Ecological PrinciplesEcological Principles

Lecture 16

Ecology = the study of the interaction of organisms with their environments.

It involves understanding biotic and abiotic factors influencing the distribution and abundance of living things.

Biotic Factors• Competitors

• Disease

• Predators

• Food availability

• Habitat availability

• Symbiotic relationships

Abiotic Factors• pH

• Temperature

• Weather conditions

• Water availability

• Chemical composition of environment

• nitrates, phosphates, ammonia, O2, pollution

The word "ecology" coined from Greek word "oikos", which means "house" or "place to live”.

population growth competition between species symbiotic relationships trophic (=feeding) relationships origin of biological diversity interaction with the physical environment

• The entire proportion of the earth that is inhabited by life.

• Includes communities and ecosystems.

The BiosphereThe Biosphere

Forest

TundraSavanna

Desert

A major type of ecological community, determined largely by climate and dominate vegetation.

Population- an interbreeding group of individuals of a single species that occupy the same general areaCommunity-the assemblage of interacting populations that inhabit the same area. Ecosystem- comprised of 1 or more communities and the abiotic environment within an area.

Environmental GradientEnvironmental Gradient

Range of ToleranceRange of Tolerance

Zones of IntoleranceZones of Intolerance

Optimum RangeOptimum Range

Zones of Physiological StressZones of Physiological Stress

Parameters that effect size or density of a population:

Population (N)

Emigration

Immigration

DeathsBirths

Figure 1. The size of a population is determined by a balance between births, immigration, deaths and emigration

Birth EmigrationDeath Immigration

Generation123456789

10

Population Size1248

163264

128256512

Pop

ulat

ion

Siz

e

0

100

200

300

400

500

600

0 1 2 3 4 5 6 7 8 9 10 11 12Number of Generations

Exponential Population Growth

Unlimited resources

k

k

k = carrying capacity

k is affected by:• food production• resource supply• the env.’s ability to

assimilate pollution

exponential

sigmoidal

limiting resources (e.g., food & shelter) production of toxic wastes infectious diseases predation stress emigration

Increasing population density reduces resources and limits pop growth

severe storms and flooding sudden unpredictable severe cold spells earthquakes and volcanoes catastrophic meteorite impacts

Ecological niche = the "role" a species "plays" in the ecosystem.

An organisms use of biotic and abiotic resources in its environment

Contrast the ecological niche with the "habitat" which is the physical environment in which the organism lives.

The ecological niche of a species, therefore includes:

species’ habitat

abiotic & biotic interactions

No two similar species occupy the same niche at the same time.

Extinction of one species

G. F. Gause (1934) tested competitive exclusion principle

Constant food supply

extinction

Resource partitioning: splitting the niche

Sympatric species consume slightly different resources or use resources in slightly different ways

Insect-eating warblers

Character displacement:

two similar species evolve in such a way as to become different from each other by accentuating their initial minor differences

Allopatric vs Sympatric populations

Allopatric populations:

Similar beak morphologies and eat similar sized seeds

Avoids competition

Offset oscillations in the population sizes of the predator and prey

Coevolution of predator and prey

CC66HH1212OO66 + 6O + 6O2 2 6CO 6CO22 + 6H + 6H22O + energyO + energy

Animal cell

6CO6CO22 + 6H + 6H22O + energy O + energy C C66HH1212OO66 + 6O + 6O22

Carbon CycleCARBON CYCLE

Humans affect the carbon Humans affect the carbon cyclecycle Burning fossil fuels moves carbon from the ground to the air.

Cutting forests and burning fields moves carbon from organisms to the air.

Today’s atmospheric carbon dioxide reservoir is the largest in the past 800,000 years.

• The driving force behind climate change

The phosphorus cycleThe phosphorus cycle

Humans affect the Humans affect the phosphorus cyclephosphorus cycle

Mining rocks for fertilizer moves phosphorus from the soil to water systems.

Wastewater discharge also releases phosphorus, which boosts algal growth and causes eutrophication.

May be present in detergents• Consumers should purchase phosphate-free

detergents.

Nitrogen Cycle

Humans affect the nitrogen cycleHumans affect the nitrogen cycle Excess nitrogen leads to hypoxia in coastal areas. Synthetic fertilizers doubled the rate of Earth’s nitrogen

fixation. Burning forests and fossil fuels leads to acid precipitation. Wetland destruction and increased planting of legumes has

increased nitrogen-rich compounds on land and in water. Increased emissions of nitrogen-containing greenhouse

gases Calcium and potassium in soil are washed out by fertilizers. Reduced biodiversity of plants adapted to low-nitrogen

soils. Changed estuaries and coastal ecosystems and fisheries

Human inputs of nitrogen Human inputs of nitrogen into the environmentinto the environment

Fully half of nitrogen entering the environment is of human origin.

Eutrophication

Mississippi River

Eutrophication

runoff

Eutrophication

Gulf of Mexico Dead Zone

2006 Seamap Hypoxia Map

Eutrophication

Fish kills

Biogeochemical Biogeochemical CyclesCycles

Ecological Ecological SuccessionSuccession

The progressive change in the species composition of an ecosystem.

Ecological Ecological SuccessionSuccession

Climax StageClimax Stage

New Bare SubstrateNew Bare Substrate

Colonizing StageColonizing Stage

Successionist StageSuccessionist Stage

PRIMARY SECONDARY

Growth occurs on newly exposed surfaces where no soil exists

Ex. Surfaces of volcanic eruptions

Growth occurring after a disturbance changes a community without removing the soil

2 types of succession

For example, new land created by a volcanic eruption is colonized by various living organisms

Disturbances responsible can include cleared and plowed land, burned woodlands

Mount St. Helens

prior 1980

Mount St. Helens

May 18, 1980

Sep. 24, 1980

Mount St. Helens

Fireweed 1980 after eruption

2004

2012

Hanauma Bay Tuff Ring(shield volcano)

Succession after Volcanic Eruption

What organisms would appear first?

How do organisms arrive, i.e., methods for dispersal?

Volcanic eruption creates sterile environment

Mechanisms of Succession

Facilitation

Inhibition

Tolerance

Early species improve habitat.

Ex. Early marine colonists provide a substrate conducive for settling of later arriving species.

As resources become scarce due to depletion and competition, species capable of tolerating the lowest resource levels will survive.

Competition for space, nutrients and light; allopathic chemicals.

First arrivals take precedence.

r & K Selected Species

Pioneer species- 1st species to colonize a newly disturbed area

r selected

Late successional species

K selected

low competitive abilityshort life spanhigh growth rate

higher maternal investment per offspringlow reproductive output

high reproductive output

slow growth ratelong life spanhigh competitive ability

r & K refer to parameters in logistic growth

equation

Keystone SpeciesKeystone Species

A species whose presence in the community exerts a significant influence on the structure of that community.

Keystone predator hypothesis - predation by certain keystone predators is important in maintaining community diversity.

Paine’s study on Pisaster and blue mussels

Kelp Forests

Keystone Species

Keystone Species

Keystone Keystone SpeciesSpeciesKeystone Keystone SpeciesSpeciesAlgal turf farming by the

Pacific Gregory (Stegastes fasciolatus)

Antarctic Ecosystem

krill

Ecological Succession on a Ecological Succession on a Coral ReefCoral Reef

Successional Models and Successional Models and their Impactstheir Impacts

Case 1: No Disturbance (Competitive Exclusion Model)

Case 2: Occasional Strong Disturbance (Intermediate Disturbance Model)

Case 3: Constant Strong Disturbance (Colonial Model)

Case 1: No Disturbance(Competitive Exclusion Model)

• As the reef becomes complex, organisms compete for space.• Dominant organism outcompetes other species.• Occurs in stable environments. • Results in low species diversity.• Highly protected patch reefs within lagoons or protected bays• Deeper water

Case 2: Occasional Strong Disturbance(Intermediate Disturbance Model)

• Storms and hurricanes allow for other species to move in

• Dominant species would not be allowed to reach competitive exclusion

• After each disturbance have a recovery period

• Area of high diversity

Case 3: Constant Strong Disturbance(Colonial Model)

• Constant exposure to disturbance• Shallow environment• High turnover of species• r-selected species

Reef

Case 3

Case 2

Case 1Deep reef slope

Reef slope beneath reef crest

Near reef crest

Ecological Succession on a Coral Ecological Succession on a Coral ReefReef

The Big IslandThe Big Island

Ecological Succession on a Coral Ecological Succession on a Coral ReefReef

Ecological Succession on a Coral Ecological Succession on a Coral ReefReef

Ecological Succession on a Coral Ecological Succession on a Coral ReefReef

Ecological Succession on a Coral Ecological Succession on a Coral ReefReef

Ecological Succession on a Coral Ecological Succession on a Coral ReefReef

Ecological Succession on a Coral Ecological Succession on a Coral ReefReef

Ecological Succession on a Coral Ecological Succession on a Coral ReefReef

Successional Models and their Successional Models and their ImpactsImpacts

Successional Models and their Successional Models and their ImpactsImpacts

The definition of ecology means that:

Ecosystems are often hard to study because:

The "abiotic" part of the environment:

The "Principle of Competitive Exclusion" predicts that:

Questions

A species habitat may be thought of as its "_____" and its niche as its "_____.“

The removal of a keystone species may cause:

A density independent factor that may affect a population is __________.