Sexual Reproduction: Red beetles mating

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Sexual Reproduction Red beetles mating
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Asexual reproduction sea anemone
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Lets Review

• What are the advantages of sexual reproduction?
• What are the advantages of asexual reproduction?
• How are genes passed on during asexual
  reproduction?
• And sexual reproduction?

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Figure 13.6 Overview of meiosis how meiosis
reduces chromosome number
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Lets Review

• What is the difference between sexual
  reproduction in plants (mosses and ferns) and
  animals.

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Three sexual life cycles
Figure 13.5
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Germ Cell Development

• Spermatogenesis
• Oogenesis

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Reproductive Anatomy Males

• Testes (Testis)
• Seminiferous tubules (produce sperm)
• Germinal Cells
• Sertoli Cells (support cells)
• Leydig cells (produce testosterone)
• Epididymis (sperm collection)

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head (DNA in enzyme-rich cap)
tail (with core of microtubules)
midpiece with mitochondria
The head encloses a compact nucleus and a vesicle
called an acrosome. The acrosome contains enzymes
that aide in sperms ability to penetrate the
zona pollucida (protective coating on the
oocyte) The midpiece contain many mitochondria to
provide energy for movement.
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Spermatogenesis Seminiferous tubules (left),
sperm in semen (right)
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Figure 46.11 Spermatogenesis
When do chiasmata form?
When do homologous pairs separate?
When do sister chromatids separate?
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Interesting Fact

• Production of normal sperm must occur at
  temperatures lower than 37oC (about 2 degrees
  lower)
• Organisms with lower body temperatures often have
  internal testes.

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Hormonal Control of Spermatogenesis
Testosterone stimulates development of primary
and secondary sexual characteristics and sperm
development LH stimulates secretion of
testosterone by Leydig cells FSH Stimulates
spermatogenesis by germinal cells GnRH released
by hypothalamus and stimulates release of LH and
FSH Inhibin released by testes and regulates
GnRH and LH
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Hormonal Control of Spermatogenesis
What would happen if testosterone production was
inhibited?
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Reproductive Anatomy Females

• Ovary
• Follicles (egg surrounded by support cells)
• Corpus luteum (secretes estrogens and
  progesterone)

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Figure 46.9x Ovary (left) and follicle (right)
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Release of Ovum
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Figure 46.13b Oogenesis
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Figure 46.15 The reproductive cycle of the human
female
GnRH released by hypothalamus and stimulates
release of LH and FSH FSH Primary follicles have
receptors for FSH, which stimulates
growth Estrogen secreted by growling follicles,
and induces final maturation of follicle LH
stimulates stimulates formation of corpus
leuteum, which secretes estrogen and
progesterone. Progesterone Prepares the uterus
for pregnancy
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