Tuesday 11:00 – 1:50 Thursday 11:00 – 1:50 Instructor: Nancy Wheat Ecology Bio 47 Spring 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 Methods  Observations 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.