Life Sciences Course Introduction and Understanding Diversity

Hypothesis

What are the possible relationships among variables?

Dependent Variable

What we measure / ”result” / value depends on that of another / ”y”

Independent Variable

Affects dependent / variation does not depend on that of another / “x” / what we change to look for changes in dependent

Numeric Variables

values are numbers and represent quantities that can be measured or counted

Continuous Numeric Variables

Form a continuous line, can be infinitely divided (ex: height, weight, temperature, time, and speed)

Discrete Numeric Values

Set of points, not continuous line, can only take on a countable number of distinct values, typically whole numbers (ex: number of family members, the number of goals scored in a game, or the number of defects in a product)

Categorical Variables

Values don't have any numeric relationships to one another

Ordinal Categorical Variables

A type of data that involves categories with a meaningful, inherent order or rank, but without fixed intervals between the categories (ex: | low, medium, high | )

Control Variables

Factors held constant in a study to ensure that they do not influence the dependent variable

The Null Hypothesis

A fundamental concept in statistical testing that states there is no significant relationship, effect, or difference between the variables being studied (assumed)

Error

Mistakes made by the people doing the research. Examples include measurement error, incorrect species identification, or data entry mistakes. Error cannot be fixed by a change in experimental design.

Bias

Ways in which the experiment may not fully explain the relationships between the variables which could be corrected by a change in experimental design. In ecology, this is most commonly related to other variables that affect the dependent variable, but which were not measured.

Correlation

A relationship where variables move together

Causation

A direct cause-and-effect link between variables

Coincidence

A purely random occurrence of two events or variables

Control

Manipulating experiments to isolate cause-and-effect relationships and rule out confounding factors

Sampling

Selecting representative subsets of an environment to study its characteristics, such as organism distribution and abundance, without having to count every individual / the fundamental tool of ecology: collecting data on a portion of the system

Abiotic Factors

Factors that are non-living. A community interacting with these factors becomes an ecosystem.

Diversity

The number of species in a defined area (this also includes a consideration of the balance of the numbers of species and must recognize that these figures change over time and over space)

Individual

An identifiable member of a group

Population

A group of interacting individuals of the same species

Community

A group of interacting populations

Ecosystem

A community and the abiotic factors that exist in the location

Landscape

A general description of an area that frequently supports several ecosystems

Species Area Curves

The idea that a defined area can only support so many populations, resulting in the graph of alpha-diversity’s inevitable plateau

Alpha Diversity / Simple Diversity

Species richness at a site/habitat area / number of populations in a community

Gamma Diversity

Species richness in the larger landscape / all of the species that occur in a network of habitat areas

Shannon Weiner Diversity

Includes both simple diversity and the equitability of distribution of the species (min: 1, max: alpha diversity

Evolutionary Time

Occurs over thousands of generations - the creation of new species

Ecological Time

Short term: extinction and colonization - changes which happen quickly

Island Biogeography

Equilibrium between extinction and colonization | Extinction is a function of population size which is a function of area | Colonization is a function of the distance from the “mainland” or an area that supports all species

Metapopulation

Network of interacting but not directly connected subpopulations | Can persist if some of the patches remain occupied

Green World Hypothesis

Suggests that predators keep the world green by controlling herbivore populations, preventing them from overgrazing plants

Trophic Cascade

Powerful indirect interactions that can control entire ecosystems. These occur when predators limit the density and/or behavior of their prey and thereby enhance survival of the next lower trophic level | The loss of ecosystem diversity associated with the elimination of predators from the ecosystem

Keystone Species

A species on which other species in an ecosystem largely depend, such that if it were removed the ecosystem would change drastically | A species that plays a critical role in determining the structure of the ecosystem