Question
Angiospermophyta are vascular flowering plants.
Describe the transport of organic compounds in vascular plants.
The flowers of angiospermophyta are used for sexual reproduction. Outline three processes required for successful reproduction of angiospermophyta.
Growth in living organisms includes replication of DNA. Explain DNA replication.
Answer/Explanation
Markscheme
a. phloem transports organic compounds/sucrose
b. from sources/leaves/where produced to sinks/roots/where used
c. through sieve tubes/columns of cells with sieve plates/perforated end walls
d. loading of organic compounds/sucrose into /H+ ions out of phloem/sieve tubes by active transport/using ATP
e. high solute concentration causes water to enter by osmosis (at source)
f. high (hydrostatic) pressure causes flow (from source to sink)
g. companion cells help with loading / plasmodesmata provide a path between sieve tubes and companion cell
h. translocation/mass flow
a. meiosis / production of male and female gametes
b. pollination / transfer of pollen from anther to stigma
c. fertilization happens after pollination / fertilisation is joining of gametes
d. seed dispersal / spread of seeds to new locations
Reject fruit dispersal.
a. helicase unwinds the double helix
b. gyrase/topoisomerase relieves strains during uncoiling
c. helicase separates the two strands of DNA/breaks hydrogen bonds
Accept unzips here but not for mark point a.
d. each single strand acts as a template for a new strand / process is semi-conservative
e. DNA polymerase III can only add nucleotides to the end of an existing chain/to a primer
f. (DNA) primase adds RNA primer/short length of RNA nucleotides
g. DNA polymerase (III) adds nucleotides in a 5’ to 3’ direction
h. complementary base pairing / adenine to thymine and cytosine to guanine
Do not accept letters.
i. DNA polymerase (III) moves towards the replication fork on one strand and away from it on the other strand
j. continuous on the leading strand and discontinuous/fragments formed on the lagging strand
k. DNA polymerase I replaces primers/RNA with DNA
l. ligase joins the fragments together/seals the nicks
Question
Angiospermophyta have vascular tissue (xylem and phloem) that bryophyta lack. Suggest advantages that vascular tissue confers.
Answer/Explanation
Markscheme
would make it easier to stand upright (against gravity)/structural support / allows (angiospermophytes) to be bigger;
could put leaves higher in the air to get more sunlight;
transport of water supply/nutrients from roots to other tissues;
could (more efficiently) transport/translocate sugars/food from leaves for storage;