D3.1 Reproduction SL

asexual reproduction

• 1 parent

• all genes passed on to offspring

• no gametes formed, offspring genetically identical to parent and siblings if no mutations

examples of asexual reproduction

• regeneration in flatworms (planaria)

• fragmentation and regeneration in sea stars

• budding in hydra

• budding in yeaast

• binary fission in bacteria

• propagation in some plants

examples of plant asexual reproduction

• formation of plantlets in spider plants

• formation of plantlets in kalanchoe

• vegetaative propagation in potatoes or tubers

• negative propagation in strawberries by runners

advantages of asexual reproduction

• efficient (e.g, bacteria every 20 minutes)

• no STDs

• mating partner unnecessary - less energy used

• more offspring produced

• not season dependent

disadvantages of asexual production

• no genetic variation, less adaptable to environmental changes

• selective pressures cause more competition

• only locally disperseed

sexual reproduction

• 2 parents

• haploid gametes formed, sexual intercourse and fertilization form diploid zygote; offspring receives half genetic material from each parent

• offspring has unique combination of genetical and phenotypical characteristics inherited from each parent

examples of sexual reproduction

mammals, fish, reptiles, flowering plants, conifers

advantages of sexual reproduction

• genetic recombinations allow more potential to adapt to selective pressures

• offspring is widely dispersed, allowing for more resource availability

• safeguard against erroneous alleles

disadvantages of sexual reproduction

• needs mating partner - requires time and energy

• often season-dependent

• risk of failed continuity due to small number of offspring produced

anisogamy

trend of different male and female gametes in eukaryotes

features of male sex cells

• motile, often move by own means (e.g. tail, wind, pollinators)

• smaller size (human sperm ~30 μm)

• limited food reserves, enough to support movement but not development

• large number (millions) produced

reproductive strategies of male sex cells

• large number of gametes and production throughout lifetime means only few succeed

• more competition to fertilize the limited number of female gametes

• fuels evolution of mating competition

features of female sex cells

• sessile, move within very limited parameters

• relatively large size (human egg cell ~120 μm)

• large food reserves for development of embryo over an extended period of time

• fewer produced, often only 1-2 egg cells during time from where fertilization can occur

reproductive strategies of female sex cells

• small number and large gametes only produced once peer moth and until menopause indicates better provision of food sources and reproductive success due to more investment

• enhances female choice and drives selective pressure for males

male reproductive system

• ureter

• urinary bladder

• scrotum

• testis (plural testes)

• epididymis

• sperm duct

• seminal vesicles

• prostate gland

• urethra

• erectile tissue

• foreskin

• glans penis

ureter

transports urine from kidney to bladder

urinary bladder

stores urine

scrotum

holds testes at a lower temperature than core body temperature

testis

produces sperm and testosterone

epididymis

stores and matures sperm until ejaculation

sperm duct

transports sperm from testis

seminal vesicles

produces and secretes lubricating and nutritious liquid

prostate gland

secretes fluid containing proteins, alkali, fructose that are added to the sperm

urethra

transports urine and sperm

erectile tissue

required to stabilize the penis during penetration/sexual intercourse

foreskin

protects glans penis and prevents irritation of sensitive tissue

female reproductive system

• ovaries

• ligaments

• fallopian tubes/oviducts

• myometrium

• endometrium

• uterus

• cervix

• vagina

• vulva

ovary

• place of egg cell/ovum production

• acts as endocrine gland, producing estradiol/estrogen

ligament

holds ovary in place

fallopian tube/oviduct

collects mature egg at ovulation, provides a site for fertilization by a sperm cell

myometrium

muscular tissue of uterus

endometrium

inner lining of uterus, place of zygote implantation

uterus

site where embryo grows and develops during pregnancy

cervix

protects fetus during pregnancy, dilates at birth

vagina

muscular tube which enlarges during penetration by the penis and stimulates ejaculation

vulva

protects internal parts of reproduction and includes major and minor labia

zygote

formed when male and female nuclei fuse during fertilization

embryo

formed when cells begin to take up positions they will occupy in the young animal

phases of the menstrual cycle

follicular phase and luteal phase

follicular phase

follicles develop inside the ovary and the female egg cell matures

follicles

nourishing cells surrounding the egg cell

ovum

female gamete, egg cell

ovulation

• ovum is released into the oviduct from one of the ovaries

• ovum moves down oviduct by peristalsis and cilia

peristalsis

rhythmic contractions of muscles in wall of oviduct

luteal phase

cells which released egg cell turn into corpus luteum

• if no fertilization takes place, corpus luteum degenerates and new cycle begins

cycles of the menstrual cycle

ovarian cycle and uterine cycle

uterine cycle

• uterine membrane breaks down during menstruation

• uterine membrane is rebuilt slowly with blood vessels and tissue growth

• endometrium becomes thicker and more richly supplied with blood vessels in preparation for egg cell implantation

follicle stimultaing hormone (FSH)

• secreted by pituitary gland

• stimulates development of follicles, each containing an oocyte

• stimulates follicles to secrete estradiol

• determines ovarian cycle

estradiol/estrogen

hormone responsible for repair and thickening of the endometrium in the uterus after menstruation, prepares for a potential implantation of a fertilized egg cell

• ovarian hormone produced by developing egg inside ovary

estradiol in low concentration

• stimulates increase in FSH receptors

• makes follicles more receptive to FSH

• estradiol secretion increases

estradiol in high concentration

• inhibits FSH release

• stimulates secretion of LH by pituitary gland

luteinizing hormone (LH)

• peaks at the end of follicular phase in response to high estradiol concentration

• stimulates completion of meiosis in the oocyte, causes ovulation

• promotes conversion of follicle wall into temporary corpus luteum gland

• stimulates corpus luteum to secrete estradiol and progesterone

• hormone released from pituitary gland deetermining the ovarian cycle

progesterone

• secreted by corpus luteum

• reaches peak by end of luteal phase

• promotes thickening of endometrium

• inhibits FSH and LH through negative feedback loop

biological processes at the end of the luteal phase

• levels of FSH and LH in bloodstream decrease due to high progesterone levels

• low levels of FSH and LH cause the corpus luteum to degenerate