Animal Reproduction Chapter 46 Rick L. Knowles Liberty Senior High School A.P. Biology

Concept 46.1: Both asexual and sexual reproduction occur in the animal kingdom. Asexual reproduction – “without sex” all genes come from one parent; derived by mitosis. Sexual reproduction – fusion of haploid gametes to form zygote; derived from meiosis.

Types of Asexual Reproduction Fission – separation of parent into equal sizes (sea anemone, Fig. 46.2). Budding - outgrowths of existing organisms (corals, hydra). Fragmentation – breaking the body into several pieces that can develop into complete adults (starfish).

Fission in Sea Anemones Figure 46.2

Reproductive Cycles and Patterns Most animals have cycles of reproductive activity – seasons favorable to survival of offspring. Periodic reproduction saves energy. Regulated by hormones and/or env. cues. Animals may either be asexual, sexual or both.

Special Type of Asexual Reproduction Parthenogenesis – an unfertilized egg (1 n) undergoes mitosis w/o cytokinesis (male bees, several fish, reptiles). May be an alternative to sexual reproduction.

Can haploid cells develop into functioning animals or plants? Bees Do It!

How to make a bee colony? Fertilized Egg, (2n) Female Worker, (2n) Meiosis Mitosis w/o Cytokinesis Unfertilized Egg, (1n) Queen, (2n) Male Drone, (1n)

Strawberry Plants do both Asexual and Sexual Reproduction Sexual Flowers Asexual Stolon

Whiptails Reproduce Exclusively by Parthenogensis (a) Both lizards in this photograph are C. uniparens females. The one on top is playing the role of a male. Every two or three weeks during the breeding season, individuals switch sex roles. (b) The sexual behavior of C. uniparens is correlated with the cycle of ovulation mediated by sex hormones. As blood levels of estrogen rise, the ovaries grow, and the lizard behaves like a female. After ovulation, the estrogen level drops abruptly, and the progesterone level rises; these hormone levels correlate with male behavior. Figure 46.3a, b

Sexual Reproduction in Sessile Animals If you’re lonely, you better be flexible! Hermaphroditism – each individual has male and female reprod. systems; each produce sperm and ova. Figure 46.1 – Mating Earthworms

Sequential Hermaphroditism Individual may reverse its sex during its lifetime; may be female-first or male-first. Figure 46.4: Caribbean bluehead wrasse – all born female, but the largest becomes male within a week. Show Me! Bizarre Breeding, video #132

External Fertilization Eggs are released into water by female where they are fertilized by the male. Egg release triggered by hormones, env. conditions, male behavior. Figure 46.5 Eggs

Internal Fertilization Sperm deposited in or near the female reproductive tract. An adaptation to terrestrial life. Requires cooperative behavior (for mating) and development of copulatory organs.

Fig. 46.9

Fig. 46.9

Several (Primary) Follicles in Ovary

Mature (Graafian) Follicle Fluid-filled Cavity Secondary Oocyte Follicle (Granulosa) Cells

Female Reproductive Tract Ovaries – female gonads; in pelvic cavity and flank the uterus; held by mesentery. Follicle – consists of one egg cell and many layers of follicle (granulosa) cells – produce estrogen and progesterone. Ovulation – secondary oocyte and follicle cells rupture from the ovary. Corpus Luteum – remaining solid mass of follicular tissue that grows and produces estrogen and progesterone in the ovary.

Fig. 46.10

Fig. 46.10

Male Reproductive Tract Testes – male gonads; many highly coiled tubes; suspended in scrotum (not all mammals). Seminiferous Tubules – site of spermatogenesis and sperm maturation. Leydig (Interstitial) Cells – in between tubules; secrete testosterone. Sertoli (Sustentacular ) Cells – induce primary spermatocytes into spermatogenesis.

Male Accessory Glands Seminal Vesicles (pair) – secretions of fructose, prostaglandins (smooth muscle contraction), fibrinogen (coagulant); alkaline. Prostate Gland – largest of the glands; secretes an antibiotic, fibrinolysin (anticoagulant). Bulbourethral Glands (pair) – pre-ejaculation secretion of alkaline mucus to neutralize acidity of urethra (acidic urine); may have sperm present.

Increasing Levels of LH Figure 46.11

Increasing FSH + Testosterone Figure 46.12

Female Mammal Reproductive Cycles Menstrual Cycle – some primates and humans; endometrium shed through the cervix and vagina; bleeding = menstruation; may mate regardless of ovulatory status. Estrous Cycle – all other mammals; most of the endometrium reabsorbed by uterus; little bleeding; marked by intense mating activity – estrus (heat) – only time receptive to mating (ovulating).

Human Female Reproductive Cycle An integrated cycle involving two organs uterus and ovaries. Uterine Cycle – changes in the uterus (menstrual cycle); caused by the ovarian cycle. Ovarian Cycle – cyclic events in the ovaries.

Reproductive Hormones You Need to Know Gonarotropin-releasing Hormone (GnRH) Follicle-stimulating Hormone (FSH) Luteinizing Hormone (LH) Estrogen Progesterone Testosterone Inhibin Human Chorionic Gonadotropin (HCG)

Fig. 46.13

Negative Feedback Inhibin Fig. 46.14 (Interstitial Cells) (Sustentacular Cells) Fig. 46.14

Figure 46.15a, b Cleavage (cell division) begins in the oviduct as the embryo is moved toward the uterus by peristalsis and the movements of cilia. Cleavage continues. By the time the embryo reaches the uterus, it is a ball of cells. It floats in the uterus for several days, nourished by endometrial secretions. It becomes a blastocyst. Fertilization occurs. A sperm enters the oocyte; meiosis of the oocyte finishes; and the nuclei of the ovum and sperm fuse, producing a zygote. The blastocyst implants in the endometrium about 7 days after conception. Ovulation releases a secondary oocyte, which enters the oviduct. Figure 46.15a, b

Fig. 46.16

Fig. 46.17

Fig. 46.18

The process of labor has three stages Figure 46.19 Placenta Umbilical cord Uterus Cervix Dilation of the cervix Expulsion: delivery of the infant (detaching) Delivery of the placenta 1 2 3

Fig. 46.20