The Arctic cod, ringedg2ql)c6 psn3 t. i*g*noojw3 rlj6j(q seal, killer whale, polar bear and other organisms live and interact with each other in the cold waters of the Arctic Oceanqlg)2r 3cjn*oijn3.o66 p*j(twl s q g. Which of the following terms best describes them?

  Rain forests are known to hr1snj+ y;bwjy 6m 3erx1ot-o5ave tall trees and a large biomass with high productivity, despite infertile soils. The growing conditions have ;job 5wer +x yjs1on1t63- yrmbeen known to nurture the presence of many interdependent organisms. These species also interact with the physical environment they inhabit.
Which of the following is described here?

  A wetland plant called sea-blite, which has narro 95nncoz 2 /sntjb80kb+1f jpu)bpui,w succulent leaves, and a tough perenial salt grass both grow on the edge of a salt marsh in Bolsa Cj8utn si1k5/pf o20j z,b uc)+pnn bb9hica, California. What statistical test can be used to determine if the two species are found growing together more than would be expected by random chance?

  Which of the following can be dete3h+* *m r1,dawp2fie)tmz s jxjr (tf5rmined using the chi-squared test?

  Which parts of insect-pollinated flowers are ada,; t1ec1n:o7voiy df,vn:qb tptations for mutualistic relationships with pollinators?7t et qcn:fi,; 1o :vvondby1,
I.
Nectary
II.
Coloured petals
III.
Stigma

  The okapi looks like a small-sized giraffe and has stripes that resemble thece0 ek rnvx1or*w wzv377 r9z4 zebra. It lives in the Ituri Forest in the Democratic Republic of the Congo. Okapis eat the leaves and buds of trees they can reach. They also graze on grass and ferns and eat fruit. Okapis tend to be solitary animals and the mother gives birth to one offspring which continues to be dependent on the mother’s milk for six months. When they are four to five years old, they are mature and can brew7cze74x0we n3v9 kzr* 1orr ved, but only with other okapis.
Which of the following statements is applicable to the okapi?
I. Okapi is a hybrid of a giraffe and a zebra
II. Okapi is an herbivore
III. Okapi is its own species

  From the statements lilwaw6 *)k *qhk/:su yrsted, which can be considered true of invasive but not native : k6/ral) wqk*uwsy*h species?

  What is the correct descriptio br;(kx qb(px+2 qyjsk: fe,ov8 : ihf9nbw)6on of 'interspecific competition’?

During a field day, students were asked to*ausr) ( z- a2e6pmdfp investigate the effect of soil salinity on the distribution of plant species. Students designed an experiment that measured the number of plant species found up the s6ps)a-paz*ed (urm f2hore at varying distances from the high tide line. Three groups of students investigated three sites on the same shore. The distance from the high tide line was taken as an indication of the salinity levels. The results are shown in the table.


1.1Identify the independent variable.

1.2Outline the steps students could take, and the equipment they could use, to collect their results.

2.1Suggest a reason for the discrepancy in the number of species sampled in areas 1, 2, and 3.

2.2Describe a way the students could reduce the impact of discrepancies on their collected data.

3.The different species of plants found in each area were recorded in a table.



Calculate how many times greater the number of plant species found in Area 1 was compared to Area 2.

4.Evaluate the students’ investigation into salinity's effect on plant species distribution.

  Which statement(s) descr syhaj177hburnd,(di :- io 8aibes allelopathy in plants?
I. Allelopathy is the process by which a plant releases secondary metabolites that inhibit the growth of other plants.
II. Allelopathy is the presence of mechanical defences such as thorns and spines in plants.
III. Allelopathy may involve a decreased cell elongation rate in one plant species in response to a chemical secreted by another plant species.

A student wants to set /p/6b+, thndb ug 6gx cuo7-rjup an aquatic mesocosm using seawater to simulate conditions in the food web (shown in the image below) and test its stability. He used seawater and sand from the area to set up the system and added some small organisuxdhp6rj6 g bn+t7gcu, /b /-oms to the mesocosm.



[Source: Cmglee. (2003, October). File: Arctic Food Web.svg - Wikimedia Commons. Wikimedia Commons. Retrieved April 14, 2022, from https://commons.wikimedia.org/wiki/File: Arctic_food_web.svg. Copyright under CC BY-SA 3.0]
1.In the food web shown, identify an autotroph.

2.State a reason why phytoplankton shown in the food web would be a good addition to the mesocosm.

3.Discuss how saprotrophs perform a necessary function for the mesocosm.

4.Describe the disadvantages of using mesocosms in scientific investigations.

1. A student had a small pond in5qptp8 9zrm3 r4/dems the backyard and wanted to add some fish. The fish would be predators of the pond and feed on the zooplankton (prey) growing in the pond. Zooplankton are small fls3mrq4mt8zep /rd9p 5oating or weakly swimming organisms that are dependent on the phytoplankton or algae for their supply of nutrition.
She wanted to first determine whether Fish A or Fish B would be more suitable, or if both fish could be added to the pond. As a trial, she set up four mesocosms using water from the pond. She monitored the mesocosms and then added the fish to three of the mesocosms as shown. She took samples of water from the different mesocosms and tested it for chlorophyll content at a research lab nearby.



[© Revision Village, 2023]
1.Outline why the mesocosms used would be considered a ‘closed system’.

2.Describe why adding mud or soil to the mesocosms would be advantageous.

3.Outline the reason for including ‘Mesocosm A’ with the experiment.

4.Explain the reason for monitoring chlorophyll content to analyze the effects of the fish as a predator.

5.State another variable that could be monitored to see the effect of adding fish to the mesocosms.

The following table shows the results obtained for chlorophyll (μg dm
-3
) with the different additions of fish.



Source: Adapted from Froneman, P. W. (2022, July 22). Predator diversity does not contribute to increased prey risk: Evidence from a mesocosm study. MDPI. Retrieved March 23, 2023, from https://www.mdpi.com/1424-2818/14/8/584, Copyright under CC-BY 4.0]
6.From the results obtained, suggest why the student decided to add both fish A and fish B to the pond.

[Maximum mark: 16]
1.Describe the process by which detritivores and saprotrophs obtain nutrition.

2.Describe how a quadrat can be used to estimate the population of poppies in a field.

3.Energy and nutrients move through ecosystems differently. Describe how energy and nutrients move through terrestrial ecosystems.

  The cyclical variations in the population densities of a predatu uo+v/v6r)vzc b u55lor and its prey are shown 55vu+c6lvu/ru ovzb) in the image below.


[©Revision Village 2023.]
Which of the following factors may have the least direct effect on the populations of the predator and prey species depicted here?

  Which of the following does ne5bx im9a9(ck ot apply to predator-prey relationships?

[Maximum mark: 3]
Two different mesocosms were used for a study to understand the population dynamics of two ecosystems, one without fish (C ) and one with fish (F). Each mesocosm had the following added to it: two different species of snails and the same (one) species of phytoplankton. The snails feed on the phytoplankton and are, in turn, preyed upon by the fish.
The following diagrams show the mesocosms used for the study. C is the control without fish, and F is the experimental mesocosm with one fish added. Both mesocosms were maintained at the same temperature and light conditions.


[© Revision Village 2023]
After a period of time, as shown in the graph below, the density of phytoplankton was seen to vary in the two mesocosms used in the study.


[Source: adapted from Cheng, H., Feng, M., Zhang, P., Zhang, H., Wang, H., Xu, J., & Zhang, M. (2022, December 30). Effects of warming on aquatic snails and periphyton in freshwater ecosystems with and without predation by common carp. MDPI. Retrieved January 10, 2023, from https://www.mdpi.com/2073-4441/15/1/153, Copyright under CC-BY 4.0]
1.Outline a reason for the variation seen in the density of the phytoplankton in the two mesocosms, as shown above.

2.Explain whether this is indicative of a top-down or bottom–up control of the simulated ecosystem.

[Maximum mark: 10]
The white clover (Trifolium repens) is native to the fields around Cornell University. The image shows a 10m x 15m area of the park, where quadrats (1m
2
) were used to measure the number of white clover in the fields. The results from 10 of the quadrats are also shown below.



[Source: adapted from: NY State IPM Program at Cornell University, N. Y. S. I. P. M. P. at C. U. (2014, June 19). White Clover in soccer field. Flickr. Retrieved March 8, 2023, from https://www.flickr.com/photos/99758165@N06/14273941729 Copyright under CC BY 4.0]
1.Describe how quadrats could be used to estimate the mean number of white clover in the field.

2.Calculate the mean number of white clover in the field, showing your working.

3.Explain why this type of sampling can only be used for sessile or immobile organisms.

4.Suggest two limitations of quadrat sampling.

5.State the statistical test that could be conducted to check if white clover are associated with another organism in the field.

6.There are nitrogen fixing bacteria in the root nodules of the white clover. State two ways that the white clover uses the nitrogen provided by the bacteria.

[Maximum mark: 9]
Scientists conducted studies to understand interspecific foraging behaviour overlap in Fiji’s forest birds. They observed the foraging behaviour of three types of birds on the main island of Viti Levu: nectarivores, insectivores and omnivores. The recorded data on the vertical partitioning of the different birds are shown below.
On the island of Viti Levu, the box and whisker plots below show the range, interquartile range and median for the results obtained for three species of nectarivores, two species of insectivores and two species of omnivores.



[Source: Adapted from Naikatini, A. N., Keppel, G., Brodie, G., & Kleindorfer, S. (2022, March 18). Interspecific competition and vertical niche partitioning in Fiji’s forest birds. MDPI. Retrieved 1 July 2023 from https://doi.org/10.3390/d14030223 Copyright under CC-BY 4.0]
1.Distinguish between the terms ‘intraspecific’ and ‘interspecific’.

2.Describe the differences seen in the foraging heights of the different species of nectarivores, as seen in the interquartile range shown in the box and whisker plots.

3.Outline the similarities in foraging heights of nectarivores, insectivores and omnivores, based on the interquartile range shown in the box and whisker plots.

Further studies were carried out on the birds. The vertical foraging height of the Orange-breasted Myzomela honeyeater bird was recorded in the coastal forest in Leleuvia island, where they are the only honeyeater species, and on the main island of Viti Levu, where it lives alongside two other honeyeater species. The average height of the trees on Leleuvia was 15 m and on Viti Levu it was 26 m. The data is therefore normalised for comparison and shown as relative foraging height (foraging height/mean height of tree). The box and whisker plots show the range, interquartile range and median for the results when competitors are absent (Leleuvia island) and when competitors are present (Viti Levu).


[Source: Adapted from Naikatini, A. N., Keppel, G., Brodie, G., & Kleindorfer, S. (2022, March 18). Interspecific competition and vertical niche partitioning in Fiji’s forest birds. MDPI. Retrieved 1 July 2023 https://doi.org/10.3390/d14030223 Copyright under CC-BY 4.0]
4.Discuss the foraging behaviour of the Myzomela honeyeater species with and without the presence of competing nectarivore bird species. 1
5.Comment on the challenges of obtaining data in field studies compared to laboratory experiments.