Maintaning a Balance Flashcards
(132 cards)
1
Q
what is an enzyme?
A
an enzyme is a biological catalsyst, a chemical that speeds a reaction without being used up in the reaction
2
Q
what is the structure of an enzyme?
A
enzymes are high molecular weight proteins . they consist of many amino acid chains held together by strong peptide bonds
3
Q
what do enzymes express and what is it for?
A
enzymes express an active sight, a region on the enzyme where a subtrate will interact and a chemical reaction with entail
4
Q
what is the effect of:
- ph on an enzyme
- temperature on an enzyme
- subtrate on an enzyme
A
- ph : a change in ph will effect the enzyme, an enzyme works best at a particular ph called the optimum ph
- temp : at low temps the reaction proceeds very slowly. as temp increases the rxn speeds up. if temp gets to high the enzyme will become denatured
- subtrate conc : increasing subtrate concentration will increase the rate of reaction, this rate will be at maximum once a plateau is reached, this is when the active sites of the enzymes are full
5
Q
what are the models for subtrate, enzyme activity?
A
- lock and key theory
- induced fit model
6
Q
why is the maintanence of a constant internal environment important for optimum metabolic efficiency ?
A
a constant internal environment, one that maintains a constant temp, ph and subtrate concentration encourages enzymes to work at optimum efficiency.
varying conditions may denature these enzymes, resulting in slower metabolic rates which could be fatal
7
Q
what is hemostasis?
A
hemostasis is the process in which organisms maintain a relatively stable internal environment. this is achieved through the use of feedback systems.
ext: it is a coordination for the body to maintain a balance
8
Q
what are the two stages of hemostasis?
A
- detecting changes
- counteracting the change
9
Q
what happens during the detecting changes stage?
A
an organsism with detect information coming from the internal and external environment with a receptor, an organ which picks up a stimulus and transmits it to the organisms control center (brain)
10
Q
what is the technical name for the information?
A
stimuli , any information which provokes a reponse by an organism
11
Q
what are some examples of stimuli found in the external environment?
A
- smell
- light
- heat
- sound
- temperature
- texture
- day length
12
Q
what are some examples of stimuli found in the internal environment?
A
- temperature
- levels of carbon dioxide, oxygen, salts , water, wastes
13
Q
how do organisms counteract changes?
A
organisms will initiate hemostatic responses if the stable state has not been maintained. these responses are carried out by effectors
14
Q
what is an effector?
A
an effector is a muscle or gland which will initiate a hemostatic response to counteract a change in the environment
15
Q
what is the nervous system?
A
the nervous system is a system in organisms which works to regulate and maintain an animals internal environment and respond to changes in the external environment.
16
Q
what are the two main parts of the nervous system?
A
- the central nervous system
- the peripheral nervous system
17
Q
what is the central nervous system?
A
the central nervous system consists of the brain and spinal chord. it acts as a control centre to coordinate all the organisms response. it recieves information, interprets that information, and then initiates a response.
18
Q
what is the peripheral nervous system?
A
a system of branching nerves throughout the entire body which connnect the receptors to the effectors
these nerves act as communication pathways which sends messages rapidly to the control centre and back again
19
Q
what is the step by step process in hemostasis?
A
stimulus receptor control centre effector response
20
Q
what is an ecototherm?
A
an ectotherm is an animal which has a limited ability in controlling its core temperature. its core temperature changes with ambient temperature
21
Q
what is an endotherm?
A
an endotherm is an animal which is able to maintain a core body temperature. its metabolism and bodily processes are able to generate the heat required. because of this, endotherms require more energy than ectotherms, thus they eat more food.
22
Q
what adaptive mechanisms are available for an endotherm to maintain its body temperature?
A
- panting
- sweating
- Insulation in the form of fat or hair
- Migration
- Hibernation
- burrowing
- nocturnal types of behaviour
- control of blood vlow, vasodilation and vasocontriction
23
Q
How does the Red Kangaroo thermoregulate?
A
- shelters during the heat of the day
- releases heat by panting and sweating
- redirects blood flow through a dense network of blood vessels in the forelimbs in times of heat stress, then licks limbs to increase heat loss through evaporation. called vasodilation
24
Q
how does the central netted dragon thermoregulate?
A
- the lizard may burrow into the ground or hide behind rocks or bushes to escape the hottest part of the day
- increases its body temperature by basking in the sun in the mornings
- when basking, it may raise its body slightly off the ground to allow convectional currents to flow to remove heat
- changes its colour
25
what are some respones by plants to temperature change?
- closing of stomates in response to high temperature to reduce water loss
- the ability to orientate leaves vertically to reduce the surface area exposed to the sun, reducing heat absorption and supporting convective cooling
- budding as temperature and length of the day increases in the spring
- germination(some seeds will only germinate upon sufficient exposure to the cold) --> this is called vernalisation
26
what is haemoglobin and what is its function?
haemoglobin is a complex molecule that gives blood its red colour. it enables red blood cells to carry oxygen. the protein-globin consits of peptide chains, each of wich has an iron-containing haem group. oxygen is carried in a loos combination called oxyhaemoglobin
27
whats bad about oxygen in the blood?
unlike CO2, oxygen is not very soluble in water. In 100ml of blood (which is mostly water) only 0.2ml of oxygen would dissolve, which is hardly any when considering the complexity and energy requirements of most mammals
28
what is the adaptive advantage of haemoglobin?
the haemoglobin molecule provides four sites in which oxygen can become attached. haemoglobin and its presence increases the oxygen carrying capacity of the blood by 100X.
haemoglobin also has the ability to loosely bind with carbon dioxide, aiding in CO2 transport to the lungs for its release
hence the adaptive advantage of haemoglobin is to give mammas the ability to transport large quantities of oxygen to the tissues and thus provide more than enough oxygen for living processes needed for growth and repair (cellular respiration)
29
what happens to the blood when it enters the lung tissue?
blood recieves oxygen and carbon dioxide is released
30
what happens to the blood when it enters general body tissue?
blood recieves carbon dioxide and oxygen is released, less glucose and amino acids
31
what happens to the blood when it enters the stomach tissue?
water diffuses into the blood increasing blood volume
32
what happens to the blood when it enters small intestinal tissue?
glucose and amino acids from foods diffuse into the blood, as well as more vitamins, glycerol, fatty acids and there is less oxygen
33
what happens to the blood when it enters the kidney tissue?
urea, excess water and salts are filtered by the kidneys ready to be excreted
34
what happens to the blood when it enters the liver tissue?
glucose is added or removed. unwanted substances such as alcohol are removed. some vitamins, excess lipids and iron are removed. excess amino acids are removed and converted into urea, which then re-eenters the blood
35
what happens to the blood when it enters the large intestine?
water, salts and vitamins are absorbed into the blood
36
what happens to the blood when it goes through endocrine tissue?
hormones are secreted into the blood stream
37
why is oxygen needed in living cells?
oxygen is vital for all living cells because it is one of the essential reactants in cellular respiration, a process which is used for growth, repair, maintencance, reproduction and heat productive for endotherms.
if an adequate oxygen supply is not available for a living cell, it will quickly die
38
why does carbon dioxide need to be removed from the body? come on just stick around for a bit
carbon dioxide when dissolved in water forms carbonic acid. in cells this becomes toxic as it lowers the pH of the cytoplasm, altering the environment to a more acidic one and ultimately denaturing enxymes which are essential to many important living chemical reactions and processes
this would also mean metabolic processes would become under regulated
carbon dioxide also forms carbonic acid in the blood, which is 90% water. this acid that forms in the blood reacts with special buffer systems so that it does not upset the pH of blood plasma
39
what are the five main mechanisms used to transport water in xylem?
- transpiration
- cohesion
- adhesion
- root pressure
- tension
40
how does transpiration help transport water through the xylem?
water in the plant is evaporated through the stomates, caused by heat from the sun and the surrounding environment
-water that is lossed through this evaporation draws other water molecules up due to a difference in pressure. this initiates what is called a transpiration stream
41
how does cohesion help transport water through the xylem?
water molecules stay tightly packed together due to hydrogen bonding. this establishes liquid columns, which have the ability to instantaneously transfer pressure or tension
42
how does tension help transport water through the xylem?
due to the strong cohesive forces, water is pulled up like a wire through the xylem. this helps resist the formation of bubbles in the stream
43
how does adhesion help transport water through the xylem?
water molecules are naturally attracted to the cellulose walls of the xylem. this force of attraction helps in pulling the water molecules up the xylem tubes
at night when transpiration stops, the water does not fall down the xylem but remains stuck to the walls of the xylem
44
how does root pressure help transport water through the xylem?
internal fluid pressure in the roots can somtimes cause water to rise up the stem in the xylem
pressure builds up and water is pushed up the stem
45
why must the concentration of water in cells be maintained within a narrow range for optimal function?
-cells are very sentisite to changes in solute concentration and thus may take in or release water in an attempt to restore this balances, which could kill them
-the concentration of water also effects enzyme- substrate interactions
if the concentration becomes to dilute, there are insufficient interactions between enzyme and subtrate leading to slower metabolic rates
if the substrate becomes to concentrated, dehydration occurs, there is insufficient water to carry out metabolism and waste conentration becomes higher, effecting the pH and enzymes in a negative way
-because of waters very high heat capacity, adequate amounts of water help to maintain contant temperatures in cells
46
why is the removal of wastes essential for continued metabolic activity?
- waste products such as ammonia and carbon dioxide take up space and change the pH of cell environments, denaturing enzymes and slowing metabolism. this metabolic deficiency can ultimately kill living cells
- excess salts can also be harmful as it can affect osmotic pressure
- nitrogenous wastes, those formed from the breakdown of proteins and amino acids are also toxic and can intefere with membrane transport. thus substances such as ammonia need to be removed very quickly and or transformed into a less toxi form (urea)
47
what is the urine concentration like in freshwater fish?
because freshwater fish are constantly absorbing water due to their high solute concentrations inside their body relative to their environment, these organims must excrete dilute urine in order to maintain a balance of water concentrations
48
what is the urine concentration like in saltwater fish?
because saltwater fish live in an environment where solute concentrations are higher outside of their bodies as compared to inside, water is constantly being released due to osmotic pressures. as such, these fish must excrete highly concentrated urine in order to retain water and maintain the balance
49
what is the function of a kidney, in general terms, in all organisms?
the kidney is an organ responsible for adjusting the levels of water and mineral ions in the body in order to maintain a constant concentraion of internal fluid for the cells
it is also responsible for the removal of waste material, in particular urea, which is a by product of the breaking down of proteins and amino acids, removing the amino group, NH2(deamination)
50
what are the parts of the kidney?
```
medulla
renal artery
renal vein
pelvis
cortex
```
51
what are the issues of diffusion in terms of the removal or dissolved nitrogenous wastees in some organisms?
- they are not selective process and rely on the RANDOM movement of molecules and a concentration gradient
- thus, some particles needed by the organism may be manipulated by these mechanisms without any repurcussion
- diffusion does not occur fast enough to maintain the required solute concentrations in cells. it also results in the loss of substances which are often needed by cells
52
whats the down side with osmosis in terms of the removal of dissolved nitrogenous wastes in some organisms?
- again, random movement of molecules and a concentration gradient required
- not fast enough by itself to maintain required solute levels in organisms
- as osmosis is only the movement of solvent molecules, water, water often is the subtance which is leaving cells due to differences in osmotic pressure, whilst still leaving some waste behind
53
outline the parts of the nephron in relation to the movement of blood within it
- bowmans capsule
- glomerulus
- promixal convuluted tubule
- loop of henle
- distal convuluted tubule
- collecting duct
54
explain the process occuring in the bowmans capsule and gomerulus in the nephron
FILTRATION
-blood pressure is so high that some substances and fluid from the blood is forced into the bowmans capsule, forming a fluid called the glomerular filtrate
55
is filtration in the glomerulas/bowmans capsule passive or active transport?
it is passive transport
56
can is included in the glomerular filtrate?
- substances the body can reuse (glucose, water, amino acids
- wastes: urea and poisons
- hormones
- some ions
- minerals and vitamins
57
what process occur in the proximal tubule in the nephron?
- bicarbonate ions, water and potassium ions absorbed passively
- glucose and amino acids are absorbed actively
- hydrogen ions are secreted
- drugs and other poisons are secreted
58
what process occur in the loop of henle in the nephron?
- water is reabsorbed through osmosis through a dense network of capillaries (descending)
- salt is reabsorbed passively through a thin walled section, then actively through a thick walled portion (ascending)
59
what processes occur in the distal convuluted tubule in the nephron?
sodium and potassium ions are selectively reabsorbed in order to regulate the pH of the blood and concentration of salts
60
what processes occur in the collecting duct in the nephron?
water is reabsorbed through osmosis back into the body based on its needs
walls are only permeable to water
the final flitrate is then formed and is called urine
61
what controls the amount of water and salts lost in the urine?
hormones called aldosterone and anti-diuretic hormone, which aid in maintaining homeostatic balance
62
what is the role of aldosterone in the regulation of the bodies internal fluid/salt composition?
aldosterone is a hormone produced in the adrenal gland which controls the amount of salt in the blood by regulating the reabsorption of salts in the nephrons. it helps regulate the transfer of sodium and potassium ions in the kidneys.
63
when is aldosterone production in the body going to be a maximum?
aldosterone production will be at its peak when the body requires salt and their is little blood volume and pressure
due to then osmotic pressure, water will become retained
64
when is aldosterone production in the body going to be a minimum?
aldosterone production will be at its lowest when there is high salt concentrations and hence increased blood volume. thus, less salt and water is reabsorbed by the nephron tubules and increased amounts of salts and water are then lost as urine
65
what is the role of anti-diuretic hormone in relation to the regulation of salts and water levels in the body?
ADH or anti-diuretic hormone regultes the amount of water in the body by adjusting the permeability of the collecting duct and distal tubules to water in correlation with the bodys needs
66
when is ADH production in the body going to be a maximum?
ADH production will be at its highest when their is high salt concentrations inside the bodys cells. this will trigger ADH production and increase the permeability of collecting ducts and distal tubules to water. thus more water is reabsorbed into the body and concentrated urine results with increased blood volume.
67
when will ADH production be at its lowest?
ADH production will be at its lowest when there is low salt conentrations in the bodys cells. the permeability of the collecting ducts and distal tubules will decrease, water will not be reabsorbed and more water will be lossed as urine, resulting in dilute urine with decreases in blood volume and pressure.
68
what is the process called which describes the movement of material in the phloem vessels?
translocation
69
name the most accepted theory/mechanism for the movement of material in the phloem
the source to sink mechanism
70
what are the steps in the source to sink mechanism?
1. transport begins at the source(leaves), where photosynthesis occurs. sugars, commonly sucrose, are then loaded into the phloem via active transport.
2. As the sugar concentration in the phloem increases, water in the xylem enters the phloem through osmosis. this subsequently increases the turgid pressure within the phloem and initiates the flow of material within it. this material includes water, sugars, and other photosynthetic material
3. this material then gets to the sinks(sites where this sugar is needed for use or storage). sugar is unloaded from the phloem via active transport to these cells.
4. this causes water to enter the cells also via osmosis, lowering the water pressure at the sink. therefore the high water pressure at the source causes water and dissolved sugars to flow to the low water pressure at the sink.
71
what are the common products extracted from donated blood?
- red blood cells
- white blood cells
- plasma
- cyroprecipitate
- platelets
- immunoglobins
72
what are the uses of red blood cells, including their main function
red blood cells are used to increase the oxygen carrying capacity of the blood and hence the amount that can be carried to the bodys tissues
- often provided to anaemic patients, whose bone marrow does not make enough red blood cells
- provided to those who have suffered in a major accident resulting in a loss of blood
73
what are the uses of platelets, including their main function
platelets are essential in making the blood clot
- given to pateints with cancer of the blood or lymph such as leaukimia or lymphoma
- also given to patients undergoing chemotherapy, as they fail to make anough platelets.
74
what is plasma, what are its uses and describe its main function
plasma is the liquid portion of the blood which is 90% water. contains many dissolved nutrients including blood clotting factors such as immunoglobins. also increases blood volume and pressure
- given to pateints with clotting disorders such as haemophillia
- plasma is also uded to adjust the osmotic pressure of blood and to pull fluids out of tissues
- some donated blood products are derived from blood plasma
75
what are immunoglobins, what are their functions and what are their uses
immunoglobins are infectious fighting parts of the blood plasma
-provided to people who have difficulty fighting infections and whose immune system is not working properly, for example, people with aids
76
what are white blood cells, what are their main functions and list their uses
white blood cells are another infection-fighting component of the blood
white blood cells are rarely given to patients and is only given in extreme life threatening circumstance such as in treating life threatening infections in which the cell count is very low or when the white blood cells arent working properly
77
what is cyroprecipitate, what is its main function, and describe some of its uses
cyroprecipitate is a concentrate of clotting proteins used in the treatement of severe bleeding
- provided to patients who suffer from haemophilia or von willebron disease
- given to patients who require replacements of clotting proteins(such as fibrogen)
- given to patients with a variety of bleeding disorders
- given to patients who are undergoing liver transplants
78
why is research needed in the development of artificial blood?
- artificial blood is free of infectious agents and allergens, making them non toxic and disease free
- they are universally accepted by all blood types, allowing transfusion to people with no tests required
- it is readily available in large supply, unlike real blood donors
- they do not need to be refrigeratedand can be stored for a longer period of time(2-3 years) as compared to 3 weeks for human blood
79
if artificial blood is so spectacular, why do we need to further research them?
artificial blood is only designed to carry oxygen and carbon dioxide. they play no role in immune defense, clotting and coagulation
thus more research is required
80
what is a Xerophyte?
plants which are adapted to survive in dry or arid conditions where liquid water is scarce.
81
describe some adaptations of the bottle to minimise water loss
- able to shed their leaves during dry spells which minimise water losses through transpiration
- able to store water in its fibrous trunk
- leaves are very small which reduces the surface area for transpiration to occur
- leaves express a thick waxy cuticle which minimises water losses through transpiration
82
describe some adapatations of the eucalypt to minimise water losses
- thick waxy cuticle which minimises the affect of transpiration and may reflect some light
- has microscopic leaves on the stem which can carry out photosynthesis
- vertically hanging leaves which reduces the surface area of the leaf which is exposed to the hot sun during midday, reduces water loss and heat which cause evaporation
- deep root system which can absorb and store water
- has small amounts of stomata which again reduces the effect of transpiration of water
83
describe some adaptations of the xanthorrhoea to minimise water loss
- leaves are shaped so that water runs down them to the soil and can get reaboserbed back into the plant through the roots
- can store food such as sap in the stem
- needle like leaves have a reduced surface area which minimises water losses
84
what is a pulse oximeter?
a pulse oximeter is a small non-invasive probe that slips onto a patients finger, earlobe or toe that measures the oxygen saturation in the blood
85
how does the pulse oximeter work?
the device measures the transmission of light through the tissues. it does this because oxygenated blood is bright red, while deoxygenated blood is dull red
86
what are the advantages of the pulse oximeter?
-completely non-invasive(no needle sticks, syringes, catheters, IVS), saves money
- no expensive calibration required
- low cost hardware
- provides an instantaneous reading which can be monitored 24/7
87
what are the disadvantages of the pulse oximeter?
- the device is ineffective in poor perfusion states. these states include when the body is in shock, vasocontriction. the oximeter probe may read a normal hemoglobin saturation level even though there is not enough blood moving through the area.
- for patients who have anemia, or who have experienced a loss of red blood cells, the pulse oximeter is inaccurate because despite if all the haemoglobin in the blood is filled with oxygen, this will still give a normal reading if the number of red blood cells in the blood is low
88
when would a pulse oximeter be used on a patient?
- given to patients who are undergoing procedures requiring anaesthia or sedation
- given to patients who have abnormal breathing or circulation
- given to patients who are undergoing stress testing
89
what is arterial blood gas analysis?
arterial blood gas analysis is a technique used in medicine where the amounts of oxygen and carbon dioxide in the blood are measured. it also measures the amount of biocarbonate ions and hence the pH of the blood
it essentially evaluates how well the lungs are receiving oxygen and how well they are releasing carbon dioxide
90
how is oxygen concentrations in the blood measured in arterial blood gas analysis?
electrochemical procedures are used . because ozygen in blood produces current when diffusing, the amount of current correlates to the amount of O2. amount of oxygen in proportional to the amount of O2 in the sample
91
What are the two main types of oxygen carrying artificial blood that has been produced?
- perfluorocarbons
| - haemoglobin based oxygen carriers
92
What are perflurocarbons?
Synthetic materials that can dissolve about 50 times more oxygen than normal blood plasma
93
What are the properties of perflurocarbons?
- they are cheap
- synthetic, which means there's no risk of the material being infected or diseased
- they're not soluble in water
- they must combine if other materials such as lipids in order to mix in with the bloodstream. This affects how well the material moves through the bloodstream
94
What are the uses of perflurocarbons?
- they can form an implosion and be injected into a patient
| - given during surgery, trauma and the oxygenation of tumours during radiation and chemotherapy
95
What are haemoglobin based oxygen carriers?
Made from haemoglobin extracted from red blood cells. They are not contained within a membrane and thus do not require cross matching of blood and blood typing.
96
What are the disadvantages of haemoglobin-oxygen based carriers?
- current blood substitutes do not have the enzymes to stop haemoglobin from oxidising
- blood substitutes only stay in circulation for 20-30 hours , unlike the 100'days red blood cells last
- haemoglobin must be modified before it can be used
97
What are the advantages of haemoglobin based oxygen carriers ?
Can be stored for a long time
98
What is renal dialysis?
Dialysis is the artificial process of eliminating waste(diffusion) and unwanted water (ultrafiltration) from the blood in patients whose kidneys are not functioning properly
99
For people whose kidneys are fucked, how often do they have to use the machine?
3 times a week 4-5 hours at a time
100
How does a dialysis machine work?
- first, the blood of a patient is passed through a coil of semi permeable tubing which is located in a bath of dialysing solution
- urea in the patients blood diffuses through osmosis out of the tubing into the solution as a result of the steep concentration gradient. Urea concentration is in low concentration in the dialysing solution
- the dialysing solution is constantly monitored in order to maintain a steep concentration gradient
101
Are hormones involved in dialysis?
No
102
What is the filtering unit when comparing kidneys and the dialysis machine?
Kidney--> nephron
| Renal dialysis --> machine
103
What is the filter when comparing a kidney and renal dialysis?
Kidney--> walls of the glomerulus inside the bow mans capsule
Renal dialysis--> an artificial membrane of peritoneal membrane which is semi permeable
104
How do the transport mechanisms differ when comparing kidneys and renal dialysis?
Kidney--> both passive and active transport are used
| Renal dialysis--> only passive transport
105
How does osmoregulation compare between a kidney and renal dialysis?
Kidney--> highly effective
Renal dialysis--> small ions tend to accumulate in the blood as they do not move out quickly enough by diffusion. Dialysis is only able to remove limited amounts of fluid from the blood. Cannot reabsorb due to no hormones being present
106
What is the most common disease which affects a persons ability to produce aldosterone?
Addison's disease
107
What is Addison's disease caused by?
Addison's disease is caused by mostly from the shrinking or destruction of the adrenal cortex
108
What are the MAJOR side effects of Addison's disease?
People suffering from the disease produce insufficient levels of all adrenal cortex hormones and require multiple hormone replacements to obtain these vital hormones
One of these hormones is aldosterone
109
How do people with Addison's disease get treated?
They are injected with a synthetic form of aldosterone called fludrocortisone
110
Why do people with Addison's disease need daily injections of fludrocortisone ?
If the body cannot secrete the hormone aldosterone, or have any other similar hormone at its disposal, water and salt balance cannot be achieved. When this balance is upset, the volume of the blood falls dangerously low, there is a drop in blood pressure and severe dehydration occurs. Hormone replacement therapy stops this from happening
111
What are halophytes?
Plants which are adapted to living in salty environments
112
What are the main three processes used by halophytes in the regulation of salts ?
Salt exclusion/barriers
Salt secretion
Salt accumulation
Reduce of transpiration
113
Describe salt exclusion/barriers
Some Halophytes have special tissues in the roots or lower stem which stop salt from entering the plant but allow water uptake? These tissues are usually glands which can actively exclude the salt from the water, so that the water absorbed has a lower salt concentration than the water in the environment
114
What are some examples of plants which have salt barriers?
Grey, red and orange mangrove
115
What is salt secretion?
Salt secretion is a mechanism used by a halophytes where salt becomes so concentrated that glands located on the leaves excrete salt by active transport. These are seen as salt crystals on the leaf
116
What halophytes excrete salt through there leaves?
Grey mangrove, salt bush and river mangrove
117
What is salt accumulation?
Salt accumulation is when salt builds up in a part of a plant that can be shed, removing the salt in the process. These parts are usually bark or old leaves
118
What plants salt accumulate?
Milky mangrove, samphire plant
119
What is reduce transpiration?
Basically how a plant restricts the affect of evaporating water and dissolved salts. Because water in a halophyte is always being loosed to the environment via osmotic pressure, the mangrove must formulate ways to restrict water loss, hence vertically hanging leaves
120
what are the main characteritics of an artery?
- oyxgenated blood moves at high pressure away from the heart
- touch elastic muscular walls help to withstand this pressure
121
what are the main characteristics of a capillary?
-endothelium which is one cell thick
122
what are the main characteristics of a vein?
- larger endothelium than the artery
- smaller elastic fibres and smooth muscle
- v for valves dissallow backflow
- deoxygenated blood moves at low pressure towards the heart
123
in what way does material in the xylem flow in a plant?
one direction
124
what moves through the xylem ?
water
125
is the tissue of the xylem living or dead?
dead
126
in what way does material in the phloem flow in a plant?
up and down
127
what moves through the phloem?
photosynthetic material --- sugars
128
is the tissue of the phloem living or dead?
living
129
define enantiostasis
the maintenance of metabolic and physiological functions in response to variations in the environment
130
what is an osmoconformer?
an organism which tolerates changes in the external environment by altering the concentration of internal solutes to match the external environment. MANGROVES
131
what is an osmoregulator?
an organism which avoids changes in the external environment
132
when is enantiostasis fully observed?
in estuarine environments, where high tide gives high salt concentrations and low tide where that gives low salt concentrations.
