Ecology Bio 47
Spring 2015
Tuesday 11:00 – 1:50
Thursday 11:00 – 1:50
Instructor: Nancy Wheat
Why & How to Study Ecology
 What

is Ecology?
Ecology is the study of the interactions
between organisms and between
organisms and their environment.
Why & How to Study Ecology
 Ecology
can be studied at the level of
individuals, populations, communities,
and ecosystems.


How do individuals interact with each other
and their environment? What effects do
physical characteristics (temperature,
salinity, etc) have on individuals?
What affects population density in a given
species?
Why & How to Study Ecology


How do various species interact in a
community? If one species in a community
is removed, what happens to the others?
How do all the organisms in a particular
area interact with the physical
environment?
Behavioral Ecology
 Behavioral
ecology focuses on the
ecology of the individual organism and
how its behavior, including its interaction
with other individuals, affects its
reproductive success and the population
density.
Population Ecology
 Populations:
Groups of individuals from a
single species which can potentially
interbreed.
 What controls the abundance of a
species? We need to know how
populations grow.

Populations are limited by food,
competitors, and predators.
Population Ecology
 Knowledge



of population ecology:
Prevents extinctions.
Lessens species endangerment.
Maximizes sustainable yields in fisheries and
forests.
Community Ecology
 Community
ecology is concerned with
biodiversity, what influences the numbers
of species in an area. This type of
information is very important in
conservation biology.
 Interest in species richness.


Preservation of species-rich areas.
Linkages between species richness and
community function.
Community Ecology
 Emergence
of Earth’s biological diversity
as a critical issue.
 Loss of biodiversity could disrupt a
community’s ability to perform ecosystem
functions such as absorbing carbon
dioxide, maintaining soil fertility, &
retaining water to prevent flooding.
Ecosystems Ecology
 In
ecosystem ecology we view the
community as a user of nutrients and
energy, and we examine nutrient
availability and energy flow. This type of
information is important, for example,
when following pesticides through a food
web.

How have human alterations of global
nutrient cycles including carbon, sulfur and
nitrogen affected ecosystems?
Ecological Methods
 Development
of study plan.
 Example: Study of locust outbreaks
Interaction web to show interactions that
influence the population.
 Natural enemies (predators, parasites).
 Competitors (other insects, vertebrate
grazers).
 Host plants (quantity and quality).
 Physical factors (temperature, rainfall).
Ecological Methods
 Observations
 Graph
and Interpretations
results to show significant correlations
as in figures a & b, or insignificant as in c.
 If locust density is linearly related to
predation, we say that they are correlated.
Ecological Methods
 Observations


and Interpretations (cont.).
Statistical tests are used to determine
significance of relationships.
Correlation does not always imply
causation!
 Locust
density could be correlated with large
plants – but is this because large plants supply
more food or because they provide shelter
from predators?
Correlation does not always
imply causation!
Ecological Methods
 Experimentation


– Predator study
Hypothesis: Increased predators will
decrease locust population.
Two study groups:
 Treatment
Group: Locusts with predators
removed.
 Control Group: Locusts with nothing done –
predators present.


Measurements
Replications – performing experiments
many times.
Ecological
Methods
 Experimentation
Predator study
(cont.)


Statistical Tests –
ANOVA and ttests.
Means and
Standard error.
–
Ecological Methods
 Types



of Experimentation
Laboratory
Field
Natural
Ecological Methods
 Laboratory




Experiments
Most exact regulation of abiotic and biotic
factors.
Vary only the factor of interest.
Disadvantage: Oversimplification of the
biotic community.
Best uses: Physiological responses of
individuals.
Ecological Methods
 Field



Experiments
Conducted outdoors.
Manipulation of abiotic or biotic factors
(e.g. Elimination of a competitor).
Disadvantage: Methods of exclusion are
unlikely to be generated by nature.
Ecological Methods
 Natural



Experiments
Uses natural perturbations to disrupt biotic
community.
Used to follow the trajectory of the
perturbation over time.
Results can be extrapolated to other
communities.
Ecological Methods
 Experimental

Problems
Logistic problems lead to low replication.
 Which
leads to a Type I error; declaring that a
hypothesis is false when in fact it is true.
 Low replications lead to greater standard
error (SE) values.
Ecological Methods
 Mathematical




Models
Experiments may not be possible.
Models give valuable signposts on how
natural systems might work.
Indicate need for further data.
Indicate need for further observations.
Spatial Scale
A
space occupied by an individual
(behavioral ecology).
 A local patch occupied by many
individuals (a population).
 A large enough space to comprise
multiple populations (a community).
 A biogeographic scale large enough to
encompass a community, and its nutrients
and energy cycles (an ecosystem).
Spatial Scale
 Ecological
phenomena
occur on a variety
of spatial and
temporal scales.
 The
correct scale
of investigation
depends on the
question being
asked.
Temporal Scale
 Short
time scale studies for behavioral
responses.
 Longer time scale studies for population
dynamics and ecosystem processes.
Summary
 Importance
of ecology in addressing
human perturbations.
 Four broad areas of ecology: behavioral
ecology, population ecology, community
ecology and ecosystems ecology.
Summary
 Understanding
ecological processes
through the use of different ecological
methods: laboratory, field and natural
experiments, and modeling.
 Investigations must be conducted at the
right spatial and temporal scale.