Community Ecology Ch 20 20 1 Species Interactions

Community Ecology Ch. 20

(20 -1) Species Interactions • 5 major types – Predation – Competition – Parasitism – Mutualism – Commensalism

Predation • 1 species benefits (predator) while the other species gets eaten (prey) • Adaptations: – Mimicry – Secondary compounds – Physical abilities

Predation (cont. ) • Mimicry: harmless species resembles a poisonous or distasteful species – Ex: king snake mimics poisonous coral snake • Secondary Chemicals: poisonous or bad-tasting chemicals made from metabolism – Ex: poison ivy/oak

Competition • Caused by niche overlap of 2 or more species • Can lead to: – Competitive exclusion – Character displacement – Resource partitioning

Competitive Exclusion • 1 species is eliminated due to competition for same limited resource – 2 barnacle species

Character Displacement • Evolution of anatomical differences that reduce competition – Darwin’s finches

Resource Partitioning • Species reduce their use of shared resource thus decrease competition – Warbler feeding

Symbiosis • Relationship b/w different species living in close contact w/ each other • 3 types: 1. Parasitism 2. Mutualism 3. Commensalism

Parasitism • 1 species benefits (parasite) while the other species is harmed (host) • 2 types: – Ectoparasite: external • Ticks, fleas, leeches – Endoparasite: internal • Tapeworms

Mutualism • Both species benefit from one another – Pollinators & plants

Commensalism • 1 species benefits while other is not affected – Cattle egrets & Cape buffalo

(20 -2) Properties of Communities • 3 community characteristics: – Richness: # of species it contains – Diversity: how common a species is – Stability: resistance to change • Richness improves stability

Species Richness Patterns • Communities closer to the equator have more species • Species-area effect: larger areas usually contain more species than smaller areas

Succession • Gradual, sequential re-growth of species in an area

2 Types of Succession • Primary: development of a community in an area that never had life before – Bare rock, sand dune – Extremely slow process • Secondary: change of community makeup after a disturbance – Farming, flood, fire – ~100 yrs to return

Key Terms • Pioneer species: predominate in early succession – Small, fast-growing, & fastreproducing – Ex: weeds, crabgrass • Climax community: community make-up that will last for a long time – Stable end result of succession