Lifestyle, Health And Risk Flashcards
Why do animals have a heart and circulation?
Diffusion is inefficient when an organism has a low surface area to volume ratio. This is why animals use a heart and circulation to move substances around the body by mass flow instead of diffusion.
Define the term ‘mass flow’
The transport of substances in bulk from one part of an organism to another.
Define the term ‘diffusion’
The net movement of molecules or atoms from a region of high concentration to a region of low concentration until evenly distributed (dynamic equilibrium)
What do we mean by the dipole nature of water?
The dipole nature of water means that it has both positive and negative charges within the molecule.
Why is water important as a solvent?
Many chemicals dissolve easily in water, allowing vital biochemical reactions to occur in the cytoplasm of cells. Free to move around, chemicals can react. It also means the dissolved substances can be transported around organisms e.g in animals via the blood and lymph systems, or in plants through the xylem or phloem.
Why are the thermal properties in water useful?
Water has a very high specific heat capacity, meaning a lot of energy is needed to raise the temperature of 1kg of water by 1 degrees Celsius, this is due to the hydrogen bonds needing a lot of energy to be broken. This is extremely useful for organisms, helping them to avoid rapid changes in their internal temperature and enabling them to maintain a steady temperature when the environment changes.
Why is water important in plants?
Water helps keep non-woody (herbaceous) plants upright by providing structural support. This is achieved by water entering plant cells and making them turgid. The cells become more elongated. The stomata on the underside of leaves allows h2o and co2 in the guard cells around these openings are also controlled by changed in turgidity.
Describe the features of a mass flow system and explain why certain organisms need to use mass flow
MAIN FEATURES - a system of vessels to carry substances, a way of making sure the substances move in the right direction, a means of moving the substances fast enough to supply the needs of the organism, a suitable transport medium.
Large organisms cannot rely only on diffusion as this process is much too slow to meet their needs. Mass transport enables organisms to overcome the limitations of diffusion.
What is an open circulatory system?
An open circulatory system contains blood circulating in large, open spaces. A simple heart is included and this pumps blood out into cavities surrounding the animals organs. Substances diffuse from the blood into and out of the cells. When the heart muscle relaxes, blood is drawn back into the heart from the cavity through small valved openings along the length of the heart.
What is a closed circulatory system?
Animals larger in size use closed circulatory systems, as diffusion is inefficient. In a closed circulatory system, the blood is enclosed within tubes (arteries, capillaries and veins) This generates higher blood pressure as blood is forced along narrow channels. Blood leaves the ventricles of the heart under pressure, and enters arteries. Large arteries lead into small arterioles, and then into capillaries. From here the blood enters the venues, then veins, and back to the atria of the heart.
What are the key differences between an open and closed circulatory system?
In an open circulatory system, blood isn’t enclosed within blood vessels and flows in large cavities, in direct contact with body tissues whereas in a close circulatory system blood is always enclosed in blood vessels. In an open circulatory system, when blood is in direct contact with tissues only then exchange of materials takes place whereas in a closed circulatory systems, in capillaries, nutrients and waste materials are exchanged between tissues and blood by means of tissue fluid. Open circulatory systems have a lower blood pressure, with slower blood and less efficient delivery of substances around the body. Animals smaller in size use an open circulatory system whereas closed circulatory systems tend to be used by animals larger in size.
Describe the key features of a single circulatory system.
- Blood only flows through the heart once for each complete circuit of the body
- No separate pulmonary circulation
- Heart has two chambers
- Blood pressure drops through gas exchange organ e.g gills and isn’t increased again around the body
- Oxygen and food substances required for metabolic processes are usually delivered more rapidly to cells.
Describe the key features of a closed circulatory system.
- Blood flows through the heart twice for each complete circuit of the body
- Pulmonary circulation present and separate to systemic circulation
- Heart consists of three or four chambers
- Blood returns to the heart from the lungs, increasing pressure so reducing the time it takes for the blood to circulate around the whole body
- The left ventricle pumps blood faster, and at a higher pressure to the body whereas the right ventricle pumps blood slower, at a lower pressure to reduce risk of damage to the lungs and maximise gas exchange.
- Allows mammals and birds to have a high metabolic rate.
Describe the structure of pulmonary circulation
Starts at right ventricle, ends at left atrium, carries blood between heart and lungs, blood to lungs is deoxygenated via pulmonary artery, blood returning to heart via pulmonary vein oxygenated, low pressure circulation (40mmHg) Low pressure means less risk of damage to lungs plus slower speed of blood flow leading to increase gaseous exchange in lungs.
Describe the structure of systemic circulation
Starts at left ventricle, ends at right atrium, carries blood between heart and all other organ systems except lungs, blood to body is oxygenated via aorta, blood returns to heart via superior and inferior vena cava is deoxygenated. High pressure circulation (120mmHg) High pressure means faster speed of blood flow resulting in increased efficiency of blood flow to all body organs.
