1) Acclimation (reversible):

• short-term change in structure or function (biochemical pathways)

• shift in range of physiological tolerances of an individual

• requires longer periods (days or weeks) than behavioral or metabolic changes.

*** What is this fish’s response to a variable environment? Is it adaptive?Would fish have acclimation ability if livedin constant, narrow temperature range?

Changing phenotype to match prevailing conditions often involves changes in enzyme structure.

Upper critical (lethal) temperature depends on acclimation temperature.

2) Acclimitization:

• change in response to seasonal (predictable) environmental changes

• plays a prominent role in responses of long-lived organisms to seasonal change

• E.g….

3) Developmental responses (non-reversible):

• permits organism to respond to varying environments during its growth

• changes in response to persistent variation in the environment

Developmental responses are irreversible.***What’s the morphological response to sun vs. shade? What’s the advantage?

External conditions

Internalconditions

Regulation (homeostasis): maintain steady internal conditions against an external gradient.Regulators vs conformers

Conformer

Regulator

Neutral zone for regulators

Endotherms - thermoregulator Ectotherms -thermocomformerWhat are advantages / disadvantages?

Air temp

Body temp

Homeostasis: what are costs? benefits?

Air temp

Bodytemp

O2 use

Partial homeostasis: reset internal temperature control while in torpor.

Air temp

O2 use

***Compare the total annual energy budget and energy per unit mass in endotherms vs. ectotherms.Which animal would spend the >% of energy on thermoregulation? Why?

body mass kcal/yr kcal/kg/dahuman 60 kg 800,000 36.5penguin 4 340,000 233mouse .025 4,000 438python 4 8,000 5.5

Possible responses to a variable environment:

• Avoid the variable environment

• Alter the environment

• Change phenotype to better match the environment

• Expend energy to regulate internal environment

Food supplies vary in space and time, and in quality of prey items.

• Animals must make choices about when where how long what to feed that maximize their fitness.• Optimal foraging theory• Behavioral ecology

Dylan’s Hypothesis/Prediction

• If food availability limits the breeding season of grackles,

• Then the

Faced with variable E, animals forage to:• optimize net capture of resources per unit time• minimize risk• balance nutritional needs maximize fitness.

Food loads increase with travel times.

Central place foraging: • when animals are tied to a particular place • must deliver food to a fixed place • tradeoffs (costs/risks vs. size of forage area

• Risk-sensitive foraging: value of feeding area is reduced by presence of risks,

especially predation.

***Optimal foraging theory vs. actual foraging…• 1) Swingtail birds nest on oceanic island; fish food is in

an upwelling 60 km away. What kind of foraging situation is this?

• 2) Foraging cost is tied to travel time to and from upwelling.

60 km/hr - no fish 15 km/hr - 2 fish 30 km/hr - 1 fish in bill 5 km/hr - 3 fish How much time is required for a round trip with 1, 2 and

3 fish?• 3) Considering only the efficiency of foraging (hrs/fish),

how many fish returned per trip = most efficient use of bird’s foraging time?

***continued• At this latitude there are 15 hr time for fishing

each day.• 4) For fishing trips with a return of 1, 2, or 3

fish, how many fish per day can they bring to the nest?

• 5) How does total catch of fish per day compare with fishing efficiency?

• 6) From an evolutionary perspective, which behavior (return with 1, 2, or 3 fish) would you expect the bird to use? Why?

• 7) Most fish return with 1 fish from each trip. How can you explain this observation when they catch fewer fish per day than birds returning with 2 fish per trip?

Avoid high-risk areas unless plentiful food.

Why do foragers consume a mixed diet? 1) Complementarity of amino acids

2) avoid high doses of plant toxins

***Sample exam question…3 species grown in both hot + moderate temp;then PS rate of both groups of plants was measured at a range of temperatures.

Red: raised in hot TBlue: raised in moderate T

1. What is the major question being addressed in this experiment?

2. Describe how Larrea and Tiderstromia responded relative to the temperatures at which it was grown.

3. What is the likely mean temperature (high or moderate) of Larrea and Tiderstromia?

4. What is the likely temperature range during the year (high or low) of Larrea and Tiderstromia? Explain.

5. What is the major conclusion of the experiment?

EC…Feedback time…1) What do you like about teaching of lecture?2) What would you like changed/improved? 3) What would make for a better learning environment?

Summary: Caveats

There are limits to evolutionary responses to environmental change.

Evolution does not produce perfect organisms for every suitable habitat.

Not all evolved behavior remains adaptive, particularly in ecosystems modified by humans.

Populations can’t evolve overnight.

What happens when humans alter the environment rapidly and in new ways?

Do organisms have the ability to respond appropriately?

Objectives

• Responses to a variable environment• Avoidance• Alter the environment• Change phenotype to match environment• Acclimation and acclimitization• Developmental response• Regulation (vs. conform)• Responses to variable food

VocabularyChapter 9 Adaptation* to Life in Varying Environments genotype* evolution* natural selection* fitness* phenotype* alleles* heterozygous* homozygous* dominant* recessive* codominant phenotypic plasticity activity space microhabitats microenvironments acclimation migration storage dormancy hibernate diapause proximate factors ultimate factors photoperiod complementary reaction norm acclimatization developmental response regulation conformer endotherm ectotherm homeostatis partial homeostasis torpor optimal foraging central place foraging risk-sensitive foraging