EEMB 7 ch 36 reproduction and development

sexual reproduction

reproduction arising from fusion of two haploid gametes to form diploid cells

egg

female gamete

sperm

male gamete

zygote

the diploid cell produced by the union of haploid gamtes during fertilization; a fertilized egg

asexual reproduction

the generation of offspring from a single parent that occurs without the fusion of gametes, usually the offspring are genetically identical to the parent

parthenogenesis

a form of asexual reproduction in which females produce offspring from unfertilized eggs; common in crayfish, snakes, komodo dragons, bees, wasps, and ants

ovulation

the release of an egg from an ovary; an ovarian follicle releases an egg during each uterine (menstrual) cycle

hermaphroditism

a condition in which an individual has both female and male gonads and functions as both a male and female in sexual reproduction by producing sperm and eggs

fertilization

the union of haploid gametes (sperm and egg) to produce a diploid zygote

gonads

a male or female gamete-producing organ; not found in all animals

cloaca

a common opening for the digestive, urinary, and reproductive tracts found in many nonmammalian vertebrates but in few mammals

testes

the male reproductive organ, or gonad, in which sperm and reproductive hormones are produced in the seminiferous tubules

seminiferous tubules

a highly coiled tube in the testis in which sperm are produced

scrotum

a pouch of skin outside the abdomen that houses the testes; functions in maintaining the testes at the lower temperature required for spermatogenesis

epididymis

a coiled tubule located adjacent to the mammalian testis where sperm are stored to complete maturation and become motile

ejaculation

the propulsion of sperm from the epididymis through the muscular vas deferens, ejaculatory duct, and urethra

vas deferens

in mammals, the tube in the male reproductive system in which sperm travel from the epididymis to the urethra prior to ejaculation

urethra

a tube that releases urine from the mammalian body near the vagina in females and through the penis in males; also serves in males as the exit tube for the reproductive system

semen

the fluid that is ejaculated by the male during orgasm; contains sperm and secretions from several glands of the male reproductive tract, mainly the seminal vesicles

seminal vesicles

a gland in males that secretes a fluid component of semen into ejaculatory ducts that lubricates and nourishes sperm

prostate gland

a gland in human males beneath urinary bladder that secretes an acid-neutralizing component of semen before ejaculation; last minute addition to sperm

penis

the copulatory structure of male mammals whose erectile tissue fills with blood during arousal whose increasing pressure seals off veins, causing the penis to engorge with blood where it enables it to be inserted into vagina

ovaries

in animals, the female gonad that produces female gametes and reproductive hormones; flanks uterus and is held in place by ligaments in abdominal cavity

oocyte

a cell in female reproduction system that differentiates to form an egg

oviduct

a tube passing from the ovary to the vagina in invertebrates or to the uterus in vertebrates as it transports male sperm cells to egg while providing a suitable environment for fertilization; also known as a fallopian tube

uterus

a female organ where eggs are fertilized and/or developed of the young occurs, extending during pregnancy to accommodate fetus

endometrium

the inner lining of the uterus, which is richly supplied with blood vessel

vulva

collective term for the female external genitalia

labia minora

a pair of slender skin folds that surrounds the openings of the vagina and urethra

clitoris

an organ at the upper intersection of the labia minora that engorges with blood and becomes erect during sexual arousal

mammary glands

an exocrine gland that has small sacs of epithelial tissues that secrete milk to nourish the young through the production of oxytocin and prolactin

FSH

a tropic hormone that is produced and secreted by the anterior pituitary and that stimulates the production of eggs by the ovaries and sperm by the testes

LH

a tropic hormone that is produced and secreted by the anterior pituitary and that stimulates ovulation in females and androgen production in males; helps with hormone production in females needed to support pregnancy

progesterone

a steroid sex hormone that contributes to the menstrual cycle and prepares the uterus for pregnancy

ovarian cycle

the cyclic recurrence of the follicular phase, ovulation, and the luteal phase in the mammalian ovary, regulated by hormones, that allow follicle maturity and the release of oocyte

uterine cycle

the cyclic changes in the endometrium (uterine lining) of mammals that occur in the absence of pregnancy; in certain primates, including humans, the uterine cycle is a menstrual cycle

menstrual cycle

in humans and certain other primates, the periodic growth and shedding of the uterine lining that occurs in the absence of pregnancy; the endometrium thickens and develops rich blood supply before being shed through cervix and vagina

menstruation

the shedding of portions of the endometrium during a uterine (menstrual) cycle

menopause

the cessation of ovulation and menstruation, marking the end of a human female's reproductive years

estrous cycle

a reproductive cycle characteristic of female mammals except humans and certain other primates, in which the endometrium is reabsorbed in the absence of pregnancy and sexual response occurs only during a mid-cycle point known as estrus

cleavage

the succession of rapid cell divisions without significant growth during early embryonic development that converts the zygote to a ball of cells, consisting primarily of S and M phases of cell cycle

blastula

a hollow ball of cells that marks the end of the cleavage stage during early embryonic development in animals

blastocoel

the fluid-filled cavity that forms in the center of a blastula

morphogenesis

the development of the form of an organism and its structures

gastrulation

in animal development, a series of cell and tissue movements in which the blastula-stage embryo folds inward, producing a three-layered embryo, the gastrula

gastrula

an embryonic stage in animal development encompassing the formation of three layers: ectoderm, mesoderm, and endoderm

endoderm

the innermost of the three primary germ layers in animal embryos; lines the archenteron and gives rise to the liver, pancreas, lungs, and the lining of the digestive tract in species that have these structures

ectoderm

the outermost of the three primary germ layers in animal embryos; gives rise to the outer covering and, in some phyla, the nervous system, inner ear, and lens of the eye

mesoderm

The middle primary germ layer in a triploblastic animal embryo; develops into the notochord, the lining of the coelom, muscles, skeleton, gonads, kidneys, and most of the circulatory system in species that have these structures

organogenesis

the process in which organ rudiments develop from the three germ layers after gastrulation

placenta

a structure in the pregnant uterus for nourishing a viviparous fetus with the mother's blood supply; formed from the uterine lining and embryonic membranes

contraception

the deliberate prevention of pregnancy

fetus

a developing mammal that has all the major structures of an adult; in humans, the fetal stage lasts from the 9th week of gestation until birth

in vitro fertilization (IVF)

fertilization of oocytes in laboratory containers followed by artificial implantation of the early embryo in the mother's uterus

binary fission

a method of asexual reproduction in single-celled organisms in which the cell grows to roughly double its size and then divides into two cells

budding

new individual develops from some generative anatomical point of parent organism

fragmentation

cluster of cells from original organism can begin growth in new area

what are the different mechanisms of asexual reproduction?

binary fission, parthenogenesis, budding, and fragmentation

sexual reproduction advantages

1. creates genetic diversity within species

2. natural level of disease resistance throughout species

3. genetic variation can lead to evolutionary advancements

asexual reproduction advantages

1. fast and easy

2. offspring carry all of genes that their parent carried

3. enables the species to rapidly colonize habitats that are favorable to that species

sexual reproduction disadvantages

1. competition of females

2. time and energy to find suitable partner

3. can be risky proposition; vulnerable to predation, disease, and other calamitites during reproduction

asexual reproduction disadvantage

more closely an offspring's genome resembles its parent's, less likely it is that offspring will be suited to environment when it changes

how and why does climate change affect animal reproduction?

hormones released during reproduction are regulated by environmental cues like temperature, so climate change will disrupt the cycles of reproductive activity

protandry

first males and develop into females later in life

protogyny

first females and develop into males later in life, usually the larger females

external fertilization

female releases eggs into environment and male fertilizes

internal fertilization

sperm deposited in (or near) female reproductive tract and fertilization occurs within tract

what kind of species are more likely to have external fertilization and why?

species that live in aquatic environments, like many fish, amphibians, and some invertebrates, because external fertilization occurs mainly in wet and moist environments, as it provides a medium that keeps gametes from drying out and allows sperm to meet eggs

what kind of species are more likely to have interntal fertilization?

land species, such as reptiles, birds, and mammals

external reproductive organs in males

scrotum and penis

internal reproductive organs in males

pair of gonads, accessory glands, and ducts

external reproductive organs in females

clitoris and two sets of labia

internal reproductive organs in females

gonads, ducts, and chambers

vagina

muscular and elastic chamber that is site for insertion of penis and deposition of sperm during copulation (sex)

tropic hormones

act on endocrine tissues to trigger release of other hormones

estradiol

steroid hormone and major female sex hormone

what are the three characterizing steps of fertilization?

1. sperm dissolve protective layer surrounding egg and reach plasma membrance

2. molecule on surface of sperm and egg bind to one another, ensuring that egg and sperm are same species

3. successive fast and slow changes at egg surface prevent more than one sperm getting to egg

second trimester of pregnancy

fetus grows and starts to move into fetal position

third trimester of pregnancy

fetus grows to about 50cm in length and 3-4 kg in weight

order of ovarian cycle

follicular phase, ovulation, luteal phase

evolutionary enigma of sexual reproduction

sexual reproduction produces fewer reproductive offspring than asexual reproduction and only half of the offspring from sexually reproducing females are also females

cervix

the neck of the uterus, which opens into the upper vagina