chapter 6- exchange Flashcards
(41 cards)
what are insect exoskeletons composed of and why
-chitin for protection as it is hard and fibrous
-this is then covered by a lipid rich layer to prevent water loss
describe the insect tracheal system
small holes in the exoskeleton called spiracles which open to a network of fine tubes called tracheae (lined with rings of chitin). these then subdivide into tubes of smaller diameter called tracheoles which end at body cells
what are adaptations of the insect tracheal system
- large number of fine tracheoles- for large surface area for diffusion
- walls of tracheoles are thin- short diffusion pathway
-use of oxygen and production of carbon dioxide sets up steep diffusion gradients
-when insects are at rest water fills the end of the tracheoles
what adaptations do insects have when they are flying
-their muscle cells respire anaerobically and produce lactic acid
-this lowers the water potential in muscle cells
-water than moves by osmosis from the tracheoles into the muscle cells
-this reduces the distance for diffusion so the diffusion of oxygen is much faster
what is an adaptation in the tracheal system which larger insects like locusts have
they have special collapsible trachea called air sacs which inflate and deflate by ventilation movements of the abdomen
what is the gill structure of a fish
-gills are in a cavity on the side of the fishes head
-four pairs of gill arches on each side
-on each arch are two series of stacked gill filaments splayed out as a V
-disc-like projections called gill-lamellae are on the upper and lower surfaces of each gill filament
what are gill adaptations
- lamellae have a very large total surface area
-single layer of thin epithelial cells so short diffusion pathway
-dense network of capillaries carrying blood running underneath
-the fish pushes water over the gills to ensure constant ventilation
what is an advantage of he counter-current system
it ensures that there is a constant diffusion gradient between the water and blood
why is parallel flow not efficient in the exchange of oxygen in fish
this is because a diffusion gradient is only maintained for half of the distance across the gill lamellae. so only 50% of the oxygen diffuses into the blood
what is the structure of the trachea
- a tube supported by C-shaped rings of cartilage
-containing smooth muscle and elastic tissue
alveoli structure
-lining of the alveolus is composed of flattened epithelial cells
-surrounded by collagen and elastic tissue- allowing for stretching and recoil during ventilation
steps in inspiration
- external intercostal muscles contract (internal intercostal muscles relax )
- diaphragm contracts and flattens
- volume of thorax increases as ribcage moves up and out
- pressure of thorax decreases
- atmospheric air forced into lungs
expiration steps
- external intercostal muscles relax (internal intercostal muscles may contract)
- diaphragm relaxes- abdominal organs push upwards
- volume of thorax decreases as ribcage moves in
- pressure in thorax increases
- air forced out of lungs
what is the pulmonary ventilation equation
ventilation rate x tidal volume
what are the essential features of gas exchange surfaces
- large surface area to volume ratio
- very thin
-partially permeable - movement of external medium - air
-movement of internal medium- blood
what is flicks law of diffusion
diffusion is proportional to=
(surface area x difference in concentration)/ length of diffusion pathway
where does gaseous exchange occur in a pant
mostly in the leaves
what are leaf adaptation for rapid diffusion
- many small stomata, so short diffusion pathway
- numerous interconnecting air-spaces that occur throughout the mesophyll ], so that gases can readily come in contact with mesophyll cells
- large surface area of mesophyll cells for rapid diffusion
hope do stomata control the rate of gaseous exchange
guard cells surrounding the stomata close at times when water loss would be excessive
what adaptations do insects have to reduce water loss
- small surface area to volume ratio, to minimize the area over which water is lost
- waterproof coverings, over their body surfaces in the case of insects this covering is a rigid outer skeleton of chitin that is covered with a waterproof cuticle
- spiracles, the openings of the trachea at the body surface which cam be closed to minimize water loss
what is a xerophyte
plants that are adapted to living in areas where water is in short supply. without these adaptations these plants would become desiccated and die
what are adaptations that some leaves have to reduce water loss
- a thick cuticle
- rolling up of leaves
-hairy leaves - stomata in pots of grooves
- a reduced surface area to volume ratio
what is the role of the mouth in digestion
-to macerate food into smaller pieces increasing its surface area to increase the rate of digestion
-to secrete saliva (glands) which provides salivary amylase
what is the role of the oesophagus in digestion
passes food from the mouth to the stomach past the cardiac sphincter by peristalsis
