biology paper 2

Question 1

importance of osmosis in plant support

Answer 1

• water enters the vacuole of the plant
• pressure against the cell wall maintains turgor pressure

Question 2

how does density of water contribute to survival of organisms

Answer 2

• ice is less dense than water
• provides habitats for some species
• floating ice insulates the water below

Question 3

purpose of grinding leaves when obtaining DNA

Answer 3

breaks the cell wall open so organelles can float freely

Question 4

steps to purify DNA from plant cells

Answer 4

• grind the leaf to a fine pulp using a pestle and mortar.
• add salt and cold water and mix again
• add protease enzyme and mix
• add detergent
• filter the liquid into test tube and let it stand for 10min
• tilt the test tube and pour in ice-cold ethanol
  -a white layer of DNA will form between the sample and ethanol
• extract the white layer containing DNA using a glass rod

Question 5

differences between somatic and germ line therapy

Answer 5

somatic:
- cannot be inherited/passed to offpsring
- gene introduced into body cell
- only some cells get the gene
- short term/non-permanent

germ-line:
- can be inherited/passed to offspring
- gene introduced into sperm/egg/sex cell
- all cells get the gene
-long term/permanent

Question 6

how to produce timber sustainably using clear felling

Answer 6

(clear felling is cutting down of old trees)
- limit the size of area that is felled
- replant the trees that have been felled
- minimum distance between replanted trees
- allow time for new trees to grow

Question 7

process of coppicing
and benefits

Answer 7

process:
- trunk cut close to ground level
- several new shoots grow from cut surface
- protect young shoots from grazers
- process repeated after certain time
benefits:
- new stems will grow more rapidly
- lifespan of the tree will be extended
- provides variety of light levels
- fewer large trees means more light for smaller plants
- maintains soil quality
- prevents succession

Question 8

how to clone a plant by taking a cutting

Answer 8

• cut the stem at a slant between nodes
• dip it into rooting powder/auxin
• place into soil and water
• cover with bag to reduce transpiration

Question 9

three advantages of vegetative propagation

Answer 9

• some crop plants cannot reproduce sexually
• uniform/predictable shape/size/yield
• it can be done in any season