Tuesday 11:00 – 1:50Thursday 11:00 – 1:50

Instructor: Nancy Wheat

Ecology Bio 47Spring 2015

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 MethodsObservations and Interpretations

Graph 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 t-tests.

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.