Energy and

1

• Energy and
• Thermoregulation

2

• Maintaining internal environments Challenge for
  all living environments

3

• Regulators use internal control mechanisms to
  regulate internal change in the face of
  fluctuations in the external environments.
• Conformers allows internal environment to
  conform to external changes (for a particular
  environmental variable)

4

• Regulating and conforming are extremes of a
  continuum Organisms may conform to some
  environmental factors and regulate others. e.g.
  fish thermoconformers, osmoregulators.

5

• Homeostasis (steady state) Maintaining
  relatively steady internal environment even when
  external environment changes significantly.
• Dynamic equilibrium external factors try to
  change internal environment, internal control
  mechanisms oppose such changes.
• Body temperature 37oC
• pH 7.4
• blood glucose 90mg/100mL of blood

6

• Mechanisms of homeostasis
• Set point the desired temperature (variable)
• Stimulus fluctuations in the variable
• Sensor detect stimulus and triggers an
  appropriate change
• Response activity that helps return the
  variable to the set point

7

• Home heating system as an example of homeostasis

8

• Do you see the machanism of homeostasis here ?

9

• Negative feedback loop response that reduces
  the stimulus. (exercise and sweting)
• Positive feedback loop responses amplify the
  stimulus (labor)

10

• Regulated changes of setpoint e.g. temperatures
  change when asleep and awake, hormone levels in
  womens menstrual cycle
• Acclimatization change in normal range of
  homeostasis in response to internal environment.
  e.g. increased blood flow and red blood cell
  production
• Acclimatization is not adaptation
  acclimatization is temporary adaptation is
  natural selection working on a population over
  several generations.

11

• Homeostatic process for thermoregulation
  Essential to maintain internal temperatures
  within tolerable range.
• Enzymes have narrow optimal temperature range.
• 10oC change in temperature reduces enzyme
  activity 2 to 3 fold
• Proteins start to denature and loose activity

12

• Endothermy warm themselves by heat generated by
  metabolism (birds and mammals). Have ways of
  warming and cooling their bodies. Consume more
  food than ectotherms
• Ectothermy gain their heat from external
  sources (amphibians, lizards, snakes, turtles,
  fishes). Mostly change body temperature by
  behavior.
• Endotherms may have some ectothermic behavior.
  Two strategies are not mutually exclusive.

13

• Poikilotherm Animal whose temperature varies
  with environment
• Homeotherm Has a relatively constant body
  temperature
• Common misconception poikilotherms are
  coldblooded homeotherms are warmblooded.

14

• Balancing heat loss and gain
• Heat exchange is regulated by four physical
  processes
• Conduction
• Convection
• Radiation
• Evaporation

15

• Thermoregulatory organ major role played by the
  integumentary system (skin, hair, nails, fur,
  scales, claws)

16

• Theromregulatory adaptations
• Insulation
• Circulatory adaptations
• Evaporative loss of heat
• Behavioral adaptations
• Adjusting thermogenesis

17

• Theromregulatory adaptations
• Insulation
• Circulatory adaptations
• Evaporative loss of heat
• Behavioral adaptations
• Adjusting thermogenesis

18

• Insulation
• Prevent flow of heat between animal and
  environment
• Hair, feather traps air and insulates, raising
  hair traps more air
• Goose bumps
• Some animals ooze oil into their hair to prevent
  them from getting wet

19

• Theromregulatory adaptations
• Insulation
• Circulatory adaptations
• Evaporative loss of heat
• Behavioral adaptations
• Adjusting thermogenesis

20

• Circulatory adaptations
• Regulate blood flow near body surface and
  maintain core body temperature
• Vasodialation nerve signals relax muscles of
  the superficial blood vessel walls, increased
  blood flow to the surface, heat directed to the
  skin, increase in surface temperature, heat
  dissipated by radiation, example jack rabbits
  ears
• Vasoconstriction Diameter of superficial blood
  vessels decrease, reduces blood flow to the
  surface and prevents heat loss.

21

• Circulatory adaptations contd.
• Countercurrent exchange arrangement of tissues
  and blood vessels in a particular way that
  maximizes heat exchange.
• Example goose and dolphin

22
Skin
Artery
Vein
Blood vessels in gills
Capillary network within muscle
Heart
Artery and vein under the skin
Dorsal aorta
Great white shark
23

• ..also helps maintain core body temperature in
  essential tissues, like flight muscles

24
21
23
25
27
29
31
Body cavity
Bluefin tuna
25

• Theromregulatory adaptations
• Insulation
• Circulatory adaptations
• Evaporative loss of heat
• Behavioral adaptations
• Adjusting thermogenesis

26

• Evaporative heat loss
• Water evaporates considerable heat during
  evaporation
• Panting in dogs
• Sweating
• Fluttering of pouch at the base of the mouth

27

• Theromregulatory adaptations
• Insulation
• Circulatory adaptations
• Evaporative loss of heat
• Behavioral adaptations
• Adjusting thermogenesis

28

• Behavioral responses
• Migration
• Body orientation
• Hibernation
• Bathing
• Huddling
• Storing high calorie food (honey)

29

• Theromregulatory adaptations
• Insulation
• Circulatory adaptations
• Evaporative loss of heat
• Behavioral adaptations
• Adjusting thermogenesis

30

• Adjusting thermogenesis
• Shivering thermogenesis heat production as a
  result of increased muscle activity
• Nonshivering thermogenesis some specialized
  chemical reactions results in heat production
  instead of ATP in mitochondria

31

• Adjusting thermogenesis contd
• Some ecothermic animals can do some endothermic
  regulation (egg incubation by Burmese python,
  resulting from spasmodic muscle contraction)

32

• Adjusting thermogenesis contd
• Some insects perform warm-up preflight
  shivering to get critical muscles warmed up

33

• Acclimatization in Thermoregulation
• Thicker coat during winter
• Enzymes with different optimal temperatures but
  same function
• Cells with antifreeze compounds

34

• Physiological thermostats temperature
  regulation in humans

35

• Fever increase in set point of body
  temperature in the hypothalamus, for instance
  response to infections
• Fever has some defensive functions
• Fever is observed in endotherms
• Ectotherms have behavioral adaptations that
  function like development of fever, during an
  infection

36

• Bioenergetics
• Related to animals size, activity, environment
• Determines food need
• Overall flow and transformation of energy in an
  animal

37

• Energy allocation and use
• Animals obtain energy for various activities from
  food
• Food is digested in the body by enzymatic
  hydrolysis
• Digested food generates ATP as a result of
  cellular respiration
• ATP is used for biosynthesis, growth, repair,
  reproduction etc. and for generating heat

38

• Quantifying energy use
• Metabolic rate sum of all energy requiring
  biochemical reactions over a given time interval.
  
• Can be measured by heat production, carbon
  dioxide production, food consumption etc.

39

• Basal Metabolic Rate (BMR) Minimal metabolic
  rate of a nongrowing endotherm at rest, in an
  empty stomach, at comfortable temperature with no
  generation or shedding of heat.
• Human males 1,600 to 1,800 kcal (C) per day
• Human females 1,300 to 1,500 kcal per day

40

• Standard metabolic rate (SMR) metabolic rate
  of a fasting nonstressed ectotherm at a
  particular temperature.
• Alligator 60 kcal per day

41

• Maximum metabolic rate (MMR) Highest rate of
  ATP use is inversely related to the duration of
  the activity.

42

• Size and metabolic rate
• Relationship between metabolic rate and body mass
  is constant across a wide range of sizes and
  forms
• Metabolic rate is roughly proportional to the
  body mass, to the ¾ power (m ¾)
• The reason for this is not yet known

43

• Energy budgets

44

• Torpor, Hibernation, Energy conservation
• Physiological state of low activity, low
  metabolism, body temperature drops, allowing the
  animal to save energy and avoid situations where
  it is more vulnerable
• Hibernation is long term torpor.

45

• Small animals with higher metabolism go into
  torpor
• bats torpor during the day,
• hummingbirds at night.

46

• Certain squirrels show prolonged torpor with
  brief arousals in winter.