TOPIC 3 - A: exchange and transport systems 1 Flashcards
(29 cards)
Do most animals have a higher or lower surface area: volume ratio than small animals?
Lower
Give 2 reasons why diffusion is too slow in multicellular organisms for them to absorb and excrete substances in this way
Some cells are deep within the body so the distance between them and the environment is too great for diffusion to take place quickly. Larger animals have a small surface area: volume ratio so they don’t have a large enough area exposed to environment
What is meant by a ‘mass transport’ system?
A system in a multicellular organism that carries substances to and from individual cells
Will the rate of heat loss at a given temperature be greater for an animal with high or low surface area: volume ratio?
High
Explain how an animal’s shape can help control its temperature
An animal with a compact shape has a low surface area: volume ratio. This means they lose less heat
Other than body size or shape, give two adaptations a small animal may have to survive in cold environments
Higher metabolic rate, thick layers of fur
Other than body size or shape, give two adaptations a small animal may have to survive in hot environments
Features that increase surface area such as large ears, may spend a lot of time in water
Give 2 things that all gas exchange surfaces have in common
Large surface area, thin, steep concentration gradient
Explain why single-celled organisms do not need a gas exchange system
Single-celled organisms can exchange gases directly through their cell-surface membrane which has a large surface area, is thin and has a short diffusion pathway.
Describe the structure of fish gills
Each gill is made of lots of thin plates called gill filaments which are covered in lots of tiny structures called lamellae which have a thin surface layer of cells and a good blood supply
Describe how the ‘counter-current’ system in fish aids gas exchange
Works by maintaining a steep concentration gradient between the water and the blood along the entire length of the gill. Blood flows through the lamellae in the opposite direction. This means that water with a high oxygen concentration always flows next to blood with a lower concentration. Oxygen then diffuses into the blood from the water down the concentration gradient
What is the main gas exchange surface for a dicotyledonous plant?
The surface of mesophyll in the leaf
Where do gases move in and out of a leaf?
Through the stomata in the epidermis
How does air get into an insect’s tracheae?
Through the spiracles on the surface of the insects body
Describe how carbon dioxide moves out of an insects cell into the atmosphere
Carbon dioxide form cells moves down its concentration gradient through the tracheoles towards the spiracles to be released into the atmosphere
What is a xerophyte?
A plant specially adapted for life in a warm, dry or windy habitat
Give 3 adaptations that xerophytic plants have to reduce water loss
Stomata sunk in pits, curled leaves with stomata inside, a layer of hairs on the epidermis, reduced number of stomata, waxy and waterproof cuticles on leaves and stems
Describe what happens to make the volume of the thorax increase during inspiration
The external intercostal and diaphragm muscles contract, which causes the ribcage to move upwards and outwards and the diaphragm to flatten
What happens to make air leave the lungs during forced expiration?
During forced expiration, the external intercostal muscles relax and the internal intercostal muscles contract, pulling the ribcage further down and in
Describe how oxygen gets from the lungs into the blood
Oxygen diffuses out of the alveoli, across the alveolar epithelium and the capillary endothelium, and into haemoglobin in the blood
Describe the features of alveoli and explain how they affect the rate of diffusion
Alveoli have a thin exchange surface, which means there’s a short diffusion pathway. This speeds up the rate of diffusion into the blood. There is a large number of alveoli so there’s a large surface area for gas exchange, which speeds up the rate of diffusion. Theres also a steep concentration gradient of oxygen and carbon dioxide between the alveoli and the capillaries, which increases the rate of diffusion. This is constantly maintained by the flow of blood and ventilation
What is forced vital capacity?
The maximum volume of air its possible to breathe forcefully out of the lungs after a really deep breath in
A person with fibrosis scar tissue has a reduced tidal volume explain why
Scar tissue is thicker and less elastic than normal lung tissue so lungs are less able to expand and can’t hold as much air as normal, thus reducing tidal volume
What is tuberculosis?
Lung disease caused by bacteria - the immune system cells build a wall around the bacteria in the lungs which forms small hard lumps
