Extensive areas of the rainforest in Cambodia are being cleared for large-scale rubber plantations. Distinguish between the sustainability of natural ecosystems such as rainforests and the sustainability of areas used for agriculture.

Describe the roles of the shoot apex in the growth of plants.

Research suggests that many living plant species are polyploid. Explain how polyploidy occurs and, using a named example, how polyploidy can lead to speciation.

a. sustainable communities/ecosystems allow continued survival of organisms/OWTTE ✔

b. natural ecosystems can be sustainable over long periods of time/OWTTE ✔

c. natural ecosystems/rainforest more sustainable than agricultural areas/plantations ✔

d. diverse community/high biodiversity/higher biodiversity in natural ecosystems/rainforest
OR
less/low biodiversity in agricultural areas/agricultural soils ✔

e. agricultural areas/monocultures more affected by pests/diseases ✔

f. nutrient recycling «efficient» in natural ecosystems/rainforest ✔

g. nutrients removed with crops/nutrients removed when crops are harvested
OR
less formation of humus/less organic matter in agricultural soils ✔

h. more water recycling/more rainfall/more transpiration in natural ecosystems/rainforest ✔

i. larger biomass/more carbon stored «in biomass» in natural ecosystems/rainforest ✔

j. shallower soils/less soil erosion/degraded soils/infertile soils in agricultural areas ✔

a. shoot apex is an «apical» meristem/has undifferentiated cells ✔

b. mitosis «in shoot apex» ✔

c. cell division/cytokinesis/cells produced «in shoot apex» ✔

d. cell elongation «in shoot apex» ✔

e. stem/shoot growth «due to the cell division and elongation in the shoot apex» ✔

f. produces auxin ✔

g. auxin stimulates growth/cell elongation ✔

h. growth towards light ✔

i. differentiation of cells «produced by the shoot apex» ✔

j. leaf initiation/leaf development begins/leaf «primordia» formation «at shoot apex» ✔

k. flowers produced «by shoot apex» ✔

a. polyploidy is having more than two sets of «homologous» chromosomes ✔

b. triploid has three sets/is 3n ✔

c. tetraploid has four sets/is 4n ✔

d. Allium/vizcacha rats/other named example» ✔

e. details of chromosome numbers in diploid and polyploid species in the example ✔

f. non-disjunction/failure of chromosome pairs to separate during meiosis ✔

g. diploid gamete «can lead to polyploidy» ✔

h. fusion of diploid and haploid gamete produces triploid cells ✔

i. DNA replication but no subsequent mitosis doubles the chromosome number/produces tetraploid «from diploid»
OR
fusion of two diploid gametes produces tetraploid/4n ✔

j. polyploid/tetraploid «crossed» with diploid/non-polyploid produces infertile offspring ✔

k. meiosis fails in triploids because «homologous» chromosomes cannot pair up ✔

l. polyploid individuals are reproductively isolated
OR
polyploidy causes instant/immediate speciation
OR
tetraploids can form a new species because they can cross with each other
OR
polyploids cannot cross/produce fertile offspring with diploids ✔

m. speciation by polyploidy is common in plants/commoner in plants than animals ✔

n. polyploid individuals tend to be larger ✔