ECOLOGY - sfu.ca

ECOLOGY

•  Def’n: Scientific studies of the interactions that determine the distribution and abundance of organisms

3 LOOKS AT ECOLOGY

•  Levels and principles •  Population Ecology •  Conservation Biology

ECOLOGICAL LEVELS

•  Biosphere •  Biome •  Ecosystem •  Community •  Population •  Organism

(Individual)

BIOSPHERE

•  Def’n: That portion of the earth where all living organisms reside

BIOME •  Major terrestrial and aquatic life zones

usually named after the dominant vegetation of the region.

FRESH WATER •  Def’n - less than 500 ppm dissolved salts.

LAKE ZONATION •  Defined by access to light to support

photosynthesis.

MARINE ZONATION •  Defined by access to light to support

photosynthesis.

ECOSYSTEM

Def’n: unique communities of organisms that interact with one another and their surrounding environments in a given area

ECOSYSTEM

.

ECOSYSTEM COMPONENTS

•  Abiotic resources •  Abiotic conditions •  Primary producers •  Consumers •  Decomposers

COMMUNITY

•  Def’n: Unique assemblage of populations

POPULATION

•  All individuals within a species that exchange genes

BIG PROBLEM FOR ECOLOGICAL THEORY

•  Connections across levels (bridge laws)

dNdt = r K −N

K( )N

DESCRIPTIVE PARAMETERS FOR COMMUNITIES

•  Diversity •  Stability •  Trophic Structure

DIVERSITY COMPARISON

Community 1 Community 2

COMMUNITY RICHNESS AND ABUNDANCE

Compare 2 deciduous forests

ANOTHER COMMUNITY DESCRIPTOR

Compare 2 deciduous forests

ANOTHER COMMUNITY DESCRIPTOR

•  ni = number of individuals in species i, N = total number of individuals in the entire community, M = number of species in the community

D =niN

⎛⎝⎜

⎞⎠⎟i

M

∑2

AN EXAMPLE •  Compare Community A with 1 species, 100

individuals

•  Community B with 3 species, 50, 30 and 20 individuals of each

D =100100

⎛⎝⎜

⎞⎠⎟i

1

∑2

= 1

D =50100

⎛⎝⎜

⎞⎠⎟2⎛

⎝⎜⎞

⎠⎟+

30100

⎛⎝⎜

⎞⎠⎟2⎛

⎝⎜⎞

⎠⎟+

20100

⎛⎝⎜

⎞⎠⎟2⎛

⎝⎜⎞

⎠⎟= 0.38

STABILITY

•  Def’n: Ability to return to original composition following perturbation

TROPHIC STRUCTURE

•  Def’n: feeding relationships across the different trophic levels

TROPHIC STRUCTURE

•  Quantitative Food Web

COMMUNITY STRUCTURE���3 DETERMINANTS

•  Historical processes •  Resource utilization and tolerance •  Interactions:

– Competition – Predation – Symbiotic

RESOURCE UTILIZATION AND TOLERANCE

MIN MAX

PARTICLE SIZE

NICHE

MAX

MIN SALI

NIT

Y

A FACT

•  Only rarely does the realized niche of an organism approximate its fundamental niche; usually it is smaller