misconceptions in scientific inquiry what is scientific inquiry? methods used by scientists nature...

Misconceptions in Scientific InquiryMisconceptions in Scientific Inquiry

What is scientific inquiry?What is scientific inquiry?

Methods used by scientistsMethods used by scientistsNature of scientific knowledge Nature of scientific knowledge

Historical examples :Historical examples :Theory of spontaneous generationTheory of spontaneous generationWhat is the genetic material?What is the genetic material?Cause of gastric ulcer - MarshallCause of gastric ulcer - Marshall

Key steps of scientific inquiry:1.1. Observation Observation:

Maggots are often found on rotten meat. QuestionQuestion: Where do the maggots come from?

2.2. HypothesisHypothesis: The maggots are hatched from eggs laid by flies.

3.3. Testing the hypothesisTesting the hypothesisPredictions Design experiments / observation

If the hypothesis is correct, …..ResultsResults: (a) No maggots were found inside Flask 1.(b) Maggots were found inside Flasks 2 and 3.

ConclusionConclusion: The maggots were developed from eggs laid by flies.

Concept of assumptionsConcept of assumptions

What is the aim of the What is the aim of the experiment?experiment?

What is the conclusion?What is the conclusion?

What do I actually measure?What do I actually measure?What is my assumption(s) ?What is my assumption(s) ?

Assumptions made:Assumptions made:

• Only oxygen is used up during Only oxygen is used up during

burning.burning.

• All oxygen in the air is used up. All oxygen in the air is used up.

• No air has escaped from the gas jar.No air has escaped from the gas jar.

• All carbon dioxide released out All carbon dioxide released out

during combustion is dissolved in during combustion is dissolved in

water. water.

Growth of seedlingsGrowth of seedlings

What do you want to measure?What do you want to measure?

How is this parameter related to what How is this parameter related to what you want to measure?you want to measure?

What parameter do you actually What parameter do you actually measure?measure?

• length of radicle, length of radicle, • fresh mass fresh mass • dry massdry mass




• length of root length of root • fresh mass fresh mass • dry massdry mass

Which assumptions may not hold true Which assumptions may not hold true under specific situations?under specific situations?

We want to measure the growth of germinating seeds We want to measure the growth of germinating seeds - - formation of new cells or protoplasm..We actually measure the increase in length of the We actually measure the increase in length of the root/the fresh mass /the dry mass of the seedlings.root/the fresh mass /the dry mass of the seedlings.Assumptions:Assumptions: all changes in the parameter we all changes in the parameter we measure are caused by changes in the quantity of measure are caused by changes in the quantity of new cells or protoplasm.new cells or protoplasm.The assumptions may not hold true in the following situations:

At the initial stage when the dry seeds are soaked At the initial stage when the dry seeds are soaked in in water, the increase in fresh mass of the seeds is water, the increase in fresh mass of the seeds is not not caused by growth but by the absorption of caused by growth but by the absorption of water.water.

The growth of a seedling during germination cannot The growth of a seedling during germination cannot be be measured by the change in dry mass - affected measured by the change in dry mass - affected by the by the oxidation of organic substances in oxidation of organic substances in respiration. respiration.

Van Helmont’s experiment [1668]

Aim?Assumptio

ns?Conclusion

?

Aim of experimentAim of experimentTo test the hypothesis:To test the hypothesis: Plants absorb soil Plants absorb soil as food through the roots for growth.as food through the roots for growth.

Conclusion: Conclusion: (CE 2003 Q4)(CE 2003 Q4)

Plants do not absorb Plants do not absorb soilsoil as food through as food through the roots for growth.the roots for growth.They absorb They absorb waterwater through the roots. through the roots.

Assumption:Assumption:Plants obtain their nutrients through the Plants obtain their nutrients through the roots.roots.

Measuring the rate of transpiration Measuring the rate of transpiration using a bubble potometerusing a bubble potometer




Measuring the rate of transpiration Measuring the rate of transpiration using a bubble potometerusing a bubble potometer

What is your What is your assumption?assumption?

Under what situations will the Under what situations will the assumption fail to hold true?assumption fail to hold true?

TThe rate of water absorption is he rate of water absorption is identical to the rate of identical to the rate of transpiration.transpiration.

• Using a dehydrated shootUsing a dehydrated shoot• Transpiration rate >> rate of water Transpiration rate >> rate of water

absorptionabsorption

Other examples:Other examples:

• To find out the water potential of potato cells To find out the water potential of potato cells

by measuring the length or mass of potato by measuring the length or mass of potato

cylinderscylinders• To measure the rate of respiration of To measure the rate of respiration of

mealworms using a respirometer mealworms using a respirometer • To compare the vitamin C content of fresh and To compare the vitamin C content of fresh and

boiled orange juice using DCPIP solutionboiled orange juice using DCPIP solution • To compare the sweet taste of green and red To compare the sweet taste of green and red

grapes using Benedict’s test grapes using Benedict’s test • To find out which brand of tissue paper absorbs To find out which brand of tissue paper absorbs

water bestwater best

Drawing conclusions from negative Drawing conclusions from negative resultsresults

Suppose you have performed a number of food tests on milk and got the following results:

Benedict’s test Iodine test Biuret test Grease spot test

+++ ++ +

What would be your conclusion on the food content of milk?


Corn plants were grown in fields A and B of different soil conditions. To test for N sufficiency in the soil, each field was separated into two plots. One plot was supplied with N fertiliser and the other plot without N fertiliser. After 15 weeks, the corn in the two fields was harvested.

(a) What conclusion can you draw from the results of field A?(b) What conclusion can you draw from the results of field B?


(a) N is deficient in field A. (93%)(b) N is not deficient in field B. Besides N, the plants need other minerals. No conclusion about N content of Field B.

1818%%


(a) If germination occurs in set-up B but not in set-up A, what would be your conclusion?

(b) If no germination occurs in both set-ups, what would be your conclusion?

see d sm o is t c o tto n w o o ld ry c o tto n w o o l

S et-u p A S et-u p B


(a) Water is necessary for germination. (96%)

(b) Water is not necessary for germination.Besides water, other factors are necessary.No conclusion can be obtained. (31%)




What conclusion can be made if:(a) germination occurs in B but not

in A.(b) germination occurs in both A and

B.(c) no germination occurs in both A

and B.



CognitivCognitiv

e e conflictconflict

Misunderstanding on concept of Misunderstanding on concept of hypothesis hypothesis

Problem: Problem:

What are the effects of air currents on What are the effects of air currents on

the rate of transpiration of a plant?the rate of transpiration of a plant?

Hypothesis: Hypothesis:

The rate of transpiration is greater in The rate of transpiration is greater in

windy conditions than in still air.windy conditions than in still air.

Investigations that do not need a Investigations that do not need a hypothesishypothesis

Problem: Problem: What are the energy values of 3 food What are the energy values of 3 food samples: samples: cheese, peanut and biscuitcheese, peanut and biscuit??

Hypothesis: Hypothesis: It is hypothesized that peanut will generate It is hypothesized that peanut will generate the largest amount of energy and biscuit the the largest amount of energy and biscuit the lowest.lowest. It is because peanut is rich in oil, It is because peanut is rich in oil, which can provide 2x of energy as that of which can provide 2x of energy as that of biscuits, which is mainly made up of biscuits, which is mainly made up of carbohydrates. carbohydrates.

Investigations that do not need a Investigations that do not need a hypothesishypothesis

Further examples Further examples (p.102)(p.102)

Objective of the investigation Hypothesis put forward by students

1. To determine the rate of oxygen uptake of mealworms

The respiration rate (i.e. the rate of oxygen uptake) is constant throughout the experiment. (A)

2. To study how photosynthetic rate is affected by the light intensity

The photosynthetic rate increases with increasing light intensity. (P)

3. To determine the osmotic potential of cell sap in red onion epidermal cells

When 50% of the observed cells is plasmolysed, the osmotic potential of the cells is the same as that of the surrounding sucrose solution. (T)

4. Chinese usually cook vegetables for meals. Peter wonders whether this treatment will affect the vitamin C content of the vegetables.

Carry out an investigation to solve Peter’s problem using an orange as a source of vitamin C.

Vegetables will contain less vitamin C after cooking (P) because heat destroys vitamin C.

Investigations that involve hypothesis Investigations that involve hypothesis (p.103)(p.103) Problems to be investigated:

1. Green bananas are not yet ripe and taste flat. However, after storing for several days, they turn yellow and become sweet in taste. What has happened to the banana during storage?

2. In Coleus leaf, more stomata are present on the lower epidermis than on the upper epidermis. What is the significance of this uneven distribution of stomata?

3. If a potted plant is placed outside the laboratory for two days without any water supply, it becomes wilted. A similar plant inside the laboratory will not show wilting. How would you explain these observations?

4. Potatoes stored for a long time becomes soft to the touch. Why does this occur?

Students’ performance in exam Students’ performance in exam questionsquestions

Gastric ulcer can be cured by antibiotics. Helicobacter pylori can survive in the low pH of stomach. The bacteria can be killed by antibiotics.

2005 CE Biology Q3(c) & (d)2005 CE Biology Q3(c) & (d)Marshall observed that all his ulcer patients had a Marshall observed that all his ulcer patients had a type of bacteria called type of bacteria called Helicobacter pyloriHelicobacter pylori’. He treated ’. He treated his patients with antibiotics his patients with antibiotics What was Marshall’s hypothesis about gastric ulcer?What was Marshall’s hypothesis about gastric ulcer?

2005 CE Bio Q32005 CE Bio Q3

How to test Marshall’s hypothesis?How to test Marshall’s hypothesis?

Wrong answers:Inject antibiotics into the patient’s body. If the

hypothesis is correct, all bacteria will be killed.

After injecting antibiotics, examine the cells of stomach under a high-power to check whether the bacteria are killed or not.

2004 CE Bio Q22004 CE Bio Q2What did Engelmann wish What did Engelmann wish to find out by setting up to find out by setting up the experiment? the experiment?

Wrong answer:Wrong answer:Engelmann wanted to test the hypothesis that blue and red lights are most effective for photosynthesis. No hypothesis is No hypothesis is needed.needed.


What was the aim of performing experiments?What was the aim of performing experiments?To determine whether the active substance for To determine whether the active substance for

treating diabetes was a protein or a fat.treating diabetes was a protein or a fat.

Treatment Result

(a) Diabetic dogs injected with extracts of pancreas

Symptoms of diabetes disappeared

(b) Diabetic dogs injected with extracts of pancreas pre-treated with protease

Symptoms of diabetes remained

(c) Diabetic dogs injected with extracts of pancreas pre-treated with lipase



If the active substance is a protein If the active substance is a protein predictions predictions Control and experimental Control and experimental set-upsset-ups

Treatment Result

(a) Diabetic dogs injected with extracts of pancreas


(b) Diabetic dogs injected with extracts of pancreas pre-treated with protease

Symptoms of diabetes remained

(c) Diabetic dogs injected with extracts of pancreas pre-treated with lipase


2006 AL Biology 1 Q52006 AL Biology 1 Q5

What is the hypothesis to be tested? What is the hypothesis to be tested? Which one is the Which one is the control set-upcontrol set-up, and which , and which one one the the experimental set-upexperimental set-up?? What conclusion can be drawn from the What conclusion can be drawn from the results?results?

(a) Meat broth did not turn cloudy; no microbes found.

(a) Meat broth turned cloudy; microbes found.

What is the hypothesis to be tested? Which is the control set-up, and which the experimental set-up? What conclusion can be drawn from the results?

Went’s experiment (1928)1. Coleoptile tips are placed on

the agar plate.2. The agar plate is cut into 12

blocks.3. The tips are removed from the

coleoptiles.4. Agar block is place on one side

of the decapitated coleoptile.5. The coleoptile bends to one side.


Loewi’s experiment (1921)


In the 18th century, people noticed that a piece of meat, once in the stomach, was soon digested into a semi-fluid mass. There were two theories to account for this: the food was digested by the churning action of the stomach or by the action of digestive juice.

A scientist swallowed a hollow wooden tube (2 cm long and 0.5 cm in diameter) with small holes containing a piece of meat. 2 days later, the wooden tube passed out of his body. It was found to be empty.

How to identify misconceptionsHow to identify misconceptions

Ask high-order questionsAsk high-order questions – informal – informal /formal/formal - understanding - application in different contexts

Students construct drawings/flow Students construct drawings/flow diagrams diagrams /concept maps/concept maps

Discuss specific instancesDiscuss specific instances Challenge students to ask questionsChallenge students to ask questions

Why misconceptions ?Why misconceptions ?

• Informal preconceptionsInformal preconceptions• Lack of prerequisite knowledgeLack of prerequisite knowledge• Language – Language – everyday meaning & everyday meaning &

scientific scientific meaningmeaning• Compartmentalised conceptsCompartmentalised concepts• Too many facts Too many facts rote learningrote learning• Inaccurate text or teachingInaccurate text or teaching

Design teaching strategiesDesign teaching strategies

Re-teaching Re-teaching

Cognitive conflictsCognitive conflicts

Generating a range of conceptual Generating a range of conceptual

schemesschemes

Using ideas in a range of situationsUsing ideas in a range of situations

e.g. osmosis, grease-spot teste.g. osmosis, grease-spot test

OsmosisLock-and-key model

B. Misconceptions in Biological Knowledge

1. Cellular processes

2. Food and nutrition

3. Gas exchange and respiration

4. Circulatory system

5. Water relations in plants and mammals

6. Coordination and response

7. Reproduction and development

8. Diversity of organisms and ecology

9. Genetics and evolution

Emulsion test &fat absorptionVitamin C & carnivoreEgestion & excretion

Blood pressure, flow rate, resistance

Capillary network

Tubal ligation & menstrual cycle

Development of insecticide resistanceWhich came first, chicken or egg?

misconceptions in scientific inquiry what is scientific inquiry? methods used by scientists nature...

Documents

dry seeds

rootthe fresh mass

growth of seedlings

conclusion conclusion

absorption of water

concept of assumptions

b maggots

length of radicle