Adaptive Leaf SizeAdaptive Leaf SizeWeek Two (analysis)

HypothesHypotheses:es:

H1: Plants in wet soil do not have to conserve water, so they will be as warm as possible.  H2: Plants in dry soil must conserve water, so they will be as cool as possible.   Predictions :

Predictions: Predictions:

Sunny

Shady

Wet Dry

In the sun, the air temp is the coolest the

leaf can be, so this leaf should be small to

reach air temp and conserve water: get

cool

In the sun, a leaf can be warmed above

the air temp by the sun, so this leaf

should be large to increase photosyn.:

stay hot

Decrease water lossIncrease photosynthesis

In the shade, the air temp is as warm as

the leaf can be, so this leaf should be the air

temp to increase photosyn.: get hot

In the shade, the leaf can get below air temp

(due to evaporative cooling), so this leaf should be large to

conserve water: stay cool

AssumptionsAssumptions::

o Temperature : Temperature : PhotosynthesisPhotosynthesiso Temperature : Temperature : Water lossWater loss

Fun with Fun with Statistics!Statistics!

o We will do 4 We will do 4 t-testst-testso t-test: tells us how different the averages of two groups aret-test: tells us how different the averages of two groups are

o t-tests use t-tests use Standard deviation (SD)Standard deviation (SD)o SD: SD: ““typicaltypical”” deviation from the mean deviation from the mean

o t-tests give us a t-tests give us a P-valueP-value o P-value: probability that your result is due to chance alone. P-value: probability that your result is due to chance alone. o P ≥ 0.05 = the difference in averages is most likely due to P ≥ 0.05 = the difference in averages is most likely due to chance…chance…o P < 0.05 = the averages are “significantly” differentP < 0.05 = the averages are “significantly” different

o DonDon’’t forget where you predicted the t forget where you predicted the larger vs. smaller leaf!larger vs. smaller leaf!

t-test…t-test…

t = X X

sn

sn

1 2

12

1

22

2

t = t-test valueX = group means = st. dev.n = sample size

Food for thought…Food for thought…o According to the model, what environmental factors determine leaf According to the model, what environmental factors determine leaf size?size?

o What other environment factors could influence leaf size?What other environment factors could influence leaf size?

o Why is the model applied to vine-like plants?Why is the model applied to vine-like plants?

o What assumptions did you make to test the model?What assumptions did you make to test the model?o Do you think they were valid?Do you think they were valid?

o Which lab measurements were:Which lab measurements were:o Qualitative?Qualitative?o Quantitative?Quantitative?

Sunny

Shady

Wet Dry

Sunny

Shady

Wet Dry

Decrease water lossIncrease photosynthesis

Sunny

Shady

Wet Dry

Decrease water lossIncrease photosynthesis

Sunny

Shady

Wet Dry

Decrease water lossIncrease photosynthesis

Sunny

Shady

Wet Dry

Decrease water lossIncrease photosynthesis

Sunny

Shady

Wet Dry

In the sun, the air temp is the coolest the

leaf can be, so this leaf should be small to

reach air temp and conserve water: get

cool

In the sun, a leaf can be warmed above

the air temp by the sun, so this leaf

should be large to increase photosyn.:

stay hot

Decrease water lossIncrease photosynthesis

In the shade, the air temp is as warm as

the leaf can be, so this leaf should be the air

temp to increase photosyn.: get hot

In the shade, the leaf can get below air temp

(due to evaporative cooling), so this leaf should be large to

conserve water: stay cool