Chapter 50: Ecology
I. The scope of ecology
A. Ecology is the scientific study of the
interactions between organisms and their
environments
1. very difficult to conduct experiments and
control variables
2. models used frequently
3. multidisciplinary
4. includes biotic and abiotic components
*short-term (ecological time) interactions could
have long-term (evolutionary time) effects through
natural selection
B. Ecological research ranges from the adaptations
of organisms to the dynamics of ecosystems
1. organismal ecology: studies the behavioral,
physiological, & morphological ways individuals
meet abiotic environmental challenges
a) distribution is limited by tolerance
2. Population ecology: studies groups of
individuals of the same species living in a
particular geographic area
a) questions concern factors that affect population
size and composition
3. Community ecology: studies all organisms that
inhabit a particular area
a) questions concern predation, competition,
disease and other ways in which interactions
among organisms affect community structure and
organization
4. Ecosystem ecology: studies all abiotic factors as
well as communities of organisms in an area
a) questions concern energy flow and chemical
cycling among the abiotic and biotic components
C. Ecology provides a scientific context for
evaluating environmental issues
II. Abiotic factors of the biosphere (sum of all
earth’s ecosystems)
A. Climate and other abiotic factors are
important determinants of the biosphere’s
distribution of organisms
1. global and regional patterns reflect
differences in climate and other abiotic factors
2. temperature, humidity, salinity, and light
influence distribution of organisms
B. Major abiotic factors
1. temperature
a. most organisms are unable to regulate
their body temperature precisely
b. 0-45 degrees C are critical
temperatures
2. Water
3. Sunlight
a. provides the energy that drives all
ecosystems
b. physiology, development and
behavior of many animals and plants are
sensitive to photoperiod
4. Wind—evaporation, transpiration, etc.
5. rocks and soil
6. periodic disturbances (Catastrophic)
--Climate and topography have the greatest effect
on species distribution
1) major components of climate: water,
temp, light, wind
2) determined by annual temperature
averages, rainfall
3) results in various “biomes” around the
world
CONCEPTS OF ORGANISMAL BIOLOGY
(PHYSIOLOGICAL, MORPHOLOGICAL & BEHAVIORAL
MECHANISMS THAT ALLOW SPECIES TO MEET THE
CHALLENGES OF THEIR ENVIRONMENT
REGULATORS & CONFORMERS—REFERS TO MECHANISMS
USED TO ACHIEVE HOMEOSTASIS
1)
REGULATORS USE BEHAVIORAL AND
PHYSIOLOGICAL MECHANISMS (SUCH AS PACIFIC SALMON,
USING OSMOREGULATION TO CONTROL INTERAL SALT
CONCENTRATIONS), WHICH CONSUMES ENERGY
2)
CONFORMERS ALLOW CONDITIONS WITHIN THEIR
BODY TO VARY WITH EXTERNAL CONDITIONS, EVEN IF THE
RESULT IS DEATH (*MANY SPECIES DO A LITTLE OF BOTH,
INCLUDING US. CAN YOU THINK OF AN EXAMPLE?)
THE PRINCIPLE OF ALLOCATION—STATES THAT EACH
ORGANISM HAS A LIMITED AMOUNT OF ENERGY THAT CAN
BE ALLOCATED FOR OBTAINING NUTRIENTS, ESCAPING
PREDATORS, COPING WITH ENVIRONMENTAL FLUCTIONS,
ETC. (AND IS THEREBY UNAVAILABLE FOR OTHER
FUNCTIONS)
SHORT-TERM RESPONSES MUST OPERATE WITHIN THE
EVOLUTIONARY FRAMEWORK
1)
PROXIMATE CAUSATION (OF A BEHAVIOR OR
CHARACTERISTIC) ADDRESSES THE IMMEDIATE REASON (i.e.,
WHAT ARE THE DIFFERENCES IN THE PINEAL GLAND OF
NOCTURNAL VS. DIURNAL ORGANISMS?)
2)
ULTIMATE CAUSATION OF THE SAME
BEHAVIOR/CHARACTERISTIC ADDRESS HOW NATURE
SELECTED THAT MECHANISM INSTEAD OF SOME OTHER
BEHAVIOR OR CHARACTERISTIC
PHYSIOLOGICAL RESPONSES MAY OCCUR OVER MANY TIME
SCALES (SECONDS TO WEEKS)
--REGULATION, HOMEOSTASIS ARE FOUNDATION
RESPONSES
--ACCLIMATION INVOLVES SUBSTANTIAL BUT
REVERSIBLE CHANGES THAT SHIFTS A TOLERANCE CURVE
AND IS GENERALLY LIMITED BY A RANGE OF CONDITIONS A
SPECIES NATURALLY EXPERIENCES
MORPHOLOGICAL RESPONSES ALTER FORM OR INTERNAL
ANATOMY
--MAY DEVELOP OVER THE LIFETIME OF AN INDIVIDUAL
(MORE LIKELY ASSOCIATED WITH PLANTS) OR ACROSS
GENERATIONS
BEHAVIORAL RESPONSES MAY BE INSTANTANEOUS AND ARE
EASILY REVERSED (REFLEX, MIGRATION)