Ecology (Bio 47) Fall 2002 Friday 6:00 – 7:50 Saturday 9:00 – 9:50
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Transcript Ecology (Bio 47) Fall 2002 Friday 6:00 – 7:50 Saturday 9:00 – 9:50
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.