Block 10 - Animal physiological adaptions Flashcards
What is a physological adaptation?
The physiological adaptation to an environment:
- improved interaction with the environment
- better maintainance of internal homeostasis
- cope with intermittent food sources
What are 5 examples of harsh environments that animals can adapt to?
1) Deep sea (low oxygen, low light and high water pressure)
2) High altitude (low oxygen conc)
3) Constant darkness (caves)
4) Hydrothermal vents and volcanos (high heat)
5) Fluctuating environments (variation in temp, food and abundance) - e.g. deserts
Explain some of the adaptions of a camel for life in a desert
- wide shallow feet so camels don’t sink in the sand
- horny pads in the mouth to eat rough textures (e.g. cactus)
- fat stores concentrated in hump to minimise insulating effect
- oval blood cells to withstand osmotic variation
- kidneys and intestine able to reabsorb maximal amounts of water
Explain the adaptions to life in the dark by the mexican cave fish
Astyanax mexicanus - a model system for physiological adaptation.
Two differnt types (morphs) - surface and cave
Cave morph:
- has an almost complete loss of pigmentation
- complete loss of eyes
- more pointy jaw (can eat the food sources in the cave)
- more hair cells -neuromasts- on lateral line (can sense vibration so may compensate for vision loss)
- lower metabollic rate
- increase fat reserves (more resistent to starvation)
- increased sensitivity in the olfactory system and higher numbers of taste buds
Differences in cave populations could be due to differences in cave environments and time since separation
What are the types of animals that inhabit caves?
Troglobites: spend their whole lives underground
(fish, salamanders, molluscs, worms, crustacea, antropods)
Trogloxens: casual visitors live in the caves but have to leave to eat
(bats, cave swallows, insects)
Troglophiles: live equally well in caves or on the surface
(bats, insects)
What are some adaptions of cave animals from epigeal (surface) animals?
- Loss or reducation of pigmentation
- Loss or reducation of eye structures (reduced requirement for eyes due to lack of sunlight)
- Improved sensory systems (lateral line in fish, antennae in anthropods)
- Alterations to circadiam rhythms (usually set by the sun and causes changes in hormones throughout the day)
- Lower metabollic rate - can’t eat as often due to sporadic food supplies
What is another good model for adaptation (other than mexican cave fish)?
Darwin’s finches:
- food abundance drives changes in beak morphology
- beaks adapt quickly in response to chnaging environments
- beak shape can alter finch song structure and can lead to speciation by altering mate choices in finches
What is homeostasis?
The maintainance of a steady state or internal balance.
A dynamic equilibrium between external factors that modidy an animal’s internal environment and internal control mechanisms that oppose such changes.
^ does not imply the absence of change
What is Bernard’s Constant Internal Milieu in Humans?
Internal body temperature: 37 degrees celcius
Blood and interstitial fluid pH: 7.4
Blood sugar: 75-100mg/100ml
Oxygen content of blood: 17.2-22ml/100ml
Urea: 12-35mg/100ml
What is negative feedback?
A system whereby a change in a variable triggers a control mechanism to counteract further change in the same direction
Homeostatic reaction to changes in temperature: it gets warm so body systems cool it down
What is postive feedback?
Occurs when change triggers mechanisms that amplify it rather than reversing it e.g. oepning of uterus during childbirth
How is body temperature regulated?
The hypothalamus acts as a physiological thermostat
- to cool the body down sweat glands are activated
- to heat the body up hair on skin stands on end (piloerection)
How can regulated change occur?
Occurs over time - circadian changes, hormone levels during the menstrual cycle (internal systems are not static)
How does fever affect body temperature?
Hypothalamus can increase the core body temperature - tries to use heat to kill pathogens
How does body temperature change with the circadian cycle?
Body temperature is affected by melatonin concentration (higher during the day when melatonin is low and lower at night when melatonin levels are high)
How long are physiological cycles?
24hrs long
- Rapid rise in blood pressure early in the morning (just after waking up)
- Highest risk of cardiac arrest is just before noon
- Fasted reaction times are early afternoon
- Greatest muscle strength in the early evening
- Melatonin secretion late evening
Give examples of 4 opposing systems that provide balance in the body
Thermoregulation:
sweating vs shivering
Blood pressure:
vasoconstriction vs vasodilation
Hunger levels:
insulin vs glucagon
Osmolarity:
hypotonic vs hypertonic
What is an endotherm vs an ectotherm?
Endotherm: maintains an internal temperature ‘regulator’
- mammals, birds, some fish
Ectotherm: internal temp fluctuates with environment ‘conformer’
- amphibians, lizards, snakes, turtles, some fish
List 8 mechanisms to balance heat loss and gain
1) the integumentary system
2) insulation
3) circulatory adaption
4) evapourative heat loss
5) behavioural responses
6) adjusting metabolism
7) acclimatisation, migration and hibernation
8) physiological thermostats
What is the mammalian integumentary system and how does it control body temperature?
The skin and associated tissue
- Hairs (used for piloerection) - traps a layer of air against skin to act as an insulating material
- Sweat glands - release sweat via pores which is evapourated to cool the body
- Capillary network - vasoconstriction and vasodilation to control how close blood is to the surface of skin
How does insulation help control body temperature?
Especially important for marine animals as water temperature is typically cooler than air.
Reduces heat loss.
Occurs by:
Raising fur or reathers or by secreting oils on to feathers, blubber
What is countercurrent heat exchange?
Dolphin blood is cooled by proximity to sea water at the end of a flipper, heat is shifted from warm blood moving away from the body to cold blood moving towards the body.
Idea is because the veins and arteries are so close in the flipper that the heat from the arteries will warm the cool blood before it gets back to the core of the body ( heat loss goes from warm to cool)
Same occurs in the leg of a canada goose
How does behaviour regulate body temperature?
Both ectotherms and endotherms use behavioural patters to regulate temp.
E.g.
- lizards switch between basking in the sun and hiding under rocks
- dragonflies reduce body heat by maintaining specific body postures (elavates it’s tail, smaller surface area is exposed to the sun)
