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Announcements. Next week: THANKSGIVING, NO CLASS! Work on Group Project Presentation (p170—checklist p 171-172) In 2 weeks, Functional Response Lab. Today’s Objectives. Examine examples of adaptation & convergent evolution in the greenhouse

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  • Work on Group Project Presentation (p170—checklist p 171-172)

  • In 2 weeks, Functional Response Lab

Today s objectives
Today’s Objectives

  • Examine examples of adaptation & convergent evolution in the greenhouse

  • Explore the relationship between stomata density and climate—a study of adaptation?

  • Consider how adaptations are studied and the link between ecology and evolution


Heritable characteristic that improves organism’s fitness (survival & reproduction)

Schemske et al.

Why do organisms match their environment



Why do organisms ‘match’ their environment?

  • the ‘match’ is genetic

  • the ‘match’ is induced by environment

Natural selection:

differential survival and reproduction of individuals

based on genetic differences in some trait(s)


  • Any heritable characteristic of an organism that improves its ability to survive and reproduce in its environment.

  • Also used to describe the process of genetic change within a population, as influenced by natural selection.

Adaptation acclimation
Adaptation ≠ Acclimation

  • Acclimation

    • individual changes over short period of time to survive better in environment

    • Ex: shed winter fur in summer

  • Adaptation

    • a population evolves to be better suited to its environment via natural selection & genetic change over multiple generations

    • Ex: evolution of cryptic coloring to avoid predation


Natural selection
Natural Selection

  • Selection acts on phenotypes

    • If brown beetles are less visible to predators than green beetles

    • Then brown beetles will be more likely to survive & reproduce

  • Evidence is seen in populations over generations

Natural selection key points
Natural selection – key points

differential survival and reproduction of individuals

based on genetic differences in some trait(s)

  • For adaptations to evolve:

  • - differences in the trait must cause differences in

  • fitness

  • - differences in the trait must be heritable

  • Fitness depends on the environment.

  • local adaptation

Ecology evolution are interconnected
Ecology & Evolution are interconnected

  • Ecology

    • study of interactions between organisms and their environments

  • Adaptation

    • An evolved characteristic of an organism that improves its fitness in its environment

  • Thus, adaptations are both ecological & evolutionary

Rainforest ecology

  • Light competition

  • Lots of rain

    • Promotes fungal growth

  • High biodiversity

  • Adaptations include

    • Epiphytes, vines, leaf morphologies

Desert ecology

  • Water limited

  • Temperature extremes

  • Adaptations include

    • CAM, annual life cycle, water storage


  • Trade-off between staying open and obtaining CO2, and staying closed to reduce water loss

  • Structures on the outer layer of plants

  • “Mouth” in Greek

  • Allow gases such as carbon dioxide, water vapor and oxygen to move rapidly into and out

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Stomata density varies across plant species and habitats

Stomata study
Stomata study

  • 1. Choose a plant in the greenhouse or outside. Apply an even, thin layer of clear nail polish on to the underside of the leaf surface.

  • 2. Wait till the polish dries completely.

  • 3. Gently lift the sides to peel off the nail polish without tearing it.

  • 4. Place the peeled layer onto a slide (without any creases).

  • 5. Observe under a 10 or 40x lens and count the number of stomata. If the number of stomata is too numerous to count, just count a portion of the field of view and multiply the results accordingly.

  • 6. Calculate stomatal densities per cm2.

Slide tips and greenhouse use
Slide tips and greenhouse use

  • Stay on path and be respectful of plants

  • Use plant tips, or herbivore-attacked leaves

  • AVOID—small plants, healthy, centrally-located leaves, and Wellwichia

  • Do not choose fuzzy or moist leaves—nail polish does not come off

At greenhouse
At Greenhouse

  • IN PAIRS: Use worksheet (pg 140) to tour greenhouse & identify different adaptations

  • Find examples of 10 adaptations on sheet

  • INDIVIDUALLY: Make a stomata slide from a species you can identify. Your group must have at least one rep from desert, temperate, and rainforest habitats

    TAKE: p 140, a pencil, nailpolish

Find stomata densities
Find stomata densities

  • Count all you see in a field at either 10x or 40x

  • Divide your stomata number by the approximate area of your field (for either 10x or 40x)

  • Look up average temperature, rainfall, humidity?, etc. of your plant’s habitat

  • Put all information on the board

While you wait
While you wait

  • Answer the questions on the handout.

  • For question 2, read up on an adaptation you think is interesting (but not that we have discussed) using the web. Consider using You-Tube.

How do we know if a trait gradient is caused by a local adaptation
How do we know if a trait gradient is caused by a local adaptation?

  • Trait variation across the gradient is greater than variation within the gradient

  • Observed trait variation has a genetic basis

  • Trait variation must have evolved in that location, and not be from an already different founder population

  • Variation must have an effect on survival in that habitat

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Dry adaptation?



Testing for local adaptation

Observation: differences in stomata density is correlated with humidity and temperature


How can we test whether the difference in stomatal density

is an adaptation? What other explanations are possible?

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Testing for adaptation: adaptation?

reciprocal transplant experiment

Dry Habitat

Wet Habitat



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Prediction adaptation?

Plant Fitness




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  • If we see this pattern…. adaptation?

  • Stomata density is likely to be an adaptive trait.

    • Plants with LOW stomatal density have high fitness at DRY habitat

    • Plants with HIGH stomatal density have high fitness at WET habitat

Wrap up the study
Wrap-up the study adaptation?

  • IN PAIRS Use the info on the board. On a new sheet of paper, make either 1 bar graph of the mean stomata densities and standard errors from each climate AND 1 bar graph of the % closed in each climate OR make line graphs comparing the 3 climate variables to stomata densities.

  • Answer these questions on your separate sheet:

  • Using class data, do you think your prediction was right? Why?

  • What is one flaw of this study?

  • Could a study like this one conclusively show stomata densities are the result of a local adaptation? Explain.

  • Do you think plants grown in a greenhouse would have different #s of stomata than the same species in nature? If yes, does this support or refute the idea that s. densities are adaptive? Explain.