Yet more plant shiz. (:

Transport up the stem, due to:

• Root Pressure- generated by the active transport of ions in the endodermis, creating a water potenital gradient.
  
• Cohesion Tension.

Xylem Vessels are thinner when not transpiring.

Water molecules are polar, form hydrogen bonds. Water molecules form hydrogen bonds to make continuous stream. Water is constantly lost by transpiration. When one molecule is lost, another is pulled along. Transpiration pull is the main cause of water movement, putting the water under tension.

Water attraction = COHESION.

Cohesion Tension:

• Water lost from respiritory surface in leaves during transpiration is replaced by water from xylem in leaves.
  
• This causes a negative pressure in the xylem of the leaves which pulls up a column of water with dissolved ions up with xylem.
  
• Column of water does not break as, 1) Hydrogen bonds hold water together, and 2) water molecules are attrated to the xylem vessels.
  

Transpiration:

• Water evaporates from the mesophyll cells into the air spaces in the leaf.
  
• It diffuses out of the stomata to the atmosphere. (Air has a low water potential, as it usually has a low % of water vapor.)

Rate of transpiration is affected by four main factors:

• TEMPERATURE: temperature rises and increases the kinetic energy, and therefore, the particles move faster, and the diffusion of water vapor is quicker.
• HUMIDITY: Air spaces in the leaf are normally saturated with water, whereas the air outside is much less humid. The greater the difference in humidity, the faster the water will diffuse out.
• AIR MOVEMENTS: The more rapidly the air is moved away from the leaf surface, the more rapid the rate of transpiration, as it takes away the layer of moisture that forms, and maintains a constant water potential gradient.
  
• LIGHT: This is an indirect effect, stomata are usually open during daylight hours, to allow carbon dioxide in, but it also lets water out.
  

More plant bits.

Water/minerals go through the cell wall, can pass through fibres (apoplasric)

Endodermis controls what goes in.

Apoplastic Pathway:

• Water can move freely between fibres in the cellulose cell wall.
  
• There is very little resistance, and, as the water moves it pulls move water behind is due to the cohesive properties of water.
  

Symplastic Pathway:

• Takes place across the cytoplasm of cells of the cortex as a result of osmosis.
  
• Water passes from cell to cell along tiny passages/openings called Plasmodesmata. Each plasmodesmata is filled with a thin strand of cytoplasm.
  
• Water moves down a water potential gradient, since the cells near the centre have a more low water potential then those near the outside of the root.
  
• It is a slow route, because the membranes and cytoplasm restrict the rate at which water can move.
  

Passage of water into Xylem:

• Before water enters the xylem it has to pass through the endodermis.
• Water traveling the apoplastic way (along the cell wall) can't continue as there is the water proof barrier, the casparian strip.
  
• It has to pass through the membrane and cytoplasm and join the symplastic pathway.
  
• The ions must be actively transported through the cell, which builds up a high concentration, and the gradient goes backwards.
  
• This establishes a water potential gradient, from the root hairs, to the centre of the root, as the ions would lower the WP in the centre, and the water coming in makes it high at the tip. This is called root pressure.

Evidence for the existence of root pressure:

• The pressure increases with an increase in temperature.
  
• Metabolic inhibitors e.g. cyanide, cause root pressure to cease to exist. (It would stop the active transport, and therefore, no WP gradient is created.)
  
• A decrease in oxygen can cause a reduction in root pressures.
  

Transport into Xylem:

• ACTIVE SECRETION of mineral ions into the xylem.
  
• This lowers the water potential of the solution in the xylem
• This makes a water potenital gradient, and water passes into xylem via osmosis froma high water potential to low.
  

• 
  

Structure of root and stem (:

Plant adaptations for mass transport.

'Root Pressure'
'Cohesive Theory'

Needs water for photosynthesis in pallisade cells, and to keep it turgid. Also, evaporation from leaves has a cooling effect, stopping them from overheating, and enzymes denaturing.

Epidermis- one cell thick, single cell have out growths called root hairs.
Exodermis- protection against pathogens.
Cortex- nonspecializing cells that often store starch.
Endodermis- Surrounds Xylem/Pholem, waxxy layer called casparian strip. Impermeable to water and mineral ions, selective.
Xylem- transports water and mineral ions.
Phloem- Transports organic substances (e.g. sucrose) around the plant.

Big thick roots are used for anchoring, not taking up water.
New xylem doesn't have any lignin, lignin can take on different patterns. Thin areas in vessels called pits allows water to move laterally. When fully ligininfied, moving laterally is the only option.

Xylem Vessels:

• Responsible for the movement of water and ions in the plant.
  
• Long tubes linked end to end of dead cells containing NO cytoplasm
  
• Develop near tip of root as elongated cells and become thickened with lignin.
  
• Young cells have rings of lignin.
  
• Old cells are completely ligninfied, apart from small gaps called pits.
• Pits allow water to move sideways into tissues if vessels get blocked.
  

Uptake of water by root hair:

• Larger roots anchor plant into soil (waterproof)
  
• Branch to form finer roots, not waterproof.
  
• Epidermis have extensions called root hairs. Increase surface area.
  
• Root hairs are exchange surfaces for uptake of water and minerals.
  

Root hairs are efficient because they have a large surface area, and a thin surface layer, so there's a shorter diffusion distance.

The soil solution is mostly water and has a very high water potential. The root hairs have sugars and amino acids dissolved in them, and have a low water potential. So, water moves by osmosis down this water potenital gradient into the root hair cell. Ion can also go in by active transport, as this gradient is in reverse.

Water movement take two route across the cortex. Apoplastic and Symplastic.
Apoplastic: Has to go between fibres, and join the symplastic when it reaches the non permeable casparian strip.
Symplastic: Pushes through the membrane, and faces far more resistance.

Xerophytes :D

Xerophytes: Plants that live in very dry conditions, and have additional adaptations that enable them to conserve water effectively.

Cactus, for example:

• Have a thinner waxy cuticle
• A reduced surface area
• Stem is adapted for photosynthesis, lots of chloroplasts.
  
• Less leaves = low sa/v ratio, which reduces water loss.
  
• Stem stores water in tissues.
  
• Reduced number of stomata, water can't escape from them.
  

These factors increase the rate of transpiration:

• Windy - As water diffuses, a vapour accumulates around the stomata on the outside on the leaf. This increases the water potential, lowering the water potential gradient. Rate of transpiration is therefore, reduced, however, if it is windy, this layer of moisture is blown away, and the area become drier, allowing the water potential to lower, increasing the gradient, and speeding up the rate of transpiration.
• Light- Stomata are open in the light, when the stomata are open, water moves out and into the atmosphere, therefore, light increase rate of transpiration.
  
• Temperature- increases the kinetic energy so particles move faster, and lowers the water potential to make a gradient.
  
• Humidity- low humidity, = less water in air, better WP gradient.
  

Marram Grass:

• Leaf rolls up, only one surface expose, inside gap will be humid, creates gradient.
  
• Expose surface has thick cuticle, and no stoma. (No water can escape)
  
• Stomata on inside in grooves (microclimate, humid, gradient is backward, can't get out.)
• Hairs trap water and increase water potential.
  

Planty bits (:

Dicotelydon - 2 cotelydon- two seed leaf
Monocotelydon - one seed leaf.
In a plant, water and CO2 go in, and glucose and oxygen out go out. Oxygen and carbon dioxide are the gas exchange products.

Photosynthesis takes place in daylight hours.

Respiration takes place all the time, as all cells need to respire.

Stoma (singular)
Stomata (plural)

- Large surface area = numerous stomata.
- Thin= Short diffusion distance.
- Concentration gradient is great.

Spongy mesophyll, lots of air spaces.

Layer of moisture, gas dissolves and gas diffuse through membrane.

Vascular bundle, where xylem and phloem are. Xylem brings water into the leaf.

Gases enter the leaf through the stomata, usually in the lower surface. Stomata are enclosed by guard cells that can swell up and close the stomata to reduce water loss. The gases then diffuse through the air spaces in the leaf which are in direct contact with the spongy pallisade mesophyll cells. Plants do not need a ventilation mechanism as their leaves are exposed, so the air surrounding them is constantly being replaced.
During the hours of daylight, photosynthesis increases the oxygen concentration in the sub-stomal airspaces.
When a green plant is expose to bright light, both photosynthetic and respiritory gas exchange are taking place in the leaves. However, since the rate of photosynthesis exceeds the rate of respiration during the day, there is a net uptake of carbon dioxide and release of oxygen.
In the dark, the non photosythetic parts of the plant, that respire, there is a net uptake of oxygen and a net release of carbon dioxide.

• Long thin pallisade cells, large Surface Area.
• loosely packed, whole surface covered.
• moist layer, gases can dissolve and diffuse easily.
  
• air spaces give a constant circulation of air.
  
• thin - short diffusion distance.
  
• numerous stomata.
  

Percentage Error from equiptment used.

*An error is half the smallest possible reading.*

The errors can come from:

• Thermometer: reads to nearest degree celcius, half = +/- 0.5 degrees celcius error.
  
• Balance: Reads to two decimal places, so the error is half of 0.01, therefore, +/-0.005g

Working out errors:
Balance error- We weighed on the balance twice, therefore, times eror by two = 0.01, then:
0.01/mass weighed (calculated). You then multiply this by 100 to get the percentage error.

So:

1. Multiply error by how many times used. (I.e., two readings = multiply by two.)
2. Divide this by the mass weighed, which you should have calculated.
   
3. Multiply by 100 to reach the % error. (:
   

Thermometer Error-

1. Times the error by how many times used read off the thermometer. (So, two, would be 0.5 x 2 = 1) :D
   
2. Then you divide this by the difference in tempereature, which you should have calculated, or been given.
   
3. Multiply by 100 to get the % error.
   

Thereeeyougooo. All done for today, more tomorrow possibly, or friday. (:

Measuring energy changes.

If the energy given out is bigger then the energy put in, it's exothermic, if the energy put in is bigger then the energy given out, it;s endothermic.

q=mc(delta)T

q is the heat/enegry given out in joules.
m is the mass of the substance heated.
delta T is the rise in temperature in celcious or kelvin.
c is the specific heat capacity, usually 4.18 J/g/k

To get from equation to answer in KJmol-1, there are 3 basic steps:
1) Calculate Q from the info given, using q=mc(delta)T
2)Calculate moles of fuel from the mass of fuel burnt.
3) Divide 'q' by the moles to get the answer in joules, and then divide this by 1000 to get the answer in kJ

Insects :D

Key terms:

• Spiracles
• Trachae
• Tracheoles.
  

Some insects will have a high metabolic rate from springing, jumping, flying, etc. Need a lot of food for respiration to provide ATP for muscle contraction, in which case, they wouldwould need oxygen and some sort of system.

They are small, and therefore have a large SA/V ratio.

Exoskelton- skeleton on the outside. Hard, rigid and waxxy. Subject to dehydration,exo skeleton is waterproff to prevent this, and therefore, gases cannot be exchanged through the surface.

Tracheal System:

---------
| head |----------|-----------------)
---------| thorax |____abdomen_)
|_______|

Okay, yeah. I just drew a diagram of bug anatomy with my keyboard. Swish, eh?

Anywhoz...

Air enters the insect's body through valve like openings (spiracles) in the exoskeleton. These are located laterally along the thorax and abdomen of most insects.
Air flow is regulated by small muscles that operate one of two flap like valves within each spiracle -contracting to close the spiracle, or relaxing to open it.

Trachae are tubes that carry air directly to cells for gas exchange. They penetrate between cells and muscle fibres. After passing through a spiracle, air enters a longitudial tracheal trunk, eventually diffusing throughout a complex branching network of trachael tubes that divide smaller and smaller to recah every part of it's body.
At the end of each trachael branch, a specialised cell (tracheole) provides a thin, moist surface for the exchange of gases between atospheric air and a living cells.
Oxygen in the tracheal tube frist dissolves in the liquid of the tracheole and then diffuses into the cytoplasmof an adjacent cell. At the same time, carbon dioxide, produced as a waste product of cellular respiration, diffuses out of the cell and eventually out of the body through the tracheal system.

The muscle contracts using ATP from aerobic respiration, and then uses anerobic respiration, which produces lactic aicd, which is soluble in water, this lowers the water pressure in the muscle, and water then moves in by osmosis from the tracheole. Since the oxygen is dissolved, this makes a faster rate of movement of oxygen to muscles.

-Thoughts?

Nin. (:

SA/V ratio and temperatures. :D

What causes the higher body temperature of birds?
A high metabolic rate, so, when glucose is broken down, some is converted into heat energy, which maintains heat.

What is the relationship between bodymass and time spent feeding?
The greater the amount of time spent feeding, the lower the body mass, as, as the body mass increases the surface area to volume ratio decreases, therefore, there is less surface area to unit of body volume to loose heat through, so the rate of heat loss is slower, and hterefore, less energy is needed to maintain body temperatures (and also, food.)

Low raio of SA/V helps maintain a body temperature:
Large volume mean there are lots of cells repiring and producing heat energy. Also, surface area is relative to volume, and if it is very small there is less for heat to escape from, so rate of heat loss is slower.

How does the given trend: 'The greater body mass and length, relies on a higher latitude, and lower winter temperature', explain how possums adapt to where they live:
An increase in size means a reduction in SA/V ratio, meaning the area through which heat can be lost can be reduced, compared with the size of the posum. The conserves heat, and lowers the amount of energy required to maintain body temperature.

Suggest a reason for no adaptation in size in cooler climates:
SA/V is only one thing that can be adapted, other things like insulating fur can make a difference. As can higher metabolic rates, as more energy could be generated to compesate for heat loss. There are also behavioural habits like migrating and hibernating that could affect it.

(: That's alllll... :D

Fish and Counter Current Flow and that. (:

I have a feeling I've missed a little from what we studied, so I'll find my old notebook later and get it from there, but alas, fish: :P

Counter-current flow = Constant concentration gradient.

The water, and the blood in the blood vessels are flowing in opposite directions. Oxygen diffueses from the water into the blood, which causes the oxygen concentration in the water to fall. The concentration of oxygen in the blood, subsequently, rises. However, concentration of oxygen in water is always higher then in blood, therefore, a constant concentration gradient is maintained.

In the gills, the flow of water is in the opposite direction to the flow of blood, therefore, the concentration gradient is maintained. This means the blood is continually meeting fresh water with a higher percentage concentration of oxygen.
The concentration gradient is maintained across the gill lamellae and oxygen continues to diffuse into the blood. The same would not happen if they flowed in the same direction, as diffusion would only occur until equilibrium is reached, which is less effcient.
When in counter current flow, 90% of the oxygen the water contains if difused, whereas if it was parallel flow, only 70% would.


Thoughts?
-Nin.