Gas exchange happens in the alveoli.
The alveolus is very good at gas exchange for many reasons.
Firstly, they have a large surface area for exchanging gas via diffusion.
Secondly, they have a good blood supply to take oxygen into the blood quicker & carbon dioxide away (diffusion).
It is moist as gases need to dissolve in water in order to diffuse.
The blood cells carry oxygen (oxygenated blood).
The plasma cells carry carbon dioxide & everything else (deoxygenated blood).
Carbon dioxide comes from all respiring cells.
When you inspire, the diaphragm flattens & the ribcage muscles called the intercoastal muslces, contact by moving up & out. This increases the volume & the pressure decrease in the lungs (they inflate). Automatically air will rush in.
When you expire the diaphragm will contract to it's original curve & the intercoastal muscles return to their original shape. As the volume in the thorax & lungs decrease & the pressure increase (they deflate), air will be pushed out.
This is called the ventilation of the lungs & it is a passive mechanical action (reflex action).
Cigarettes contain nicotine, tar & carbon monoxide.
Nicotine is an addictive drug. It raises blood pressure, narrows arteries and raises the heart beat. Nicotine is the cause of heart disease in smoking.
Tar coats the lining of the lungs, meaning the less oxygen can enter the lung. Tar also contains carcinogens, this is a mutation (chemical) that causes cancer.
Carbon monoxide is a toxic gas that joins with red blood cells making them incapable of moving oxygen around the body.
Peer pressure is when a 'friend/s' pressure you to do something you do not want to (smoke).
Passive smoking is when someone is you're beside someone who is smoking & inhale the smoke. This can also cause problems to the passive smoker.
Attitudes to smoking have changed over time. Now plain packaging is used, there is no advertisement. We also know that smoking causes emphysema, bronchitus & cancer, & that it is addictive.
Capture & Recapture
It's more difficult to count the animal population compare to counting the plant population as animals are constnatly moving. The estimated population depends on the number of marked individuals, & can change depending on the environment.
The capture & recapture is when a portion of the population is captured & marked, the number recordered, then set back into the wild. The second time, the same portion is captured & the number which are already marked are recorded.
This is equation is used to find an estimate for the population:
N = MxC (divided by R)
N - estimate of popuation
M - total no. animals captured on 1st vist
C - total no. animals captured on 2nd vist
R - no. animal captured on 1st visit that were recaptured
Biological conrol is when you introduce a new living species to conrol a pest, for example the ladybird & the greenfly.
The biological control species can be a problem if there is no natural predators of them, this can then mean that they grow in population & eat all resources, decreasing biodiveristy
The biological control is specically chosen to attack the pest, they are usually alien species. The bilogical control involues raising & releasing the species. An alien species is a species not native to an envirnment.
Sometimes the control is used to control other alien species from the same area which has no predators.
The advantages to using biological control is that the predators are usually naturally found in the environment, the predators only feed on the pest & that when the pest die so do the predator.
However there are disadvangtages to biological control. The time to breed & release the predators is long, if the predator population increases they could harm the envirnment & that there is no conrtol on the predaor once it is released.
Anaerobic respiration in muscles
The muscles work hard & the oxygen levels decrease in the cells.
Humans can respire anaerobically, but only for a short time.
The glucose will be converted to energy + lactic acid.
However, the glucose doesn't release all the energy.
The lactic acid will build up in the muscle cells, causing cramps & stiches.
To fix this, an oxygen must be paid. This is when oxygen is required to break down the lactic acid & release all energy. To do this, we pant & this increases the amount of oxygen inspired.