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