B3 Species Interactions

Ecology

How organisms interact with biotic and abiotic environments

Ernst Haeckel and Ellen Swallow Richards

Defined ecology as “the study of the household of nature”

What is competition?

Competing for limited resources; arises from scarcity

• Both species’ fitness are negatively impacted

Intraspecific competition

Competition between individuals of the same species

Interspecific competition

Competition between individuals of different groups

Carrying Capacity

The phenomenon describing an environment that can only hold so many people

What kind of graphs does carrying capacity yield?

Logistic growth curve

Niche

Tells you which part of the environment a species will exist in

• Total range of all biotic/abiotic conditions that will be tolerated and all of the resources will be used

• Resulting from requirements of life AND competition

  • Niches are unique to species

Fundamental niche

Niche that species COULD potentially occupy in the absence of pressure

Realized niche

Where the species actually lives

What was the chthamalus vs balanus barnacles example?

Chthamalus barnacles can live in both dry/wet sand, but balanus barnacles compete with them and reduce the Chthamalus barnacles’ niche to only live in dry sand

Competitive Exclusion Principle

Complete competitors CANNOT coexist because the worst competitor will always go extinct

• Force each other’s niches to be reduced

  • Competing for the same limited resources

Mutualism

Relationship where both species’ fitness increases

Facultative mutualism

Organisms can survive independently without each other, but they benefit from the relationship

What was the ants and aphids example?

Aphids (small buggies) produce honeydew ingested by ants; ants protect aphids from larger competitors

• Facultative mutualism

Obligate mutualism

Both species rely on each other for survival

What was the corals and dinoflagellates examples

Obligate mutualism example

• Corals protect dinoflagellates

• Dinoflagellates provide sugars from photosynthesis

Benefits of mutualism

1. Nutrition

2. Defense

3. Communication/attraction

4. Dispersal

Antagonism

One species benefits, one species hurts

Three examples of antagonism

1. Predation

2. Parasitism

3. Herbivory

Commensalism

One species does better, the other is unaffected

Ammenalism

One species is hurt, one is unaffected