Organisms and Their Relationships

Limiting Factors• Abiotic factors:

Physical– Example: Climate,

water

• Biotic Factors: Biological– Example: Food

abundance, competing/cooperating species, habitat (flora)

Abiotic Factors

Biotic Factors

Levels of organization

Organism

• The lowest level of organization is the individual organism itself.

Population• A population is

made up of many individuals within a species in the same location.

Biological Community• A biological community is a group of

interacting populations that occupy the area.

Ecosystem• An ecosystem is

a biological community and all of the abiotic factors that affect it.

Biome• A biome is

a large group of ecosystems that share the same climate and have similar types of communities.

The Biosphere• A thin layer

around Earth• Extends several

kilometers above the Earth’s surface

• Extends several kilometers below the ocean’s surface

POPULATION INTERACTIONS

• Populations do not exist alone in nature. They are found in the presence of many potential competitors, predators and mutualists.

• The presence or absence of another species can have a profound or little impact on the abundance of the other species.

FIVE IMPORTANT INTERACTIONS BETWEEN TWO SPECIES

• COMPETITION (-/-)• PREDATION (+/-)• COMMENSALISM (+/0)• MUTUALISM (+/+)• PARASITISM (+/-)The symbols +, - and 0 refer to the effect of one species on

another when both are living together.

Population Interactions Influence Abundance

• When populations of different species interact, the effects of one on the other may be positive (+), negative (-) or neutral (0).

• By comparing populations living alone and together, several types of interactions can be identified.

Ecosystem Interactions• A habitat is an

area where an organism lives.

• A niche is the role an organism has in its environment.

Competition• When one or more organisms

compete for the same resource.– Trees in the Rainforest– Hawks and Owls– Lions, Hyenas, Cheetahs

COMPETITION• Mutual use of a limited resource by populations of

two or more species.• Each individual adversely affect another in the quest

for food (nutrients), living space, mates, or other common needs.

• When individuals harm one another is attempting to gain a resource.

• Abundance of both is greater when alone, than when together.

COMPETITION• May be: interspecific, or intraspecific• Due to: exploitation, or interference• Result in: mutual extinction, or exclusion of one, or

coexistence

Categories of Competition• When competition is between individuals of: ---- same species (intraspecific) ---- different species (interspecific)• When a resource is in short supply that used by

one it is not available to the other (exploitation).• When an action or substance produced by one is

directly harmful to the other (interference).

Exploitation and Intraspecific Competition

• A seed company advises gardeners to “spread seeds thinly in a furrow, after plants grow then thin to 8 inches apart”. Why?

• Plants too far apart or too close together will only produce a few seeds. Why?

Interference and Intraspecific Competition

• Territorial behavior has evolved in many species as a response to intraspecific competition.

• Male red wing blackbirds stake out a territory in defense of nests and mates.

Interference and Intraspecific Competition

• The red grouse males stake out territories that are defended against other males.

• The size of a territory determines red grouse density.

• This is called territorial behavior.

Herbivory • The relationship between plant

eaters (herbivores) and their food.–Manatee vs. Lettuce– Deer vs. Grass– Koala vs. Eucalyptus

Predation• The relationship between predators

and their dinner.– Owl vs. Mouse– Lion vs. Gazelle–Wolves vs. Moose

Dinner time!!

Oh Dear!

Symbiotic Relationships• Ectosymbiosis – where one organism

lives on another–Mistletoe

• Endosymbiosis- where one organism lives inside another– Lactobacilli in humans

MUTUALISM• Populations interact to the benefit of both.• Mutualism may be obligate (necessary for survival of

one or both species) or facultative (advantageous to one or both species).

• The basis for agricultural domestication of plants and animals by humans.

• Common in nature, but the effect on population dynamics is difficult to demonstrate and often complex.

Mutualism• The relationship

between 2 different species where both benefit.– Clown fish and

Anemones – Goby Fish and

blind Shrimp

MUTUALISM• One of the most

commonly observed mutualism is the pollination of flowering plants by an insect or humming bird.

• The pollinator benefits from the interaction by receiving nectar.

• The plant gets its pollen transferred from one plant to another.

MUTUALISM

• The lichen is a mutualistic association between a species of algae and a species of fungus.

• The fungus retains water and takes up minerals.

• The algae provides carbohydrates and other organic nutrients as the result of photosynthesis.

Commensalism • The relationship between 2

organisms where one benefits and the other is not significantly harmed– Spiders building webs on plants– Hermit crabs using gastropod shells

COMMENSALISM

• The cattle egret and cattle or other grazing African ungulate species.

• The egret benefits from catching insects that cattle “scare-up” while grazing.

• Cattle unaffected.

COMMENSALISM

• E. coli (Escherichia coli) is a common bacteria found living in the guts of mammals, including humans, where it gets all it needs to thrive.

• In most circumstances, humans are not harmed by its presence and no benefit has been discovered.

COMMENSALISM

• Bromeliads are a group of flowering plants that attach to trees (epiphytes). They gain access to sunlight and catch water.

• The trees are not harmed or benefited.

Parasitism• The relationship

between 2 organisms where one benefits and the other is harmed– Tape Worm– Liver Fluke– Bot Fly Larva

Interacting Populations

Explore: Wolves & Moose Of Isle Royale

Isle Royale

Isle Royale

Video

• Science of Isle Royale:http://www.youtube.com/watch?v=PdwnfPurXcs

Moose probably swam to Isle Royale in 1900

For the next 50 years, the moose population fluctuated with weather conditions and food supply.

Wolves crossed an “ice bridge” onto Isle Royale in the late 1940’s.

The lives of the Isle Royale moose have not been the same since.

The lives of the Isle Royale moose have not been the same since.

The lives of the Isle Royale moose have not been the same since.

The lives of the Isle Royale moose have not been the same since.

The lives of the Isle Royale moose have not been the same since.

The lives of the Isle Royale moose have not been the same since.

Moose and Wolf Population - Isle Royale 1960 to 2008

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1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

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ves

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Moose