Topic 3 Bio last Flashcards
(26 cards)
What is the rend of surface area to volume ratio in organisms?
- As organisms increase in size, its volume increases faster than its surface area so the SA:V ratio decreases
What is the SA:V ratio of single celled organisms?
- Large surface area to volume ratio
- Rely on solely diffusion
- Diffusion is fast because substances only travel small distances.
What is the SA:V ratio of multicellular organisms?
- Small surface area:volume ratio
- Cannot rely on diffusion of substances through its surface to meet needs of the organism.
How have multicellular organisms adapted to their SA:V ratio?
- Large surface area
- Good blood supply
- Thin membranes
What is the main system for gas exchange in insects?
- The Tracheal System
What is the process of gas exchange in the tracheal system?
- Oxygen diffuses down a concentration gradient towards the cells.
- Tracheae branch off into tracheoles, which have thin, permeable walls that border respiring cells.
- Oxygen diffuses from branches directly to respiring cells
- CO2 diffuses from cells towards spiracles, to be released into the atmosphere.
WHy do fish need an adapted gas exchange system?
- Much lower concentration of O2 in water than in air
- Diffusion of O2 and Co2 is slower in water.
How are fish gas exchange systems adapted?
- Fish have gills which are gas exchange organ, adapted to overcoming these problems
How does water enter fish
- Fish open their mouths and allow the water to flow through the gills, and out via the operculum (gill cover)
How are fish adapted for gas exchange
- Each gill is made of filmanet providing a large surface area
-Lots of lamellae - One cell thick provides a short diffusion pathway
- Good blood supply
- Maintains a favourable concentration gradient.
What is the counter current system?
- Blood flows through the llamellae in the opposite direction to the flow of water.
Why is the counter current system important?
- Maintanance of a favourable O2 concentration gradient between water and blood across the entire length of the gill lamellae.
Where does most photosynthesis take place?
- Palisade mesophyll cells contain lots of chloroplasts.
What is the role of the upper epidermis?
- Protects internal tissues from mechanical damage or the invasion of bacteria
How are leaves adapted?
- Stomata allow the diffusion of gases in and out of the leaf.
- Many stomata means a short diffusion distance
- Air spaces allow for diffusion of gases
- Large surface area means greater rate of diffusion.
How do plants control water loss?
- By regulating the opening and closing of stomata by guard cells
- This is affected by light intensity, water avaliability and carbon dioxide concentration
What happens to the stomata at night?
- Stomata closes as the cell can’t photosynthesise so there is no need for CO2 and O2 to diffuse in and out of the leaf so closing the stomata helps prevent unneccesary water loss.
Outline the process of gas exchange in the lungs
1) As you breathe in, air enters the trachea
2) Splits into 2 bronchi
3) Split into bronchioles
4) Lead to alveoli
5) Uuse diaphgram, internal and external intercostal muscles work together to allow ventilation
What is the path taken by CO2 and O2 at the alveoli?
- O2 diffuses out of the alveoli across the alveolar epithelium + capillary endothelium, into haemoglobin in the blood
- CO2 diffuses into the alveoli from deoxygenated blood and is breathed out
What is important about red blood cells slowing down in capillaries?
- They are pressed against the capillary wall which :
- allows time for diffusion of gases
- increases the surfaces area avaliable of red blood cells exposed
- Minimises the diffusion distance
Process of inspiration?
1) External intercostal muscles contract
2) Internal intercostal muscles relax
3) Diaphgram contracts
4) Volume of cavity increases
5) Pressure of thoracic cavity decreases
6) Air flows from of an area of high pressure to an area of low pressure down a concentration gradient
Is inspiration an active or passive process?
- Active process
Outline the process of expiration?
- External intercostal muscles relax
- Internal intercostal muscles contract
- Diaphgram relaxes
- Pressure increases
- Volume decreases
- Air moves out of the lungs
How is the alveoli adapted for gas exchange?
- Alveolar epithelium is only 1 cell thick which shortens the diffusion distance
- Large surface area for gas exchange
- Rich blood supply (Maintains the conc gradient)
- Ventilation
