Transcript PPT - Environmental Literacy

The Role of Heredity and Environment
in Students’ Accounts of Adaptation
by Selection and Phenotypic Plasticity
JENNIFER DOHERTY, JONATHON SCHRAMM, AND ANDY ANDERSON
MICHIGAN STATE UNIVERSITY
What is adaptation by selection?
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Environmental Literacy
Change in the distribution of individuals with
specific hereditary information in a population
as due to differential reproductive success.
What is phenotypic plasticity?
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Environmental Literacy
Phenotype: the morphology, behavior, and
physiology and organism
Phenotypic plasticity: the ability of an organism
to change its phenotype in response to
changes in the environment.
What is phenotypic plasticity?
Phenotype
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genotype 1
genotype 2
Environment
MI 11th grader: I don't know what exactly is involved with that because like
it's weird because like people, some people can keep their tan all winter
long. And then others just can't. And then there are the people that can't
even tan at all, they just burn and then go back to pale.
What is phenotypic plasticity?
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Pfenning et al 2010
Why is this important for
Environmental Literacy?
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Environmental Literacy
• Limits to adaptation by selection
−
−
selection must act on variation within population
organisms don’t have traits because we or they want to
• Limits to phenotypic plasticity
−
organisms have a limited ability to acclimate to changes or
variation their environment
• Understanding both adaptation by selection and
phenotypic plasticity
−
Necessary for predicting effects of disturbances, including
climate change and other human impacts, on ecosystems
• Human managed ecosystems
– Food and Fiber sustainability
• Natural ecosystems
– Ecosystem services
Research literature regarding
populations and evolutionary change
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• Lamarckian (inheritance of acquired characteristics)
• Teleological (trait acquisition is for a purpose)
• Teleological reasoning is predominant among
students at all levels
A key characteristic of all of these misunderstandings
is that they fail to consider the existence of standing
variation in populations and its role in evolutionary
change.
Anderson et al, 2002; Bishop & Anderson,
1990; Clough & Driver, 1986; Cummins et
al1994; Scharmann & Harris, 1992;.
Bishop & Anderson, 1990, Brumby, 1984; Chan,
1998; Clough & Wood-Robinson, 1985; Evans,
2008; Lawson & Wesser, 1990; Nehm et al 2009,
Rudolph & Stewart, 1998; Settlage, 1994; Tamir &
Zohar, 1991
Proposed Learning Progression
for Adaptation by Selection
Levels
4
Origin of trait in population
and
Variation in population for that trait
Change in population
Over time
Individuals are variable,
due to variation in hereditary information,
from standing variation, random mutation,
sexual recombination, or migration
Increase individuals with
hereditary information for
trait due to differential
reproductive success.
multiple
generations
Individuals pass on
acquired traits
from parent to offspring
multiple
generations
3 Some/all individuals acquire trait,
often in part or incremental steps,
in response to environmental change
2
All individuals acquire trait
by a hidden mechanism
in response to an environmental change
“long time”
1
All individuals acquire trait
by a familiar or undescribed mechanism
in response to an environmental change
near
immediate
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Change in Population Questions
Insecticide
Farmers often spray their crops with
chemicals to stop insects from eating their
crops. Over time, more and more insects in
the population are resistant to these sprays,
so the farmers have to use different sprays
to protect their crops.
Describe how this increase in resistance
happens.
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Change in Population Questions
Level 4 for change in a population:
NY 12th grader: This occurs because the pesticide
wipes out all of the non-resistant insects thus
leaving the resistant insects to breed and
reproduce and become a dominate trait in the
population.
INTERVIEWER: Okay. How does an insect become
resistant?
NY 12th grader: It's born with natural variation in genetic
population. If there's a 100 bugs maybe 10 are
resistant and then when the whole population is
sprayed those 10 are left. So when the population
eventually recovers those 10 will be the, will now be
the entire 100 or they will be make up a large part
of it and if the same pesticide is used over and over
again eventually it won't have an effect because the
entire population will be resistant to it.
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Change in Population Questions
Level 1 for change in a population:
CO 7th grader: The increase in resistance is most likely
caused by the evolving animals in the environment
of a farm. Lately we have talked about the changes
animals and/or organisms use to change and adapt
to their environment. These insects highly adapt to
avoid the chemicals.
INTERVIEWER: Okay. How do they evolve?
CO 7th grader: They evolve by adapting to their
surroundings or doing something to make them
– make better use of their surroundings.
INTERVIEWER: Okay. And so – do you know anything
about mechanism? So how does – how do they
adapt?
CO 7th grader: Probably just by finding different
ways to use their surroundings or finding
different ways to do something.
Change in Population: Insecticide
Proportion of Answers
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n = 187
L1-4 = 80%
n = 160
L1-4 = 85%
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Change in Individual: Forest Edge
Forest Edge
A forest and the sunny field along the forest’s edge have the
same species of plants. In the forest, the plants grow taller
and have wider leaves, while in the field, they are shorter and
have smaller leaves.
A. Why do you think you see this kind of difference between
the plants?
B. What do you think might happen to the plants if you
moved the plants grown in the field into the forest?
– 4% of middle school and 13% of high school
responses were scored a level 4 for selection
items
– 0% of middle school students and 1% of high
school students recognized phenotypic
plasticity.
Proposed Learning Progression
for Nature of Phenotypic Traits
Levels
Nature of phenotypic traits
4
Shaped by fixed hereditary information whose expression can be modulated in
response to the environment. Hereditary information cannot be changed by the
environment.
3
Shaped by fixed hereditary information. Hereditary information cannot be changed
by the environment. Phenotypes may be able to change in response to the
environment without a connection to gene expression.
2
Shaped by heredity and response to the environment “pulling in different directions.”
Parents can pass all of their traits, inherited and acquired, to offspring.
1
Shaped by heredity, response to the environment, and choice “pulling in different
directions.” Parents can pass all of their traits, inherited and acquired, to offspring.
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Plasticity Interview
INTERVIEWER: OK well what would you say a gene is?
MI 9th GRADER: Just a trait that they give from the parents
.…
MI 9th GRADER : I don't really think genes change.
…
INTERVIEWER: What kind of differences might there be in traits between a coyote that lived up here in
this range and one that lived, say, down in Arizona?
MI 9th GRADER : Well the fur is definitely going to be lighter down here since the temperature is warmer
and probably not as much food down here as in up here because more populated down here.
…
INTERVIEWER: So if we captured our coyote up here in this range and we trucked it down to the border
there or to the Arizona dessert and let it go would you expect it to survive?
MI 9th GRADER : Yeah I think it could adapt.
…
INTERVIEWER: Do you think that, again, going back to the idea of genes they might have anything to
do with the changes that would be happening in it's body? Would the genes be able to help the
coyote to respond to that different environment do you think? [0:10:41]
MI 9th GRADER : I don't think they would. Because, like, a coyote down here is going to have
different genes in the north.
INTERVIEWER: And the genes it has that were allowing it to live up here would not be very useful down
there?
MI 9th GRADER : I don't think so. It's just - like hunting purposes it would be good but - that and breeding
but as far as surviving I don't think so.
Conclusions
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•
Understanding adaptation by selection and phenotypic
plasticity are both important for predicting effects of
disturbances, including climate change and other human
impacts, on both ecosystems
•
We propose understanding the mechanism of adaptation by
selection is not what is limiting students understanding of
how individuals and populations change.
•
Instead we propose that understanding the nature of
phenotypic traits is their largest hurdle.
•
Phenotypic plasticity is rarely addressed at the K-12 level in
the context of evolution and we suggest it should be.
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Types of traits affected by the
environment
1. Increase or decrease in size or
health of organism due to more
or less resources
2. Change of gene expression due
to change in environment
a) Developmental—irreversible
change in organism architecture
b) Inducible—reversible change in
organism
What is adaptation by selection?
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Environmental Literacy
Differential
Survival &
Reproduction
Differential
Survival &
Reproduction
genotype 1
Environmental
Change
genotype 2