COMMUNITY ECOLOGY

Honors Biology

OBJECTIVES

• Describe and give examples for all species interactions and arrange in a graphic organizer

• Contrast species richness and diversity• Describe stages of succession• Community are species interacting in a given

area

SPECIES INTERACTIONS

• Symbioses:– Close interactions among species– Five types• Predation• Parasitism• Competition• Mutualism• Commensalism

PREDATION

• Predator captures, kills and consumes prey• Natural Selection:– Predators: find, capture and consume prey– Prey: avoid being captured• Flee• Hide and camouflage

PREDATION

• Mimicry:– Harmless species resembles poisonous species– Poisonous resembles other poisonous

• Herbivores eat plants– Plant adaptations:

• Physical: sharp thorns, spines, tough leaves• Chemical defenses: bad tasting, irritating, poisonous

(secondary compounds)

PARASITISM

• Species interaction where one species is harmed and the other benefits

• No killing and consuming• Parasite and host• Ectoparasite: live on body; ticks• Endoparasite: live in body: tapeworm

PARASITISM

• Evolution:– Defense mechanisms: skin, chemical protection in

openings– Parasites: tapeworms absorb through skin

COMPETITION

• Fundamental niche overlap – use of same resource

• Competitive exclusion: one species is eliminated from community because of competition for resources

COMPETITION

• Character Displacement:– Differences between competitors– Beaks on finches

• Resource Partitioning– Each use part of resources– Time partitioning

MUTUALISM

• Both species benefit• Ants in the acacia plant• Flowers and pollinators

COMMENSALISM

• One species benefits and other is not affected• May not be any true cases• Egrets feeding on buffalo

SPECIES RICHNESS AND DIVERSITY

• Species Richness– Number of species in a community– Closer to equator: greater richness– Larger areas have more species: species area

effect• Species Diversity– Relative abundance of each species in a

community

SUCCESSION

• Disturbances can trigger a sequence of changes in the composition of a community

• New species come right in new species• Gradual sequential regrowth of species in an

area• Pioneer Species: small, fast growing, fast

reproducing

PRIMARY SUCCESSION

• Development where life was never supported• Slowly – minerals needed for growth are

unavailable

SECONDARY SUCCESSION

• Replacement of species in area following disruption from natural disaster or human activity

• Cleared by agriculture or natural disaster• Soil intact• About 100 years for original return; stages• Annual Grasses Perennial Grasses shrubs trees

COMPLEXITY

• Succession until climax community• Organisms alter environment to make it

favorable for next organisms