Chapter 37: ecosystems and communities

Hippos

• Hippos (herbivores, hairless)barbels, snails, and shovel-nosed gobis eat the dung crocodiles eat the fish and snails

• Microorganisms also feed on the dung and get nutrients which then go to the trees

Competition

• -/-• Ecological niche: biotic

+ abiotic resources in the environment

• Occurs when 2 species are present and fight for resources

• Decreases carrying capacity

Mutualism

• +/+• Examples: Coral reef

and photosynthetic dinoflagellates

Predators

• +/-• Benefits predator, hurts

prey• Prey uses camoulflage

Herbivory

• +/-• As plants are eaten it

must expend E to replace them

• Defenses: thorns, spines, chemical toxins

• Coevolution: Heliconius and passion flower vine

Parasites

• +/-• Example: aphids and

plants

A food web

Species Diversity

• 2 components– Species richness – Relative abundance

– Species diversity often has consequences for the species living in that community

Keystone species

• A species whose impact on the community has a large impact on its community

• Occupies a niche that holds the community in place

Ecological succession• Disturbances: events that damage biological communities,

remove organisms from them and alter the availability of resources

• Ecological succession: the disturbed area may be colonized by a variety of species which are gradually replaced by a succession of other species

• Primary succession: when ecological succession begins in a virtually lifeless area with no soil (ex: new volcanic islands)

• Secondary succession: where a disturbance has destroyed an existing community but left the soil intact (ex: floods)

Ecological succession

Primary succession Secondary succession

Carbon cycle

Phosphorous Cycle

Nitrogen Cycle