BIO 540 EXAM 3 Flashcards (Thermoregulation, Water Balance, & Reproduction)

Endothermy

Maintain an appreciable difference between body temperature and ambient temperature, due to cellular respiration.

Homeothermy

Maintain relatively stable body temperature (able to outcompete other organisms, more resistant to extreme temperatures)

Endotherms

Contain structures within nasal passage (respiratory turbinates) that are intermittent countercurrent heat and water exchangers (enabling increased ventilation rates and high resting O2 consumption)

Ectotherms

Lack respiratory turbinates, have relatively low lung ventilation and O2 consumption rates, and relatively narrow nasal passages.

Evolution of Endothermy

Two late Permian fossil lineages of Synapsids have respiratory turbinates, whereas dinosaurs did not have them.

Energy costs of Endothermy

High energetic costs; as the difference between TB and TA increases, more heat is lost.

Newton's Law of Cooling

Heat loss varies directly proportional to gradient difference between TB and TA (greater difference = greater heat loss)

Thermoregulation

A homeostatic process that maintains steady internal body temperature despite changes in external conditions.

Benefits of Thermoregulation

higher activity levels, faster movement, able to be active in diverse/fluctuating environments, increased niche exploitation, more efficient chemical reactions, enzymatic efficiency

Variation in TB in different mammal clades

Monotremes (lowest, 30-31°C), Marsupials (35-36°C), Insectivores (34-36°C), other Eutherians (36-38°C), Humans (37°C).

Basal Rate of Metabolism

A measure of the minimum cost to maintain normal TB during rest and post absorptive; scales with body mass (allometry)

Field Metabolism

The rate at which an animal expends energy in its natural habitat, measured in KJ/day (resting metabolism + energy used for all other activities)

Energy requirements depend on body size

Aquatic mammals have higher than expected RMR (2x+) due to faster heat transfer in water. Sloths have lower than expected RMR due to slow digestion, low activity

Energetic tradeoffs

High RMR leads to rapid development and population growth, higher energy demand, reproductive costs; low RMR leads to better survival and parental care, slower development, longer digestion;

The brain as an energy drain

Brain size is determined by body size; energy is expended for brain support.

Metabolism-Temperature curves

If TA < TB, lose heat passively via dry heat transfer (i.e., conduction, convection, radiation)

Thermoneutral Zone (TN)

Zone over which the basal rate of metabolism is independent of TA. Range of temps where TB is maintained without expending extra energy on heating or cooling.

Factors that Affect Insulation

Includes piloerection, alteration of blood flow (vasconstriction/vasodilation), Regional Heterothermy, changes in body posture (Behavioral Thermoregulation), fur thickness, and body size

Piloerection

Elevation or flattening of fur; involuntary response to temperature changes ("goose bumps")

Vasoconstriction

Constrict blood vessels in cold temps, reducing convective movement of heat to body surface.

Vasodilation

Dilate blood vessels in warm temps, increasing convective heat movement to body surface.

Variable distribution of fur on body

heat windows are regions with thin fur (e.g., groin area) (example of regional heterothermy)

Behavioral Thermoregulation

Changes in body posture to manage temperature exposure. Warm temps = reduce SA exposure to sun, e.g., camels huddle in long rows facing into sun; cold temps = reduce surface area exposure to wind chill, e.g., curl into ball, tuck nose, huddle in group

Fur thickness & Insulation quality

Positive correlation between fur thickness and insulation quality of fur.

Body size

Primary character influencing basal metabolic rate. Small body = larger surface area exposed relative to volume, heats faster cools faster. Large body = smaller surface area relative to volume, heats slower, cools slower.

Shrink!

Small mammals may seasonally shrink their organs to conserve energy (e.g., Dehnel Effect in shrews: reduce organ mass during winter to reduce energy requirements).

Modes of Increasing Heat Production

Shivering

Nonshivering thermogenesis (NST)

Activity

Regional Heterothermy

Shivering

high frequency, relatively uncoordinated/involuntary contraction of skeletal muscles to convert chemical energy into thermal energy.

Nonshivering Thermogenesis (NST)

Production of heat through metabolic means (increase ion pumping by Sodium-Potassium active transport pump in cell membranes, frees catabolism to permit oxidation of food reserves with immediate release of heat), primarily in brown adipose tissue.

Brown adipose tissue

(brown fat) specialized for heat production, rich in mitochondria with Thermogenin (UCP1), prominnent in cold-acclimated animals, hibernators, neonates.

Norepinephrine

A neurotransmitter and hormone released by sympathetic nervous system that serves as the primary chemical signal triggering nonshivering thermogenesis; release triggered by a drop in temperature.

Thermogenin (UCP1)

A mitochondrial protein in brown fat that generates heat by uncoupling ATP production.

Regional Heterothermy

the ability to maintain different temperatures in different parts of the body at the same time; common to all mammals.

Countercurrent heat exchange

Mechanisms allowing blood to flow to coldest part of extremity without loss of heat; related to vasodilation/vasoconstriction.

Rete Mirabile

("wonderful net") Complex network of veins and arteries, allows increased thermoregulation efficiency; efficient countercurrent exchange; commonly found in limbs and brain.

Strategies for Coping with Extreme Temperatures

Heterothermy

Hypothermia

Daily Torpor

Estivation

Hibernation

Heterothermy

The ability of an animal to vary its body temperature in response to environmental conditions; fluctuating TB = energy conservation strategy.

Hypothermia

Controlled lowering of TB, approaching TA; conserves energy.

Daily Torpor

TB lowered for only part of each day; reduces food intake demands and lowers heat loss; e.g., common in bats and some rodents.

Estivation

Summer sleep; state of dormancy during hot/dry conditions; common in small, desert mammals; conserves energy & water.

Hibernation

Seasonal lowering of TB in relation to cold temperatures and/or low food availability.

Shallow hibernation

Periods of sleep with moderate TB reduction (e.g., raccoons, skunks, badgers, bears).

Deep hibernation

TB drops within 2-3°C of TA; sleep bouts (entry, deep sleep, arousal); e.g., bats, ground squirrels, woodchucks/marmots.

Responses to High Heat Loads

1. Behavioral Thermoregulation

2. Alter insulation (e.g., shedding fur)

3. Cyclic TB (allow body temp to fluctuate daily/seasonally)

4. Hyperthermia

5. Evaporative cooling

Hyperthermia

Controlled elevation of TB to tolerate high TA.

Evaporative cooling

Water loss to reduce body temperature; e.g., panting, sweating, or licking.

Vertebrate Kidney

filtration reabsorption system; excrete waste as hypertonic urine relative to blood

Loop of Henle

Part of kidney tubule which forms long loop in medulla of kidney from which water and salts are reabsorbed into the blood. Longer LOH = more concentrated urine.

Antidiuretic Hormone (ADH)

Produced by Hypothalamus and released by posterior Pituitary; key hormone regulating kidney function; regulates water balance in the body.

ADH & Dehydration

ADH production increases; increases permeability of end of distal tube & collecting duct of Loop of Henle, increasing the multiplier effect; concentrates urine.

ADH & Hydration

ADH production decreased; not released; multiplier effect decreases; distal tube & collecting duct of Loop of Henle permeability is lowered; [Urine] decreases; extra water leaves the body.

Strategies for Water Regulation in Arid Habitats

1. Consume wet food

2. Thermoregulation (e.g., Hyperthermia)

3. Periodic trips to water holes/rivers

4. "Water Independence"

Water Independence

Rely on water via cellular respiration (metabolic water); diet mainly seeds = high in carbohydrates = can extract large concentrations of water via Catabolism. Long LOH relative to body size; dry feces

Water independent mammal

Survives without drinking water by relying on metabolic water, water in food; adaptations to minimize water loss: concentrated urine, dry feces, nasal countercurrent system; common in desert environments, rodents

Strategies to Reduce Water Loss via Respiration

1. Heat exchange systems

2. Forage at night

3. Rest in burrow during day

Heat exchange systems

Exhale air cooler than TB results in condensation of water before air leaves nasal passage (regional heterothermy = nasal passages).

Forage at night

Respiratory water loss lowest; increase metabolism in accordance with low night TA thereby increasing metabolic water production & need to obtain more seeds.

Rest in burrow during day

Plug entrance with soil; Lower TA and higher humidity in burrow relative to above ground = lower respiratory water loss.

Lactation & Water Loss

Tremendous seasonal loss of water for females; recycle as much water as possible (behavioral adaptation, e.g., ingest urine & feces of young) and/or drink frequently.

Mammalian Reproduction Strategy

Relatively few intrauterine young (high survival rate compared to other species); nourish neonates with milk; young remains with mother until weaned; greater amount of energy invested per young

Cost of lactation

Breeding females required more energy.

Follicle Stimulating Hormone (FSH)

Secreted by the pituitary; triggers follicle growth.

Luteinizing Hormone (LH)

Secreted by the pituitary; triggers ovary to secrete Estrogen.

Estrogen

Hormone that regulates the reproductive cycle and promotes the development of female reproductive tissues and traits.

Corpus Luteum

Spongy body which forms in place of ruptured follicle; secretes Progesterone for uterine wall preparation.

Progesterone

Prepares and maintains the uterus for pregnancy; secreted by Corpus Luteum.

Corpus Albicans

Nonfunctional, fibrous remnant of Corpus Luteum after it regresses if no fertilization occurs.

Feedback from Mammaries

Stimulates Prolactin (stimulates milk production) release and inhibits Gonadotropin (hormones that regulate reproductive organs, gametes).

Major Parts of Embryonic Membranes

1. Yolk Sac

2. Amnion

3. Allantois

4. Chorion

Yolk Sac

Part of primitive intestine lying external to embryo; forms from Endoderm.

Amnion

Forms from Ectoderm and Mesoderm around the embryo; filled with serous fluid; prevents shock/desiccation

Allantois

Out-pocket from the hindgut of embryo; movement of nutrients and O2.

Chorion

Outer embryonic layer (Ectoderm); envelopes entire assemblage, contains villi; contact with uterine wall

Placenta

Includes embryonic membranes & lining of uterine wall (Endometrium).

Endometrium

Mucous membrane lining the uterus; thickens during menstrual cycle.

Diffuse placenta

Villi scattered over entire surface of chorion; increased surface area for absorption; e.g., lemurs, perissodactyls, some artiodactyls.

Polycotyledonary placenta

Islands of villi scattered over chorion; e.g., Bovids (cattle, bison, sheep, goats)

Zonary placenta

Band of villi encircle center of Blastocyst; e.g., carnivores

Discoidal placenta

Regional restriction of villi; e.g., most mammals, rodents, primates, humans

Nondeciduate placenta

Loose-fitting of villi with Endometrium; pull-free without disrupting endometrium during parturition; e.g., whales, ungulates

Deciduate placenta

Close-fitting of villi-endometrium; pull free & cause erosion of Endometrium during parturition; e.g., rodents, carnivores

Choriovitelline placenta

Blastocyst lies in the Endometrium depression; does Not embed; e.g., Marsupials

Chorioallantoic placenta

Villi, blastocyst rests against Endometrium at Allantois-Chorion contact point, specialized regions, longer gestation; e.g., Eutherian mammals

Chorioallantoic Placenta Types in order of most layers to least

Epitheliochorial

Syndesmochorial

Endotheliochorial

Hemochorial

Hemoendothelial

Epitheliochorial placenta

Epithelial cells of chorion in contact with epithelial cells of uterus, villi in pockets in endometrium (most layers); e.g., lemurs, cetaceans, equids, suids

Syndesmochorial placenta

Lacking uterine epithelial barrier; contact uterine tissue; e.g, Artiodactyls

Endotheliochorial placenta

Epithelial cells of chorion in contact with lining of uterine capillaries; e.g., Carnivores

Hemochorial placenta

Villi in direct contact with maternal blood; e.g., insectivores, bats, higher primates, humans

Hemoendothelial placenta

Lining of villi blood vessels only barrier to maternal blood; e.g., lagomorphs, some rodents

Continuous Embryonic Development

Ova fertilized in oviduct; Zygote begins Mitosis, descends towards uterus; zygote reaches uterus, blastocyst stage as implanting into endometrium; placental connection; uterus to embryo; continual development until parturition

Deviations from Continous Development

Delayed Fertilization

Delayed Development

Delayed Implantation

Delayed Fertilization

Ovulation and fertilization delayed until an extended time after copulation; viable sperm retained in female; ovulation occurs months after copulation; common to temperate bats

Delayed Development

Blastocyst embeds into the endometrium and then becomes dormant; e.g., common in bats

Delayed Implantation

Blastocyst forms but does not embed and ceases to develop; floating blastocyst remains dormant for weeks to a year; e.g., weasels, seals, bears

Types of Breeding Seasons

Continuous: year-round breeding; Restricted: optimal timing for mating and birth.

Influences on Puberty & Reproduction

Light

Temperature

Nutrition

Precipitation

Social Effects/Density

Lee-Boot Effect

psuedo-pregnancy induced among crowded females

Whitten Effect

synchronized ovarian cycles when male introduced into population of females

Bruce Effect

implantation blocked; pregnancy aborted if females exposed to strange new male;

Blastocyst

Early mammalian embryo (hollow ball of cells); implants into uterus.