Seven Prescribed Practicals

1. USING A LIGHT MICROSCOPE TO CALCULATE MAGNIFICATION. a. A student, observing a micro-organism under a magnification of 40X, calculates that it is about

100 micrometers long.   If she then draws the microorganism 2 cm long, what is the magnification of her drawing?

b. A student draws a cell diagram 24mm long, which is 400X larger than life size.  How large is the actual cell?

c. A cell is 80 um in length. If drawn 600 times actual size, how long will the drawing be in cm?

d. If a red blood cell has a diameter of 8 um and a student shows it with a diameter of 40 mm in a drawing, what is the magnification of the drawing

ANSWERS

a.  First convert 100 micrometers to mm: 100 um / 1000 = 0.1 mm

Then convert 2 cm to mm:2 cm * 10 = 20 mm

Now that we have the same unit, we can calculate drawing magnificationMagnification = drawing size (which is 20 mm) divided by actual specimen size (which is 0.1mm)Magnification = 20 mm / 0.1 mm = 200X

b. This problem gives us the magnification as 400x and the drawing size (24mm).  So, we rearrange the formula to be:

Actual specimen size = drawing size (which is 24 mm) divided by magnification (which is 400X)Actual specimen size = 24 / 400 = 0.06 mm

c.  First convert 100 micrometers to mm: 80 um / 1000 = 0.08 mm

This problem gives us the magnification as 600x and the specimen size (0.08mm).  So, we rearrange the formula to be:Drawing size =  magnification (which is 600X) times actual specimen size (which is 0.08mm)Drawing size = 600 times 0.08 = 48 mm

The answer is needed in cm, so convert 48 mm to cmcm = 48mm/10 = 4.8 cm  

d. We are given the actual size of the cell as 8 um, and the size of the drawing of 40 mm.In order to calculate the magnification the units must be the same.40mm * 1000 = 40,000um

Mag= what you measure (40,000 um)/scale (8um) = 5000X

2. ESTIMATION OF OSMOLALITY IN HYPOTONIC AND HYPERTONIC SOLUTIONS a. Osmolarity: the concentration of solutes in a solution

i. Isotonic: The Osmolarity of the two solutions are the sameii. Hypotonic: a solution with a lower Osmolarity (less solutes) is compared to another solution

iii. Hypertonic: a solution with a higher Osmolarity (more solutes) is compared to another solutioniv. Water Potential: the tendency of water molecules to move from an area of higher concentration

to an area o flower cncnetration b. Questions often involve a calculation of percent change:

i. Percent change = Final – initial X 100 initial

ii. The Osmolarity of a sample is the position at which the %change in mass is 0

3. INVESTIGATIONS INTO FACTORS THAT AFFECT ENZYME ACTIVITY a. Explain how temperature affects the rate of enzyme activity.

b. Draw a graph of depicting the effect of temperature on the rate of enzyme activity.

c. Explain how pH affects the rate of enzyme activity.

d. Draw a graph of depicting the effect of pH on the rate of enzyme activity.

e. Identify the optimum temperature or pH for enzyme activity on a graph.

f. Explain how substrate concentration affects the rate of enzyme activity.

g. Draw a graph of depicting the effect of substrate concentration on the rate of enzyme activity.

4. CHROMATOGRAPHY OF PHOTOSYNTHETIC PIGMENTS a. Step 1: Grind leaf pieces in a pestle and mortal. Add propanaone and continue to grind. Cover and leave

until liquid has turned a dark grean

b. Step 2: Use a capillary tube to apply the extract to chromatography paper or a thin layer strip. Repeat until a small dark spot is formed

c. Step 3: Place the chromatography strip into a narrow glass tube containing a *little* chromatography solvent. Let sit and pigments will be carried upwards.

i. Lighter pigments will travel further than heavier onesd. Step 4: The pigments can be identified by using an Rf value. The number is specific for each pigment

i. Rf = distance moved by pigment distance moved by solvent

5. SETTING UP AND MONITORING A MESOCOSM a. Mesocosm—small scale self-sustaining natural system

i. Allows scientists to mirror conditions that may occur on a larger scaleii. Observe events of an ecosystem under controlled conditions

1. Used to observe how temperature & light can affect an ecosystem2. Used to observe feeding habits of fish3. Effects of climate change on dissolved carbon dioxide concentrations in small ponds

6. MONITORING THE VENTILATION IN HUMANS

7. MEASUREMENT OF TRANSPIRATION RATES USING A POTOMETER a. Make sure you can describe using a photometer to investigate the effect of light, wind, temperature, or

humidity on transpirationi. Light Intensity increase will speed up rate of transpiration

ii. Temperature increase will speed up rate of transpirationiii. Humidity increase in humidity will reduce rate of transpirationiv. Wind speed Increase will increase rate of transpiration

Option C1: Species and Communities

8. Outline six factors that affect the distribution of plant species. a. Water—needed for metabolic processesb. Space—needed for growth of roots and shootsc. Mineral nutrients—in soil or waterd. Sunlight – for photosynthesise. Temperature—to influence enzyme activity

9. Explain how the following factors affect the distribution of animal species:a. Water – for metabolic processesb. Territory – to find mates & rear youngc. Nutrients – from food

d. Temperature – to influence enzyme activity10. Explain the following interactions between species::

a. Herbivory – consumption of plant or primary producer materialb. Competitive—two species occupying the same territory compete for limited resourcesc. Predation—One consumer feeding of anotherd. Parasitism—parasites that live on or in a host; parasite benefits and host is harmede. Mutualism—two species that both benefit

i. Algae Zooanthllae have develop a mutualistic relationship with coral polyps1. Algae provide oxygen and produce nutrients for coral2. Coral offers production and provides algae with CO2

11. Explain what is meant by the niche concept. a. Niche concept—the area an organisms inhabits and how that organisms interacts with living and non

living components of an ecosystemi. Spatial habitat

ii. Feeding activitiesiii. Interactions with other species

b. No two species can occupy the same niche

12. Distinguish between fundamental and realized niches. Fundamental: potential mode of existence. Total range an organism could live with its adaptations

Realised: that actual niche that a species occupies; actual mode of existenceCaused by competition and species interactions

13. Outline the method and importance of GF Gause’s paramecium experiments. (http://www.ggause.com/gfg05.htm)

Paramecium aurelia and Paramecium caudatum have similar adaptations and food sources. When grown separately they are able to surivive. However, when grown in the same niche P. Aurelia will outcompete P. caudatum. This experiment demonstrated that no two species can occupy the same niche.

14. Explain the competitive exclusion principle. a. No 2 species can occupy the same niche if they are competing for limited resourcesb. One species will outcompete the otherc. Will lead to the extinction of the outcompeted species or force the outcompeted to find a new niche

15. Random Sampling and Quadratsa. Explain the importance of randomness in selection of quadrat locations in a sample site.

i. Allows for each member of a population to have an equal chance of being selected.ii. Helps reduce bias and increase accuracy

b. Outline two simple methods for generating random coordinates or otherwise ensuring that selection of a sample site is random.

i. Quadrat Sampling—Using quadrats of equal area to randomly survey a larger area1. Used to compare how different populations of stagnant species compare

a. Ex. Grass vs. cloverii. Transect Sampling—Using quadrats on either side of transect line

1. Used to compare how a population is affected by an abiotic factora. Ex. # of hermit crabs vs. water availability

16. Explain what is meant by a keystone speciesa. Species in an ecosystem that plays a large impact on the biodiversity of the ecosystem.b. If the species were removed, over time biodiversity would decrease in the ecosystem

i. Ex. Sea otter1. Feeds on sea urchins2. Without otters urcins over consume kelp3. Reduction in kelp prevents breeding and habitats for a variety of organisms

17. Explain what is meant by species tolerancea. Species tolerance—the environmental factors that effect a species ability to surviveb. Zone of tolerance—the range of an ecosystem that a species can survive

i. Optimal range—will have the highest population of species1. Little no homeostatic ability or stress

ii. Upper and lower limits—will have smaller populations of species1. Causes stress and limits reproductive abilities

C2: Communities and Ecosystems

18. Monitoring productivitya. Define biomass.

i. Total amount of organic material derived from individual organisms in an ecosystem. b. Suggest some reasons for studying the biomass of an ecosystem.

i. Used to evaluate success of organisms in various nichesii. Changes in biomass could indicate change ins success

iii. Calculate the # of organisms inhabiting a particular trophic levelc. Outline one method for estimating the biomass of different trophic levels of an ecosystem.

i. Samples are taking using a random sampling methodii. Samples are sorted according to trophic level & dehydrated

iii. Mass of organisms in each trophic level are measurediv. Masses are compared for analysis

d. State some of the ethical concerns associated with measuring biomass and how these may be alleviated. i. Determining biomass requires the death of sample organisms

ii. Samples should be kept small and limit the destruction of organisms found in the environmentiii. Tables have been developed to help estimate biomass based on size and height to prevent

deathiv. Human methods of capture and release must be used

19. Explain why biomass is generally low at higher trophic levels. a.

20. Define the following terms:Gross production: the total amount of organic matter produced by plants in an ecosystem. Net production: Gross production minus the amount of energy loss due to respiration

NP = GP -Ra.

21. Describe the role of the food industry and productivity.a. Food production industry relies on the ability of organisms to produce products efficientlyb. Uses a food conversion ratio to measure productivity

i. How much food is required to produce desired productsii. The lower the FCR the more efficient and sustainable the organisms

22. Explain the shape of the pyramid of energy. a. Used to represent the amount of energy available for each trophic level b. Energy transfer is inefficient

i. Almost 90% is lost 1. Respiration2. Not all of the organisms is eaten3. Not all of the organism is digested and energy is lost by defecations

c. As trophic levels increase, the bar should only be approximately 10% of the previous trophic leveld. ***Energy is measured in Kj m-2 yr-1 or kilojoules/meter/year

23. Study the energy flow diagram below.

From the IB Biology QuestionBank CDRom

a. Calculate the net production of the autotrophs. a. NP = GP –R

b. NP = 43,510 – 23,930c. NP = 19,580 Kj m-2 yr-

b. Calculate the percentage of energy lost as heat in:

i. Autotrophs: Heat/gross X 100 =~55%

ii. Heterotrophs: heat/gross X 100 = 96%24. Discuss the difficulties of classifying organisms into trophic levels.

a. It is difficult to class organisms into a specific trophic leveli. Organisms can exist in more than one trophic level depending on their diet

b. Food webs are used to show complex feeding relationships25. Describe what is meant by ecological succession.

a. Succession – changes in an environment over timeb. Primary Succession—Pattern of development of an ecosystem where living organisms did not previously

existi. Soil is not developed

ii. Ex. New volcanic islandc. Secondary Succession—pattern of development of an ecosystem where living organisms have previously

existed but have been disrupted by environmental changesi. I.e. forest fires

d. Pioneer species—the first organisms to appear in an ecosystemi. Change the composition of soil

1. Depth, minerals, organic materialii. Make soil suitable for additional plant life

1. Plant structures break down rock a. increasing soil depthb. increases mineral availability from minerals stored in rockc. Roots prevent mineral loss by erosion

iii. Are often mosses26. Distinguish between biome and biosphere.

a. Biome: type of ecosystem that is characterized by climate and life formsb. Biosphere: overlapping and interacting biomes on earth

27. Explain how rainfall and temperature affect the distribution of biomes. a. Climate determines the amount and types of organisms that can be present in a biomeb. Depends on temperature and rainfall

28. Whittaker’s Climograph is a well-known representation of temperature, rainfall and distribution of biomes in the world:

29. Outline how climate change leads to species migration, redistribution and possible extinction.

a. Organisms found in a biome are adapted to certain conditions.

b. If climate change causes temperature or precipitation changes outside of their zone of tolerance species will need to migrate in order to survive.

c. If unable to migrate successfully could lead to the extinction of the species30. Distinguish between an open and closed ecosystem

a. Closed ecosystem exchange energy with the surrounding environment but do not exchange matteri. Contained within sealed environments

ii. Matter cannot be shared with other environmentsiii. Organisms must consume waste produced by other organismsiv. Must include photosynthetic organisms to survivev. Energy must enter in the form of light

b. Open systems can exchange matter between surrounding environmentsi. Biosphere is an open system

C3: Impacts of Humans on Ecosystems

31. Introduction of non-native species. a. Define alien species.

i. Species that is non-native to an environmentii. Can affect the ability of native organisms survival success

iii. If presence disrupts the ecosystem they are referred to as invasiveb. Outline the impacts of three examples of introduction of alien species:

Intentional Introduction: prevention of soil erosion

Kudzu was intentionally introduced into the US from Japan Originally used as decoration, but due its rate of growth was advertised as a way to prevent soil erosion Kudzu

o Rapid growtho Efficient absorption of nutrients of soilo **crushes plants that it grows on top of; breaks limbs of treeso **outcompetes native plants for mineral supply in soil

Intentional Introduction: biological control

Cane Toadso Were introduced into Australia from South America to control the insect population that was

destroying sugar cane plantso Cane Toad did not feed on ‘grub’ but fed on native specieso No native predators to maintain populationo Produces a poisonous toxin that kills non-native predatorso Rapid rate of reproduction allows it to cover large territories

Accidental Introduction: shipping or globalization

Zebra Mussels: accidently introduced by Cargo Shipso Mussels were found in ballast water of ocean shipso Reproduce rapidly

Clog pipeline and destroy water supplies Eat lots of algae and small organisms Causing small ponds to become clearer

c. Explain the effects of invasive alien species on native species, with examples:i. Interspecific competition

1. Invasive species will outcompete native species for resourcesa. Ex. Kudzu and soil nutrients and lightb. Ex. Cane Toads and Skinks

ii. Predation1. Invasive species prey on native species2. No natural predator to keep population in check3. Native species lack behaviors and adaptations to avoid invasive species

a. Ex. Cane toads and native insects to Australiaiii. Extinction

1. If invasive outcompetes native species or overeats native species could cause extinction32. Pollution & the food chain

a. Define biomagnification. i. Increase in the concentration of a substance as it moves throughout the food chain

ii. Higher trophic levels have higher concentrations of toxinb. Describe the cause and consequences of one named example of biomagnification.

i. DDT is a pesticide used to control mosquito populations to prevent the spread of malariaii. Biomagnification caused top trophic level consumers to suffer

1. Birds of prey—Egg shells were weak and fragile; cracked and died when mother sat to warm them

2. Humans—passed to children via breastmilk33. Outline how plastic pollution affects marine environments

a. Micro plastics—less than 5 mmi. Are easily mistaken for food and are not able to be digested by organism

ii. Are able to absorb chemicals influencing Biomagnification in food chainsb. Macro plastic—greater than 5 mm

i. Mistaken for food1. Animals feel full, but die of starvation2. Death by damage to digestive tract

ii. Trapped in debrisc. Ex. Laysan albatross

i. Skims the surface of water to catch fishii. Often accidently intakes plastic

iii. Adults are able to regurgitate, but young cannot and die of starvation

C4: Conservation of Biodiversity

34. Monitoring ecological systems.a. Define biodiversity:

i. Used to describe the amount and variety of species found in an ecosystem1. Includes species richness: total amount of organisms found in an ecosystem2. Species evenness: how the organisms are distributed

a. **Environments without evenness are not considered to be diverse

b. State the function of Simpson’s Diversity Index. i. Used to calculate and evaluate the biodiversity of an

ecosystem.ii. Often calculate to compare changes in diversity over time

iii. D= diversity indexiv. N= total # of organisms presentv. n= Number of organisms of a particular species

35. Outline how indicator species can be used to monitor environmental conditions.a. Indicator species are organisms that are highly sensitive to environmental change

i. Their presence or absence can determine the health of an ecosystem. ii. Very sensitive to abiotic factors

b. Ex.i. Lichen—Used to measure air quality

1. Sensitive to acid rain and air pollutionii. Mayfly larvae—used to measure water quality

1. Sensitive to low oxygen levels in watera. Low oxygen levels caused by introduction of waste into water supply or lack of

oxygen caused by eutrophicationiii. Tubifex worms—used to measure water quality

1. Tolerant to metal deposits in water2. High population indicates water pollution

36. Differentiate between in situ conservation measures and ex situ conservation measuresa. In situ conservation

i. Attempts to preserve a species in its native environment; allows for an increase of adaptations in natural conditions

1. Maintaining the population of an environment of which it survives best2. Encouraging natural evolution of species3. Protection from environmental stresses4. Greater genetic diversity by maintaining a larger gene pool

b. Ex situ conservationi. Last resort measures when in situ are no longer effective

1. Captive breeding2. zoos3. Seed banks4. Botanical gardens

ii. Cons1. Gene pool is limited to individuals in ex situ conservation site2. Decreasing genetic diversity3. Reintroduction of species is difficult4. Does not offer protection to natural habitat

C5: Population Ecology (HL)

37. Species’ reproductive cycles are the product of natural selectiona. Distinguish between r- and K- reproductive strategies:

Short life span (days, weeks or months) (1) Life span Longer life span

Small adult body size Growth Larger adult body size

Reach sexual maturity early Maturity Reach sexual maturity later

Reproduce only once; but have many offspring Offspring Can reproduce often; but have few

offspring

Minimal impact on R species Competition Affect population sizes of K species

Unstable (changing) Environment Stable (unchanging)

Bacteria, rodents, insects examples Whales, elephants, humans

38. Populations of animal species can be monitored using capture-mark-recapture methods.a. Annotate the Lincoln Index calculation below, as an example of a capture-mark-recapture method of

estimating the population size of an animal species.

N1= # of individuals caught in first catch

N2= Total # of individuals caught in second catch

N3= # of individuals marked in second catch

**Lincoln index is used to measure populations of organism that are motile.

39. Outline techniques for estimating size of Commercial Fish Stocks:a. Capture-Mark-Release-Recapture

i. Useful for monitoring populations in contained bodies of water (lakes)ii. Not effect for large bodies of water (i.e. oceans) where fish are able to travel large distances and

depthsb. Echo Sounders

i. Used to measure fish populations based on density and locationsii. Sample fish must be capture to identify the species of fish detected

c. Fishermen reportsi. Documentation of size, amount, and sex of fish caught

ii. Depends on accurate reporting informationiii. Inaccuracy due to disagreements between industry and conservationists

d. Research involving tagging fishi. Allow for motility and population estimations

40. Explain what is meant by maximum sustainable yield with regards to commercial fish stocka. The maximum # of fish that can be harvested without causing a decline fish stocks

i. The amount of fish required to maintain the populationb. Important that harvesting does not limit ability of fish population to be maintained

41. Define population. “A group of organisms of the same species living in the same area at the same time.” (1 p. 36)

42. Outline the effects of natality, mortality, immigration and emigration on a population: a. Natality (birth rate)—will increase the size of a population

i. Heavily influenced by density independent factors1. Non-contagious disease2. Natural disasters 3. Etc.

ii. Mortality (death rate)—will decrease the size of the populationiii. Heavily influenced by density independent factors

1. Non-contagious disease2. Natural disasters 3. Etc.

iv. Immigration (movement into an area)—will increase the size of the population1. Caused by density dependent factors in other environments

a. Limited resourcesv. emigration (movement out of an area)—will decrease the size of a population

1. Caused by density dependent factors in other environmentsa. Limited resources

43. Outline under which conditions a population will: a. Grow

i. N + I > M + Eb. Remain stable

i. N + I = M +Ec. Decline

a. N + I < M + E44. In the space below, draw a population growth curve.

Annotate it to explain the exponential, transition and plateau phases and carrying capacity (K). Lag phase—slow growth due to small population Exponential phase—rapid growth due to plenty of

resources Transitional phase—growth rate begins to slow as competition for resources begins to increase Plateau phase—end of population growth, when a population reaches its carrying capacity, K

45. Differentiate between top down & Bottom up Limiting Factors

a. Top Down—organisms in higher trophic levels prey on organisms in lower trophic levels to maintain their populations

b. Bottom Up – Organisms at the producer level limit the amount of organisms in higher trophic levels

C6: Nitrogen and Phosphorous Cycle (HL) 46. Explain why nitrogen is essential for life processes.

a. Nitrogen makes up the amine group of amino acidsb. Found in nucleic acids

47. Explain why nitrogen gas is not useable for most organisms.a. Nitrogen gas, N2 is a highly stable structure. Most organisms do not contain the enzymes to break down

structure. b. Depends on Nitrogen fixation to convert to useable forms.

48. Outline how Nitrogen fixation is performed.a. Nitrogen fixation is responsible for converting nitrogen gas into useable form ammonia.b. Performed by the following:

i. Nitrogen Fixing bacteria1. Azobacter2. Rhizobium

a. *Mutualistic relationship with plants

ii. Lightningiii. Haber Process

49. Outline why nitrification is essential for living organisms. a. Ammonia and nitrites are toxic in high quantities to

plantsb. Nitrosomas converts ammonia into nitritesc. Nitrobacter converts nitrites into nitrates

i. Nitrates are passed through the food web and are recycled into the soil as organisms excrete waste and decompose

50. Outline how nitrogen gas is returned to the atmospherea. Denitrification is the process of converting nitrates into N2b. Performed by Pseudomonas denitrificans

i. Occurs in anaerobic conditions & waterlogged areasii. Peat bogs

51. Outline why the phosphorous cycle has a slower turnover than the nitrogen cyclea. Phosphorous cycle is dependent on the rock cycleb. Phosphorous is stored inside of rocks as phosphate

i. Must wait for weathering and erosion to occurc. Phosphate is returned to abiotic environments as sedimentary rock

i. Accumulates at the bottom of the ocean52. Outline the consequences of Eutrophication

a. Caused by algal bloomsb. When Nitrogen or Phosphorous are increased in a water supply allow for algae to increase their

population sizec. Use up a majority of the oxygen due to respiration.d. Creates a biological oxygen demand in other organisms in the water.e. Organisms begin to die due to lack of oxygen