23.2Lab #23 -- Biological Sciences 102
Animal BiologyLAB PROCEDURE
You must answer ALL questions in the lab procedure for full credit.
Finish them at home as you will not have time to complete them in lab.Your instructor will review basic vertebrate male and female reproductive structures and early embryonic development.
Refer to the notes at the end of this lab regarding this discussion.Answer the following questions on the following pages using the notes found at the end of this lab, your lab manual, textbook, instructor feedback, the Internet and collective discussions with your classmates.Clearly label the diagrams of the human male and female reproductive systems shown
23.3Lab #23 -- Biological Sciences 102
Animal BiologyHUMAN FEMALE REPRODUCTIVE SYSTEM
If asexual reproduction works well for many animals, including when they colonize new environments, then why do most metazoan animal go to the trouble and energetic cost of sexual reproduction? Animal Reproduction
23.4Lab #23 -- Biological Sciences 102
Animal BiologyPart of todays lab discussion will involve a demonstration of the process of fertilization and the formation of the fertilization membrane in sea urchins.
While the process of fertilization has been studied in many animals, the sea urchin has for decades been a model system for investigating the highly conserved process of fertilization.
Refer to the following website for further pictures and details of fertilization in sea urchins: In the space below, sketch a simple diagram of what the outer layers of the sea urchin look like before and after fertilization.
AFTER FERTILIZATION What is the purpose of the fertilization membrane?Normally (in most cases), at the molecular level, what prevents the sperm of one species from effectively fertilizing the egg of a different species? Animal Reproduction
23.5Lab #23 -- Biological Sciences 102
Animal BiologyCleavage, the earliest stage in embryonic development, consists of a succession of regular mitotic cell divisions that partition the egg into a multitude of small cells clustered together.
In lower animals, cleavage is so rapid that hundreds, sometimes thousands, of cells are produced in a matter of hours.
In animals such as sponges and cnidarians, cleavage is irregular and seemingly disorganized; egg cytoplasm is partitioned randomly into daughter cells of highly variable size and shape with no apparent relevance to future cell fates.
As the metazoa evolved, however, cleavage began to follow precise patterns and rhythms
Imagined More Than Women: Lesbians As Hermaphrodites, 1671 …
Though hermaphroditism was discussed in a wide range of texts that reached all sections of society, from court poems to pseudo-medical treatises ... Dirty pictures and (inter-disciplinary.net)
Animal Reproduction 23.1 Lab #23 -- Biological Sciences 102 ...
(true hermaphroditism in vertebrates is rare). ... ¾Refer to the following website for further pictures and details of fertilization in sea ... ¾ In humans, how do … (hawaii.edu)
Chemicals And Health - What You Need To Know
future in which humans live in harmony with ... condition termed “pseudo-hermaphroditism”. ... STILL PICTURES R CHAPMAN, WWF-UK 1631 Leaflet for pdf … (biosciweb.net)
In virtually all animal groups above the cnidarians, cleavage is regular; the egg cytoplasm is segregated into specific cells called blastomeresblastos, bud, + meros, part) occupying discrete positions and having specific developmental fates.Patterns of regular cleavage depend greatly on amount and distribution of yolk in the egg.
In eggs having a large amount of yolk, cleavage may be either complete (= holoblastic), as in amphibians, or incomplete (= meroblastic), as in birds and reptiles.
In birds and reptiles with extreme telolecithal (Gr.telos, end, + lekithos, yolk) eggs, cleavage is restricted to a small disc of cytoplasm on the animal pole; this type of cleavage is called discoidal.The eggs of most insects follow another pattern of cleavage called .
In these the nuclei divide mitotically into hundreds or thousands of "free" nuclei, which later migrate to the egg surface.Only then do cleavage furrows form, rapidly partitioning the cytoplasm into a superficial layer of cells.In most invertebrates, eggs have little yolk (= isolecithal ["equal-yolk"]), and cleavage is complete (holoblastic) and equal.
Two major kinds of holoblastic cleavage exist:
and radial (see text page 156, fig 8-7).
The first two cleavages are the same in both kinds of eggs: the cleavage planes are along the animal-vegetal axis, producing a quartet of cells.At the third cleavage, however, these two patterns-spiral and radial-can be distinguished from each other by the geometric positioning of the cells.
In radial cleavage, the third cleavage is perpendicular to the first two, yielding two quartets of cells, with the upper quartet lying directly on top of the lower.
In spiral cleavage, the third cleavage planes are oblique to the polar axis and typically produce an upper quartet of smaller cells that come to lie between the furrows of the lower quartet of larger cells.There are other important differences between these two cleavage patterns.Spiral cleavage is typically mosaic, meaning that the embryo is constructed as a mosaic, with each cell fitting into its predetermined location in the larval body.
If cells of the embryo are experimentally separated at this early stage, each cell will develop into partial or defective larvae because the developmental fate of each cell has already been determined.
Spiral cleavage is found in several phyla, including annelids, many molluscs, some flatworms, and ribbon groups showing spiral cleavage belong to the grouping of animal phyla called the Protostomia, in which the embryonic blastopore forms the mouth.
Radial cleavage is characteristically regulative because cell fate does not become fixed until after the first few cleavages.Radial cleavage is found in eggs of echinoderms and many chordates, especially protochordates, amphibians, and mammals.(As mentioned earlier, eggs of birds and reptiles, as well as many fishes, show discoidal cleavage.)
All of these belong to the Deuterostomia, a group of phyla in which the mouth is formed from a secondary embryonic opening.
23.6Lab #23 -- Biological Sciences 102
Animal BiologyDefine the foll
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