Community Ecology

Ecological Niche

• Ecological Niche – The role a certain species plays in an ecosystem

• How does it:o Interact with other organismso Interact with abiotic factorso What sort of things may these include?

Example: American Alligator

Alligator: Resources

• Resources that it uses:o Opportunistic Feeders: Fish, Turtles, Smaller

Gators, Small Mammals, Birdso So what?o Gators eating these animals keeps populations

of dozens of other species in check

Alligator: Interactions

• Alligators are not aggressive unless threatened

• Opportunistic feeders and will attack if hungry, and within striking range

• Known to attack pets, livestock, and humans

Alligator: Cycling of Matter

• Contribute to food chain as top predator

• Human hunting has jeopardized alligator populations

• Gators hunted for meat, skin, and for sport

• Killing alligators effects the ecosystem

• How?

Competitive Exclusion Principle• AKA – Gause’s Principle• When 2 species compete for the same

resources, one is more likely to be more successful

• The result will be in the second species being eliminated

• Basically: 2 animals cannot occupy the same niche

Resource Partitioning

• Some animals appear to compete for the same resources, however when examined closely, they occupy slightly different niches

• Examples: o Anole Lizards in the rain foresto Warblers in the same tree

Character Displacement

• AKA – Niche Shift • Due to resource partitioning, organisms

may adapt differently to their ‘micro-niches’

• This would result in less competition, and eventually evolutiondivergent

Realized vs. Fundamental Niche

• Fundamental Niche – The niche an organism occupies when no competition is present

• Realized Niche – The niche an organism occupies when competition is present (NO niche overlap)

Energy Flow • All living things need energy in order to

survive• Energy flows throughout the biosphere to

all living things• Energy needs to be put into a living

system, otherwise it cannot function• (DNW) What energy is constantly put into

the biosphere?

Producers

• Autotrophs – Organisms that produce their own foodo Because they make their own food, they are

also called producers

Producers

• Producers are the base of all ecosystems on earth

• Producers directly and indirectly produce all the food that goes into an ecosystem

Producers

• The most well known autotrophs used solar energy and use Photosynthesis

• When sunlight is not present, autotrophs use chemicals to produce food in a process called chemosynthesis

Consumers

• Heterotrophs – Organisms that must consume other organisms to obtain energyo These are also known as consumerso (DNW) There are many different categories of

heterotrophs

Herbivores

• Herbivores – Organisms that obtain energy by eating only plants

Carnivores

• Carnivores – Organisms that obtain energy by consuming animals

Omnivores

• Omnivores – Organisms that obtain energy by consuming both plants and animals

Scavengers/Detritivores

• Scavengers/Detritivores – Organisms that feed on the tissue of dead organisms

Decomposers

• Decomposers – Organisms that break down organic matter into simple nutrients or fertilizers

Trophic levels

• Energy moves from one organism to another when it is eaten

• Each step in this transfer of energy Is known as a trophic level

• Main trophic levelso Producerso Consumerso Decomposers

Energy Flow

• It is impossible to obtain all the energy in an organismo When a rabbit eats grass, it does not obtain all

of the energy in the grasso When a hawk eats the rabbit, it does not obtain

all the energy in the rabbit• About 10% of energy is transferred from

one trophic level to the next• This is known as the 10% law

Food Chain

• Energy flow from 1 trophic level to the next is called a food chain

• A food chain is simplified• Only one organism at each level are

shown

Food Chains

• Typical food chain order:o Producers (Autotrophs)o Primary consumers (Eat autotrophs)o Secondary consumers (Eat primary consumers)o Tertiary consumers (Eat secondary consumers)o Decomposers (Break down anything dead)

Food Chain - Example

Food Web

• Animals typically eat more than just one organism

• Food webs show a greater variety in the diets of organisms

Arrows

• The arrows point in the direction that the energy is transferred

• Basically, the arrows point from the prey, to the predator

Ecological Pyramid

• Shows the relationship between consumers and producers at different trophic levels in an ecosystem

• Shows the relative amounts of energy at each trophic level

• Shows what levels have the most energy and highest # of organisms

Ecological Pyramid

Symbiosis

• Symbiosis – a close and permanent association between different organisms

• There are three main categories of symbiosis:o Commensalismo Mutualismo Parasitism

Commensalism• Commensalism – When

one organism benefits, and the other is unaffected

Mutualism

• Mutualism – When both organisms benefit

Parasitism

• Parasitism – When one organism benefits, and the other is harmed

Coevolution

• Animals interacting with one another over long periods of time have led to coevolution

• Examples:o Secondary Compoundso Camouflageo Aposematic (Warning) Colorationo Mimicry

Secondary Compounds• Secondary Compounds – Toxic

chemicals produced in plants that are harmful/distasteful to herbivores

• Examples:o Nicotine o Poison Oak/Ivyo Mustard oil=Toxic to insectso Hotness of Peppers

Camouflage

• Camouflage – Any color, pattern, or shape that enables an organism to blend in with its surroundings

Aposomatic Coloration

• A conspicuous pattern of coloration that warns other animals that they should not be eateno Poisonouso Stingingo Bad Tasting

Mimicry

• Mimicry – When two or more species resemble one another

• 2 types:o Mullerian Mimicry – Animals with similar

defenses have similar colorationo Batesian Mimicry – When animals with no

defenses resemble organisms that do have a defense mechanism

Mullerian Batesian