Community Interactions

QUICK REVIEW

•What is community?•What is population?

Community Interactions

• Powerfully affect an ecosystem• Include:

– Competition– Predation– Symbiosis

Competition

• When organisms of the same or different species attempt to use an ecological resource at the same place and the same time– Resource any necessity to life– Plants and animals compete– Winner and losers

• Interspecific competition– Competition between same two species– When 2 or more species rely on same limited

resource in a community– Ex. African savannah

Niche• Each species unique living arrangement in

a community• “Role”

– Think about a specific position player on a team i.e. pitcher on a baseball team

• Ex. Lizards in a rainforest• Includes:

– Habitat– Food sources– Time of day organism is most active

Rules, rules, rules• Fundamental rule in ecology

– Competitive Exclusion Principle• Russian biologist G.F. Gause

– Paramecium caudatum vs. Paramecium aurelia– Separately, both thrive in a culture– P. aurelia could gather food more quickly than the P.

caudatum, therefore, if they are grown together, P. aurelia will thrive while P. caudatum will die out

• 2 species so similar in requirements that the same resource limits both population’s growth, and one species may succeed over another

• No two species can occupy the same niche in the same habitat and the same time

• Prevents un necessary competition

9

Competitive Exclusion:

The Ciliate Paramecium over 24 d

Grown inSeparateFlasks

Grown inthe SameFlask

Predation

• Interaction where an organism captures and feeds on another organism

• Predator– Organism that does the killing and eating

• Prey– Organism that is being killed and eaten

(victim)

Predator Adaptations

• Speed• Agility• Coloring/camouflage to ambush prey• Packs/teams

– Ex. Wolves• Acute senses

– Ex. Rattle snake heat sensor organs• Claws, teeth, fangs, stingers, poison

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Camouflage Assists Predators(a)

(b)

Cheetah

Frogfish

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Camouflage by Blending in

Sand dab (fish)

Nightjar (bird)

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Camouflage

• To avoid detection by predators, some animals have evolved to resemble objects such as bird droppings, leaves, or thorns

Chapter 27 20

A Plant That Mimics a Rock

Cactus

Prey adaptations• Safe locations• Flee• Coloring/camouflage to hide• Defensive coloration

– “warning coloration”• Mimicry

– Organisms imitate dangerous organisms by appearance and actions• Hawk moth larva

• Plants– Thorns, spines, poisonous chemicals

Chapter 27 22

Camouflage byResembling Specific Objects

Moth

droppings

Leafy Sea Dragon-sea leaves/weed

Treehoppers- leaves

Chapter 27 23

Warning Coloration

Chapter 27 25

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Protection Through Mimicry

• Snowberry flies avoid by jumping spider predation by mimicking them both visually and behaviorally

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Visual and Behavioral Mimicry(a)

(b)

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Protection Through Mimicry

• Some animals deter predators by employing startle coloration

– Have spots that resemble eyes of a large predator

Chapter 27 29

Startle Coloration

Swallowtail butterfly caterpillar

Peacock moth

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Chemical Warfare

• Both predators and prey have evolved toxic chemicals for attack and defense

• Spiders and poisonous snakes use venom to paralyze their prey and deter predators

• Many plants have evolved chemicals to deter herbivores

• Bombardier beetle sprays hot chemicals from its abdomen

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Chemical Warfare

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Coevolutionary Adaptations

• Plants have evolved a variety of chemicals to deter herbivores

– Example: the toxic and distasteful chemicals in milkweed

• Some animals evolve ways to detoxify these chemicals, allowing them to eat the plants

– Plants may then evolve other toxic substances

Chapter 27 33

The monarch butterfly uses deterrent chemicals of milkweed, acquired by a feeding caterpillar, to make itself distasteful to its predators

Symbiosis

• Any relationship where two species live closely together

• Symbiosis literally means “living together”

• 3 main types– Parasitism– Mutualism– commensalism

What type of relationship is this?• Who is helping who?

Mutualism

• Both species benefit from the relationship

• A Happy couple• Flowers and bees

– Flowers need bees for pollination, bees need flowers nectar

What type of relation ship is going on here?

•Who is helping who?

Commensalism

• One member of the relationship benefits while the other is neither harmed nor helped

• One-sided• Rare in nature• Food or shelter• Barnacles on whale• Seaweed on back of crab

What type of interaction is going on here?

Parasitism• One organism lives on or inside another

organism and harms it• Parasite obtains all or part of its nutrients from

the other organism• Host

– Organism that is harmed in relation ship; the one that provides the nutrients to the parasite

• Parasite– Organism that gets its nutrients from the host

• Do they want to kill their host?– No, because they need them…they will weaken or

hurt the host in some way

Chapter 27 48

Symbiosis

Recap

• What are the three types of interactions in a community?– Competition– Predation– Symbiosis

• What types do we have?– Mutualism– Commensalism– Parasitism

Ecological Succession

• Do all ecosystems stay the same all the time?

• What are some things that cause changes to ecosystems?– Natural and unnatural– Quickly and slowly

• Ecosystems are constantly changing in response to human and natural disturbances.

• As an ecosystem changes, older habitants die out and new organisms move in, causing more change

Ecological Succession

• Series of predictable changes that occur in a community over time– Physical environment– Natural disturbance– Human disturbance

Primary Succession• Succession on land

that occurs on surfaces where no soil exists

• Volcanic eruptions• Glaciers melting

Stages of Primary Succession

• Start with no soil, just ash and rock• First species to populate this area

– “pioneer species”– For example, pioneer species on volcanic

rock are lichens (LY-kunz)• Lichens made up of fungus and algae that can

grow on bare rock• When lichens die, they for organic material that

becomes soil…now plants can grow

Secondary Succession

• Succession following a disturbance that destroys a community without destroying the soil

• Natural – hurricane– fires

• Human disturbances– Farming– Forest clearing

Succession in Marine Ecosystems

• Deep and dark• Can succession happen?• 1987 dead whale off of California

– Unique community of organisms living in remains

– Represents stage in succession in an otherwise stable, deep-sea ecosystem

– Whale-fall community

Whale-Fall Succession• Begins when large whale dies

– Sinks to barren ocean floor– Scavengers and decomposers flock to carcass , our first community

• Amphipods• Hagfish• sharks

• After a year, most tissues have been eaten– Now, second small community of organisms live here– Body is decomposing, releasing nutrients into the water

• Small fishes• Crabs• Snails• worms

• Only skeleton remains…– Third community moves in

• Heterotrophic bacteria• Decompose oil in bones release of chemical compounds• Who uses these chemical compounds?

– Chemoosynthetic autotrophs• In come the crabs, clams, and worms that feed on this bacteria

Human Activity and Species Diversity

• Land clearing– Farmland– Diverse forest replaced with single crop– Decreases species diversity

• Introduced species– Humans move a species from its native land

to a new location, intentionally or accidentally

Teacher,

Study Intro to Ecology

and Community Interactions