Analyzing college students

1
Analyzing college students learning about
carbon-transforming processes

• Jonathon Schramm, Jennifer Doherty, and Charles
  W. Anderson
• Michigan State University

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Carbon-Transforming Processes in Socio-Ecological
Systems

• Underlying many crucial processes commonly
  discussed in biology courses (photosynthesis
  cellular respiration, global carbon cycling,
  etc...), and
• Central to understanding several crucial issues
  facing global society, particularly climate
  change.
• Despite centrality and import, our work has
  demonstrated that many students at all levels
  struggle to successfully master conservation
  principles in their explanations.

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Reasoning in college biology

• Typical college biology courses spend a great
  deal of time on carbon-transforming processes
  (photosynthesis, respiration, carbon cycling,
  etc).
• Earlier work (Hartley et al. 2011) had shown that
  many college students still struggle to apply
  scientifically-principled reasoning in their
  explanations.
• Current college bio students, both majors and
  non-majors, very likely to effect societal policy
  positions and stances over coming decades.

4
Study Design

• Analyzed written pre/post assessments from 1218
  biology students in courses taught by 16
  different instructors (9 institutions).
• Students randomly assigned assessments built
  around one of key carbon-transforming processes
  (cellular respiration, photosynthesis,
  biosynthesis).
• Instructors implemented a variety of
  instructional approaches in period between tests.

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Summary of General Findings

• College biology students often struggle in
  similar ways to younger students with the
  fundamental reasoning transition from informal
  to scientific. Two important differences
• Wealth of terminology vocabulary available is
  generally higher
• Which of the following are energy for plants?
  Water...sunlight...air...soil nutrients?

Middle School High School College
High (L4) Sun is the only form of energy and plants convert energy Although photosynthesis leads to the production of ATP (energy... The source of the energy responsible for all subsequent reactions comes from the sun Light is a form of energy while the non-energy sources are made of atoms and are considered matter...bonds between atoms are chemical energy
Med. (L2) Plants need water to help it grow and blossom, sunlight for energy to make food, air to help make glucose, nutrients to help nourish the plant, and plants do not make their own energy they get it from sunlight and us it to make glucose. Plants use sunlight to make their own energy. Water, air, and nutrients in soil help the plant but they do not give the plant energy because they make their own using sunlight. Water and air have stored energy in chemical bonds, light is a type of energy. Nutrients do not have stored energy. Plants use energy to make their own food.
Low (L1) They all help the plant grow and make the food (sugar). By using these materials the plant then photosynthesizes to make their food and help to multiply their cells and grow. Sunlight, helps them with photosynthesis, nutrients in the soil help them grow along with water, and plants are producers. plants need the light and the nutrients and the carbon sources to power photosynthesis to then generate ATP through the one other cycle
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Summary of General Findings

• Rates of improvement following targeted
  instruction tend to be higher

Principles-first Instruction
EAP
Status quo instruction
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Sample Responses - Photosynthesis

• Sunlight helps plants to grow. Where does light
  energy go when it is used by plants? Please
  choose the ONE answer that you think is best.
•  a. The light energy is converted into glucose of
  the plants.
• b. The light energy is converted into ATP in the
  plants.
• c. The light energy is used up to power the
  process of photosynthesis.
• d. The light energy becomes chemical bond energy.
  
• e. The light energy does not go into the plants
  body.

Low (24 of n 185) Medium (42) High (29)
C Light is the most important aspect of photosynthesis C plants need some type of energy to fuel the process of photosynthesis A plants absorb the light energy from the sun that energy is then converted into glucose B it is converted to atp because all organisms need atp for this process D light energy is transformed into the chemical energy in the glucose... Energy cannot become matter D Light energy is absorbed by the chloroplasts and transformed into chemical energy
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Sample Responses Cell Respiration

• When a person loses weight, what happens to the
  fat in the persons body? Circle True (T) or
  False (F) for each option.
• T F Some of the fat is broken down and leaves
  the persons body as water and gas.
• T F Some of the fat is converted into energy.
• T F Some of the fat is used up and
  disappears.
• T F Some of the fat is broken down and leaves
  the persons body as feces and urine.
•  b. Is weight loss connected to anything going on
  in the persons cells?

Low (56 of n 326) Medium (43) High (1)
T,T,F,T Fat cells make up adipose tissue and weight loss happens when you get less fat cells F,T,F,T Cells need more glucose, glucogenesis is initiated to help that need T,T,F,T The cells go through cellular respiration. Which is just the controlled using of nutrients F,T,F,T Weight loss has everything to do w/ the molecular level...glucose and triglycerides are broken down with the use of ATP T,F,F,F The fat is not converted into energy, rather the carbon-hydrogen and carbon-carbon bonds are full of potential energy that is released when they are broken T,F,F,F When a person loses weight, their body will break the chemical bonds in the lipids to fuel cellular respiration, the products of which are CO2 and water
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Sample Responses - Biosynthesis

• a. An apple is eaten by a boy and digested in his
  body. What happens to the apple when it is
  digested?
•  b. Do you think the apple the boy ate can help
  parts of his body (like his fingers) to grow?
•  Please circle one YES NO
• If you answered YES, please explain how an apple
  that goes to the boys stomach can help his
  fingers to grow. If you answered NO, please
  explain how the boys body makes his fingers grow.

Low (20 of n 125) Medium (56) High (24)
Its nutrients get broken down and used up for energy Y The apple give nutrition to the boys whole body which can help any part of his body grow Its broken up by the body and used as sugars, carbs, etc. Y The apple will give the body the energy it needs to grow The bonds are broken apart and the breaking causes a release of energy Y apple gives his body the energy it needs to help his fingers grow. Energy within the apple goes to the boy and nutrients are absorbed N nutrients energy is transformed into energy that makes the body continue to grow It gets broke down and released as CO2 and H2O Y This process provides ATP which then allows the cells of his body to grow It is broken down and either burned to use as energy or used as building material Y The molecules in apple are recombined and used as building materials in all cells of the body
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Results by Process

• College student performance increased on items
  about all processes (photosynthesis PS, cell
  respiration CR, biosynthesis BS and
  multi-process)

EAP
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A Typical Sequence of Explanations

• Student (EN, Senior) Animals need the water and
  some central nutrients. They will need a carbon
  source to add to most of their cells and such,
  and that will come from like food. So humans, it
  could be anything from plants to, say, other
  animals, to nuts, that sort of stuff. But that
  will come in the form of different sugars and
  proteins and fats that can be broken down into
  the simpler sugars and then distributed
  throughout the body. Again energy transfers into
  ATP, getting energy like the last time, through
  cellular respiration.
•  Interviewer Okay. So like plants, all the
  animal cells are going to undergo respiration.
•  EN Yes, um-hmm, yes.
•  Interviewer Okay. But before we get to that
  stage, can you describe a little bit about how
  that we go from food, that we can see and touch
  and we are eating, to the cells.
•  EN To the cells?
•  Interviewer Yes.
•  EN Well, it is going to get like broken down as
  it goes through the body, so it will start in the
  mouth and with enzymes and stuff that will start
  breaking it down... And then it will go into the
  stomach where there is high acid and such. And it
  will break those down even farther into simple
  sugars, which will then go into the small
  intestines, and then there it can start absorbing
  the simple sugars and such and getting those into
  the bloodstream.
•  Interviewer Okay.
•  EN And then it can pass those around through
  the bloodstream to different cells, which will
  then take those simple sugars and they can break
  those down, or they can break those apart and get
  the energy out of the bonds into the new bonds,
  so the ATP molecules.

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Original Biosynthesis Items

• Typically asked about organismal growth in a way
  that allowed students to emphasize the energetic
  requirements, rather than transformations of
  matter.
• Ex. the apple provides glucose that the boys
  body can then use in the Krebs cycle to generate
  chemical energy for growth
• Pointed to a need for more direct way to probe
  thinking about biosynthesis.

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Revised Biosynthesis Items

• Focus on asking students to identify materials
  and/or molecules that are taken in by organisms
  and used for growth (i.e. avoid only use in CR)
• Explicitly asking students to explain catabolic
  processes.
• How does tree build chemically complex wood from
  very simple precursors like glucose?
• Attempts to connect knowledge about organ systems
  to processes happening at molecular scales.
• Administered to 67 students in three introductory
  biology courses (post-test only).

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Revised Biosynthesis Items

• Simple food chain of grass to rabbits to
  decomposing bacteria
• Please identify materials that would be found in
  all three groups of organisms, using specific
  molecules where possible.
• Are there any materials that would be unique to a
  particular type of organism? If so, where would
  those materials have come from (How did they get
  into the organism)?
• A boy growing
• When a boy grows, he grows larger muscles
  throughout his body, including his legs. How do
  you think that other parts of the boy help to
  make muscles in his leg? How does his digestive
  system (stomach, intestines, etc) help?How does
  his blood help?
•  The boy also needs food throughout his life, but
  much more so during childhood and youth, when he
  is actively growing. Why does the body need this
  excess food (i.e. more than baseline for his
  metabolism) during these times? How does the food
  cause his body to grow and actually build muscle
  mass?
• A tree growing
• When a tree grows, it builds wood tissues
  throughout its body, especially in the trunk. How
  do you think that other parts of the tree help to
  make wood in the trunk? How do the leaves help?
  How do the roots help?
•  The wood inside trees is very chemically
  complex, much more so than the smaller molecules
  taken in by the tree. How does the tree build
  this complex wood? If youre not sure about
  details, please take your best guess!

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Food Chain Similarities Differences

• ID specific molecules found in all 3 groups, as
  well as any that would be unique to one group.
• Commonalities carbon, carbohydrates, lipids,
  steroids, DNA/RNA, proteins, ATP, glucose,
  phosphorus, sulfur, energy from respiration, H2O
• Idiosyncrasies cellulose, chlorophyll,
  hemoglobin, energy from eating thing before it on
  chain, prokaryote, CO2 in plants, O2 in animals,
  methane (bacteria)
• Punchline 40 (26 of 67) of students noted
  basic biological molecules as common to all three
  forms of life, but only 12 (8 of 67) of students
  could name even basic unique molecule types

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Biosynthesis in Plants (Tree)

• Describe how the tree builds wood in its trunk
  during
• growth. How are leaves and roots involved? How
• does the tree build the complex molecules of wood
  
• from simpler ones?
• Leaves are sites of photosynthesis, supply
  energy, supply glucose, act as the mouth
• Roots take in water, capture nutrients, provide
  energy sources, act like veins
• Complex from simple? through cell division and
  growth, things brought in are converted to
  complex things, uses a combination of materials
  from environment, links the monomers taken in
  into polymers, genes code for components of wood,
  molecules are broken down and recombined in
  various ways, cell respiration and photosynthesis
• Punchline 20 (13 of 67) of students describe
  very general biosynthetic pathways, while nearly
  all revert to very general descriptions for role
  of leaves and roots in plant growth

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Biosynthesis in Humans

• Describe how a child grows larger muscles
  throughout their body as they grow. How do their
  digestive and circulatory systems help? How does
  the child build the muscles, and why does a child
  need so much excess food during childhood and
  youth?
• Digestion and Circulation food broken down into
  simpler molecules and transported throughout the
  body blood transports O2 to help cells glycogen
  is stored in the muscles release and absorb
  nutrients
• How muscles built? by working out/exercising
  eating nutritious food molecules from food
  reassembled in fibrous form cell growth/mitosis
  tearing during training and regrowing proteins
  building more tissue from production of ATP
• Why so much food? extra energy promotes growth
  nutrients to grow larger adding mass from carbon
  in CHOs and fats burning more ATP to get
  vitamins and minerals cells multiplying at a
  higher rate
• Punchline large majority of students clear on
  role of digestion blood, but 57 focused on
  exercise or good nutrition to explain how muscles
  built. Still, 43 at least hint that the extra
  food needed during growth phases was tied to
  increasing biomass.

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Implications for Instruction

• Helping students to see the fundamental
  connections between PS, BS and CR is crucial
• energy is coupled with organic matter during PS,
  stays at relatively constant levels during BS and
  is decoupled in CR
• molecules organized during PS are the basis for
  all other molecules in living organisms, with
  some supplementation from molecules of water and
  micronutrients

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Correlations to Typical Intro Biology Sequences

• Usually the processes of photosynthesis and cell
  respiration, including enzymes and electron
  transport chains, occupy a large portion of intro
  cell biology courses.
• Another typical unit is one on large biomolecules
  (proteins, carbohydrates, nucleic acids).
• Connecting these is rarely emphasized!

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Alternative Teaching Strategies

• Trace pathways in a more holistic manner (connect
  Calvin and Krebs with fatty acids and secondary
  metabolites!)
• Especially for intro courses, shift more emphasis
  from details to bigger picture (principles) to
  help students keep track of the forest
• Incorporate ecological phenomena into
  cell-focused courses, and vice versa.

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Alternative Strategies Alternative Responses

• Instruction that scaffolds all new materials
  around explicit tracing of matter (atoms) and
  energy units transforms student thinking. (Rice,
  Doherty and Anderson, reports forthcoming)

An apple is eaten by a boy and digested in his
body. What happens to the apple when it is
digested? Do you think the apple the boy ate can
help parts of his body (like his fingers) to
grow? If so, how does it work?
Traditional L3 Principled L3
Atoms that make up the apple are broken down and transfer as energy into the boys body Chemical energy released can be transformed into mechanical energy and used to build cells
The apple serves as energy for the body and energy helps in growth and development The apple is broken down and used. Burned to make energy or used to build carbs, fats, proteins