BIO 112 FINAL EXAM

Asexual reproduction

One parent; genetically identical offspring; no gametes

Sexual reproduction

Two parents; genetically different offspring; fusion of haploid gametes

Genetic recombination

Combination of two genomes that increases genetic diversity

Why sexual reproduction

Produces genetic diversity despite being energetically costly

Budding

New organism grows off the parent

Binary fission

Parent cell divides into two identical cells

Fragmentation

Organism breaks apart and regenerates

Female gametes

Large, expensive eggs produced in ovaries

Male gametes

Small, inexpensive sperm produced in testes

Hermaphrodites

Organisms with both male and female reproductive organs

Sex change in organisms

Some species switch sex due to environmental conditions

Spermatogenesis

Production of sperm in the testes

Leydig cells

Secrete testosterone and other androgens

Sertoli cells

Nourish and support developing sperm

Sperm production rate

Hundreds of millions per day

Sperm maturation time

About 7–10 weeks

GnRH

Hormone from hypothalamus that stimulates FSH and LH release

FSH (male)

Stimulates Sertoli cells and sperm production

LH (male)

Stimulates Leydig cells to secrete testosterone

Testosterone

Promotes spermatogenesis and regulates hormones via negative feedback

Inhibin

Reduces FSH secretion

Spermatozoa

Mature sperm cells

Seminal vesicles

Produce fructose and prostaglandins

Prostate gland

Produces alkaline buffers

Bulbourethral gland

Produces mucus for lubrication

Oogenesis

Formation of eggs in females

Timing of oogenesis

Begins before birth; completes years later

Ovarian cycle

Cycle of follicle development and hormone release

Follicular phase

Follicle growth and rising estradiol levels

Luteal phase

Corpus luteum secretes progesterone and estradiol

LH surge

Triggers ovulation

Uterine (menstrual) cycle

Thickening and shedding of endometrium

Fertilization

Fusion of sperm and egg to form zygote

Location of fertilization

Fallopian tube

Polyspermy prevention

Only one sperm allowed to fertilize egg

hCG

Hormone secreted by embryo; detected in pregnancy tests

Meiosis II completion

Triggered by fertilization

Zygote

Single-celled fertilized egg

Morula

Solid ball of 16–32 cells

Blastocyst

Hollow ball of cells that implants in uterus

Inner cell mass

Forms the fetus

Gastrula

Embryo with three tissue layers

Ectoderm

Forms skin, nervous system, retina

Mesoderm

Forms heart, kidneys, muscles

Endoderm

Forms lungs, liver, digestive tract lining

Embryo

Week 2 to week 8

Fetus

Week 8 until birth

SRY gene

Triggers development of testes

DAX1 gene

Inhibits testis development

Primary sex determination

Controlled by SRY

Secondary sex characteristics

Controlled by hormones

Placenta formation

Completed by week 10

Placental exchange

Gases, drugs, viruses can cross; blood does not mix

Lanugo

Fine hair covering fetus

Vernix caseosa

White, cheesy protective coating

Age of viability

~28 weeks

Third trimester

Period of rapid fetal growth

Average newborn size

~50 cm long, 3–4 kg

Oxytocin

Stimulates uterine contractions and milk ejection

Prostaglandins

Induce labor and cervical ripening

Stage 1 labor (Dilation)

Cervix opens to 10 cm

Stage 2 labor (Expulsion)

Delivery of baby

Stage 3 labor

Delivery of placenta

Prolactin

Stimulates milk production

Colostrum

First milk; high in IgA and proteins

Oxytocin (lactation)

Causes milk release and uterine contraction