8.After a primary oocyte completes the first meiotic division, it is called a secondary oocyte (1N). In most species Meiosis I is completed just before ovulation (release of the ovum from the ovary). However, in horses and dogs Meiosis I is completed after ovulation. 9. If a secondary oocyte is not penetrated by a sperm, it will degenerate. 10. If fertilization and pregnancy do not occur, a new cycle will begin in which FSH from the pituitary gland will stimulate a few more primary oocytes to continue through Meiosis I. 11. The process is the same as previously described and a secondary oocyte is formed.12. However, some of the time a sperm will penetrate the zonapellucida and the secondary oocyte is stimulated to continue through Meiosis II, forming a second polar body and a mature ovum (1N). Again, the polar body contains half of the chromosome material, but little cytoplasm, and it eventually degenerates. 13. After a sperm enters the cytoplasm of the ovum, two pronuclei form, containing genetic material from the ovum or the sperm. 14.Fertilization is complete when the two pronuclei fuse and restore the diploid chromosome number. 15. If fertilization is completed, the zygote undergoes several mitotic changes to become an embryo; otherwise it degenerates.
"antibiotic." Encyclopaedia Britannica. Encyclopaedia Britannica Online Academic Edition. Encyclopædia Britannica Inc., 2013. Web. 26 Nov. 2013. <http://www.britannica.com/EBchecked/topic/27751/antibiotic>.
Question: is this a complete answer?
Sexual reproduction in Rhizopus: hyphae meeting (far left) and making a zygospore (far right).
Spores may be produced either directly by asexual methods or indirectly by sexual reproduction. Sexual reproduction in fungi, as in other living organisms, involves the fusion of two nuclei that are brought together when two sex cells (gametes) unite.