IB HL Biology: Ecology Review Fall 2017

Populations

1. Define the following terms associated with population ecology; population and carrying capacity.

2. What processes contribute to changes in population size?

3. What are some factors which can increase the carrying capacity of a population? Decrease?

4. What is quadrat sampling? When would it be used?

Communities

5. Define the following terms; community, autotroph, heterotroph, producer, primary consumer, secondary consumer, detritivore and

saprotroph.

6. What is the initial energy source for all communities?

7. Be able to read food webs and determine the trophic level of different species.

8. Choose 2 regions below and determine the Simpson’s Diversity Index value for these regions. Which region is more diverse?

A. An area of the Black Forest in Germany contains 134 pitch pines, 24 douglas firs, and 53 red pines. B. A meadow contains 1532 chestnut oaks, 342 black cherry trees, 12 white ash trees, and 1022 yellow birches. C. You school science classroom contains 12 beetles, 34 termites, 84 ants, 93 fleas, and 1 butterfly. D. An African park contains 15 lions, 94 giraffes, 1000 wildebeests, 50 elephants, and 5 hyenas.

Choose more areas if you need more practice.

9. What is a keystone species?

10. Distinguish between primary and secondary succession.

Ecosystems

11. What is an ecosystem?

12. Explain the 10% rule of energy transfer. How is the energy lost between trophic levels?

13. Review the Carbon Cycle. What are the main sources of carbon dioxide on earth?

14. Review the Nitrogen Cycle.

15. Distinguish between Gross Primary Productivity and Net Primary Productivity.

16. What is the Greenhouse effect?

17. How have human activities influenced climate change? When did human activities begin to influence climate change? Why?

18. What are the most common greenhouse gases?

Human Impact on the Environment

19. What are invasive species? Why are they able to take hold in a new habitat?

20. Describe biomagnification. Name one toxin / substance that experiences biomagnification in the environment.

21. Distinguish between In-situ and ex-situ conservation methods.

22. What impact do plastics have on ocean ecosystems?

PRACTICE PROBLEMS

1.. A researcher is trying to estimate the population abundance of Lodge Pole Pine Trees in Rocky Mountain National Park. He divides the park into

quadrats and counts the number of trees in a number of randomly selected quadrats. Below is a representation of his data.

Rocky Mountain National Park

5 9 2 8 11 2

5

8 8

9

3

7 2

2 4

6 1

5 7

What is the population estimate for Lodge Pole Pines in Rocky Mountain National Park?

Average number of trees in the sampled quadrats = 5.47 number of quadrats = 180

N = 180(5.47)

N = 984.6

985 Lodge Pole Pines

What would you need to know and do to determine the density of trees in the park?

You would need to know the area of the park Density = number plants / area (be sure to include correct units)

2. Another researcher is trying to estimate the number of Fox Squirrels living in Lakewood.

3. During a several-year period of drought, the population abundance of mice, voles, rats and chipmunks in an oak forest remains at a relatively constant, low level. Then a period of heavy rainfall ends the drought and results in a large increase in the population of acorns – a favorite food of rodents. The rodent population during this year would be expected to

a. decline because of excess rainfall. b. decline due to the competition from other species. c. remain almost constant, with little or no variation. d. increase in direct proportion to the increase in acorns. e. increase much more rapidly than the increase in acorns.

4. A mouse population lives in a semi-desert environment that has been affected by global warming. In the past twenty years, temperatures in the area have increased by an average of three degrees Fahrenheit, and rainfall has decreased by about five inches per year. Over this time period, it is likely that the mice in this population have a. grown larger and produced more offspring. b. lived longer and produced more offspring. c. gotten smaller and produced fewer offspring. d. had shorter life spans and produced more offspring. e. not changed; they are well adapted to any changes in the environment.

5. Sparrows eat both insects and seeds. To which trophic level do they belong?

a. primary consumer b. secondary consumer c. tertiary consumer d. omnivore

6. Food webs describe the ______ within a community.

a. uptake of solar energy

b. distribution of organisms

c. flow of nutrients and energy

d. competition among organisms

7. Decomposers obtain energy from which trophic level or levels of a food web?

a. All levels

b. Omnivores only

c. All producers only

d. All consumers only

e. Secondary and tertiary consumers only

8. A rough measure of the flow of both energy and materials through ecosystems can be obtained by measuring

a. gross primary productivity

b. net primary productivity

c. output of biogeochemical cycles

d. geographic distributions of plants

e. flow through the hydrologic cycle

She uses the mark – recapture method to estimate the population size. The following data

was collected.

Number of squirrels initially caught and released = 42

Total number of squirrels caught in second sample = 23

Number of marked squirrels in the second sample = 4

What is the population estimate? N = (42)(23) / 4 N = 241

9. Complete the diagram of the nitrogen cycle by naming the organisms involved in processes A, B and C below.

(3)

A = decomposers / saprophytes B = nitrifying bacteria C = nitrogen fixing bacteria 10. The graph below shows the variation in the concentration of atmospheric carbon dioxide since 1970.

[Source: C D Keeling and T P Whorf, Atmosphere CO2 concentrations (ppm) derived from in situ air samples,

collected at Mauna Loa Observatory, Hawaii] The annual fluctuation is mainly the result of changes in the levels of photosynthesis associated with the seasons

in Northern Hemisphere forests.

C.

A.

B.

N in atmospheredenitrification

lightning

feedingProteins inplants

Proteins inanimals

death

Fertilizers

Nitrates in soil

absorption

excretion

decomposition

Nitrites in soil

Ammoniumsalts in soil

Denitrifyingbacteria(Pseudomonasdenitrificans)

Nitrifyingbacteria(Nitrosomonas)

2

375

370

365

360

355

350

345

340

335

330

325

320

19

70

19

75

19

80

19

85

19

90

19

95

20

00

COconcentration

/ ppm

2

(a) (i) Describe the overall trend shown in the graph. (1)

(ii) Suggest a cause for the overall trend throughout the period 1970–1999. (1)

(b) (i) Using a clear label, identify any one point on the graph which shows the CO2 level in mid-summer.

(ii) Explain why the concentration of CO2 varies with the seasons. (2)

Think about trees that lose their leaves (c) Identify one gas, other than CO2 , which is contributing to the enhanced greenhouse effect. (1)

Methane , water vapor 11. Understanding the ecological mechanism that causes extinction is fundamental to conservation as not all organisms

are threatened by the same factors. A total of 1012 threatened bird species in 95 families were studied to see how they were threatened by different factors:

habitat loss persecution by humans and introduced predators other factors (introduced competitors, hybridization and disease) and unknown risk factors.

Scientists investigated the relationship between body size and the risk of extinction, both due to habitat loss and to persecution/predation. Birds were classified as small (mean body mass 1 to 1000 g) and large (mass greater than 1000 g). The results are shown in the pie chart and bar charts below.

[Source: Modified from B Owens et al., Proceedings of the National Academy of Sciences, (2000), 97,

pages 12144–12148. Copyright 2000 National Academy of Science, USA] (a) (i) State the percentage of species affected in some way by habitat loss. (1) 70%

(ii) Calculate the approximate number of bird species threatened by predation / persecution only. (1)

101 +/- 1

6

5

4

3

2

1

0

6

5

4

3

2

1

0

Extinction risk from habitat loss

Extinction risk from persecution/predation

Percentage ofspecies in

family at risk

Percentage ofspecies in

family at risk

Small

Small

Large

Large

Body size

Body size

Percentage of all 1012 speciesthreatened by each type of factor

20%

10%

25%

45%

Habitat loss only

Habitat loss and predation / persecution

Predation / persecution only

Other / unknown

(b) State two factors that could have caused habitat loss. (2) Fire, climate change, logging, pollution, drought

(c) Outline, using the bar charts, the effect of body size on the risk of extinction. (2)

(2) Small = habitat loss Large = persecution / predation (d) Discuss the methods of conservation that would avoid the extinction of large species. (3)

In situ examples or ex situ examples (size of the animal really doesn’t matter)

12. The total solar energy received by a grassland is 5 × l05

kJ m–2

y–1

. The net production of the grassland is 5 × 102

kJ m–2

y–1

and its gross production is 6 × l02

kJ m–2

y–1

. The total energy passed on to primary consumers is 60 kJ m–

2 y

–1. Only 10% of this energy is passed on to the secondary consumers.

(a) Calculate the energy lost by plant respiration. (2) Plant respiration = gross – net 6 – 5 = 1 x 102 kJm-2 y-1

(b) Construct a pyramid of energy for this grassland. (3) 13. The energy flow diagram below for a temperate ecosystem has been divided into two parts. One part shows

autotrophic use of energy and the other shows the heterotrophic use of energy. All values are kJm–2

yr–1

.

(a) Calculate the net production of the autotrophs. (1)

43 510 – 23 930 = 19 580 kLm-2 yr-1 (b) (i) Compare the percentage of heat lost through respiration by the autotrophs with the heterotrophs.

Autotroph = 23 930 / 43 510 = 55% Heterotrophs = 14 140 / 14 690 = 96% (ii) Most of the heterotrophs are animals. Suggest one reason for the difference in heat losses between

the autotrophs and animal heterotrophs. (1) The heterotrophic community can be divided into food webs based upon decomposers and food webs based upon herbivores. It has been shown that of the energy consumed by the heterotrophs, 99% is consumed by the decomposer food webs.

(c) State the importance of decomposers in an ecosystem. (1) Responsible for recycling nutrients / minerals in the ecosystem (d) Deduce the long-term effects of sustained pollution which kills decomposers on autotrophic productivity.

Autrotrophic productivity would decrease because nutrients would not longer be recycled in the ecosystem

grossproduction

43 510

feeding14 690

photosynthesis

heat23 930

heat 14 140

net productionX

storage4 900

storage540

autotrophicrespiration

heterotrophicrespiration

Autotrophs Heterotrophs

14. The diagram below is a simplified version of a food web from Chesapeake Bay. The arrows indicate the direction of energy flow and the numbers indicate species within the food web.

At which trophic level or levels does species II function? A. 2nd and 3rd consumer B. 3rd consumer C. 3rd and 4th consumer D. Producer

15.

Which is the best prediction about biomass?

A. The biomass of X is more than the biomass of W. B. The biomass of X is less than the biomass of Y. C. The biomass of V + X + Z is equal to the biomass of W. D. The biomass of Y is less than the biomass of Z.

16 The diagram below represents an energy pyramid and four trophic levels.

[Source: adapted from www.bio.miami.edu/dana/160/pyramid.gif]

IV

III

II

I100 000 kJ m yr–2 –1

(i) Identify the trophic level of the organisms indicated below. (2) I. ....................producer........................ IV. ................tertiary concumer.........................................

(ii) Calculate the approximate amount of energy in kilojoules transferred in m–2

yr–1

from trophic level I to trophic level II. (1) ...10 000 (assuming 10%)................................................... kJ

16. The diagram below is part of a carbon cycle diagram for an ecosystem in a pond.

(a) State the names of the processes that

(i) convert carbon dioxide into organic compounds in pond weeds and algae (1) photosynthesis (ii) convert organic compounds in pond weeds, algae and primary consumers into carbon dioxide. (1)

Cellular respiration (b) (i) Draw arrows on the diagram above to show how the saprotrophs obtain carbon. (1)

(ii) Explain the role of saprotrophs in recycling carbon. (2)

Saprotrophs will consume dead organic material, using the material for cellular respiration the organisms will release carbon back into the environment as carbon dioxide.

(c) Draw a box on the diagram in an appropriate position, labelled organic compounds in secondary consumers. Draw arrows to show the links between secondary consumers and other parts of the carbon cycle. (2)

(2) There has been a significant increase in the concentration of carbon dioxide in the Earth’s atmosphere during the last fifty years. (d) (i) Suggest two reasons for this increase in atmospheric carbon dioxide concentration.

1. .........burning of fossil fuels........................ .......................................................................................................................... 2. ....deforestation......................................... ..........................................................................................................................

(2) (ii) Suggest one effect of an increase in carbon dioxide concentration on organisms in a pond. Include in

your answer the reason for the effect and the type of organisms that are affected. Carbon dioxide dissolves in water to produce carbonic acid. The pond would become more acidic

which would impact the productivity of plants in the pond (decrease growth) which would impact the food webs within the pond.

(2) (Total 11 marks)

Secondary

consumers