Homeostasis prac questions...

[jane1234]

Hey just have a few questions about out homeostasis SAC...

1. All organisms need respond to their environment in order to survive. Bacteria use a process called "chemotaxis" (where, essentially, they move towards or away from stimulus). Why do bacteria use this process to respond to their environment?

2. Do bacteria need to use homeostasis more than other organisms because they can't move as far away? What is significant about them using homeostasis?

3. How is chemotaxis part of the negative feedback model?

Any help appreciated, thanks

[Russ]

1. Think about why you move (on a primitive level) - to find food, to find shelter, to find a mate etc. Bacteria don't have a brain to make these decisions, so they respond to things that they've evolved to recognize as being indicative of those desires. So if a bacteria can grow well in the urinary tract, it will move towards molecules that are in a high concentration in the urinary tract etc. They use chemotaxis because they can't evaluate their environment consciously.

2 and 3 confuse me: what do you mean "significant". I don't see it as being any more significant than any other organism - without it, they'd die. And what negative feedback model? The collection of the entire organism's biochemical processes?

[shinny]

Re: 2, Their restriction to movement means that they have a lesser ability to control their external environment. If we're cold, we go indoors or put something on. Similarly for other environmental factors. Bacteria however cannot do much. If they're exposed to antibiotics, they can't really run away. Likewise, if the temperature or acidity of their environment changes, they need to be able to rapidly adapt to survive.

And honestly, you should be able to do 3 yourself. Have a try first and see what you come up with. Application of the negative feedback model is almost a definite question on the exam, and there's no point memorising answers for this. They'll come up with some completely random example and get you to apply it, so it's best for you to actually attempt it rather than just grabbing answers.

[jane1234]

Okay thanks guys that was really helpful.
And yeah I could do #3 I just wanted to verify my answer...