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biology > Homeostasis > Flashcards

Homeostasis Flashcards

1
Q

Define homeostasis

A

Maintaining a constant internal environment despite changes in the external environment

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2
Q

What is Negative Feedback

A

Bringing the body back to homeostasis. NF reverses the stimulus

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3
Q

Describe the negative feedback loop

A
  1. Stimulus (Deviation from set point)
  2. Receptors (Constantly monitors conditions)
  3. Co-ordinating centre (compares condition to set point)
  4. Effector (causes changes to compensate for deviation)
  5. Response (Return to set point)
    Negative feedback loop completed and continues cycle 3, 4 and 5
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4
Q

What is thermoregulation

A

Maintain temperature within a tolerable range

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5
Q

List and explain the 4 heat exchange types

A

Conduction - A transfer of heat energy from a relatively hot object to a relatively cool object by direct contact
Convection - the transfer of heat by means of rising currents of warm air or water
Radiation - The transfer of heat from a hot object by infrared waves
Evaporation - The process in which liquid water changes to water vapour through heating

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6
Q

What are the 2 sources of body heat

A

Ectotherm - heats body temperature from an external heat source. Conformer
Endotherm - heats body temperature internally. Regulator

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7
Q

Define Poikilothermic

A

An organism whose body temp changes with the temp of its surroundings

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8
Q

Define Heterothermic

A

Regulates body when active, but allows it to fluctuate when inactive eg platypus

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9
Q

Define Homeothermeric

A

The ability to maintain a relatively constant internal body temp

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10
Q

Define Osmosis

A

Diffusion of water - from high concentration to lower concentration (across a membrane)

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11
Q

What are the two responses to environmental changes?

A

Conformers- allow internal conditions to change with external changes

Regulators - keep relatively constant internal conditions

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12
Q

Define Osmotic pressure

A

a solution’s tendency to take in water by osmosis.

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13
Q

Osmolarity

A

the solute concentration in solution.

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14
Q

Solutions can be?

A

Hypertonic - higher osmotic pressure than other fluid
Hypotonic - lower osmotic pressure than other fluid
Isotonic - same

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15
Q

Osmoconformers are…

A

in osmotic equilibrium with their environment.

eg marine animals like jellyfish.

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16
Q

Osmoregulators expend energy to…

A

maintain a constant blood osmolarity despite their environment.
eg most vertebrates.

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17
Q

Osmoregulation in saltwater fish

A 
Problem
Hypertonic water (body fluid hypotonic)
water loss from gills
salt invasion
Solution
drink lots of salty water
excretes very little but very concentrated urine
active transport salts out gills
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18
Q

Osmoregulation in freshwater fish

A 
Problem
 Hypotonic water (body fluid is hypertonic)
 water enters gills
 salt loss from gills.
Solution
don’t drink 
excrete lots of dilute urine – reabsorb salt in nephron
active uptake salt in gills
eat ‘salty’ food.
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19
Q

What are nitrogenous wastes?

A

Made when amino acids & nucleic acids are catabolised.

20
Q

Type of nitrogenous wastes depends on?

A 
class of animal you are 
where you live (habitat)
21
Q

Ammonia (NH3)

A

Distadvantage: very toxic and must dilute in large quantities to get rid of through gills
Advantage: very soluble and easily crosses membranes

Common in aquatic organisms

22
Q

Urea

A

Excreted by kidneys with medium water
Advantage: needs less water than ammonia (less toxic)
Disadvantage: energy costly, larger molecule means less soluble

Common in terrestrial animals

23
Q

Uric Acid

A

Not toxic
requires least water to excrete (paste-like)
Insoluble in water – precipitates out of solution.
most energy costly
Doesn’t harm embryo in egg due to large molecule
Birds and reptiles

24
Q

Tolerance range

A

the range within which an organism can function and reproduce

25
Q

Explain countercurrent

A

A current that follows in the opposite direction of another current.
Effective for blood vessels in extremities to reduce heat loss to the environment.

26
Q

Piloerection

A

elevation of the hair by contraction of tiny muscles.

traps warm air between outer skin surface & hair follicle.

27
Q

Mechanisms of Thermoregulation in hot ectotherms

A 
Localized vasodilation (dilation of blood vessels)
Avoidance
Change orientation
Retain urine
Shade, burrow
28
Q

Mechanisms of Thermoregulation in hot endotherms

A

Evaporative cooling, sweating
Relax temp set point
Avoidance – burrow, nocturnal, migrate
Vasodilation (increase of size of blood vessels)
Stretching out, finding shade, swimming, summer coat, long thin ears & limbs & body to increase SA:Vol.

29
Q

Mechanisms of Thermoregulation in cold ectotherms

A

Basking
Regional heterothermy
Antifreeze in blood
Freeze tolerance

30
Q

Mechanisms of Thermoregulation in cold endotherms

A
  1. Heat production: Shivering, increase metablosim rate, thyroxin
  2. Insulation: hair, feathers, piloerection, fat, Round body shape, small ears – low SA:Vol.
  3. Behaviour: Migration, huddling, torpor or Hibernation, Vasoconstriction, Counter current exchange
31
Q

Explain Torpor

A

State of dormancy produced by a reduction in metabolic rate & body temperature. Reduces the need for food.
Eg Hummingbirds & bats.

32
Q

Surface area to volume ratio

A

Smaller animals have:
Very high metabolic rate/ unit body mass.
High SA:Vol.
High heat gain/loss.
Therefore have to eat their body weight everyday

33
Q

Metabolic rate

A 
Rate animals respire food. 
Measured by: 
heat energy released 
O2 consumed
CO2 produced.
34
Q

Negative feedback on a hot day example

A

Stimulus: blood/skin temperature increases
Receptor: Thermoreceptors in skin and hypothalamus
Modulator: Hypothalamus
Effectors: blood vessels, sweat, hair, thyroid
Response: Swear, decreased BMR, hair lies flat, behaviour,
Blood temp returns to nomral

35
Q

Adaptions

A

Special structures and internal processes to enable organisms to live in their environment

36
Q

Leaf structure

A 
Wax cuticle
Upper epidermis
Palisade mesophyll
Spongy mesophyll
Airspace
Lower epidermis
Guard cell with chloroplasts
Exchange of gases through stoma
Wax cuticle
37
Q

Adaptions of leaves to photosynthesis

A
  1. Waxy Cuticle - Forms a waterproof layer to limit loss of water.
  2. Upper Epidermis - These have no chloroplasts.
  3. Palisade cells - These contain lots of chloroplasts, which contain lots of chlorophyll. This is where photosynthesis is carried out.
  4. Spongy Mesophyll Layer
  5. Air Spaces - allow for diffusion of water vapour etc…
  6. Guard Cells - These form stomata (pores) which allow for the diffusion of gases in and out of the plant.
  7. Leaf Vein - containing xylem and phloem tubes.
38
Q

If guard cells gain H2O

A

Stomata open

39
Q

If guard cell loses H2O

A

Stomata closes

40
Q

Photosynthesis

A

Transforms sunlight energy into clemical energy
Produces glucose and oxygen
6CO2 + 12H2O –light–> C6H12O6 + 6O2 + 6H2O

41
Q

Transpiration

A

Evaporation of water from leaves while their stomata are open for the passage of CO2 & O2 during photosynthesis.

42
Q

Abiotic factors affecting the rate transpiration

A

light intensity - increases rate. stimulates guard cells to take in water & open, to allow CO2 to diffuse in for photosynthesis

temperature - increases rate. Water evaporates & diffuses quicker as the temperature rises.

humidity - decreases rate

wind - increases rate. When a breeze is present, the humid air is carried away and replaced by dry.

soil water - more water reduces rate.

43
Q

Xerophyte adaptations

A
  1. Seasonal shedding leaves in dry or cold.
  2. Leaf hairs trap a layer of moist air to stop wind removing moisture from stomata.
  3. Leaves reduced to spines or stiff hairs - small surface area.
  4. Waxy epidermis reduces evaporation.
  5. Wide-spreading, shallow roots.
    • absorbs lots of water immediately after rain.
44
Q

Hydrophyte adaptation

A
  1. Reduced roots – lots of nutrients in sediment. Poor xylem.
  2. Thin leaves
    increase SA of photosynthetic tissue
    reduce internal shading
    increase diffusion.
  3. Thin cuticle – enables plant to absorb water & minerals directly from water.
  4. Many stomates
  5. Massive leaf air spaces (O2 from photosynthesis) assist floatation & gas exchange.
45
Q

Vasodilation

A

Blood vessels dilate

biology (5 decks)

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