Transcript Ground Rules, exams, etc. (no “make up” exams) Text: read

Leaf Tactics
• Light
• Water availability
• Prevailing winds
• Herbivores
• Costs and Profits of Leaf Size, Shape, and Placement
Leaf Tactics
Similar types of leaves have evolved independently in
different plant lineages subjected to comparable
climatic conditions
Compound leaves conserve woody tissue
Small leaflets in hot dry regions, but larger under
warm moist conditions
Shade tolerant understory species usually have larger
and less lobed leaves than canopy species
Lobed leaves do not cast as dense and solid a shadow
as do leaves with continuous margins
In lowland wet tropical rainforest,
trees tend to have large evergreen leaves
In chaparral, plants tend to have small
sclerophyllous evergreen leaves
Arid regions tend to support leafless
stem succulents such as cacti or plants
with entire leaf margins
Cold wet climates tend to support plants
with notched or lobed leaf margins
Plant Life Forms
Evergreen vs. Deciduous
Monolayered vs Multilayered plants
Shade Tolerance
Xerophytic vs. Mesophytic leaves
Also Hydrophytes (water lilies)
Foraging Tactics and Feeding Efficiency
Costs and Profits of Foraging
An optimal foraging tactic maximizes the difference between
foraging profits and their costs
Food = matter and energy for maintenance and reproduction
Hazards: exposure to predators, loss of time for other activities
Sit-and-Wait ambush predators (e.g. spiders at webs)
Widely foraging active hunters (go out and find prey)
Search Time (per item eaten) versus Pursuit Time (per item eaten)
Search for all possible prey items, but pursue them one at a time
Prey items can be ranked from most preferred to least desirable
“Economics of Consumer Choice”
Assumptions:
a) Environmental structure is repeatable, with
statistical expectation of finding a given resource
(habitat, microhabitat, or prey item)
Robert MacArthur
b) Food items can be arranged along a continuous spectrum, such as by
size or energy reward
c) Similar phenotypes are closely equivalent in harvesting abilities
d) Principle of Allocation applies: no one phenotype can be maximally
efficient on all prey types
e) An individual’s economic “goal” is to maximize its total intake of food
resources
“Economics of Consumer Choice”
Four Phases of Foraging:
1) deciding where to search
2) searching for palatable food items
3) upon locating a potential food item,
deciding whether or not to pursue it
Robert MacArthur
4) pursuit itself, with possible capture and eating
Search and pursuit efficiencies for each food type in each habitat are
entirely determined by preceding assumptions about morphology and
environmental repeatability. These efficiencies dictate probabilities
associated with search and pursuit (phases 2 and 4) . Thus, need to
consider only the two decisions: where to forage and which prey items to
pursue (phases 1 and 3 above)
“Economics of Consumer Choice” (R. H. MacArthur)
Clearly, an optimal consumer should forage where its expectation
of yield is greatest — an easy decision to make, given knowledge
of efficiency probabilities and the structure of the environment (of
course, in reality, animals are not omniscient and must make
decisions based on incomplete information).
The decision as to which prey items to pursue is also simple.
Upon finding a potential prey item, a consumer has just two
options: either pursue it or go on searching for a better item
and pursue that one instead. Both decisions end in the forager
beginning a new search, so the best choice is clearly the one that
returns the greatest yield per unit time.
An optimal consumer should opt to pursue an item only when it
cannot expect to locate, catch and eat a better item during the time
required to capture and ingest the first prey item.
Physiological Ecology
Homeostasis: maintenance of a relatively stable
internal state under a much wider range of
external environmental conditions
Temperature regulation (thermoregulation)
Physiological Optima and Tolerance Curves
Acclimation
Performance plotted against temperature
Hypothetical response curves showing interactions
Energetics of Metabolism and Movement
Ingestion = Assimilation + Egestion
Assimilation = Productivity + Respiration
Productivity = Growth + Reproduction
Ingestion = Egestion + {Respiration + Growth + Reproduction}
{Assimilation}
-----------------------------------------------Homeotherm versus Poikilotherm
Ectotherm versus Endotherm
Body Mass, grams