Hi guys:
This cycle we will understand and compare different type of organisms breathing mechanisms.
Use this information and other in the "Bitácora", to look for information and images and design a Power Point presentation about unicellular, plants and animals breathing parts and funtcions.
Here you have some ideas and information, Read this before you go to school.
Gas Exchange in Plants
The gases diffuse into the intercellular spaces of the leaf through pores, which are normally on the underside of the leaf - stomata. From these spaces they will diffuse into the cells that require them.
Stomatal opening and closing depends on changes in the turgor of the guard cells. When water flows into the guard cells by osmosis, their turgor increases and they expand. Due to the relatively inelastic inner wall, the guard cells bend and draw away from each other, so the pore opens. If the guard cells loose water the opposite happens and the pore closes. The guard cells lower their water potential to draw in water from the surrounding epidermal cells, by actively accumulating potassium ions. This requires energy in the form of ATP which, is supplied by the chloroplasts in the guard cells.
Respiration occurs throughout the day and night, providing the plant with a supply of energy. Photosynthesis can only occur during sunlight hours so it stops at night. A product of respiration is carbon dioxide.
This can be used directly by the plant in photosynthesis.
However, during the day, photosynthesis can be going 10 or even 20 times faster than respiration (depending on light intensity), so the stomata must stay open so that the plant has enough carbon dioxide, most of which diffuses in from the external atmosphere.
Read more at http://www.s-cool.co.uk/a-level/biology/gas-exchange/revise-it/gas-exchange-in-plants#FQzWCEeIX4zqqG0c.99
Gas Exchange in Insects: Insects, being larger and having a hard, chitinous and therefore impermeable exoskeleton, have a more specialised gas exchange system.
Insects have no transport system so gases need to be transported directly to the respiring tissues.
There are tiny holes called spiracles along the side of the insect.
The spiracles are openings of small tubes running into the insect's body, the larger ones being called tracheae and the smaller ones being called tracheoles.
The ends of these tubes, which are in contact with individual cells, contain a small amount of fluid in which the gases are dissolved. The fluid is drawn into the muscle tissue during exercise. This increases the surface area of air in contact with the cells. Gases diffuse in through the spiracles and down the tracheae and tracheoles.
Ventilation movements of the body during exercise may help this diffusion.
The spiracles can be closed by valves and may be surrounded by tiny hairs. These help keep humidity around the opening, ensure there is a lower concentration gradient of water vapour, and so less is lost from the insect by evaporation.
Read more at http://www.s-cool.co.uk/a-level/biology/gas-exchange/revise-it/gas-exchange-in-insects#oRz0b2XHjpHtebTm.99
Different organisms have different mechanisms for obtaining the gases they require.
Diffusion is required to supply all organisms with oxygen.
The efficiency of diffusion is increased if there is:
- A large surface area over which exchange can take place.
- A concentration gradient without which nothing will diffuse.
- A thin surface across which gases diffuse.
Unicellular Organisms do not have specialised gas exchange surfaces. Instead gases diffuse in through the cell membrane.
The smaller something is, the smaller the surface area is but, more importantly, the bigger the surface area is compared to its volume.
Multicellular Organisms are bigger than Unicellular organisms. This makes efficient diffusion of gases more difficult.
However, if they are small, or large but very thin (like the flatworms, Platyhelminths), the outer surface of the body is sufficient as an exchange surface because the surface area to volume ratio is still high.
Plants obtain the gases they need through their leaves. They require oxygen for respiration and carbon dioxide for photosynthesis.
The gases diffuse into the intercellular spaces of the leaf through pores, which are normally on the underside of the leaf - stomata. From these spaces they will diffuse into the cells that require them.
Insects have no transport system so gases need to be transported directly to the respiring tissues.
There are tiny holes called spiracles along the side of the insect.
The spiracles are openings of small tubes running into the insect's body, the larger ones being called tracheae and the smaller ones being called tracheoles.
The ends of these tubes, which are in contact with individual cells, contain a small amount of fluid in which the gases are dissolved. The fluid is drawn into the muscle tissue during exercise. This increases the surface area of air in contact with the cells. Gases diffuse in through the spiracles and down the tracheae and tracheoles.
Ventilation movements of the body during exercise may help this diffusion.
The spiracles can be closed by valves and may be surrounded by tiny hairs. These help keep humidity around the opening, ensure there is a lower concentration gradient of water vapour, and so less is lost from the insect by evaporation.
Fish use gills for gas exchange. Gills have numerous folds that give them a very large surface area.
The rows of gill filaments have many protrusions called gill lamellae. The folds are kept supported and moist by the water that is continually pumped through the mouth and over the gills.
BREATHING
The primary function of the respiratory system is to deliver oxygen to the cells of the body’s tissues and remove carbon dioxide, a cell waste product. The main structures of the human respiratory system are the nasal cavity, the trachea, and lungs.
All aerobic organisms require oxygen to carry out their metabolic functions. Along the evolutionary tree, different organisms have devised different means of obtaining oxygen from the surrounding atmosphere. The environment in which the animal lives greatly determines how an animal respires. The complexity of the respiratory system is correlated with the size of the organism. As animal size increases, diffusion distances increase and the ratio of surface area to volume drops. In unicellular organisms, diffusion across the cell membrane is sufficient for supplying oxygen to the cell (Figure 1). Diffusion is a slow, passive transport process. In order for diffusion to be a feasible means of providing oxygen to the cell, the rate of oxygen uptake must match the rate of diffusion across the membrane. In other words, if the cell were very large or thick, diffusion would not be able to provide oxygen quickly enough to the inside of the cell. Therefore, dependence on diffusion as a means of obtaining oxygen and removing carbon dioxide remains feasible only for small organisms or those with highly-flattened bodies, sucs as many flatworms (Platyhelminthes). Larger organisms had to evolve specialized respiratory tissues, such as gills, lungs, and respiratory passages accompanied by a complex circulatory systems, to transport oxygen throughout their entire body.
Organisms that live in water need to obtain oxygen from the water. Oxygen dissolves in water but at a lower concentration than in the atmosphere. The atmosphere has roughly 21 percent oxygen. In water, the oxygen concentration is much smaller than that. Fish and many other aquatic organisms have evolved gills to take up the dissolved oxygen from water (Figure 3). Gills are thin tissue filaments that are highly branched and folded. When water passes over the gills, the dissolved oxygen in water rapidly diffuses across the gills into the bloodstream. The circulatory system can then carry the oxygenated blood to the other parts of the body. In animals that contain coelomic fluid instead of blood, oxygen diffuses across the gill surfaces into the coelomic fluid. Gills are found in mollusks, annelids, and crustaceans.
The folded surfaces of the gills provide a large surface area to ensure that the fish gets sufficient oxygen. Diffusion is a process in which material travels from regions of high concentration to low concentration until equilibrium is reached. In this case, blood with a low concentration of oxygen molecules circulates through the gills. The concentration of oxygen molecules in water is higher than the concentration of oxygen molecules in gills. As a result, oxygen molecules diffuse from water (high concentration) to blood (low concentration), as shown in Figure 4. Similarly, carbon dioxide molecules in the blood diffuse from the blood (high concentration) to water (low concentration).
Insect bodies have openings, called spiracles, along the thorax and abdomen. These openings connect to the tubular network, allowing oxygen to pass into the body (Figure 5) and regulating the diffusion of CO2 and water vapor. Air enters and leaves the tracheal system through the spiracles. Some insects can ventilate the tracheal system with body movements.
See you on class!!!!
