Review Sheet #2 B Test 3                 Biology 1108                     Dr. Adams

Reproductive Systems

Asexual Reproduction B Mitosis; produces individuals that are genetically identical (clones)
        Problem with this is with environmental change and extinction.

Sexual Reproduction B Involves fusion of two gametes (fertilization/syngamy) from separate (usually; some exceptions in plants) individuals to form a zygote. Costs are several (more energy in finding mates, potential loss of gametes, exposure to predation, etc.) but the advantage is the generation of variation. Almost any organism has shown at least some ability to reproduce sexually under certain conditions (i.e., stress).

External fertilization B In all species, at least one gamete (typically the sperm) must swim (typically to the egg cell). For external fertilization to be possible, must take place in water. Does not require an external copulatory organ; does require soft-shelled eggs to allow penetration of sperm. Potential for loss of gametes is great, and soft-shelled eggs more open to predation, etc.

Internal fertilization B Requires development of some method of delivery (often a copulatory organ [penis]). Fewer gametes, particularly eggs, need be produced because the individuals are more protected (by hard-shelled eggs, often with some parental care, or by carrying the developing embryo inside the mother [mammals]).

Gametogenesis B Meiosis
        You will need to have a semblance of an idea as to what happens during meiosis B two divisions
                with the first being the reduction division.

I.  Spermatogenesis B each meiotic division in males results in four fully functional haploid sperm, each of which consists of a head (with acrosome and nucleus), midpiece with mitochondria), and tail. Goes through series of divisions from spermatogonium (2N), through primary spermatocyte (2N), through secondary spermatocyte (1N), through spermatids to the very streamlined sperm (sperm are cheap!).

Hormonal control:

  1. LH stimulates interstitial cells to release testosterone.
  2. FSH, along with testosterone released by interstitial cells, stimulate seminiferous tubules to produce sperm

II.  Oogenesis B each meiotic division results in one fully functional haploid egg (ovum) and three polar bodies (non-functional). Goes through series of divisions from oogonium (2N), through primary oocyte (2N), through secondary oocyte (1N [ovulated) to ovum (actually only completed after fertilization).

Hormonal control: two organs cycle, the ovary (which releases hormones to control the) uterus

  1. Ovarian Cycle (controlled by FSH and LH from Ant. Pit.). At beginning of cycle, FSH increases and stimulates follicle development (egg from primary oocyte to secondary oocyte). Follicle cells release estrogen which generates negative feedback to hypothal./ant.pit. (reduces FSH so no more follicles develop). Estrogen reaches a critical level, however, and exerts positive feedback on hypothal./ant.pit. so that there is a spike of LH release. Promotes ovulation (release of sec. oocyte and Anurse@ cells) and change of follicle cells into corpus luteum, which produces progesterone. With no implantation, progesterone exerts negative feedback on hypothal./ant.pit.; with reduced LH, corpus luteum atrophies.
  2. Uterine cycle B estrogen from ovary promotes proliferative phase of endometrium; this continues until corpus luteum (in ovary) releases progesterone which matures endometrium (enters secretory phase -- ready for implantation). With no implantation, degeneration of corpus luteum means progesterone production ceases; progesterone is necessary to maintain the developed lining, which means at this point the lining will be lost.

Be sure you know the structures and function thereof of both the male and female human reproductive systems, as presented on the handout for the lab practical.

Secondary sexual characteristics and events at puberty
    Hypothalamus and Anterior Pituitary become less sensitive to target gland hormones at puberty B  
        exact mechanism is unknown.

Events of Sexual Response

Development B mainly in chordates

    Fertilization leads to zygote B said to be totipotent (see chapter 16)
                in humans, typically occurs in upper one third of Fallopian Tubes
            Prevention of polyspermy (fast block and slow block [cortical reaction])
Cleavage in zygote and early pre-embryo; differentiation and determination
         Yolk formation (animal and vegetal poles)
    Blastulation B blastula and blastocoel; blastodisc in organisms with copious yolk (as well as in mammals)
    Gastrulation B gastrula and blastopore, formation of archenteron (gut lumen) and coelom         
(actual body cavity for organs in adult in some); in some animals (cnidarians), development 
                essentially Astops@ here
            Know what the terms Protostome and Deuterostome mean, and examples of each
            Main event -- development of the primary tissue (germ) layers: ectoderm, mesoderm, and 
. KNOW derivatives (Table 49-1, page 1081; I will add some!)
    Neurulation B neural groove/folds/tube formation; in response to chemicals released from 
                underlying notochord (cartilaginous rod derived from mesoderm; replaced by vertebrae 
                [backbone] in vertebrates)

Similarity of virtually all early chordate embryos indicates genetic and evolutionary relatedness.

Arthropods: incomplete (hemimetabolous) and complete (holometabolous) metamorphosis

Indeterminate and determinate development