Community Relationships

Ecology & Levels of Organization• Ecology

– Is the scientific study of the interactions between organisms and the environment

• Organisms and their interactions with one another and the environment have led scientists to organize nature into different levels as follows:– Organism– Population– Community– Biome– Ecosystem– Biosphere

Organism

Organism - an individual animal, plant, or single-celled life formAn organism’s job in a community is called its niche.

Population

Population - the collection of organisms of a particular species, living in a given geographic area or space

Community

Community - various collections of organisms sharing an environment

Biome

Biome - is a major regional group of distinctive communities best adapted to the region's physical natural environment, latitude, elevation, and terrain. (ex: savanna, steppe, prairie)

Ecosystem

Ecosystem - the collection of biotic (living) and abiotic (nonliving) components and processes in one particular area of the biosphere

Biosphere

Biosphere - the outermost part of the planet's shell — including air, land and water — within which life occurs

Habitat vs. Niche• Different Species have different niches.• A niche is the organism’s “Job”:– What does it contribute to the community?

• It can absorb sunlight to produce food for others.• It can be preyed upon by others.• It can be parasitized by others.• It can go to the bathroom and fertilize the ground.• It can die and its body will go back to the earth.

• Niche is different than habitat, because habitat describes the conditions in which the organism lives. A niche describes the organism’s purpose.

• Niche is often described by an organism’s relationship with other organisms in the community.

Organisms Can Have Symbiotic Relationships

– Symbiosis – a relationship where two species live closely together• Mutualism

– Symbiotic relationship in which both species benefit from the relationship

Ant-aphid mutualism: the aphids are protected against predators by the ants who cultivate the aphids for their secretions of honeydew, a food source.

The Roridula gorgonias plant is sticky and captures bugs, but does not eat the bugs. This bug eats the captured bugs and its feces fertilizes the soil and feeds the plant.

Students Should Be Able to Identify and Describe Symbiotic Relationships

– Symbiosis – a relationship where two species live closely together• Mutualism

– Symbiotic relationship in which both species benefit from the relationship

• Commensalism– Symbiotic relationship in which one organism benefits and the

other organism is neither helped nor harmed

A small copepod crustacean (note paired egg sacs) on Phyllidia

The commensal shrimp Periclimenes imperator on Chromodoris tinctoria

Students should be able to identify and describe symbiotic relationships

– Symbiosis – a relationship where two species live closely together• Mutualism

– Symbiotic relationship in which both species benefit from the relationship

• Commensalism– Symbiotic relationship in which one organism benefits and the

other organism is neither helped nor harmed

• Parasitism– Symbiotic relationship in which one organism lives in or on

another organism (the host) and consequently harms it

Mites parasitising a harvestman.

This plant is a Holoparasite; a plant that is completely parasitic on other plants and has virtually no chlorophyll.

Organisms can have Predator/Prey relationships

• Many predators specialize in hunting only one species of prey. – The specialists are usually particularly well suited to capturing

their preferred prey. – The prey in turn, are often equally suited to escape that

predator. – This tends to keep the populations of both species in

equilibrium.

• Other predators are more opportunistic and will kill and eat almost anything.

Specialist Predator

Specialist Predator

Opportunistic Predator

Opportunistic Predator

Prey/Predators Continued

• When hunger is not an issue, most predators will generally not seek to attack prey because it costs them too much energy. – (This is why sharks in an aquarium will not attack

the fish in the tank)

Prey/Predators Continued

• Predators at the top of the food chain (such as large sharks, crocodiles, and humans) are called the apex predators and can often greatly affect the food chain beneath them.– Species that have a strong influence on the food

chain are called keystone species.

The Clean Up Crew

• And of course, you have to have organisms that return dead organisms back to the eart:– Scavengers eat freshly dead material, like

opossums and buzzards.– Detritivores eat detritus (decaying matter), like

maggots.– Decomposers complete the conversion of organic

material to the earth; like bacteria and fungus(mold).

The Food ChainEnergy Comes to Earth

Energy is Absorbed by Plants

Producer

Primary Consumer

Secondary Consumer

Tertiary Consumer

Producer

Primary Consumer

Secondary Consumer

Tertiary ConsumerQuaternary Consumer

Decomposers

Energy Pyramid