Animal Reproductive Strategies and Structures Flashcards
Internal Fertilization
occurs inside the body of the female
-mostly land-based animals
3 ways to reproduce with internal fertilization
- fertilized eggs are laid outside the female’s body and receives nourishment from the yolk (most bony fish, reptiles, all birds, amphibians, and 2 mammals)
- fertilized eggs are inside the female’s body but the embryo receives nourishment from egg’s yolk and are fully developed when hatched
-retained inside the female, receives nourishment from the mother’s blood through a placenta - offspring develops in the female and is born alive (most mammals)
External Fertilization
occurs outside the body of the female
-usually occurs in aquatic environment where eggs and sperms released in water (spawning)
How do we get sperms and eggs to be released at same time and location
- environmental cues or biological (pheromones) cues with massed together animals
-amphibians: males will induce female to release the eggs for male to release the sperm on
Adaptations and Biological Fitness
anything that increases an individual’s reproductive success
– occur without conscious thought or individual intention
-Biological fitness: reproductive success relative to others in the population
– SURVIVING offspring who can reproduce as well?
examples of adaptaion for maxing biological fitness:
parental investment, direct and indirect male compeitition
Sexual Selection
results from one sex (or both) selects specific individuals to mate with
- type of natural selection where one sex has a preference for certain characteristics in individuals of the other success - leads to increased reproductive success of that particular characteristic
secondary sexual characteristics
sexual dimorphism
exaggerated or showy traits that are associated with mating behaviors and reproductive success
ex. breasts, tails, headpieces, etc
Sexual Dimorphism
distinct differences in size or appearance between males and females
Why are females more likely to be “choosy” when selecting a mating partner
females invest more in offspring than males do - females have limited num of eggs while males basically have unlimited sperm: females must be choosy because they don’t want to waste their energy or time
- females maximizes reproductive success by choosing the best male and males maximize success by mating with as many females as possible
- SO females are often the sex that sexually selects traits in males - males compete with each other for access to females or a specific female
parental investment
any energy, effort, or resource that a parent provides to increase the offspring’s chances of survival AT THE COST of investing in other offspring
-providing energy and nutrients
Direct Male Competition (intrasexual selection)
occurs when females mate only with a single male - the winner
ex:
male-male aggression, courtship rituals, lekking
male-male aggression
males fight with each other for access to females
courtship rituals and Lekking
males engage in “dances” or displays for females
Lekking: special form where many males gather together in one and “display” at the same time, allowing the females to choose among them
female choice or intersexual selection
selection of the “best” male by females
-intersexual and intrasexual selection can lead to selection for more “showy” traits even if it decreases its chances of survival because it will improve biological fitness
good genes hypothesis
idea that sexually-selected, show male traits are “honest indicators” of good genetic quality
Indirect Male Competition or Sperm Competition
after mating has already occured: one male is more successful than another at fertilizing female’s eggs
- if female mates with more than one male, then the more successful one will fertilize more eggs, have more offspring, and increase the trait
-first male vs second male advantage!!
mate guarding
first male advantage
male remaining close to female after mating, prevent other males from mating with her until there is time for his sperm to fertilize the eggs
copulatory plugs
first male
- leaves a sticky residue which blocks the entry into the female reproductive tract so that other males can’t mate
Second Male Advantage examples
elaborate penis morphology to help remove previous males’ sperms
large ejaculation volume and large testes to flush out previous sperm
cryptic female choice
female can preferentially use sperm from a specific male even if she mated with multiple males based on female anatomy
when is there competition in males (internal vs external!)
usually both internal and external fertilization! females can control when the eggs are released so males must compete
monogamous systems
one male and one female are paired for at least one breeding season
- can last a lifetime
- “male-assistance hypothesis” with a male’s help to guard and rear young, healthier offspring!
- environments with widely scattered resources! need both parents
true monogamy (sexual monogamy) vs social monogamy
true: both partners mate only with each other - rare!
social: two individuals partner together to rear offspring BUT also engage in “extra pair” copulations
— helps both males and females because increases survival of who they raise while also being able to mate with others: males might be taking care of those not his own and females might be abandoned if found out she mated with another
polygamy - polygyny vs polyandry
polygyny - many females, one male, females take care of children, harem mating with alpha males, lek systems - females choose their favorite male from lekking
polyandry - one female with multiple males, rare because sex role reversal, males investing more; females competition with each other to access males
promiscuous
multiple females with multiple males
-no possible monopoly like in large social groups or the females range more widely than territory size of a single male
Competition for mates influence mating systems and vice versa
ADD LECTURE NOTES
ALWAYs competition for fertilization except in true monogamy (and promiscuous?)
Spermatheca
some invertebrates have this specialized sac that stores sperm for later use (up to a year); timed fertilization with optimal conditions
Cloaca
non-mammal vertebrates liek birds and reptiles can have a single opening which functions in the digestive, excretory, reproductive systems
Ovary
where ovum/eggs mature
Testes
where males produce sperms in humans
Epididymis
where sperm is stored until ejaculation
Sperm
small, mobile, low-cost, high numbers
Ovum
female eggs, typically large
Uterine Tubes
when eggs are released from the ovary, where they travel for fertilization or are released in the aquaeous environment
-oviducts and fallopian tubes
Uterus
mammals have separate openings in the female; placental mammals have this for supporting offspring; can have one or two chambers depending on how much offspring is reproduced
gonadotropin-releasing hormone (GnRH)
hormones released by the hypothalamus to the anterior pituary which releases FSH and LH into the blood that are used in both regulation of male and female reproduction
Follicle Stimulating Hormone and Luteinizing Hormone
during pubertyproduced by the pituary gland - stimulate the ovaries to produce female sex hormones estrogen and progesterone;
FSH - stimulates development of egg cells that develop in follicles in the ovaries
LH - promotes development and maturation of eggs and induction of ovulation
Estrogen and Progesterone
female sex hormones that results in development of secondary sex characteristics (breasts) and causes ovaries to produce mature eggs;
Estrogen assists in ovulation and regrowing of the lining of the uterus and secondary characteristics
Progesterone: endometrial re-growth and inhibition of FSH and LH release
Ovaries
produces and develops eggs
Oviducts
transports egg to uterus, acts as site of fertilization; not connected directly to ovaries
Uterus
supports a developing embryo
Vagina
receives penis during intercourse, acts as birth canal, passes menstrual flow
cervix
allows passage between uterus and vagina
breasts
milk
follicles
where egg development occurs
lined with follucular cells that surround the egg and promote development
-during menstrual cycle, a batch of these cells develop and prepares eggs for release
at ovulation, one follucle ruptures and one egg is released
corpus luteum
ruptured follicle that remains in the ovary: secretes hormones that prevent menstruation until the egg has had time to be fertilization
if fertilization and implanatation of uterine wall occurs - corpus luteum continues preventing menstruation; else it degenerates and menstruation occurs
Oogenesis
producing an egg cell, occurs in the ovaries;
begins when female is still an embryo undergoing development - oocytes begin process of meiosis and pause during meiosis prophase I
oogonia
egg stem cells
-divide by mitosis to produce 2 million oocytes (precursors to egg)
Spermatogenesis
Spermatogonia doesn’t begin producing spermatocytes until the male hits puberty
Process to egg maturation
- FSH and LH cause some of the follicles to begin developing and oocyte in the follicle finish first meiotic division
- oocyte pauses again at metaphase 2 (is this when it matures?)
- while several follicles are activated during each cycle, only one will release an oocyte which begins traveling through the oviduct where it is still paused/arrested
- if fertilized, it finishes meiosis I and undergoes unequal cytokinesis to make an embryo/zygote and another polar body else it degrades without completing meiosis II
Ovarian vs menstrual Cycle
ovarian governs the preparation of endocrine tissues and release of eggs while menstrual governs the preparation and maintenance of the uterine lining
follicular phase
slowly rising levels of FSh and LH: growth of follicles - preparing egg for ovulation
-estrogen levels increase over the course of the follicular phase
-menstrual cycle: menstrual flow occurs at the beginning when estrogen levels are low - rising estrogen cause endometrium to replace the blood vessels and glands that deteriorated during the end of the last cycle
ovulation
right before the middle of the cycle: highest level of estrogen causes FSh and LH to peak rapidyly then fall - follicles that didn’t rupture degenerate and eggs are lost; level of estrogen decreases when the extra follicles degenerate
Luteal phase of Ovarian and secretory phase of menstrual cycle
corpus luteum forms which produces estrogen and progesterone: progesterone facilitates the regrowth of the uterine lining and inhibits future LH and FSH, preventing further eggs and follicles; uterus is prepared to accept a fertilized egg; estrogen increases and enhances the effects of progesterone
Fertilized vs unfertilized egg in the ovarian/menstrual cycle
takes 7 days for egg to travel to the uterus
no fertilized: corpus luteum degerneates, estrogen and progesterone decrease, endometrium degenerates when progesterone decreases leading to the next menstrual cycle: GnRH starts releasing FSH and LH again and cycle restarts
fertilized egg: embryo produces a hormone that maintains the corpus luteum so still high progesterone and menstrual cycle is arrested for rest of pregnacy
testicals/testes in scrotum
produces sperm and some reproductive hormones;
Sperm and temperature
body temp: immobile
scrotum and penis are external to body so that proper temp is maintained for motility
- sperm are warmed to body temp when it enters the female reproductive tract - gives them a burst in swimming activity before losing motility after several hours
seminiferous tubules
where sperm are produced inside the testes
Sertoli cells and cells of Leydig
Sertoli: “nursemaid” cells that protect germ cells and promote development
Leydig: produce high levels of testosterone when ale reaches adolescence and regulate sperm development
Epididymis
when sperm have flagella and near mature, leave trsticles and enter epididymis where sperm mature
Vas Deferens
sperm leave epididymis and enter the vas deferens which carries the sperm, behind the bladder, and forms ejaculatory duct with duct from the seminal vesicles during ejaculation
Semen
mixture of sperm and spermatic duct secretion and fluids from 3 other internal accessory glands which is where most of the semen come from
Seminal Vesicles
alkaline solution so basic pH to reverse acidity of vaginal environment, some nutrients and energy source and local hormones that’ll help with the sperm and smooth muscle contraction in uterus (60% of semen)
Prostate Gland
smooth muscle and glandular tissue: provides force needed for ejaculation to occur with citrate and enzymes to stimulate sperm motility (30% of semen)
Bulbourethral Gland
secretes before the release of the bulk semen and help lube and neutralize any acid residue in uretha from urine; only a couple drop with some sperm possibly
Spermatogenesis
seminiferous tubules; spermatogonia is sperm stem cells which are present at birth but inactive until puberty - continues into old age once activated; spermatocyte undergoes meiosis and produces 4 haploid spermatids and once it develops a flagellum it makes a sperm cell (4 total)
FSH, LH, and Testosterone in Spermatogensis
FSH: stimulates spermatogensis in the testes
LH: testosterone production
Testosterone: spermatogensis; hormone responsible for secondary characteristics in male (deep voice, hair, sex drive)
- if sperm counts get too high, rising testerone levels cause Sertoli cells to release inhibitin which stops release of FSH and LH and slows spermatogensis
Eggs vs Sperm production
when gametes start to form: egg production begins during embryonic development and then arrested during meiosis until puberty AND then sperm production doesn’t begin until puberty
gametes finish being made: sperm is done before ejaculation while egg is not done until after fertilization
how many from stem cell: eggs only result in one from each egg stem cell while sperm production results in 4
rate of production: egg is one-at-a-time at each menstrual cycle while sperm production is continuous like mass production
Contraception methods
see powerpoint slide
Plan B - emergency contraception
