Tyler Mcall, Glenn Himan
Mr. DeVera
Biology (P.5)
5/20/13
Chapter 53:
1. Differentiate sexual reproduction from asexual reproduction.
Sexual reproduction a requires a specialized form of cell division, meiosis, to produce haploid
gametes (eggs and sperm), each of which has a single complete set of chromosomes. Asexual
reproduction produces offspring with the same genes as the parent organism.
2. Define:
a. parthenogenesis: females produce offspring from unfertilized eggs; the development of
an egg without fertilization, as in aphids, bees, ants, and some lizards.
b. hermaphroditism: condition in which an organism has both male and female functional
reproductive organs.
3. Describe the role of the SRY gene in determining sex in mammals.
SRY can be understood as the “sex-determining region of the Y chromosome.” If the embryo
lacks the SRY gene, the embryo develops female external genitalia and accessory organs. All
mammalian embryos will develop into females unless a functional SRY gene is present.
4. Explain the functionality of external fertilization in vertebrate fish and internal fertilization in
land vertebrates.
For vertebrate fish, fertilization in most species of bony fish is external, and the eggs contain
only enough yolk to sustain the development embryo for a short time. The female fish will
deposit unfertilized eggs in the substrate and the male will swim by and fertilize them. For land
vertebrates, after the eggs are fertilized internally, they are deposited outside the mother’s body
to complete their development.
5. What reproductive strategies have evolved as a result of internal fertilization? Describe them.
Sexual reproduction is a method for producing a new individual organism while combining
genes from two parents. A single sperm and egg fuse during fertilization, and their genomes
combine in the new zygote.
6. Describe fertilization in fish, amphibian, reptile, and birds:
Birds: all bird species have internal fertilization; the male transmits its sperm cells directly to the
female’s genital opening, allowing them to reach and fertilize her mature eggs inside her ovaries.
From there, the sperm is carried through the oviduct, where it sometimes stays for several weeks
in a special chamber before it is needed for fertilization in the ovary.
Fish: During spawning season, the male fish seek out these nests of fish eggs that the female has
laid. When they find one, they swim over the nest, and fertilize them with their semen. This
allows conception to take place, and immediately the fish eggs stat to become fish.
Amphibian: the amphibians have the widest range of reproduction methods, with differences
even within the same order. Fertilization of the salamander makes for a good example, where it
is internal for most salamanders, but external for the giant and Asia tics.
Reptile: Most oviparous reptiles lay eggs and then abandon them. These eggs are surrounded by
a leathery shell that is deposited as the egg passes through the oviduct, the part of the female
reproductive tract leading from the ovary. Other species of reptiles are ovoviviparous, forming
eggs that develop into embryos within the body of the mother, and some species are viviparous.
7. Describe what happens during the three stages of the female menstrual cycle.
-Proliferative phase - here's when the stratum functional is of endometrium of uterus is 'repaired.'
Remember, this is a cycle so menstruation has just finished, and the endometrium is thin. This is
the phase when endometrium starts to thicken.
-Secretory phase - here's when the endometrium prepares for the arrival of the fertilized egg.
(The female reproductive system always assumes that fertilization occurred.) It thickens so the
embryo will be able to implant itself in the uterus wall. It is through this that the developing
embryo can receive nutrients and other things that it needs to develop from the mother.
-Menstruation - this is basically the 'shedding' of the stratum functional is when fertilization did
not occur.
8. What are the four phases of the estrous cycle?
-Proestrus
-Estrus
-Metestrus
-Diestrus