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Most eukaryotes reproduce how
sexually
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What are the positive and negative effects of asexual reproduction?
gives many offspring (positive), but are genetically identical (negative)
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Why do testes hang outside the body?
Normal sperm production can't occur at body temperature
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What is the only way the egg goes through Meiosis II?
If sperm fertilizes the egg
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Sexual reproduction
creation of an offspring by fusion of a male gamete (sperm) and female gamete (egg) to form a zygote
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Asexual reproduction
creation of offspring without the fusion of egg and sperm
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Ovulation
release of mature eggs at the midpoint of female cycle
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Hermaphroditism
each individual has male and female reproductive systems
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Fertilization
can occur externally or internally
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Ensuring the survival of offspring
all species produces more offspring than the number that can survive
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Human reproduction
Reproductive organs produce and transport gametes
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Female anatomy: ovaries
- Contains many follicles
- partially developed egg (oocyte) surrounded by support cells
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Oocyte
develops into ovum (egg) by process of oogenesis
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If egg is fertilized after ovulation:
Remaining follicular tissue forms corpus luteum, which secretes hormones to help maintain pregnancy
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If egg is not fertilized:
corpus luteum degenerates
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Male anatomy: testes
- Sperm form in seminiferous tubules
- Leydig cells produce hormones; scattered between tubules
- normal sperm production can't occur at body temperature of most mammals
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Gametogenesis
production of gametes
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Spermatogenesis
production of mature sperm
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Oogenesis
production of mature egg
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Gonadotropin-releasing hormone (GnRH)
- secreted by hypothalamus
- directs release of follicle-stimulation hormone (FSH) and luteinizing hormone (LH)
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FSH and LH
regulate gametogenesis and regulate sex hormone production
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Sex hormones
androgens, estrogens, and progesterone
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Sex hormones regulate:
- The development of primary sex characteristics during embryogenesis
- The development of secondary sex characteristics at puberty
- Sexual behavior and sex drive
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Menstruation
shedding of endometrium (lining of the uterus)
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Hormones closely link the two cycles of female reproduction:
- changes in the uterus define the menstrual cycle (aka the uterine cycle)
- changes in the ovaries define the ovarian cycle
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Menopause
- after about 500 cycles, human females undergo menopause
- mood changes/heat flashes occur from hormonal changes
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Menopause
the cessation of ovulation and menstruation
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Cleavages
early cell divisions
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Development: conception
- monozygote = one fertilized egg - it splits after fertilization from 1 sperm
- dizygotic = 2 eggs got released, fertilized by different sperm
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Development: First trimester
- begins when egg is released (period)
- implantation
- formation of placenta from trophoblast
- organogenesis
- becomes fetus at 8 weeks
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Human gestation
takes roughly 40 weeks
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Development: Second trimester
- mostly about growing
- chances of miscarriage lowers
- the fetus grows and is very active
- the mother may feel fetal movements
- the uterus grows enough for the pregnancy to become obvious (baby bump!)
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Development: Third trimester
oxytocin causes contraction, which stimulates more oxytocin. This continues until they get harder and more frequent, and the baby comes out.
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Conception
- vasectomy - guy gets vas deferons but (no sperm)
- birth control - prevents ovulation
- abstinence
- condoms
- coitus interruptus - fails. aka pull and pray method
- tubal ligation - blocking fallopian tubes (similar to vasectomy for females)
- preogestin only pill, spermicides, cervical cap
- morning after pill - causes big spike in hormones, inducing uterine shedding
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