Download BIOL 360 - General Ecology

Ecology
“Biological Systems interact and
these systems and their
interactions possess complex
properties”
Ecology Defined
Ecology is the study of the relationship between
an organism and its environment
Environment includes both the chemical / physical
and biological components of an organism’s
surroundings
Relationship includes an organism’s interaction with
its physical environment and other organisms
Ecology – term coined by Ernst Haeckel
in 1866
• Same root as economy:
oikos = “house” (Greek)
• Haeckel conceptualized
ecology as the “economy
of nature”
“…in a word, ecology
is the study of all
those complex
interrelationships
referred to by
Darwin as the
conditions of the
struggle for
existence.”
Evolution and Ecology
• Natural selection and
evolution form the
foundation of ecology
• Evolutionary theory
provides a framework for
posing and testing
ecological hypotheses
Ecology can be studied at many levels,
from the individual to the biosphere
• environmental
relationships can be
studied at multiple
spatial and temporal
scales
INDIVIDUAL
How do bobtail squid
avoid predation?
POPULATION
How does bobtail squid
population size vary
from year to year?
What factors control
population size?
INTERACTIONS
Is the Vibriosquid symbiosis
beneficial to both
species?
COMMUNITY
How does exposure
to waves affect the
species composition
of coral reefs?
ECOSYSTEM
How does human
settlement affect
nutrient availability
in coral reef
ecosystems?
LANDSCAPE
How does island age
influence the
composition of squid
species within the
Hawaiian archipelago?
REGION
How do currents
and ocean
temperature affect
the distribution of
squid species
throughout the
Pacific basin?
BIOSPHERE
What role does
ocean
temperature
play in the global
carbon cycle?
Ecologists use the scientific method
How can nutrient poor soils of rain
forests support such abundant life?
• hypothesis: a majority of
the nutrients / energy are
stored in the rainforest
canopy
• test: observation and
direct measurement of
nutrient levels in
epiphyte mats
High nutrient content in epiphyte mats
• true in both
tropical and
temperate
rainforests
rainforest trees grow adventitious
roots from branches to absorb
nutrients from epiphyte mats
Models
•
•
•
•
simplification of reality
based on our understanding of nature
allow us to predict outcomes, estimate values
can be used to generate hypotheses or to test
hypotheses
Model example: using allele
frequencies to estimate past
population size
Mullerian Mimicry
Heliconius erato (above), and H. melpomene
(below), a pair of Müllerian mimics from
different areas of Ecuador and Northern Peru.
In what context did this mimicry
evolve?
Hypothesis 1:
• both species were split up into
many isolated populations
during the last glacial period,
and divergence / co-evolution
of wing patterns occurred
simultaneously in each
species.
Hypothesis 2:
• One of the Heliconius species
diversified first (the “model”
species); then a less abundant
second species later evolved to
mimic the wing patterns of the
model species.
In what context did this mimicry
evolve?
Hypothesis 1 – Prediction:
past population sizes, age of
different wing pattern races are
similar for both species
Hypothesis 2 – Prediction:
One of the Heliconius species
had a larger past population
size, and wing pattern races
of this species have
occupied geographic areas
since before the last glacial
period. The other species
had a small population size
in the past and underwent
wing pattern diversification
more recently.
Methods / Modeling
• researchers sequenced two genes from multiple
co-occurring H. erato and melpomene races
with matching wing patterns
• using a model of gene sequence evolution and
how frequencies of gene mutations are affected
by demographic factors, researchers estimated
past effective population sizes and the ages of
the different wing pattern races.
Results
H. erato had very large
population sizes in the
past, and had occupied
geographic areas much
longer than H.
melpomene.
Small populations of H.
melpomene have
diverged to mimic H.
erato populations at
various times since the
last glacial maximum
SUMMARY
• Ecology is the
study of the
relationship
between an
organism and its
environment
• Ecology can be studied at
multiple spatial and
temporal scales:
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individual
population
community
ecosystem
landscape
region
biosphere
SUMMARY
• Ecological studies follow the scientific method
• Ecology is an integrated and multidisciplinary
field
▫ uses tools from population genetics, chemistry,
mathematics, physiology, geology, etc.
• Ecologists generate and test hypotheses using
several different approaches
▫ fieldwork
▫ laboratory experiments
▫ modeling / simulations