5 Community Ecology CHAPTER. Chapter 5 Lessons 2-3 Scientists have identified and described over 1.5 million species. Millions more have yet to be discovered

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Chapter 5 Lessons 2-3Chapter 5 Lessons 2-3

Scientists have identified and described over 1.5 million species. Millions more have yet to be discovered.

Scientists have identified and described over 1.5 million species. Millions more have yet to be discovered.

SpeciationSpeciation

Lesson 5.1 Evolution

• Process by which new species are generated

• Can occur in a number of different ways; the most important way is called allopatric speciation (geographic separation)

• Has resulted in every form of life on Earth— today and in the past

Allopatric Speciation

Allopatric SpeciationAllopatric Speciation

•One population broken into multiple smaller isolated populations• Separation may be due to glacial ice sheets, rivers changing

course, dry climate, etc.

• Any mutations that arise in one population can’t spread to the other; genetic divergence occurs• Populations may become different enough that they

can no longer mate with each other; speciation has occurred

•One population broken into multiple smaller isolated populations• Separation may be due to glacial ice sheets, rivers changing

course, dry climate, etc.

• Any mutations that arise in one population can’t spread to the other; genetic divergence occurs• Populations may become different enough that they

can no longer mate with each other; speciation has occurred

Lesson 5.2 Species InteractionsLesson 5.2 Species Interactions

The zebra mussel has completely displaced 20 native mussel species in Lake St. Clair.

The zebra mussel has completely displaced 20 native mussel species in Lake St. Clair.

The NicheThe Niche

Lesson 5.2 Species Interactions

• Describes an organism’s use of resources and functional role in a community

• Includes organisms habitat, food it eats, how/when it reproduces, and what other organisms it interacts with

• Affected by an organism’s tolerance—its ability to survive and reproduce under changing environmental conditions

• Often restricted by competition

• Competition within a species – intraspecific competition

• Competition among 2 different species – interspecific competition

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CompetitionCompetition• Organisms compete when

they seek the same limited resource.

• In rare cases, one species can entirely exclude another from using resources.(competitive exclusion)

• To reduce competition, species often partition resources, which can lead to character displacement.

• Organisms compete when they seek the same limited resource.

• In rare cases, one species can entirely exclude another from using resources.(competitive exclusion)

• To reduce competition, species often partition resources, which can lead to character displacement.




Resource Partitioning

CompetitionCompetition

•The niche is the species role in the community•Resource partitioning – a process that allows different species to share common resources.•Character displacement – when resource partitioning leads to the evolution of physical characteristics among competing species that reflect their specialized roles in the environment.

•The niche is the species role in the community•Resource partitioning – a process that allows different species to share common resources.•Character displacement – when resource partitioning leads to the evolution of physical characteristics among competing species that reflect their specialized roles in the environment.

Predation (+/–)Predation (+/–)• The process by which a predator hunts,

kills, and consumes prey

• Causes cycles in predatory and prey population sizes

• Defensive traits such as camouflage, mimicry, and warning coloration have evolved in response to predator-prey interactions.

• Some predator-prey relationships are examples of coevolution, the process by which two species evolve in response to changes in each other.

• The process by which a predator hunts, kills, and consumes prey

• Causes cycles in predatory and prey population sizes

• Defensive traits such as camouflage, mimicry, and warning coloration have evolved in response to predator-prey interactions.

• Some predator-prey relationships are examples of coevolution, the process by which two species evolve in response to changes in each other.


DidYou Know? A single rough-skinned newt contains enough poison to kill 100 people. Unfortunately for the newt, its predator, the common garter snake, has coevolved resistance to the toxin.

DidYou Know? A single rough-skinned newt contains enough poison to kill 100 people. Unfortunately for the newt, its predator, the common garter snake, has coevolved resistance to the toxin.

Rough-Skinned Newt

Parasitism and Herbivory (+/–)

Parasitism and Herbivory (+/–)


Did You Know? One study of Pacific estuaries suggests that parasites play an important role in keeping these ecosystems healthy by controlling host populations.

Did You Know? One study of Pacific estuaries suggests that parasites play an important role in keeping these ecosystems healthy by controlling host populations.

Hookworm (a parasite)

• Parasitism: One organism (the parasite) relies on another (the host) for nourishment or for some other benefit

• Ex: tapeworms, ticks, etc.• Symbiosis – a long-lasting

and physically close relationship in which at least one organism benefits.

• Herbivory: An animal feeding on a plant

Mutualism (+/+) and Commensalism (+/0)Mutualism (+/+) and Commensalism (+/0)


Did You Know? Symbiosis describes a long-lasting and physically close relationship between species in which at least one species benefits.

Did You Know? Symbiosis describes a long-lasting and physically close relationship between species in which at least one species benefits.

• Mutualism: a relationship in which two or more species benefit• Ex: pollination

• Commensalism: a relationship in which one species benefits while the other is unaffected

Lichen: a symbiotic relationship between a fungus and a photosynthetic partner, such as an alga

Lesson 5.3 Ecological CommunitiesLesson 5.3 Ecological Communities

The sun provides the energy for almost all of the ecological communities and species interactions on Earth.

The sun provides the energy for almost all of the ecological communities and species interactions on Earth.

Primary Producers (Autotrophs)Primary Producers (Autotrophs)• Capture energy from the sun or

from chemicals and store it in the bonds of sugars, making it available to the rest of the community

• Energy from the sun is captured by plants, algae, or bacteria through photosynthesis.• Sunlight used to convert carbon

dioxide and water into sugars, releasing oxygen along the way

• Energy from chemicals is captured by some bacteria through chemosynthesis.

• Capture energy from the sun or from chemicals and store it in the bonds of sugars, making it available to the rest of the community

• Energy from the sun is captured by plants, algae, or bacteria through photosynthesis.• Sunlight used to convert carbon

dioxide and water into sugars, releasing oxygen along the way

• Energy from chemicals is captured by some bacteria through chemosynthesis.

Lesson 5.3 Ecological Communities

Deep-sea vents, far from sunlight, support entire communities of fish, clams, and other sea animals, which depend on energy converted through chemosynthesis.

Deep-sea vents, far from sunlight, support entire communities of fish, clams, and other sea animals, which depend on energy converted through chemosynthesis.

Consumers (Heterotrophs)Consumers (Heterotrophs)•Rely on other organisms for energy and nutrients

• Herbivores: plant-eaters

• Carnivores: meat-eaters

• Omnivores: combination-eaters

• Detritivores and decomposers: recycle nutrients within the ecosystem by breaking down nonliving organic matter

• Detrivores consume nonliving organic material; decomposers break down nonliving organic material

•Use oxygen to break bonds in sugar and release its energy through cellular respiration (primary producers do this, too)

•Rely on other organisms for energy and nutrients

• Herbivores: plant-eaters

• Carnivores: meat-eaters

• Omnivores: combination-eaters

• Detritivores and decomposers: recycle nutrients within the ecosystem by breaking down nonliving organic matter

• Detrivores consume nonliving organic material; decomposers break down nonliving organic material

•Use oxygen to break bonds in sugar and release its energy through cellular respiration (primary producers do this, too)


California Condor

Did You Know? Scavengers, such as vultures and condors, are just large detritivores.

Did You Know? Scavengers, such as vultures and condors, are just large detritivores.



Energy in CommunitiesEnergy in Communities• An organism’s rank in a

feeding hierarchy is its trophic level.• Primary producers always

occupy the first trophic level of any community.• In general, only about

10% of the energy available at any trophic level is passed to the next; most of the rest is lost to the environment as heat.• Eating at lower trophic

levels decreases biological footprint

• An organism’s rank in a feeding hierarchy is its trophic level.• Primary producers always

occupy the first trophic level of any community.• In general, only about

10% of the energy available at any trophic level is passed to the next; most of the rest is lost to the environment as heat.• Eating at lower trophic

levels decreases biological footprint


Pyramid of Energy

Numbers and Biomass in Communities

Numbers and Biomass in Communities

• A trophic level’s biomass is the mass of living tissue it contains.

• In general, there are more organisms and greater biomass at lower trophic levels than at higher ones.

• A trophic level’s biomass is the mass of living tissue it contains.

• In general, there are more organisms and greater biomass at lower trophic levels than at higher ones.




Food Chains

and Webs

Food Chains

and Webs• Food chain: Linear

series of feeding relationships

• Food web: Shows the overlapping and interconnected food chains present in a community

• Food chain: Linear series of feeding relationships

• Food web: Shows the overlapping and interconnected food chains present in a community




• Species that have strong and/or wide-reaching effects on a community

• Removal of a keystone species can significantly alter the structure of a community.

• Species that have strong and/or wide-reaching effects on a community

• Removal of a keystone species can significantly alter the structure of a community.

Keystone SpeciesKeystone Species


Lesson 5.4 Community StabilityLesson 5.4 Community Stability

A 2010 report on invasive species suggests that they cost the U.S. $120 billion a year in environmental losses and damages.

A 2010 report on invasive species suggests that they cost the U.S. $120 billion a year in environmental losses and damages.

Invasive kudzu

Ecological DisturbancesEcological Disturbances

Lesson 5.4 Community Stability

• A community in equilibrium is generally stable and balanced, with most populations at or around carrying capacity.• Disturbances or changes in

the environment can throw a community into disequilibrium.• Severe disturbances can

cause permanent changes to a community and initiate a predictable series of changes called succession.

• A community in equilibrium is generally stable and balanced, with most populations at or around carrying capacity.• Disturbances or changes in

the environment can throw a community into disequilibrium.• Severe disturbances can

cause permanent changes to a community and initiate a predictable series of changes called succession.

Forest fire

Primary SuccessionPrimary Succession


• Occurs when there are no traces of the original community remaining, including vegetation and soil• Bare expanse of rock, sand, or sediment is exposed for the first time

• Pioneer species, such as lichens, are the first to colonize.• The environment changes as new species move in, adding

nutrients and generating habitat.

• Occurs when there are no traces of the original community remaining, including vegetation and soil• Bare expanse of rock, sand, or sediment is exposed for the first time

• Pioneer species, such as lichens, are the first to colonize.• The environment changes as new species move in, adding

nutrients and generating habitat.



Secondary SuccessionSecondary Succession


• Occurs when a disturbance dramatically alters a community but does not completely destroy it• At least the soil from the previous ecosystem remains

• Common after disturbances such as fire, logging, or farming

• Occurs significantly faster than primary succession

• Occurs when a disturbance dramatically alters a community but does not completely destroy it• At least the soil from the previous ecosystem remains

• Common after disturbances such as fire, logging, or farming

• Occurs significantly faster than primary succession



Succession in WaterSuccession in Water


• Primary aquatic succession occurs when an area fills with water for the first time.• Disturbances such as floods or excess nutrient runoff

can lead to secondary aquatic succession.

• Primary aquatic succession occurs when an area fills with water for the first time.• Disturbances such as floods or excess nutrient runoff

can lead to secondary aquatic succession.



Climax CommunitiesClimax Communities


• Ecologists once thought succession leads to stable “climax” communities.• Stable community that

completes the succession process

• Today, ecologists see communities as temporary, ever-changing associations of species.• Communities are influenced

by many factors and constant disturbances.

• Ecologists once thought succession leads to stable “climax” communities.• Stable community that

completes the succession process

• Today, ecologists see communities as temporary, ever-changing associations of species.• Communities are influenced

by many factors and constant disturbances.

Beech-maple forest, a classic “climax community”

Invasive SpeciesInvasive Species


•Nonnative organisms that spread widely in a community• A lack of limiting factors such as predators,

parasites, or competitors enables their population to grow unchecked.•Not all invasive species are harmful.

•Nonnative organisms that spread widely in a community• A lack of limiting factors such as predators,

parasites, or competitors enables their population to grow unchecked.•Not all invasive species are harmful.

Did You Know? Although the European honeybee is invasive to North America, it is beneficial because it pollinates our agricultural crops.

Did You Know? Although the European honeybee is invasive to North America, it is beneficial because it pollinates our agricultural crops.

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5 Community Ecology CHAPTER. Chapter 5 Lessons 2-3 Scientists have identified and described over 1.5 million species. Millions more have yet to be discovered