Chapter 50 – Sex and Reproduction
The theme of this chapter is obvious and doesn’t need amplification.
Our main focus will be on Chapter 50, the
types of reproduction, the reproductive systems of male and females, birth control, and sexually transmitted diseases
We will delve into Chapter 51 as appropriate.
The Concept Outline (P. 1061) and the Concept
Review (P.1079) provide excellent coverage of the subject.
We have not always known how human conception occurred.
Our understanding of sexual gratification has a long
and entangled history, but the basics of human creation was a mystery until recently.
The following information is
not in your textbook, but it is important.
There is a history about a perceived human being called
and this individual is the center piece for our
early ideas about human conception.
At about the time the microscope was invented, scientists believed they could
see a small human in the sperm cell (or egg).
Therefore, there were two camps: the
Some scientists, those mathematically inclined, calculated how many smaller humans the microscopic human could
have, and therefore when the end of the human species would occur!
The story of
This theory goes back a long way - ~ 2,000 years, to Aristotle who proposed it.
We assume our understanding is more accurate at the present time.
Types of Reproduction:
: binary fission, budding, and parthenogenesis.
: Gametogenesis; dioecious vs monoecious vs hermaphrodites.
that practice sexual
reproduction do not exhibit “Alternation of Generations” as seen in plants,
the haploid reproductive
cells that result from meiosis (gametes) do not divide by mitosis before fusing to form a 2N
(Chpt. 31, P.
Advantages of metamorphosis:
Different environments – think about it.
External Fertilization and the different types of Internal Fertilization:
Reproduction in vertebrates evolved in the marine environment before vertebrates colonized land.
It began with the
Most marine bony fish practice external fertilization where the female releases eggs into the environment
and males release sperm into the same area.
The sperm find the eggs, fertilization occurs, a zygote is formed, and
Cartilagenous fish, such as sharks, have more advanced fertilization.
Once vertebrates began to live on land, the goal was to escape having to return to water to reproduce.
amphibians (Fig. 50.5) never evolved internal fertilization methods and hence were never “true” land animals.
vertebrates that did evolve into “true” land animals developed three strategies for embryonic development:
These terms are very important in your education – memorize them
They are the noun forms (I think I am correct in saying they are nouns).
The adjective forms are: