Chapter 46 ~ Animal Reproduction

Overview

Asexual (one parent)

fission (parent separation)

budding (corals)

gemmules (porifera)

fragmentation & regeneration (inverts)

Sexual (fusion of haploid gametes)

gametes (sex cells)

zygote (fertilized egg)

ovum (unfertilized egg)

spermatozoon (male gamete)

Reproductive cycles

Parthenogenesis unfertilized egg development; haploid, sterile adults (honeybees)

Hermaphroditism both male & female reproductive systems; sessile & burrowing organisms (earthworms)

Sequential hermaphroditism reversal of gender during lifetime •protogynous (female 1st) •protandrous (male 1st)

Mechanisms of sexual reproduction

Fertilization (union of sperm and egg) • external • internal

Pheromones chemical signals that influence the behavior of others (mate attractants)

Mammalian reproduction, I

The Human Male

Testes ~ male gonads

Seminiferous tubules ~ sperm formation

Leydig cells ~ hormone production

Scrotum ~ outside body temp.

Epididymis ~ sperm development

Vas deferens ~ sperm propulsion

Seminal vesicles ~ semen

Prostate gland ~ anticoagulant; nutrients

Bulbourethral glands ~ acid neutralizer

Penis/urethra ~ semen delivery

Male Reproductive Structures

Mammalian reproduction, II

The Human Female

Ovaries ~ female gonads

Follicle ~ egg capsule

Corpus luteum ~ hormone secretion

Oviduct ~ fertilization

Uterus/endometrium ~ womb/lining

Cervix/vagina ~ sperm receptacle

Female Reproductive Structures

Spermatogenesis

Puberty until death!

Seminiferous tubules ~ location

Primordial germ cell (2N)~ differentiate into….

Spermatogonium (2N) ~ sperm precursor

Repeated mitosis into….

Primary spermatocyte (2N)

1st meiotic division

Secondary spermatocyte (1N)

2nd meiotic division

Spermatids (1N)~ Sertoli cells….

Sperm cells (1N)

Oogenesis

As embryo until menopause...

Ovaries

Primordial germ cells (2N)

Oogonium (2N)

Primary oocyte (2N)

Between birth & puberty; prophase I of meiosis

Puberty; FSH; completes meiosis I

Secondary oocyte (1N); polar body

Meiosis II; stimulated by fertilization

Ovum (1N); 2nd polar body

The female pattern

Estrous cycles/estrus (many mammals)

Menstrual cycle (humans and many other primates):

Ovarian/Menstrual cycles~ •follicular phase ~follicle growth •ovulation ~ oocyte release •luteal phase ~ hormone release

Ovulation

Post-ovulation

Embryonic & fetal development

Gestation ~ pregnancy

1st trimester :

organogenesis

fetus (week 8; all adult features)

HCG hormone (menstruation override; pregnancy test detection)

Parturition ~birth

Labor ~uterine contractions

Lactation ~prolactin & oxytocin

Modern technologies