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

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

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

AdaptationHeritable characteristic that improves organism’s fitness

(survival & reproduction)

Schemske et al.

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)

fitness

adaptation

Adaptation

• 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• 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

flickr

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

evolution.berkeley.edu

• Fitness depends on the environment.

local adaptation

• For adaptations to evolve:

- differences in the trait must cause differences in fitness

- differences in the trait must be heritable

Natural selection – key points

differential survival and reproduction of individuals based on genetic differences in some trait(s)

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

RainforestEcology

• Light competition

• Lots of rain– Promotes fungal growth

• High biodiversity

• Adaptations include– Epiphytes, vines, leaf

morphologies

DesertEcology

• Water limited

• Temperature extremes

• Adaptations include– CAM, annual life cycle, water

storage

Stomata

• 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

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

http://radio-weblogs.com/0105910//2004/01/22.html

http://www.microscopy-uk.org.uk/micropolitan/botany/frame1e.html

http://www.scienceclarified.com/Io-Ma/Leaf.html

Stomata density varies across plant species and habitats

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

• 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• 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

• 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

• 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?

• 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

Testing for local adaptation

How can we test whether the difference in stomatal densityis an adaptation? What other explanations are possible?

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

morph:

Dry Wethabita

t:

Testing for adaptation:

effectivepredators

Dry Habitat

reciprocal transplant experiment

Wet Habitat

Wet

Habitat

Pla

nt

Fit

nes

s

Dry

Prediction

If we see this pattern….

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• 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:

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

2) What is one flaw of this study?

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

4) 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.