Animal ReproductionChapter 46

Rick L. KnowlesLiberty 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?

Queen, (2n)

Female Worker,

(2n)

Male Drone, (1n)

Meiosis

Fertilized Egg, (2n)

Unfertilized Egg, (1n)

Mitosis w/o Cytokinesis

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

Secondary Oocyte

Fluid-filled Cavity

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

Figure 46.12

Increasing FSH + Testosterone

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

(Interstitial Cells)

(Sustentacular Cells)

Inhibin

Negative Feedback

Fig. 46.14

Ovulation releases asecondary oocyte, which

enters the oviduct.

Fertilization occurs. A sperm enters the oocyte; meiosis of the oocyte finishes; and the

nuclei of the ovum and sperm fuse, producing a zygote.

Cleavage (cell division)begins in the oviduct

as the embryo is movedtoward the uterus

by peristalsis and themovements 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.

The blastocyst implants in the endometrium

about 7 days after conception.

Figure 46.15a, b

Fig. 46.16

Fig. 46.17

Fig. 46.18

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

• The process of labor has three stages

Figure 46.19

Placenta

Umbilicalcord

Uterus

Cervix

Dilation of the cervix

Expulsion: delivery of the infant

Uterus

Placenta(detaching)

Umbilicalcord

Delivery of the placenta

1

2

3

Fig. 46.20