Download Chapter 46: Animal Reproduction

Joshua Chandra
Shannen Guarina
- Sexual reproduction: the fusion of haploid gametes to form a diploid cell (zygote).
- The egg
- The sperm
- Asexual reproduction: generation of new individuals without the fusion of egg and
sperm
- Fission
- Budding
- What advantage does sex provide?
- Produces offspring of different genotypes/phenotypes that enhances reproductive
success of parents
- Most animals reproduce sexually or asexually; but some alternate between the two.
- parthenogenesis: asexual reproduction in which an egg develops without it being
fertilized
- Hermaphroditism
- Sex reversal
- External fertilization - sperm fertilizes eggs shed into the external environment
- Internal fertilization – egg and sperm unite within the female’s body
- Fertilization requires coordinated timing which can be mediated by environmental
cues, pheromones, or courtship behavior
- Internal fertilization requires behavioral interactions between males and females as
well as compatible copulatory organs
- Internal fertilization usually results in a small amount of offspring
- It is usually accompanied by the greater protection of embryos and parental care
- Reproductive systems range from undifferentiated cells in the body cavity that creates
gametes to complex assemblages of male and female gonads
- Although it usually occurs in a partnership, competition emerges between individuals
and between gametes
- Female reproductive anatomy:
- External: labia majora, labia minora, clitoris – these form the vulva
- Internal: vagina is connected to the uterus, which connects to two oviducts
- There are two ovaries which is stocked with follicles containing oocytes
- Male reproductive anatomy:
- External: scrotum and penis
- Male gonads (testes) are held in the scrotum
- These contain the hormone-producing cells and sperm-forming
seminiferous tubules
- Human sexual response:
- Sexual response cycle:
- Excitement
- Plateau
- Orgasm
- Resolution
- Orgasm: rhythmic, involuntary contractions of the reproductive structures
- Gametogenesis is the production of
gametes
- It consists of oogenesis in females and
spermatogenesis in males
- Sperm develops continuously
- Oocyte maturation is discontinuous
and cyclic
- Meiosis results in one large egg that is
created in oogenesis
- Meiosis also results in four sperm in
spermatogenesis
- Hormonal control of the male reproductive system
- Androgens from the testes cause the development of primary and secondary sex
characteristics in the male
- Androgen secretion and sperm production are both controlled by hypothalmic and
pituitary hormones
- The reproductive cycles of females:
- Cyclic secretion of the GnRH from the hypothalmus and of FSH and LH from the
anterior pituitary orchestrate the female reproductive cycle
- FSH and LH bring about changes in the ovary and uterus via estrogens and
progesterone
- Estradiol is produced by the developing follicle
- The progesterone and estradiol is excreted by progesterone
- Menstrual Cycles
- Menstrual Flow Phase
- Proliferative Phase
- Secretory Phase
http://www.youtube.com/watch?v=WGJsrGmWeKE
- After fertilization and meiosis occurs in the oviduct , the zygote will eventually
undergo cleavage and will from there develop into blastocyst
- From there the blastocyst will be implanted in the endometrium
- Human pregnancy is divided into three trimesters
- All majors will have begun to develop by the eight week mark
- Positive feedback by prostaglandins and the hormones estradiol and oxytocin will help
regulate labor
- By accepting the “foreign” offspring it shows that the mother partially suppresses the
immune response
- Contraceptive methods may be used to prevent fertilization
- Modern reproductive technologies can be used in multiple fashions
- Detect problems before birth
- Assist infertile couples through hormonal methods or in vitro fertilization