Ecology

What is Ecology?

• =

“The environment”

• Abiotic –

Levels of organization in Nature

Subatomic particle

• protons• electrons• neutrons• tachyons• baryons• mesons• etc.

Subatomic Particles

Atom

pp

n

e-

e-

Subatomic Particles

atoms

Molecule C

H

H COOH

NH2 OH

H H

OCH2OPOPOP

HO

N

NN

N

NH2

HO

O O OH H

OH OH OH

H2O

N2

O2

Cl2

Subatomic Particles

atoms

Molecules

Organelle

• Sacs or their compartments that separate different activities inside the dell

Subatomic Particles

atoms

Molecules

Organelle

Cell

• (smallest living unit) May live independently or part of a multicellular organism

Subatomic Particles

atoms

Molecules

Organelle

Cell

Tissue

• A group of cells and surrounding substances functioning together in a specialized activity.

Subatomic Particles

Atoms

Molecules

Organelle

Cell

Tissue

Organ

• A group of tissues working together to perform a common task.

Subatomic Particles

Atoms

Molecules

Organelle

Cell

Tissue

Organ

Organ system

• Two or more organs interacting to contribute to the survival of the whole organism.

Subatomic Particles

Atoms

Molecules

Organelle

Cell

Tissue

Organ

Organ System

multicellular organism

• An individual composed of specialized interdependent cells arrayed in tissues, organs, and often organ systems

Subatomic Particles

Atoms

Molecules

Organelle

Cell

Tissue

Organ

Organ System

Multicellular Organism

Population: • A group of individuals of the…

Subatomic Particles

Atoms

Molecules

Organelle

Tissue

Organ

Organ System

Multicellular Organism

Cell

Population

Community

• = a group of organisms of different species (i.e. many populations)….

Subatomic Particles

Atoms

Molecules

Organelle

Tissue

Organ

Organ System

Multicellular Organism

Cell

Population

Community

Ecosystem

• All biotic and abiotic components of a certain area

Organ System

Multicellular Organism

Subatomic Particles

Atoms

Molecules

Organelle

Tissue

Organ

Cell

Population

Community

Ecosystem

Biome

• Major types of ecosystems on earth, occupying large geographic regions

Organ System

Multicellular Organism

Subatomic Particles

Atoms

Molecules

Organelle

Tissue

Organ

Cell

Population

Community

Ecosystem

Biome

Biosphere

• Those regions of the earth’s waters, crust and atmosphere in which organism can exist.

Organ System

Multicellular Organism

Subatomic Particles

Atoms

Molecules

Organelle

Tissue

Organ

Cell

Population

Community

Ecosystem

Biome

Biosphere

Is Life uniformly distributed?

•

Is life uniformly distributed?

Why isn’t all life everywhere?

Factors affecting distribution of organisms (biogeography)

1. Dispersal limitations– Not all areas are accessible – geographic

isolation

2. Habitat selection• Animals

3. Biotic Factors

4. Abiotic Factors

3. Biotic Factors

• Absence of symbioses• Lack of pollinators

• Competition

Competition

• Whenever the quantity of useful matter or energy falls below the level needed for the maximal growth of two or more organisms which must draw on the same supply, a contest begins.

• Competition from introduced species can shrink an organism’s actual range

What do plants compete for?

4. Abiotic Factors

• Vary from place to place, season to season.• Each organism has an optimum environment

needed for maximum growth.

……Thus scientists predict that global warming may radically alter the distribution of organisms/ecosystems on earth

Fig 50.18

Effects of climate on biogeography

• Solar radiation creates wind currents, ocean currents, and precipitation (from evaporation

Fig 50.10

Fig 50.10

Effects of climate on biogeography, continued

• Local climate– .– .– .– S slope drier than N slope (thus different plant

communities)• Microclimate

– .– Under a log– Within the litter layer

Fig. 50.12

Your ecosystem type: coastal temperate rainforest

Terrestrial Biomes

• Locations of the earth’s biomes due to:1. .2. .

• One biome type may occur in different areas of the world

– Different plant species but same:– Physiognomic structure –

– Similarities due to convergent evolution – similar phenotypes due to similar selection pressures over time• Similar climate, soils, disturbance patterns,…

Fig. 50.19

1. Tropical rainforest

• Very diverse!• Large vertical stratification due to competition for

light

2. Savanna

• Rainy & dry season• Fire adapted

3. Desert

• CAM plants• Unique plants with adaptations to harsh

environment

4. Chapparal

• Fire-dependent! – seeds germinated after fire, roots fire-resistant

5. Temperate grassland

• Occasional fire• Fertile soils

6. Temperate deciduous forest

• 4 seasons (cold winter – dormant)• Open forests

7. Coniferous Forest

• 4 seasons, large amounts of snowfall

8. Tundra

• No trees or tall plants• 20% of land area on earth• Low annual precipitation

4 types of ecological investigation:

1. Organismal ecology• “plant autecology”• organism’s response to environment – ability to

exist/adapt2. Population ecology

• Population size, distribution3. Community ecology

• Community structure, organization• Competition• Diversity• Disturbance• Succession

4. Ecosystem ecology• Energy flow/nutrient cycling• Interactions of biotic & abiotic components

Plant Population Ecology

Characteristics of Populations

1. Dispersion –

2. Size –

3. Density - the number of individuals living in a specified area

1. Dispersion

• Patterns of Dispersion:– Clumped –

– Uniform – evenly spaced due to:• Competition for resources• Allelopathy –

– Random – unpredictable; position of one individual cannot be predicted from position of another.

Clumped lupine

Random trees

Uniform dispersal of sagebrush

2. Population Size

• Demography = study of factors that affect the growth & decline of populations

• Life Histories = events from birth through reproduction to death

– Trade-offs between investments in reproduction & survival when there are limited resources

Controls at every stage of life history

Dormancy (seed bank)

seedling

growth

mature plant

reproduction

death

Seeds washed away, eaten, decomposed

Seed rain from mature plants

Herbivory, disease, competition, drought, flood, freeze

Demography

• Change in Population size = (B + I) – (D + E)

Exponential Growth

• occurs when resources are abundant or when an important constraint has be removed.

• Ex.

The j-shaped curve

Time

Number of

Individuals

Biotic Potential (r)

• = Intrinsic/ maximum rate of natural increase, given:

• Habitat is free of predators and pathogens.

Limits on Population Growth

• Given their biotic potential what keeps organisms from filling up the planet?

Limits on Population Growth

• Density & competition for resources will cause reproduction rates to decline or stabilize

Any essential resource that is in short supply

is a limiting factor on population growth.

• living space• pollution-free environment

• Environmental resistance affects the number of individuals of a given species that can be sustained indefinitely in a particular area.

Time

Number of

Individuals

K

Introduction

Colonization

Naturalization

Carrying Capacity (K)

• =

• Is not fixed - K may decrease when a large population damages or depletes its own resource supply.

Time

Number of

Individuals

Initial carrying capacity

New carrying capacity

Logistic growth

3. Density-Dependent Control of Population Size

• When population density is low, a population grows rapidly.

• When density is high, populations may grow slowly, remain stabile (zero growth) or decline – why?.

• High density puts plants at greater risk of …..

Density-Independent Control of Population Size

• = events that cause more deaths or fewer births regardless of population density

• Examples?

Plants have developed adaptations to population density

• At low density, population is limited only by intrinsic rate of growth (r)

• At high density, population is limited by carrying capacity (K)

• R selection and K selection

Pop. Size

Time

Low density

High density

introduction

Colonization

Naturalization

r - selection

• Disturbance creates low-density conditions, frees resources (fire, flood, volcano)

• Biotic potential (r) limits population size• Adaptations that are successful for these

conditions:

K-selection

• High density, population size close to K• Not much “new” space – competition for

resources• Adaptations that are successful for these

conditions:

• K & r selected species exist together because small-scale disturbances create space (exposed soil) for r species (colonizers)– Ex. Downed tree, badger holes, grazing

disturbance

Plant Community Ecology

Review: definition of community

• Group of organisms of different species living together in a particular habitat

Characteristics of communities

• Diversity – composed of:

1. Richness –

2. Evenness –

• Relative abundance = # individuals of species X divided by total # of individuals in the community

Which community is more diverse?

What factors determine the plant species composition & the relative of abundance of

different species in a community?

• Biotic & abiotic components of the habitat

Abiotic components of habitat & their effect on community structure:

• Each species has a tolerance range –

• Climate – temp, moisture• Soil – types, pH• Latitude & altitude• Disturbance

Disturbance

• = decrease or total elimination of the biotic components of the habitat

• Results: decrease in biomass, diversity• Natural events –

• Human-caused –

• Frees resources, creating opportunities for new species, different composition

• All communities have evolved with some type of disturbance, varying in type, frequency, & severity

Small-scale, frequent disturbance

• Ex. Trees downed in wind storm

• Can prevent large-scale disturbance – fire!– Ex. Yellowstone fire of 1988– Fire suppression in fire-dependent ecosystem

caused massive, stand-replacing fire

Human - caused disturbance + introduced species = disaster

• Ex. Cheatgrass – wildfire cycle1. Overgrazing in ecosystem that did not evolve

with large herbivores2. Cheatgrass introduction3. Decrease in fire frequency (100 yr to 5 year

cycle)4. Conversion of ecosystem with tremendous loss

of diversity• These types of problems creating mass extinction

worldwide

Biotic components of habitat & their effect on community structure

1. The plant itself

• Benefit ex: beech/oak forest creates shade needed for other young beech & oak to grow

• Detriment ex: pine forest creates shade but pines need lots of light to grow (succession)

2. Other plant species

• Theory of competitive exclusion: when two species compete for the same limiting resource (occupy the same niche), the species that is less adapted will be excluded from the community by the superior competitor

• One will become extinct or evolve to use a slightly different set of resources

low highLight intensity

Spe

cies

Abu

ndan

ce Species A Species B

A B C D

A B C D

Species A Species B

• If this theory is true, then actually very little competition in nature, because each plant occupies a niche.

• Niche• =

• Includes all aspects of a species’ use of biotic & abiotic resources (microclimate, rooting zone, pollinators, etc)

3. Other (non-plant species)

• Interactions with animals, insects, fungi, bacteria• Mutualism –

– Ex.

– Ex. Pollinator gets nectar and plant gets pollen transfer

– Ex. Animals eat fruit (nutrition) and seeds are dispersed

– Ex. Acacia trees get defense from herbivores & ants get home, food

• Commensalism – one species benefits & other is not affected

• Competition –

• Predation – one harmed, other benefits– Herbivory– pathogens

Controls on community structure

• Dominant species = species with the highest abundance or biomass in the community

– Controls occurrence & distribution of other species

– If eliminated, other species take over– Ex. Douglas fir

• Keystone species

– Ex. Sea otter – reduction in populations caused boom in sea urchin population, destroying kelp forests (drastic decline in diversity)

SuccessionSuccession

Succession

• =

• Species replacement continues until the composition of species becomes relatively steady under prevailing climatic conditions & disturbance regimes (dynamic equilibrium, not climax).

Two major types of succession

• Primary Succession• Secondary Succession

1. Primary succession

• Sequence:

1..

2.As these decay, acids weather the rock & primitive soil forms

3.Pioneer plants establish (r-selected)

4.Pioneers replaced by K-selected species

The Nature of Pioneer Species

• typically small plants, short life cycles, producing an abundance of small seeds which are quickly dispersed (wind & water)

• can grow in N-poor soil because of their mutualistic interactions with nitrogen-fixing bacteria.

Example of primary succession: glacial retreat

Fig 53.23

Fig 53.20

.

Mosses, lichens, fireweed

Dryas stage

Alders & cottonwoods dominate

Spruce enter forest and replace alders/cottonwoods

Hemlock slowly replace Spruce. Hemlock is “climax”

What Pioneers Do: Facilitation

• accumulation of their wastes and remains adds volume to the soil and enriches it with nutrients that allow other species to take hold.

2. Secondary Succession

• Plant community is destroyed but soil remains/ new soil exposed

• Examples?

• Typical progression: small herbs & grasses shrubs trees

Pioneer species

• Sometimes these opportunistic species (especially invasive weeds!) inhibit the growth of the native climax species changing the structure and type of climax community forever.

• Ex. cheatgrass

Ecosystem Ecology

Ecosystems

• An ecosystem is an association of organisms and their physical environment,

Structure of Ecosystems

1. Physiognomic structure • =

• Relative abundance of trees, shrubs, herbs, mosses, etc.

• Phenotypes, physical characteristics• Vertical & horizontal stratification

                                                               

http://www.mightytrees.com/science/foreststrat.html

2. Temporal Structure

• Diurnal (Daily) patterns

• Seasonal changes

3. Species composition

• Determined by soil resources, climate tolerance ranges, stresses (ex. Competitive interactions, herbivory)

4. Trophic levels

• = Feeding levels• Autotrophs

– First level of all food webs---- primary producers

• Heterotrophs – consumers - depend directly or indirectly on energy stored in tissues of primary producers.

Types of Heterotrophs• Herbivores

• Parasites

• Detritivores

• Carnivores – eat herbivores & other carnivores – secondary consumers

• Omnivores partake of a variety of edibles• Decomposers - extract energy and recycle nutrients from

organic matter.

Decomposition links all trophic

levels

Fig 54.2

• Some organisms like man extract energy from more than one trophic level so it is hard to assign them to a specific trophic level.

• Actual feeding relationships in an ecosystem are complex –.

Energy Flow Through Ecosystems

Primary Production

• =

• How much energy actually get stored depends on:• 1) how many plants are present and • 2) the balance between photosynthesis and aerobic

respiration.• Ecosystems differ in their PP:

Fig 54.4

Fig 54.5

• Other organisms tap into the energy that is conserved in plant tissues, remains, or wastes.

• They, too, lose heat to the environment.

• All of these heat losses represent a one-way flow of energy out of the ecosystem.

Secondary Production

• =

• Ex. Caterpillar eating a plant:– 50% loss to feces (energy transfer to detritus)– 34% to respiration (heat loss)– 16% to growth

Trophic efficiency

• =

• Thus 85-90% of available energy at one level is not transferred to the next– Instead lost as heat, not consumed, or

transferred to detritus

Fig 54.11:Energy pyramid

Fig 54.12 Biomass pyramid

Fig. 54.13 Pyramid of numbers