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