Chapter 5 class (exam2) Flashcards
Endogenous Hypothesis:
An internal biological clock
Environmental stimulus hypothesis:
environmental cues are used
Zeitgebers (time givers)
Cues from periodicities in environmental variables such as light cycle, temperature, tides
Long-Term Cycles
- Epicycle or Ultradian
- Tidal
- Lunar
- Circadian
- Circannual
- Intermittent
- Diapaurse Phase
Epicycle or Ultradian
Variable
Ex: Vole Feeding
Tidal
- 4 hours
ex: Oyster shell opening - 8 days
ex: Grunion egg-laying
Lunar
- 5 days
ex: Kangaroo rat foraging
Circadian
24 Hours
Diurnal ————–Active during the day———Squirrel
Nocturnal ———–Active at night————-Owl
Crepuscular——–Active and dusk and dawn—Rabbit
Circannual
12 months
ex: Bird reproduction, migratory cycle, etc.
Intermittent
Days to years
ex. Desert insect breeding (often in desert)
Diapaurse Phase
Dormancy during bad season
ex. Hibernation
Humans internal clock gets___if not exposed to ___
off if not exposed to external cues (same for most animals
Cricket Clock
o 12 hour light, 12 hour dark cycles produce normal timing of singing, and entrained cycle
o Crickets show a free-running cycle for singing without a day-night cycle
o Continuous light = 25 – 26 hours, continuous dark = 23.5 hours
If crickets eyes are ___, you get ___…
o If crickets eyes are disconnected from optic lobes, you get a free running cycle where cricket is continuously in dark, but the clock is still running
Thus, the eyes simply provide environmental ques
Optic lobes disconnected from the brain =
o random singing. This looks like the location of the clock (as brain by itself doesn’t seem to keep the clock running)
Such light cycles are seen in animals and in plants
Sand Crickets
o … show different light cycles depending on long-winged or short-winged morph, based on their environment
o The rodent/mammal biological clock seems to be located in …
the suprachiasmatic nucleus
Mammal light cycle:
- Light –> Retina –> Suprachiasmatic Nucleus –> SCN pacemaker –> (PER protein, PK2 protein, tau, and CREM Gene (Pineal Gland) –> ICER protein –> Melatonin from Pineal Gland … base of the 24-hour cycle
o ICER Protein builds up –> Inhibits CREM Gene Ends ICER production –> Cycle Ends
o Photoperiod –> Alters CREM sensitivity to inhibition Adaption to day length
o Mice: normal cycle =
23 + hours
Heterozygous for clock allele = 25 hours
Homozygous for clock allele = 28 hours, then complete breakdown
Anole (green lizard) Reproduction
o Temp/Light driven clock –> displaying male
o Pituitary gonadotropins –> Egg development
o Ovaries releasee estrogen –> Target brain cells receptivity
o No predator –> Mating –>Proglastaglandin –>Stop receptivity
Mating act itself is what elicits the Proglastaglandin
o Egg laying –> ovaries –> Still summer? –> cycle again
Cycle stops come August, even should the females be injected with hormones. Appears that light cycle determines
What elicits Proglastaglandin?
Mating act itself
What does Proglastaglandin do?
stop mating receptivity (I think?)
The mechanical stimulation associated with mating ends…
sexual receptivity in females. In some species like rabbits, this stimulation causes ovulation- Ovulation on Demand.
In temperate and polar regions, day length often …
starts breeding. The time between mating and birth is a factor:
o Short times (birds): Triggered by increasing day length
o Long times (deer): Triggered by decreasing day length
Second full moon after the fall equinox theory about
when deer mate?
o Full moon seems to also influence reproduction of
Worms in coral reef
o External factor of rainfall
o Kangaroos in Australia
Delayed Implantation:
Hill kangaroos breed do not implant fertilized eggs in the uterus until rain occurs and the food is abundant
• Mother kangaroo will throw baby out of pouch if there is not enough food. This leads to better chance of success in next reproductive cycle
In Pinon Jays, breeding is initiated by…
seeing growing pinecones
White crown sparrows:
migrate annually from south to Alaska
White Crown Sparrows Circadian Clock:
Must have well timed departure, and based off length of day. But eyes are not involved in the process
Not based on vision, but on photoreceptors in the brain, maybe in the pineal gland
A photosensitive clock is set at dawn. For the next 12 hours, it is insensitive to light. Then sensitivity peaks at 16-20 hours
A photosensitive period exists at the end of the day. Additional light during that period begins fat deposition and gonadal development (develops by 100x)
• Photoperiod que is effective in spring but not in fall
Male Mice
o Take over a territory and mate
o Will kill any pups for the next three weeks
As these would have been the offspring of previous male
o Then care for pups parentally
o Kill pups again about 7 weeks after mating, when their pups would be gone
o Number of light-dark cycles is the main factor in timing, not number of hours
o Territorial males mate with a harem of females (offspring of previous male). Their presence facilitates sexual maturation in females; inhibits it in males.
Provides reproduction for these females more rapidly
Other males take advantage of territory and not appear competition to territorial male
Main factor in timing for male mice is:
number of light-dark cycles (not number of hours)
Females mice without a male
stop ovulating. Those exposed to urine of strange male resorb embryos or abort (Bruce effect).
Basically not investing in any offspring at this point, as the offspring could be killed by strange male
COMPARISON of mice to humans
Male contact/smell regularizes female cycle
Female contact/smell increases male testosterone production and beard growth
Expose men to nursing women/babies – aroused
Around ovulation: changes in skin tone, pitch of voice increases, dress more provocatively
Ring Dove Reproduction
o Males begin courting after placement with female
But castrated ones don’t (need of testosterone)
o Courtship stimulates female pituitary to release FSH (follicle stimulating hormone), causing ovarian follicle development
o Follicles secrete estrogen, causing uterine growth and development
o Within day or two, nest construction and copulation (mating) begins
o Next, presence stimulates production of progesterone in females (and some in males)
Progesterone promotes incubation in both sexes after eggs are laid
o Egg laying is activated, in part, by pituitary secretion of LH (lutinizing hormone).
o Incubation, maintained by progesterone secretion, lasts 14 days. Male and female take turns on the nest
Egg in nest and stimulation from incubation behavior causes both sexes’ pituitary glands to secrete prolactin
What role does prolactin play in ring dove reproduction?
Prolactin inhibits PSH and LH secretion, and all sex behavior ceases. Prolactin stimulates crop development and production of crop milk, may help maintain incubation
o Squabs hatch in 2 weeks, eat crop milk for the next 10-12 days. Feeding wanes toward the end, probably because prolactin secretion decreases
o Prolactin decreases, pituitary secretes FSH and LH, and the sequence recurs.
At each stage, a bird’s internal state interact with external variables to produce behavior. The variables are:
Hormones: Hormonal state of both sexes, including feedback loops
Behavior: Each dove’s behavior stimulates changes in mate hormone levels and behavior
Environmental Cues (nest and eggs): Influence hormonal and behavior changes in both
Hormonal Mediation
- Organizational Effects
- Activational Effect
- Associated Reproductive Patterns
- Dissociated Reproductive Patterns
- Testosterone
- Stress
Organizational Effects
Control brain development – irreversible
Activational Effect:
Initiate or regulate behavior – reversal
Associated Reproductive Patterns:
Hormones control reproductive patterns
Typically what is thought of with behavior following hormones
Dissociated Reproductive Patterns:
Hormones do not control some elements of reproductive patterns
- -> Example of doves: if in area where it is possible to raise second family, this can happen, but hormones are way down – testosterone possibly more associated with territorial claim than reproduction?
- -> Example of red sided garter snake: Males produce testosterone in fall, causing sperm production. Then hibernate. Spring, no big testosterone production, but they still mate without hormone appears to be the temp more than the hormones involved with mating behavior
Testosterone:
Promotes sperm production, sexual behavior, aggression, and suppresses the immune system
o Last feature is quite a down-side, and it is reflected in poor health
Stress
Environmental factors
Acute Stressors: like a predator, cause glucocorticoid hormones to be produced as part of the flight or fight response
Chronic Stressors: (such as low dominance rank, little food, etc.) activates the hypothalamic-pituitary-adrenal (HPA) axis
• Not healthy
Acute Stressors:
like a predator, cause glucocorticoid hormones to be produced as part of the flight or fight response
Chronic Stressors:
(such as low dominance rank, little food, etc.) activates the hypothalamic-pituitary-adrenal (HPA) axis
• Not healthy
