Animal Reproduction

Sexual Reproduction

Sexual Reproduction

fusion of haploid gametes forms a diploid cell, the zygote

Zygote

fertilized egg cell

Zygote

can give rise to gametes by meiosis

Egg

large, nonmotile female gamete

Sperm

male gamete, generally much smaller and motile

Asexual Reproduction

generated without the fusion of egg and sperm

Asexual Animals

relies entirely on mitotic cell division

Budding

new individuals arise from outgrowths of existing ones

Fission

splitting and separation of a parent organism into two individuals of approximately equal size

Fragmentation

breaking of the body into several pieces, followed

Regeneration

regrowth of lost body parts

Fragmentation and Regeneration

one form of asexual reproduction that has two steps

Parthenogenesis

egg develops without being fertilized.

Parthenogenesis

offspring can be either haploid or diploid.

Hermaphroditism

each individual has both male and female reproductive systems

Hermaphroditism

blurring the distinction between male and female; common among sessile (stationary) animals

Hermaphrodites

can also self-fertilize

Sex Reversal

maximizes gamete production

Releasing gametes into the surrounding water

tends to result in more offspring

Ovulation

release of mature eggs, occurs at the midpoint of each cycle.

Sexual Reproduction

number of sexual offspring will remain the same at each generation because both a male and a female are required to reproduce

Asexual Reproduction

daughters that will each give birth to two more reproductive daughters

'“Twofold Cost”

asexual condition will increase in frequency at each \n generation

Sexual Reproduction

may enhance the reproductive success of parents when environmental factors; change relatively rapidly

Asexual Reproduction

expected to bemost advantageous in stable, favorable environments because it perpetuates successful genotypes precisely

Sexual Reproduction

beneficial gene combinations arising through recombination might speed up adaptation

Fertilization

union of sperm and egg

Fertilization

an be external or internal.

External Fertilization

the female releases eggs into the environment, where the male then fertilizes them

Internal Fertilization

sperm deposited in or near the female reproductive tract fertilize eggs within the tract

Moist Habitat

almost always required for external fertilization, both to prevent the gametes from drying out and to allow the sperm to swim to the eggs

Shedding their eggs and sperm into the surroundings

fertilization occurs without the parents making physical contact

Spawning

individuals clustered in the same area release their gametes into the water at the same time

Chemical Signals

one individual generates in releasing gametes trigger others to release gametes

Environmental Cues

cause a whole population to release gametes at one time; ex: temperatures, day length

External Fertilization

not synchronous across a population; individuals may exhibit specific “courtship” behaviors leading to the fertilization of the eggs of one female by one male

Triggering the release of both sperm and eggs

behaviors increase the probability of successful fertilization

Internal Fertilization

enables sperm to reach an egg even when the external environment is dry

Internal Fertilization

requires sophisticated and compatible reproductive systems, as well as cooperative behavior that leads to copulation.

Male Copulatory Organs

delivers sperm

Female Reproductive Tract

eceptacles for storage and delivery of sperm to mature eggs.

Pheromones

chemicals released by one organism that can influence the physiology and behavior of other individuals of the same species

Pheromones

small, volatile or water-soluble molecules that disperse into the environment ; active at very low concentrations

Pheromones

function as mate attractants, enabling some female insects to be detected by males more than a kilometer away

Internal Fertilization

produce fewer gametes than species with external fertilization, but a higher fraction of their zygotes survive because sheltered from potential predators

Internal Fertilization

more often associated with mechanisms that provide greater protection of the embryos and parental care of the young

Uterus

allows species to be nourished by the mother’s blood supply through a temporary organ, the placenta

Gonads

organs that produce gametes; are found in many but not all animals

Lack Distinct Gonads

he eggs and sperm develop from undifferentiated cells lining the coelom (body cavity)

Spermathecae

sacs in which sperm may be kept alive for extended periods, a year or more in some species

Cloaca

in nonmammalian vertebrates, it is the common opening to the outside of the digestive, excretory, and reproductive systems

Cloaca

releases sperm, in species with lacking a well-developed penis

True

animals often mate with more than one member \n of the other sex

Female

plays a major role in determining the outcome of multiple matings

Testes

produce sperm in highly coiled tubes called seminiferous tubules

Epididymis

coiled duct where the sperm pass into

Ejaculation

sperm propelled from each epididymis through vas deferens

Vas Deferens

muscular duct where the sperm is propelled during ejaculation

Vas Deferens

extends aroundand behind the urinary bladder, where it joins a duct from the seminal vesicle

Ejaculatory Duct

duct from the seminal vesicle where it opens into the urethra

Urethra

outlet tube for both the excretory system and the reproductive system

Urethra

runs through the penis and opens to the outside at the tip of the penis

Seminal Vesicles, Prostate Gland, Bulbourethral Glands

Three sets of accessory glands that produce secretions that combine with sperm to form semen

Semen

fluid that is ejaculated

Seminal Vesicles

contribute about 60% of the volume of semen

Seminal Vesicles

produces thick, yellowish and alkaline fluid that contains mucus, the sugar fructose, a coagulating enzyme, ascorbic acid, and local regulators prostaglandins

Prostate Gland

secretes its products directly into the urethra through small ducts

Prostate Gland

secretes thin and milky fluid that contains anticoagulant enzymes and citrate

Bulbourethral Glands

pair of small glands along the urethra below the prostate.

Bulbourethral Glands

secrete clear mucus that neutralizes any acidic urine remaining in the urethra.

Bulbourethral Glands

carries some sperm released before ejaculation,which may contribute to the high failure rate of the withdrawal method of birth control

Penis

contains the urethra as well as three cylinders of spongy erectile tissue

Arousal

erectile tissue fills with blood from the arteries. As this tissue fills, the increasing pressure seals off the veins that drain the penis, causing it to engorge with blood

Causes an inability to achieve an erection

Alcohol consumption, certain drugs, emotional issues, and aging

Glans

the head; has a much thinner outer layer and is consequently more sensitive to stimulation

Prepuce

known as foreskin; fold of skin that surrounds the human glans which is removed if a male is circumcised

Ovaries

female gonads that flank the uterus and are held in place in the abdominal cavity by ligaments

Follicles

found in the outer layer of each ovary, consisting of an oocyte

Oocyte

partially developed egg, surrounded by support cells found in the follicles at the outer layer of each ovary

Surrounding Cells

nourish and protect the oocyte during much of its formation and development

Oviduct (or Fallopian Tubes)

extends from the uterus toward a funnel-like opening at each ovary.

Oviduct

cilia on the epithelial lining of the (blank) help collect the egg by drawing fluid from the body cavity into the oviduct

Uterus

where the egg is conveyed by the cilia from the oviduct by wavelike contractions

Uterus

think, muscular organ that can expand during pregnancy to accommodate a 4-kg fetus

Endometrium

inner lining of the uterus supplied with blood vessels.

Cervix

neck of the uterus that opens into the vagina

Vagina

muscular but elastic chamber that is the site for insertion of the penis and deposition of sperm during copulation

Vagina

lso serves as the birth canal through which a baby is born, opens to the outside at the vulva

Vulva

collective term for the external female genitalia

Labia Majora

thick, fatty ridges that protects the rest of the vulve

Labia Minora

vaginal opening and the separate opening of the urethra are located within a cavity bordered by a pair of slender skin folds

HYmen

thin piece of tissue that partly covers the vaginal open-ing in humans at birth, but becomes thinner over time and typically wears away through physical activity

Clitoris

consists of erectile tissue supporting a rounded glans, or head, covered by a small hood of skin, the prepuce.

TRUE

During sexual arousal, the clitoris, vagina, \n and labia minora all engorge with blood and enlarge.

Sexual Arousal

also induces the vestibular glands near the vaginal opening to secrete lubricating mucus, thereby facilitating intercourse

Spermatogenesis

formation and development of sperm; continuous \n and prolific in adult human males

Seminiferous Tubules

where the cell division and maturation of spermatogenesis occurs

TRUE

a single sperm, the process takes about \n seven weeks from start to finish.

Oogenesis

development of mature oocytes (eggs); prolonged process in the human female

TRUE

Immature eggs form in the ovary of the female embryo but do not complete their development until years, and often decades, later