IB MYP 4-5 Biology Chapter 6 : Interaction–Practice Questions

Question:

Can you think of any other examples of all-or-nothing, one-way, or domino effects?

▶️Answer/Explanation

Ans: Examples of answers:

  • All or nothing Japanese deer scarers/geyser eruptions/starting flow through a siphon (for example flushing a lavatory).
  • Oneway nontidal river flows/blood flow in the human circulation system/time.
  • Domino movement of waves/peristalsis in the esophagus/spread of rot in stored apples.

Question:

Discuss whether the spread of a disease within a population has the same properties as transmission of a nerve impulse along a nerve fiber.

▶️Answer/Explanation

Ans: Infectious disease is similar in that disease is passed from an individual that has it to another that doesn’t and a nerve impulse is passed from a region of a nerve fibre undergoing a nerve impulse to another region that has not yet received it; different in that nerve impulses are carried linearly along a nerve fibre and not to multiple other fibres whereas disease transmission can be
to many different individuals.

Question:

Discuss whether the movement of an impulse along a nerve fiber is an example of reaction or interaction.

▶️Answer/Explanation

Ans: Reaction because one point along the neuron influences the next region but is not itself influenced by that next region.

Question:

What does it mean when we say that the withdrawal reflex is

a) unconscious

▶️Answer/Explanation

Ans: A reflex action happens without us being aware of it; it can happen even when we are unconscious; it is controlled by unconscious parts of the brain; we do not have to think consciously about the reflex for it to happen.

b) involuntary?

▶️Answer/Explanation

Ans: We cannot override the reflex consciously; it does not happen through our free will/we cannot exert conscious choice over whether it happens or not; we do not carry out the reflex deliberately.

Question:

What is the advantage of carrying out the withdrawal reflex using the spinal cord rather than the brain?

▶️Answer/Explanation

Ans: It is faster; fewer synapses have to be crossed; shorter distances for impulses to travel if the receptors and effectors are closer to the spinal cord than the brain.

Question:

Discuss whether the withdrawal reflex is a reaction or an interaction.

▶️Answer/Explanation

Ans: Reaction because the hot water causes the leg to be withdrawn whereas the leg does not influence the hot water.

Question:

Can we be held responsible if we cause harm to others when we carry out a reflex action?

▶️Answer/Explanation

Ans: A reflex action does not occur through conscious intention; but previous acts that lead to a reflex action and the harm that it causes could make the action culpable.

Experiment

The pupillary light reflex (PLR) is a mechanism by which the pupil at the center of the eye changes its size in response to light intensity. This response is carried out by muscle tissue in the iris and is involuntary, meaning that it is not controlled by the conscious activity of the brain. There are two types of smooth muscle involved in changing the size of the pupil: circular and radial. These are antagonistic because they cause opposite movements of the iris. When one is fully contracted, the other is fully relaxed.
Hypothesis
The pupil becomes constricted in response to the stimulus of bright light entering the eye.
Materials
Video camera Torch Video analysis software
Method
1. Dim the lighting and then shine a torch into the eye of a volunteer.
2. Take a video recording before, during and after the bright light stimulus, using a phone camera.
3. Import the recording into a video analysis software program and analyze the video frame by frame. If your software allows you to measure distances, you could plot a graph of pupil diameter over time.

Results

Question:

Describe what happened.

▶️Answer/Explanation

Ans: Iris moves/extends inwards; pupil is constricted.

Question:

a) What muscle action caused the pupils to become constricted?

▶️Answer/Explanation

Ans: Circular muscle cells contracted; radial muscle cells relaxed.

b) What muscle action would cause the pupils to become dilated?

▶️Answer/Explanation

Ans: Radial muscle cells contracted; circular muscle cells relaxed.

Question:

a) What is the advantage of dilating the pupils?

▶️Answer/Explanation

Ans: Increase the amount of light entering the eye through the pupil; more photons of light reach the retina/rod cells; clearer image formed; useful in dim light conditions.

b) What is the advantage of constricting the pupils?

▶️Answer/Explanation

Ans: Reduce the amount of light entering the eye through the pupil; reduce the number of photons reaching the retina; protect the retina from damage due to an excess of light; useful in bright light conditions.

Question:

The presynaptic neurons labelled A, B and C in the diagram release neurotransmitters that stimulate impulses, but D releases an inhibitory neurotransmitter. The table shows some observations.

Do you expect an impulse in the post-synaptic neuron if there are impulses in:

a) B

▶️Answer/Explanation

Ans: Probably not; because there was no post-synaptic impulse when only A sent neurotransmitter.

b) D

▶️Answer/Explanation

Ans: No post-synaptic impulse because D sends an inhibitory neurotransmitter.

c) C

▶️Answer/Explanation

Ans: There will probably be a post-synaptic impulse because B + D = no and B + D + C =yes.

d) A, B and C?

▶️Answer/Explanation

Ans: Definite postsynaptic impulse because three neurons send stimulatory neurotransmitter.

e) Can you work out whether there would be an impulse with any other combinations?

▶️Answer/Explanation

Ans: A + C; B + C; A + B + C + D

Question:

When chasing its prey, there are multiple factors influencing a cheetah’s decision to continue.
These factors either cause inhibitory or excitatory neurotransmitters to be released. What factors would cause release of:

a) inhibitory neurotransmitters?

▶️Answer/Explanation

Ans: Distance between prey and predator increasing/prey accelerating; predator tiring; another stronger predator catches the prey.

b) excitatory neurotransmitters?

▶️Answer/Explanation

Ans: Distance between prey and predator decreases/prey decelerating; prey is running towards an impasse; predator is very hungry.

Question:

Discuss whether the chase is an example of reaction or interaction.

In this life and death chase, both the cheetah and the impala make decisions every millisecond about which way to run. The cheetah has to decide whether it is worth continuing—most of its chases end in failure

▶️Answer/Explanation

Ans: Interaction because the actions of predator and prey influence each other.

Question:

a) Display your results graphically, with the response times for different people kept separate. Include the mean response time for each person with a range bar to show the variation from the person’s fastest to slowest times.

▶️Answer/Explanation

Ans: Scale for response time on the yaxis with units and a legend; individuals on xaxis with legend; gaps between bars on the chart; range bars showing highest and lowest times for each individual.

b) Using the data displayed in your graph, discuss whether the mean response times that you found in your trials are reliable and whether the differences between the people were significant.

▶️Answer/Explanation

Ans: The smaller the range bars the more reliable the mean response times; the larger the overlap between response times of individuals and the larger the range bars the less likely that differences are significant.

Question:

The many different methods for measuring response time give different results, even for the same person. Can you explain how we respond faster in some tests than others?

▶️Answer/Explanation

Ans: Variation in concentration/distraction; chance effects; cheating by anticipation; variation in visual clues about when the ruler will be dropped.

Question:

Response times for tests such as catching a dropping ruler are usually longer than for reflexes such as withdrawing a foot from hot bathwater. Can you suggest a hypothesis to explain this?

▶️Answer/Explanation

Ans: Withdrawal reflexes are instinctive; due to neural pathways already developed; catching a dropping ruler is not a natural reflex; involves thinking; longer pathways of neurons needed to carry out the response.

Question:

How fast can a long chain of people holding hands pass on a hand squeeze signal from the first to last person in the chain? The chain reaction challenge is best done with eyes closed so the
signal cannot jump if someone sees a hand movement ahead of them in the chain. The first person in the chain should start an electronic timer as they send the hand squeeze signal and the last person should call out when the signal reaches them so the timer can be stopped.

▶️Answer/Explanation

Ans: Time taken will probably decrease over the first few trials and then reach a minimum.

Question:

What was the mean reaction time per person?

▶️Answer/Explanation

Ans: Divide the total time by the number of people in the chain minus one (because the first person starts the process rather than reacting).

Question:

How many neurons did a signal pass through in each person from the stimulus to the response?

▶️Answer/Explanation

Ans: Not known; but there are synapses between touch receptors, sensory neurons, association neurons, motor neurons and muscle fibres so even without thought processes in the brain there are four synapses per person.

Question:

In chemistry, a chain reaction involves positive feedback, so the rate of the reaction becomes faster and faster until the reactants are used up. Discuss whether the analogy of a chain is appropriate.

▶️Answer/Explanation

Ans: Not really appropriate because a chain is a linear sequence of links whereas a chain reaction in chemistry involves spread to more and more particles.

Taking penalties

In soccer (football) a penalty kick is taken 11 meters from the goal line. The average velocity of the kicked ball is 112 km/hour. Only the goalkeeper defends the goal.

Question:

Calculate the time taken for the ball to reach the goal line.

▶️Answer/Explanation

Ans: Velocity of ball is 31.11 meters per second; time taken is 11/31.11 seconds = 0.35 seconds.

Question:

The goal is 7.32 meters wide, so a goalkeeper standing in the middle may have to move 3.5 meters to reach the ball. Estimate the time taken for the goalkeeper to move far enough to intercept the ball if it is kicked to the extreme left or right of the goal.

▶️Answer/Explanation

Ans: Possible to run 100 meters in 10 seconds and therefore 3.5 meters in 0.35 seconds; but not from a standing start; so time taken would be more than 0.35 seconds.

Question:

There were 1,749 penalties in English Premier League football matches between 1992 and 2015. Of these, 1,480 resulted in a goal scored, 64 missed the goal and 205 were saved by the goalkeeper. Calculate the percentage of penalties that were scored and the percentage that were saved.

▶️Answer/Explanation

Ans: 85% of penalties scored; 12% saved.

Question:

Discuss the reasons for such a small percentage of penalties being saved by the goalkeeper.

▶️Answer/Explanation

Ans: Impossible to see which way the ball is being kicked and then jump in the correct direction in time to catch it; goalkeeper has to guess which way the ball will be kicked; even if the goalkeeper jumps the correct way he/she may fail to catch the ball; if goalkeeper jumps to left and right and the ball is kicked to the middle of the goal he/she will miss it.

Question:

Suggest strategies that the goalkeeper could use to increase the chance of saving the penalty or that the penalty kicker could use to increase the chance of scoring a goal.

▶️Answer/Explanation

Ans: Impossible to see which way the ball is being kicked and then jump in the correct direction in time to catch it; goalkeeper has to guess which way the ball will be kicked; even if the goalkeeper jumps the correct way he/she may fail to catch the ball; if goalkeeper jumps to left and right and the ball is kicked to the middle of the goal he/she will miss it.

Question:

Data suggests that the best strategy for the goalkeeper is not to move either left or right. Suggest a reason for goalkeepers being reluctant to use this strategy.

▶️Answer/Explanation

Ans: Goalkeeper looks lazy/indecisive.

Question:

Discuss whether a conditioned reflex is an example of reaction or interaction.

▶️Answer/Explanation

Ans: Modified reaction; the stimulus alters; the new stimulus causes a reaction in the animal; but the reaction doesn’t affect the stimulus.

Question:

Suggest a hypothesis for how new reflexes can be set up by the nervous system.

▶️Answer/Explanation

Ans: New connections between neurons; new synapses; growth of nerve fibres; pruning of synapses; plasticity of the nervous system.

Question:

Find an example of a conditioned reflex that is not the result of an experiment. Domestic pets such as cats are possible sources of an example.

▶️Answer/Explanation

Ans: Cat hears larder door opening/closing; responds by going to food bowl.

Question:

Explain the benefits to an animal of learning conditioned reflexes.

▶️Answer/Explanation

Ans: Animal’s behaviour becomes attuned to its environment; appropriate responses happen more rapidly; anticipation of opportunities/threats; learning how to fit behaviour to patterns in the
environment/in events.

Question:

Using only the data in the graph, deduce which of these relationships could have caused the changes: predation, competition, parasitism or mutualism.

▶️Answer/Explanation

Ans: Predation, competition or parasitism could have caused the effect; but not mutualism.

Question:

Red and grey squirrels are in the same genus (Sciurus), so they are closely related, making it unlikely that one of them is a parasite and the other is its host. Parasites and their hosts are usually from very different groups of animals. Can you think of any reasons for this? Can you find any examples of closely related species where one is a parasite and the other is its host?

▶️Answer/Explanation

Ans: Parasite uses another organism to provide services; that it cannot provide for itself; unrelated organism more likely to be able to provide services that the parasite is unable to; cuckoo/cowbird is a nest parasite; using another bird to raise its young; broomrape/toothwort/ghost orchid is parasitic on another plant.

Question:

The red squirrel disappeared from each grid square soon after grey squirrels arrived. Then in 1982, red squirrels disappeared completely from East Anglia. The spread of grey squirrels therefore had a devastating effect on red squirrels. Discuss whether competition or predation is more likely to cause the local extinction of a species.

▶️Answer/Explanation

Ans: Competition more likely to cause extinction; no advantage to a predator in driving prey to extinction; no benefit to a competitor if the species it competes with persists.

Question:

What advice would you give about introduction of alien species, based on the data in this question?

▶️Answer/Explanation

Ans: Do not introduce alien species; unless their effects on native species have been rigorously investigated; and unless it can be shown that they will not become invasive; precautionary principle.

Question:

The numbers of hares follow a cyclical pattern of rises and falls.

a) How many cycles are there between 1845 and 1935?

▶️Answer/Explanation

Ans: Nine.

b) Calculate how long each cycle lasts on average.

▶️Answer/Explanation

Ans: 1935 1845 = 90 years; 90 years/9 cycles = 10 years per cycle.

Question:

The lynx also undergoes cyclical changes in numbers over similar time periods but changes occur after those in the hare numbers. Suggest an explanation for each of these changes:

a) increases in the number of lynx

▶️Answer/Explanation

Ans: Increases in the availability of hares/more food for lynx.

b) decreases in the number of hares

▶️Answer/Explanation

Ans: Increases in the predation of hares/more lynx catching hares.

c) decreases in the number of lynx

▶️Answer/Explanation

Ans: Decreases in the availability of hares/less food for lynx.

d) increases in the number of hares.

▶️Answer/Explanation

Ans: Decreases in the predation of hares/fewer lynx catching hares.

Question:

The lynx is one of group of species that are predators of the hare.

a) What type of relationship does the lynx have with other predators of the hare?

▶️Answer/Explanation

Ans: Competition; interspecific.

b) When there are few hares, some of the other predators may kill and consume lynx. Suggest three advantages to the other predators of doing this.

▶️Answer/Explanation

Ans: Extra food source; reduces competition from lynx for prey.

Question:

Snowshoe hare numbers fluctuate even in areas where they are not predated by lynx. Suggest another factor that could cause these fluctuations.

▶️Answer/Explanation

Ans: Availability of food/plants; severity of weather conditions; prevalence of disease.

Question:

For there to be interaction between two species they must each be affected by the other.

a) How is the population of hares affected by the lynx?

▶️Answer/Explanation

Ans: Lynx prevent hare population rising as high as it otherwise might; reduces competition among hares for food; eliminates slowest hares/hares least able to escape from their predator; enables evolution of hares.

b) Does the population of hares have effects on the population of lynx?

▶️Answer/Explanation

Ans: Size of hare population limits the lynx population; fastrunning hares cause natural selection for fastrunning lynx.

c) Is the relationship between a predator and its prey an example of interaction?

▶️Answer/Explanation

Ans: Yes it’s an interaction as the predator and prey both affect each other.

Question:

Give a deflnition of “predator”.

▶️Answer/Explanation

Ans: A predator is an animal that hunts/kills another animal for food.

Question:

a) Make a list of similarities in the relationships between predator with prey and parasite with host.

▶️Answer/Explanation

Ans: Both harm their prey/their host; both obtain food from their prey/host.

b) Make a second list showing differences in these two types of relationship.

▶️Answer/Explanation

Ans: Predator lives on or in its host but parasite does not; parasite is usually smaller than its host but predator is usually larger; predator usually kills its prey but parasite often does not kill its host.

Question:

Even if parasites don’t kill their host, they tend to reduce the numbers of the host in an area. Discuss how this happens.

▶️Answer/Explanation

Ans: Reduce the health/growth rate of host; reduce the breeding rate of host; cause hosts to move to other areas with fewer parasites; intensity of parasitism increases as density of host increases (density- dependent).

Question:

With each of the animals shown in the photos, try to decide whether it is a predator or parasite of humans. You may need to research the lifestyle of some of the six animals if you are unfamiliar with them. How well do your definitions work in deciding which type of relationship each species has with humans?

▶️Answer/Explanation

Ans: Tapeworm is a parasite; mosquito is not a typical parasite because it does not live on or in its host; but it isn’t obviously a predator either as it doesn’t kill its prey; castor bean tick is a parasite; cockroach is neither a predator not a parasite of humans; cockroach is a pest in certain circumstances; hookworm is a parasite; vampire bat does not live on or in its host so does not satisfy that part of the definition of a parasite; but a predator is expected to kill and eat its prey which the vampire bat does not do.

Question:

A parasite has a clear effect on its host, but is it influenced in any way by the host?

▶️Answer/Explanation

Ans: Parasites are influenced by the density of the population of its host; the behaviour of the host can influence whether a parasite can spread to a new host; for example a ring of repugnance around cattle feces prevents transmission of gut parasites from one cow’s feces to another cow’s gut; defensive mechanisms in the host lead the parasite to evolve so that it can evade these defences.

Question:

Can all of these relationships be classified as competitive or cooperative?

▶️Answer/Explanation

Ans: Territoriality and sexual conflict are competitive relationships; group defence and parental care are cooperative relationships; monogamy is a cooperative relationship between the male and female and prevents competition from other potential partners; predation is neither competitive nor cooperative; infanticide by one male prevents competition between his offspring and the other male’s offspring.

Question:

Considering your own identity, do you consider cooperation or competition to be more important?

▶️Answer/Explanation

Ans: Answers to this question depend very much on personality

Question:

What will happen in a social group if there is initially no cheating, but then some individuals start to cheat and more and more follow their example until there is a high level of cheating?

▶️Answer/Explanation

Ans: Low levels of cheating can be tolerated by a social group/community; but beyond a certain level cooperation between members of the community will break down.

Question:

What can prevent cheating in a group of animals?

▶️Answer/Explanation

Ans: Identification of cheats; ostracization/punishment of cheats.

Question:

a) Apart from in school tests or exams, can you suggest any human examples of cheating?

▶️Answer/Explanation

Ans: Tax-avoidance/insurance fraud/stealing from shops/ignoring a red stop traffic light/selling cars that breach emissions limits.

b) What methods can human societies use to minimize cheating?

▶️Answer/Explanation

Ans: Laws; policing; strong moral values; regarding cheating as unacceptable; education.

Question:

a) If ostriches in larger groups can spend more time feeding and less time looking for predators, what prevents enormous groups of ostriches from forming?

▶️Answer/Explanation

Ans: Competition for food becomes too intense.

b) Can you suggest examples of large groups of a species forming? In what circumstances does this happen?

▶️Answer/Explanation

Ans: Shoals of fish feeding together; flocks of starlings at roosting time; herds of wildebeest migrating; Christmas Island red crabs in the breeding season.

Question:

Do you think ravens learn to cooperate or is it likelier that their genes dictate whether they are cheats or cooperators?

▶️Answer/Explanation

Ans: Both; genes will influence the predilection to cheat or cooperate; learning/experience will affect whether an individual becomes more of a cheat or cooperator.

Summative assessment

Sperm whales

The sperm whale (Physeter microcephalus) has the largest brain of any animal on Earth.
They can live for more than 70 years and grow to lengths of over 20 metres.
Sperm whales mostly feed on squid, together with octopus and rays. They dive to feed at depths of 300–800 meters, but sometimes venture more than 2 kilometers deep (2,000 m).
Sperm whales are only vulnerable to predation by orcas and pilot whales when young or weakened.
Females and young males live in stable family groups that consist of several adult females together with their offspring.
Calves are cared for cooperatively within family groups for about 10 years. Males are ejected from the group, usually when they are older than 10.
Adult males live alone except during the mating season.
Sperm whales are highly vocal, making a variety of sounds for echolocation of prey and communication within and between groups.

Question:

During the life of a sperm whale there will be many interactions between it and other animals inhabiting the oceans. What types of interaction could occur:

a) between sperm whales and other species of animals?

▶️Answer/Explanation

Ans: Predation on squid, octopus and rays; competition with other species that feed on the same prey; predation by orcas and pilot whales when sperm whales are young/weakened/injured.

b) between an individual sperm whale and others of its species?

▶️Answer/Explanation

Ans: Competition for food; cooperation/communication between individuals within family groups; parental care; courtship between males and females.

Question:

Explain possible advantages to sperm whales of living in groups. 

▶️Answer/Explanation

Ans: Protection; cooperation over finding food; cooperation over feeding calves; shared vigilance and warning of threats.

Question:

Females currently produce calves at intervals of between 4 and 20 years. In the past sperm whales were hunted and killed by humans, and the females gave birth to young more frequently. What is the explanation for a drop in the pregnancy rate since the end of whale hunting?

▶️Answer/Explanation

Ans: Less food available due to a larger sperm whale population; possible negative feedback mechanism in breeding behaviour so fewer young are produced if the population is already strong; possibility of territoriality/intolerance of other family groups in an area so some individuals fail to breed; other harmful influences that by chance correspond with the end of whaling might have had an impact on breeding.

Question:

What factors could explain the large brain size of sperm whales?

▶️Answer/Explanation

Ans: Large brain size needed for large body; sperm whales are intelligent; large brain needed for higher order tasks such as vocalization and communication.

Investigating the diving reflex

Sperm whales can dive in the oceans to depths of over 2 kilometers and spend over an hour underwater without taking a breath. Narwhals can dive to more than 1,500 meters. Diving is accompanied by major changes to the functioning of the circulatory system, which are known as the mammalian diving reflex. The first response is bradycardia (a slowing of the heart rate), followed by changes to the amount of blood flowing to different parts of the body.

Question:

Explain reasons for a slower heart rate during a long dive. 

▶️Answer/Explanation

Ans: Lungs not ventilated during the dive; therefore no oxygen absorbed into the blood stream; so pumping blood does not carry oxygen to the tissues; pumping blood through respiring tissues might cause too much carbon dioxide to enter the blood.

Question:

Humans are mammals so we might have a diving reflex. One hypothesis that could be tested is: “Heart rate slows down in humans when the face is immersed in cold water.” Explain the reasons for expecting human heart rate to slow down if the face is immersed in cold water.

▶️Answer/Explanation

Ans: Immersion of face in cold water might give same stimulus as wholebody immersion; body therefore responds as though it is diving; and therefore no ventilation of the lungs is occurring.

Question:

Design an experiment to test the hypothesis. Include all the details of how variables will be controlled. Your method should exclude the possibility that a slowing of the heart rate is due to stopping breathing rather than contact with cold water. 

▶️Answer/Explanation

Ans: Design should include clear statements of independent, dependent and control variables, a rationale for the method, practical details of the method including the number of people to be used in the trial and how they will be selected, awarding marks on a scale from 0 marks for a completely inadequate design to six marks for an exemplary design.

Question:

Explain how you can ensure that the investigation is safe and ethically acceptable.

▶️Answer/Explanation

Ans: Explanation should include how the experiment will be carried out without any risk to the people used as subjects and how it will be ethically acceptable, including how informed consent will be obtained, with marks awarded on a scale from 0 for an entirely inadequate explanation to 3 for a detailed and convincing explanation.

Estimating the ages of narwhals

The narwhal (Monodon monoceros) is the most northerly species of whale. Its most distinctive feature is a large tusk that develops from a canine tooth on the left side of the upper jaw. The tusk always has a left-handed spiral form and in males it can grow to a length of more than 3 meters.
Narwhals spend the winter in deep water where there is pack ice, feeding on halibut, cod, cuttlefish, squid and shrimp under the ice and sometimes diving to a depth of 1500 meters or more to catch them. The narwhal live in groups of between 3 and 10 individuals. These winter groups usually consist either of females with their young or of adult males, but mixed groups of males and females can also form, especially groups of juveniles.
At the end of winter the cracks in the pack ice that the narwhals have used as breathing holes open up into channels and they migrate to shallower coastal waters as they become ice-free. Much larger groups are formed during migration, sometimes with over 1,000 individuals, but having reached summering waters smaller groups reform. At the end of summer the narwhal must migrate back to deep water before the sea near the coast freezes over completely.

Narwhals emit a range of sounds. Clicks are used for navigation and echolocation of prey. Distinctive whistles and knocks are probably used for communication within groups. Mating takes place in April or May and gestation lasts 14 months, so calves are born in summer. Mothers feed their calves with milk for about 20 months during which time mother and calf always remain close together. Calves and young narwhal can be predated by polar bears, sharks and walruses but the only natural predators of adults are orca (killer whales).
The text below is from the introduction to a scientific paper entitled “Age-specific growth and remarkable longevity in narwhals (Monodon monoceros) from West Greenland as estimated by aspartic acid racemization” by Eva Garde, Mads Peter Heide-Jørgensen, Steen H Hansen, Gösta Nachman, Mads C Forchhammer. The paper was published on 27 February 2007 in the Journal of Mammology.

Question:

Explain the problems for the scientists in measuring the ages of narwhals.

▶️Answer/Explanation

Ans: No narwhals have been kept alive in captivity; no narwhal’s age is known with certainty; therefore methods of deducing age have not been correlated with known ages.

Question:

Discuss the validity of the scientists’ methods for estimating the age of the narwhals. Can you suggest any improvements to the method?

▶️Answer/Explanation

Ans: Method uses a known chemical process; which should allow a wide age range to be determined; but the ages cannot be checked against known ages of the sample individuals; relatively few older individuals could be included in the trial.

Question:

The bar chart below shows the age estimates produced by the research.

a) What was the age of the oldest narwhal? 

▶️Answer/Explanation

Ans: 110115 years

b) What was the most frequent age of the narwhals? 

▶️Answer/Explanation

Ans: 09 years

c) Suggest a reason for the scientists not being able to determine the sex of some of the narwhals.

▶️Answer/Explanation

Ans: Too young/had not yet reached puberty.

Question:

The chart below is an age pyramid for the human population in Greenland in 2014.

a) Draw an age pyramid chart for the narwhals investigated in West Greenland. 

▶️Answer/Explanation

Ans: Award marks on a scale from 0 marks for an age pyramid without merit up to three marks for a clear and accurate pyramid.

b) Suggest reasons for the differences between the human and the narwhal age pyramids.

▶️Answer/Explanation

Ans: Hunting of narwhal causes lower life expectancy/steeper decline in numbers with increasing age; human life expectancy is increased by health care/good nutrition/lack of competition for food/fewer physical dangers; any reasonable reason for larger numbers of male than female narwhal.

Hunting narwhals and Inuit identity

There are concerns about the continued hunting of narwhal. The research into survival rates in narwhal was done partly to investigate the effect of hunting.

Question:

Write a reference to the scientific paper on the ages of narwhal. The reference should be in a style suitable for a bibliography.

▶️Answer/Explanation

Ans: Award marks on a scale from 0 marks for an inadequate attempt at a reference up to 3 marks for a reference without any errors of style, such as Eva Garde, Mads Peter HeideJorgensen, Steen H Hansen, Gosta Nachman and Mads C. Forchhammer, Agespecific growth and remarkable longevity in narwhals (Monodon monoceros) from West Greenland as estimated by aspartic acid racemization. Journal of Mammalogy, 88, 4958 (Feb 2007)

Question:

Write a paragraph to explain how the narwhals’ ages were estimated, using scientific language in a way that non-scientists should be able to understand.

▶️Answer/Explanation

Ans: Award marks on a scale from 0 marks for an incomprehensible/misleading account up to 3 marks for a clear and informative account written in scientific language that nonscientists
could understand.

Question:

Narwhals have been hunted for at least a thousand years by the Inuit of Canada and Greenland, with an estimated annual catch of about 1,000. Similar numbers are reported to have been killed in recent years. The traditional method involved spearing the narwhals from boats, but high velocity rifles are now used. There are concerns that significant numbers of narwhals are fatally wounded by rifle shots but not recovered, so official catch figures underestimate losses due to hunting. Narwhals were a significant component of Inuit diets in the past, but the main products are now muktaaq (a food made from the skin and blubber) and the large ivory tusks which can be sold for $1,000 or more.

a) Predator–prey relationships can be sustained over very long periods with numbers of predator and prey remaining stable. Is the relationship between the Inuit and narwhals a predator–prey relationship?

▶️Answer/Explanation

Ans: Not a true predatorprey relationship; low numbers of narwhal cannot cause the Inuit population to decrease; not a true interaction between two populations.

b) Should the Inuit be allowed to continue to hunt narwhals because it is an important part of Inuit identity even if it threatens the survival of the narwhals?

▶️Answer/Explanation

Ans: Hunting with highvelocity rifles is not a cultural tradition; sales of tusks to collectors is not a cultural tradition; narwhal not now needed as food to sustain the Inuit population; Inuit should not be allowed to hunt narwhal unless it is done sustainably.

c) Compared with other whale species there has been very little scientific research into narwhals, but it is known that they live in groups and communicate with each other in sophisticated ways. Should hunting of narwhals be allowed if we do not know what its effect is on these social animals?

▶️Answer/Explanation

Ans: Precautionary principle states that it is up to those pursuing a policy to demonstrate that it does not have harmful effects; nothing/almost nothing is known about the effects of narwhal hunting on family groups/populations of narwhal; so it should not be permitted.

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