Chapter 37 Communities and Ecosystems

PowerPoint Lectures for

Biology: Concepts & Connections, Sixth Edition

Campbell, Reece, Taylor, Simon, and Dickey

Lecture by Brian R. Shmaefsky

Introduction: Hungry Hippos

All communities and ecosystems have certain features in common

Each type of ecosystem has its own unique structure and dynamics

Human activities can disrupt the balance of ecosystems

COMMUNITY STRUCTURE AND DYNAMICS

37.1 A community includes all the organisms inhabiting a particular area

Biological community

– An assemblage of populations living close enough together for potential interaction

– Described by its species composition

Boundaries of the community vary with research questions

– Can be a pond

– Can be the intestinal microbes of a pond organism

Interspecific interactions

– Relationships with other species in the community

Interspecific competition

– Two different species compete for the same limited resource

– Squirrels and black bears

– Compete for acorns

37.2 Interspecific interactions are fundamental to community structure

37.3 Competition may occur when a shared resource is limited

Ecological niche

– Sum of an organism’s use of biotic and abiotic resources

– Interspecific competition occurs when the niches of two populations overlap

Competition lowers the carrying capacity of competing populations

Interspecific competition between orange-crowned warbler and Virginia’s warbler

37.3 Competition may occur when a shared resource is limited

37.4 Mutualism benefits both partners

Reef-building corals require mutualism

– Photosynthetic dinoflagellates

– Live in the cells of each coral polyp

– Produce sugars used by the polyps

– Provide at least half of the energy used by the coral animals

Video: Clownfish and Anemone

37.5 EVOLUTION CONNECTION: Predation leads to diverse adaptations in prey species

Predation benefits the predator but kills the prey

Prey adapt using protective strategies

– Camouflage

– Mechanical defenses

– Chemical defenses

Video: Seahorse Camouflage

37.6 EVOLUTION CONNECTION: Herbivory leads to diverse adaptations in plants

Herbivory is not usually fatal

– Plants must expend energy to replace the loss

Plants have numerous defenses against herbivores

– Spines and thorns

– Chemical toxins

Herbivores and plants undergo coevolution

– A change in one species acts as a new selective force on another

– Poison-resistant caterpillars seem to be a strong selective force for Passiflora plants

37.6 EVOLUTION CONNECTION: Herbivory leads to diverse adaptations in plants

Sugardeposits

37.7 Parasites and pathogens can affect community composition

A parasite lives on or in a host from which it obtains nourishment

– Internal parasites include nematodes and tapeworms

– External parasites include mosquitoes and ticks

Pathogens are disease-causing parasites

– Pathogens can be bacteria, viruses, fungi, or protists

Non-native pathogens can have rapid and dramatic impacts

– American chestnut devastated by chestnut blight protist

– A fungus-like pathogen currently causing sudden oak death on the West Coast

Non-native pathogens can cause a decline of the ecosystem

37.7 Parasites and pathogens can affect community composition

37.8 Trophic structure is a key factor in community dynamics

Trophic structure

– A pattern of feeding relationships consisting of several different levels

Food chain

– Sequence of food transfer up the trophic levels

Producers

– Support all other trophic levels

– Autotrophs

– Photosynthetic producers

– Plants on land

– Cyanobacteria in water

Consumers

– Heterotrophs

– Primary consumers

– Secondary consumers

– Tertiary consumers

– Quaternary consumers

Detritivores and decomposers

– Derive energy from dead matter and wastes

Video: Shark Eating a Seal

A terrestrial food chain

Producers Phytoplankton

An aquatic food chain

Primaryconsumers

Grasshopper Zooplankton

Primaryconsumers

Secondaryconsumers

Mouse Herring

Primaryconsumers

Secondaryconsumers

Mouse Herring

Snake TunaTertiaryconsumers

Primaryconsumers

Secondaryconsumers

Mouse Herring

Snake TunaTertiaryconsumers

Hawk Killer whale

Quaternaryconsumers

Trophic level

37.9 Food chains interconnect, forming food webs

Food web

– A network of interconnecting food chains

Producers(plants)

Primaryconsumers

Secondaryand

primaryconsumers

Tertiaryandsecondaryconsumers

Quaternary,

tertiary,

and secondaryconsumers

37.10 Species diversity includes relative abundance and species richness

Species diversity defined by two components

– Species richness

– Relative abundance

Plant species diversity in a community affects the animals

Species diversity has consequences for pathogens

37.11 Keystone species have a disproportionate impact on diversity

Keystone species

– A species whose impact on its community is larger than its biomass or abundance indicates

– Occupies a niche that holds the rest of its community in place

Keystone

Keystoneabsent

37.12 Disturbance is a prominent feature of most communities

Disturbances

– Events that damage biological communities

– Storms, fire, floods, droughts, overgrazing, or human activity

– The types, frequency, and severity of disturbances vary from community to community

Communities change drastically following a severe disturbance

Ecological succession

– Colonization by a variety of species

– A success of change gradually replaces other species

Primary succession

– Begins in a virtually lifeless area with no soil

Secondary succession

– When a disturbance destroyed an existing community but left the soil intact

ShrubsAnnualplants

Perennialplants and

grasses

Softwood treessuch as pines

Hardwoodtrees

37.13 CONNECTION: Invasive species can devastate communities

Introduction of rabbits in Australia

Frontier of rabbit spread Origin: 1860

600 Km

Australia

ECOSYSTEM STRUCTURE AND DYNAMICS

37.14 Ecosystem ecology emphasizes energy flow and chemical cycling

Ecosystem

– All the organisms in a community as well as the abiotic environment

Components of ecosystems

– Energy flow

– Passage of energy through the ecosystem

– Chemical cycling

– Transfer of materials within the ecosystem

A terrarium has the components of an ecosystem

37.14 Ecosystem ecology emphasizes energy flow and chemical cycling

Energyflow

Lightenergy

Chemical energy

Chemicalelements

Heatenergy

Bacteriaand fungi

Chemical cycling

37.15 Primary production sets the energy budget for ecosystems

Primary production

– The amount of solar energy converted to chemical energy

– Carried out by producers

– Produces biomass

– Amount of living organic material in an ecosystem

Primary production of different ecosystems

37.15 Primary production sets the energy budget for ecosystems

Open ocean

Estuary

Algal beds and coral reefs

Desert and semidesert scrub

Tundra

Temperate grassland

Cultivated land

Boreal forest (taiga)

Savanna

Temperate deciduous forest

Tropical rain forest

Average net primary productivity (g/m2/yr)

1,000 1,500 2,5002,000

37.16 Energy supply limits the length of food chains

A pyramid of production

– Illustrates the cumulative loss of energy transfer in a food chain

1,000,000 kcal of sunlight

10 kcal

100 kcal

1,000 kcal

10,000 kcalProducers

Primaryconsumers

Secondaryconsumers

Tertiaryconsumers

37.17 CONNECTION: A production pyramid explains why meat is a luxury for humans

The dynamics of energy flow apply to the human population

Producers

Primaryconsumers

Secondaryconsumers

Humanmeat-eaters

Cattle

CornCorn

Humanvegetarians

Trophic level

37.18 Chemicals are cycled between organic matter and abiotic reservoirs

Ecosystems are supplied with a continual influx of energy

– Sun

– Earth’s interior

Life also depends on the recycling of chemicals

– Organisms acquire chemicals as nutrients and lose chemicals as waste products

Biogeochemical cycles

– Cycle chemicals between organisms and the Earth

– Can be local or global

Decomposers play a central role in biogeochemical cycles

37.18 Chemicals are cycled between organic matter and abiotic reservoirs

Consumers

Geologic processes

Producers

Decomposers

Nutrientsavailableto producers

Abioticreservoir

37.19 The carbon cycle depends on photosynthesis and respiration

Carbon is the major ingredient of all organic molecules

The return of CO2 to the atmosphere by respiration closely balances its removal by photosynthesis

The carbon cycle is affected by burning wood and fossil fuels

Photosynthesis

Decomposers

(soil microbes)

Cellular respiration

Detritus

Plants, algae,cyanobacteria

Primaryconsumers

Higher-levelconsumers

Burning

CO2 in atmosphere

Plant litter;death

Wastes; death

and fossil

37.20 The phosphorus cycle depends on the weathering of rock

Organisms require phosphorus for nucleic acids, phospholipids, and ATP

– Plants absorb phosphate ions in the soil and build them into organic compounds

– Phosphates are returned to the soil by decomposers

– Phosphate levels in aquatic ecosystems are typically low enough to be a limiting factor

Animals

1Plants

Detritus

Decomposers

in soilDecomposition

Phosphatesin rock

Weatheringof rock

Runoff

Assimilation

Phosphates

in solution

Phosphatesin soil

(inorganic)

Precipitated(solid) phosphates

Upliftingof rock

37.21 The nitrogen cycle depends on bacteria

Nitrogen is an essential component of proteins and nucleic acids

Nitrogen has two abiotic reservoirs

– Air

– Soil

Nitrogen fixation converts N2 to nitrogen used by plants

– Carried out by some bacteria and cyanobacteria

Nitrogen (N2) in atmosphere

8 Plant Animal

Assimilation

by plants

Organiccompounds

Death; wastes

Denitrifiers

Nitratesin soil(NO3

Detritus

Decomposers

DecompositionNitrifyingbacteria

Ammonium (NH4+)

in soil

Nitrogen fixation

Nitrogenfixation

Nitrogen-fixingbacteria in

root nodules

Free-livingnitrogen-fixingbacteria and

cyanobacteria

37.22 CONNECTION: Ecosystem alteration can upset chemical cycling

Chemical cycling in an ecosystem depends on

– The web of feeding

– Relationships between plants, animals, and detritivores

– Geologic processes

Altering an environment can cause severe losses in chemical cycling

– Erosion

– Acid rain

Deforested

Completion oftree cutting

Control

1968196719661965

37.23 TALKING ABOUT SCIENCE: David Schindler talks about the effects of nutrients on freshwater ecosystems

Major changes in terrestrial ecosystems disrupt chemical cycling

These changes can increase nutrients in aquatic ecosystems

– Algal and cyanobacteria blooms

– Eutrophication

The most serious current threats

– Acid precipitation

– Changes in land use

– Climate warming

37.23 TALKING ABOUT SCIENCE: David Schindler talks about the effects of nutrients on freshwater ecosystems

Video: Cyanobacteria (Oscillatoria)

Decomposers

Producer

Energy flow

Chemical cycling

Herbivore(primary

consumer)

Carnivore(secondaryconsumer)

chemicalelements

Ecosystems

involve the processes of

in which in which

makes a

fromareincorporated by

isconverted by

to chemicalenergy of

intocomponents of

detritivores returnelements to

which passthrough

one-waytrip

solar energy to

chemical energy

to heat

organicmolecules

(a) (b)

(d) (e)

You should now be able to

1. Describe the characteristics of a community

2. Explain how interspecific interactions affect the dynamics of populations

3. Describe the trophic structure of a community

4. Explain how species diversity is measured

5. Describe the role of environmental disturbance on ecological succession

6. Explain energy and nutrient cycling in ecosystems

Chapter 37 Communities and Ecosystems

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