19 unified

Question 1

what are ways in which a student can improve their staining techniques

Answer 1

place stain at edge of sample
ensure stain covers whole sample
lower cover slip at a slanted angle (45 degrees)
use blotting paper to remove excess stain
use more than one stain

Question 2

why does pondweed have no waxy cuticle

Answer 2

water loss is not a problem

Question 3

why does pondweed have a thin, flexible stem

Answer 3

less support needed, plant is supported by water

Question 4

how can positive feedback cause hyperthermia

Answer 4

positive feedback amplifies a change away from a set point
lower temp reduces kinetic energy
metabolism is slowed
less metabolic heat generated
temp drops lower

Question 5

give an example of a transudcer

Answer 5

converts chemical/ stimulus to action potential/ electrical energy

Question 6

reasons why some animals may be able to survive without oxygen for a long time

Answer 6

-slow metabolic rate
-less energy spent on thermoregulation
-more able to buffer H+
-Hb has a higher affinity for oxygen

Question 7

ways in which an experiment can be more valid

Answer 7

-controling factors to prevent them from affecting the results
-control group

Question 8

why should t tests be used

Answer 8

it compares 2 means

Question 9

how do genes affect immune responses

Answer 9

• organisms will inherit genes that code for immune cells
  -B/T lymphocytes
  -different alleles code for different versions of immune cells/ antibodies
  -alleles code for many different variable regions
  -mutation produces new alleles
  -autoimmune diseases

Question 10

how does the environment affect the immune response

Answer 10

exposure to different pathogens determines the immune response
vaccinations produce primary immune responses
pollen- environmental influence on allergies
autoimmune diseases

Question 11

what are the advantages of using microorganisms to produce food and why is this good

Answer 11

low cost. many microorganisms require low temp and are fed on waste materials

large numbers can be produced quickly- short life cycle

better for the environment- reduces use of land for food

can be produced in many locations- not affected by climate

suitable for vegetarians- more healthy food

easy to genetically engineer

-lactobacillus for cheese/ yoghurt
yeast for alchohol and bread
fusarium for mycoproteins

Question 12

why is the estimation of 4 colonies produced by serial dilution likely to be inaccurate

Answer 12

with small colony numbers, small (random) differences