Reproduction and Development Chapter 26. Asexual Reproduction.
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Transcript of Reproduction and Development Chapter 26. Asexual Reproduction.
Reproduction and Development
Chapter 26
Asexual Reproduction
Cost of Sexual Reproduction
• Specialized cells and structures must be formed
• Special courtship and parental behaviors can be costly
• Nurturing developing offspring, either in egg or body, requires resources (usually from mother)
frog egg
frog sperm
midsectional views
top view side view
Organs grow and assume specialized functions
Eggs and sperm form
Sperm and an egg fuse to form zygote
Mitotic cell divisions produce daughter cells
Cell divisions, migrations, and rearrangements produce primary tissues
Specialized organs and tissues form in prescribed spatial patterns at prescribed times
Gamete formation
Fertilization
Cleavage
Gastrulation
Organ Formation
Growth, tissueSpecilazation
Fig. 27-4, p.464
Stages of Development
Primary Tissues
EctodermOuter most primary tissue, Nervous Tissue,
outter portions of body coveringEndodermSource of gut inner linning and organs
derived from itMesodermForms between outter and inner primary
tissues, gives rise to muscles, most of the skeleton,circulatory, repro., excre.,connective tissue of gut and integumentary
adult,three years old
sexual reproduction (meiosis through
fertilization)
zygote
cleavageorgan formationtadpole
transformation to adult nearly completed
Development of the Leopard Frog
Fig. 27-5b-j, p.465
Development of the Leopard Frog
Morphogenesis
• Programmed growth of tissues and organs– Cells migrate along prescribed routes– Sheets of cells expand and fold– Cell deaths shape body parts
Male Reproductive
Systemvas deferens
epididymis
testis
penis
seminal vesicle
prostate gland
bulbourethral gland
urethra
bladder
scrotum
A Sperm’s Journey
• Testes– Produces immature sperm
• Epididymis– Matures and stores sperm
• Vas deferens
• Ejaculatory ducts
• Urethra
PROSTATE GLAND EJECULATORY DUCT
URETHRA
SEMINAL VESICLE
BULBOURETHRAL GLAND
VAS DEFERENS
EPIDIDYMIS
PENIS
TESTIS
urethra
erectile tissue
urinary bladder
anusanteriorposterior
Fig. 27-7, p.467
Male Components and Accessory Glands
Sperm Formation
• Spermatogonium (2n) divides by mitosis to form primary spermatocyte (2n)
• Primary spermatocyte divides by meiosis to form 4 haploid spermatids (n)
Sertoli cell
spermato-gonium (diploid)
primary spermatocyte
MITOSIS MEIOSIS I MEIOSIS II
immature sperm (haploid)
late spermatid
secondary spermatocyte
early spermatids
lumen
Fig. 27-9b, p.468
Sperm Production
A Mature Sperm
• Spermatids mature to become sperm– Head– Midpiece– Tail
• Glandular products + sperm = semen
Hormonal Control
• Testosterone– Produced by Leydig cells in testes– Controlled by luteinizing hormone (LH)
• Follicle-stimulating hormone (FSH)– Starts sperm production
• LH and FSH – produced by pituitary, controlled by
hypothalamus
Female Reproductive Organs
vagina
uterus
oviduct
ovary
vagina
clitoris
oviduct
ovary
uterus
The Uterus
• Myometrium– Thick layer of smooth muscle in walls
• Endometrium– Uterine lining
• Cervix– Connects uterus and vagina
Menstrual Cycle
• The fertile period for a human female occurs on a cyclic basis
• Menstrual cycle lasts about 28 days on average
Menstrual Cycle
• Follicular phase– Menstruation– Uterine lining regenerates– Oocyte matures
• Ovulation– Oocyte released from ovary
• Luteal phase– Hormones thicken endometrium
The Ovarian Cycle
• Girl is born with primary oocytes already in ovaries
• Oocytes are suspended in meiosis 1
• Meiosis resumes, one oocyte at a time, with the first menstrual cycle
Female Hormonal Control
Hypothalamus
Anterior pituitary
GnRH
LH FSH
OvaryEstrogen
Progesterone,estrogens
follicle growth, oocyte maturation
Rising estrogen stimulates surge in LH
Corpus luteumforms
Fertilization
• Sperm penetrates egg cytoplasm
• Secondary oocyte undergoes meiosis II, forms mature egg
• Egg nucleus and sperm nucleus fuse to form diploid zygote
zona pellucida
follicle cell
egg nucleus
Ovulation
oviduct
ovary
uterus
opening of cervix
vagina
Fig. 27-14, p.472
Fertilization
Contraception Effectiveness