Markscheme for 2.4 Reproductive strategies question bank
BY2 Jan 2012
(b) (i) lowest supply of {nutrients / food}; max
embryo cannot complete development inside egg/ {poorly/less}
developed at hatching;
embryo unable to care for itself after hatching / parents have to {feed
/ keep warm} (due to lack of feathers)/ cannot feed itself;
2
(ii) more {time / energy/ resources} used to care for offspring/ more
offspring would need too much {time / energy/ resources} to look
after;
increased chance of survival of offspring/ less competition between
offspring;
2
(c) (i) incomplete metamorphosis NOT stage metamorphosis 1
(ii) nymphs / instars 1
(iii) nymphs {go through a series of moults/ shed exoskeleton several
times} (to become the adult); NOT skin/ outer layer
exoskeleton is {hard/ limits growth};
exoskeleton can only {be stretched/ grow} when newly formed/
{length/ size} can only increase following a moult;
rapid increase in length before exoskeleton hardens 3
(d) Tracheae/ tracheoles; NOT trachea
Spiracles
1
1
Question Total 15
.
2 (a)
(b)
Alternation of generations means: sporophyte generation and gametophyte
generation; these alternate.
(2 marks)
(i)
In the life cycle of a moss, meiosis take place: between the moss plant
and spore.
(1 mark)
(ii)
The importance of meiosis in this life cycle – the following points
should be included in the answer:

Meiosis halves the chromosome number.

When gametes fuse/at fertilisation, the diploid number is
restored.

Meiosis introduces genetic variation/independent assortment.
(3 marks)
(c)
Ways in which the moss life cycle and the life cycle of a flowering plant are
similar to and different from each other – include the following points:

sporophyte generation dominates in both

gametophyte is much reduced in a flowering plant

pollen grain and megaspore mother cell.
(3 marks)
Total 9 marks
3.
(a)
(b)
(c)
Ways in which this flower is adapted for wind pollination – any two of the
following points should be included in the answer:

stigmas feathery

giving large surface area to trap pollen

anthers dangle outside flower

pollen exposed to wind.
(4 marks)
Ways in which most insect-pollinated flowers attract insects – any two of the
following points should be included in the answer:

bright colour

attractive scent

nectar production.
(2 marks)
Ways in which plants prevent self-pollination – include any two of the
following points in the answer:

anthers and stigmas ripen at different times

heterostyly, i.e. anthers and stigmas at different heights in different
flowers

dioecious (i.e. separate sexes)

pollen incompatability
(2 marks)
Total 8 marks
4.
(a)
(b)
Reasons why commercial blackberry growers use plants produced from
stolons rather than plants produced from seeds – include any three of the
following points in the answer:

daughter plants have identical genetic information to parents (clones)

seed production leads to variation

therefore daughter plants or fruits have desired characteristics

asexual reproduction is quicker; seeds take longer to produce
new plants.
(3 marks)
Reasons why a viral infection may destroy a whole plantation of blackberries
plants grown from stolons as described in (a) – include the following points in
the answer:

All plants have similar genotypes.

A reduced gene pool means that if one is susceptible, most will be.
(2 marks)
Total 5 marks
5.
(a)
The method of reproduction shown in the diagram is tissue culture;
or micropropagation.
(b)
Expected hormones to be used: auxin; cytokinin
(c)
(i)
(ii)
(1 mark)
(2 marks)
Advantages of using this technique to conserve rare plants – include
any two of the following points in the answer:

Many plants are produced quickly using this technique.

This technique requires a minimum amount of space.

This technique keeps plants disease free.
(2 marks)
A disadvantage of using this technique to conserve rare plants: plants
are clones; therefore there is no genotypic variation.
(1 mark)
Total 6 marks
BY2 June 2010
Question Mark Scheme
5 (a) (i) Meiosis (correct spelling).
(ii) Fertilisation.
(iii) Zygote. (allow: mitosis)
(iv) Mitosis. (correct spelling)
[4 correct = 2, 3 correct = 1] 2
(b) X - haploid, Y - diploid.
Colonise area quickly/reduce parasite transmission 1
(c) (i) Rapid increase in numbers/energy for mating is saved/where environment is stable/
useful features maintained.
(not: its quicker/one parent needed/clones) 1
(ii) Variation/variety in offspring needed to adapt to new conditions or example/survival
advantage;
(sexual reproduction) leads to variation. 1
1
(d) (i) Joining together gametes/fusing of sperm and eggs (sperms introduced) inside
(female's) body/reference to intromittent organ.
(not: zygote formation) 1
(ii) Reduced number of gametes produced/more chance of gametes meeting/fertilisation/less
chance of gametes being wasted;
allows (male) gamete to become independent of water ref. prevent dehydration;
embryo/zygote can be better protected; (not: it/offspring/baby)
resistant stage in life cycle/ref. shelled egg. (any 3)
3
(iii) Embryo can receive nutrition during development. 1
10 MARKS