Sexual Reproduction -involves 2 parents -Involves the process of meiosis
Background Vocabulary: - gametes – sex cells – sperm and egg - gonads – sex organs/glands – testes and ovaries - zygote – fertilized egg egg + sperm = zygote - meiosis – process by which sex cells develop - gametogenesis, oogenesis, & spermatogenesis - diploid (2n) – normal # of chromosomes (46 – human) - haploid or monoploid (n) – ½ the # of chromosomes (23 – human)
Zygote Formation - zygote fertilized egg - sperm + egg = zygote (fertilized egg) - process is called fertilization - recombination occurs (genes from mom and dad come together) - chromosomes from both parents recombine – increases variety
Internal Fertilization - fertilization occurs inside the female - usually terrestrial (land) organisms - few eggs produced - protected - could have either internal (mammals) or external (birds) development External Fertilization - fertilization occurs outside the body of the female - usually aquatic (water) organisms - many eggs – ensure survival - only external development
Embryo Formation - the zygote divides by mitosis (cleavage) to form an embryo - zygote embryo – divisions by mitosis (cleavage) - Gastrulation embryo forms layers - Differentiation occurs cells become different - take on their own identity (hair cell, skin cell, etc.)
2 major functions: 1. Make sperm 2. Deposit in female (internal fertilization) Structures and Functions: 1.Testes: Male gonads a.Sperm and testosterone production b.Location scrotum – keeps sperm 1 – 2 degrees cooler than normal body temperature
2. Vas Deferens: a. tube that connects testes to urethra b. sperm transported here c. along the way secretions from 3 glands are picked up to make semen. 3. Semen: sperm + fluids 4. Testosterone: hormone secreted by testes, regulates development of secondary sex characteristics.
Structures and Functions 1.Ovaries: a. female gonads b. produce eggs (meiosis – oogenesis) c. eggs enclosed in follicles d. once a month egg is ovulated (released – into fallopian tube) 2. Fallopian Tubes (oviducts): a. connects ovary to uterus b. fertilization here
3. Uterus: a. implantation here (embryo embeds itself into uterine wall b. development from embryo to fetus here 4. Vagina: a. birth canal (menstruate through here too) 5. Estrogen and progesterone: a. female hormones (ovaries) b. regulate secondary sex characteristics c. menstrual cycle
(Lasts about 28 days) A.Stage 1: Follicle Stage (10 days) a.Pituitary FSH b.Ovaries estrogen – thickens uterus c.Egg matures in follicle – swells B. Stage 2: Ovulation (1 day – stays in tube 2 – 3 days) a. Pituitary LH b. egg released from follicle
C.Stage 3: Corpus Luteum Stage (~ 14 days) a.Follicle dies – forms a “scar” corpus luteum b.Corpus luteum progesterone c.Causes uterine lining to stay thick D.Stage 4: Menstruation (4 days) a. egg not fertilized – uterine lining breaks down
Internal Development: Placental Mammals - development inside the female - gestation- time period between fertilization and birth 1.Placenta: a.Forms in uterus b.Feeds fetus - nutrition c.Exchanges gases for fetus – respiration d.Rids fetus of wastes – excretion e.No direct connection of bloodstreams between mother and fetus (Diffusion occurs across the blood vessels)
Multiple embryo’s: Identical twins: 1 sperm 1 egg splits same placenta/sac Fraternal twins: 2 eggs 2 sperm separate sacs and placenta
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7 weeks - Brain has the first detectable brain waves, muscles develop and get stronger
8 weeks - Eyes are well-developed, Fingers lengthen while distinct grooves (digital rays) form between the fingers
12 weeks - Fetus begins to move around, though the mother cannot yet sense these movements.
14 weeks - Fetus is more flexible with ability to move head, mouth, lips, arms, wrists, hands, legs, feet, and toes.
18 weeks - Fetus has phases of sleep and waking and may prefer a favorite sleep position, temporary hair called lanugo appears on the head
20 weeks - Fetus may suck on thumb. Extremely rapid brain growth; eyebrows and scalp hair become more visible and fetus blinks more often.
24 weeks - Fetal brain waves begin to activate auditory and visual systems, both mouth and lips show more sensitivity. Eyes respond to light, while ears respond to sounds originating outside uterus.
32 weeks - Eyes open during alert times and close during sleep. Eye color is usually blue, regardless of the permanent color as pigmentation is not fully developed. Fingernails reach over finger tips and fetus can scratch itself.