Animal Reproduction from Chapter 46 29 April 20151Animal-Reproduction.ppt

Animal Reproduction

from Chapter 46

29 April 2015 1Animal-Reproduction.ppt

29 April 2015 Animal-Reproduction.ppt 2

Phylum Rotifera

• Small aquatic & marine animals

• Usually cone or wine-glass shape

• Ring of cilia around mouth Early observers mistook

for rotating wheel


Phylum Rotifera

• Some live on mosses, lichens Can be dried and will

revive when moistened• 3-4 years common

• 50+ years reported


Phylum Rotifera

• Usually parthenogenic (exhibit “parthenogenesis”) Asexual reproduction

• Female lays asexual eggs, females, females, generation after generation.

• Copies successful genome exactly

• Favored in stable environment

Asexual Reproduction in Animals

• Sponges• Sea anemones • Platyhelminthes

Planarians Flukes (larval stages)

• Rotifers• Aphids • some Fishes• some Lizards



Asexual Reproduction• Asexual reproduction

Faster? Preserves successful genome Faster population growth

• No energy diverted to “males”


Rotifers and Aphids

• Parthenogenesis, usually, Sexual alternative

• Females produce some males (when, how ?)

• Males inseminate females, who produce sexual eggs

• Offspring more variable• Some variants survive &/or reproduce better than others


Sexual Reproduction

• Why be sexual? Variability of offspring in unpredictable

environment. • Some expected to be less fit than their parents

• Some expected to be as fit than their parents

• Some expected to be more fit than their parents

Recombination Elimination of unfavorable alleles (without

elimination of the population)

Sexual Reproduction


• Why make (so many) males? Frequency-dependent

selection When more males than

females, females favored.When more females than

males, males favored

Genetic sex determination, such as XY chromosomes1:1 sex ratio


Sexual Reproduction

• Other sex determination Temperature-dependent sex determination

• Sea turtles: males at temps below ~25-30 C, females at higher temps.

• Alligators: males at higher temps, females at lower temps

Changing sex • Population of mostly females with few males (fishes)

• Female can change to male (Bluehead wrasse)

• Male can change to female

• Tapeworm proglottids

• Male first, later female

Sexual Reproduction


• Other sex determinationHaplo-diploidy

HymenopteraBees, wasps, ants

Fertilized eggs (2n) develop into females

Queen, workers

Unfertilized eggs (1n) develop into males

“Drones”

Sexual Reproduction

• Hermaphroditism Flukes, tapeworms

• Self-fertilization possible

Earthworms • Obligate outcrossing



Sexual Reproduction

• Mammalian (human) reproductive systems Genetic sex determination,

• XY chromosomes 1:1 sex ratio.

• Testis-determining gene on Y chromosome.

• Sexual orientation [gay] gene(s) on X chromosome? o Science 21 November 2014: Vol. 346 no. 6212 p. 902.

Male Reproductive System

• Male functions: Produce viable, motile

sperm Deliver sperm to female

tract


Male Reproductive System• Testis (pl. testes)

Lobules with Seminiferous tubules• produce sperm

Interstitial cells of Leydig• produce testosterone



• Spermatogonium 2n “stem cell” Mitosis new

spermatogonium, plus

• Primary spermatocyte• 2nd spermatocyte• Spermatids• Sperm (immature)




• Epididymis Crescent-shaped at

posterior-lateral side of each testis

Site of sperm maturation (~ 20 days)

Sperm storage• 3-8 weeks ?

“Tail” connects to ductus deferens


• Vas (ductus) deferens passes through inguinal canal passes superior-lateral surface

of bladder joins ducts of seminal vesicles ejaculatory duct

• Seminal vesicles• Prostate gland • Bulbourethral glands



• Semen, = secretions from . . . Seminal vesicles, ~ 60% by volume

• NaHCO3, fructose, coagulating proteins

Prostate gland, ~ 35%• Citrate, proteins

Bulbourethral glands, ~ 4 %• Alkaline mucus

Sperm, ~ 1 %




• Endocrine regulation of male system Gonadotropin-

releasing hormone (GnRH)

FSH LH Testosterone

Female Reproductive System

• Functions produce ova receive sperm site of fertilization hold & nourish

embryo/fetus bear infant nurse infant


Female Reproductive

System• Ovary

Follicle development and oogenesis

Timing of oogenesis • Primary oocytes in fetal

ovary

• Secondary oocytes monthly,

• Sperm enter 2nd oocyte, completion of meiosis



• Uterine (Fallopian) tubes Extend laterally from

uterus Infundibulum = open,

funnel-shaped end

• Site of fertilization




• Uterus• Lies over urinary

bladder

• Fundus

• Body

• Cervix

Site of implantation• Formation of placenta


• Endocrine regulation of ovarian & uterine cycles FSH LH Estrogens Progesterone Chorionic

gonadotropin


Female Reproductive

System• Endocrine regulation of

ovarian & uterine cycles FSH LH Estrogens Progesterone Chorionic gonadotropin


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Animal Reproduction from Chapter 46 29 April 20151Animal-Reproduction.ppt