community interactions. community – all the species in a given location at a given time habitat...
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Community Interactions
• Community – all the species in a given location at a given time
• Habitat the physical environment they live in : Redwood forest
• Niche – how a species uses the resources in its habitat– Builds nest in tree top vs. lower branches
• Similar species coexist by Niche specialization.
Paramecium caudatum
Paramecium aurelia Competitive exclusion
Competitive Exclusion
• The more similar two species’ niches the more they compete.
• No two species can share the exact same niche- one dies out.
• Species evolve to diverge their niches by Resource Partitioning
Competition for space on the rocks
Weak competitors stuck higher up in the intertidal
Resource Partitioning
Smartweed
Indian mallow
Bristlyfoxtail
CharacterDisplacement
Two species with same Beak size can notCoexist on same island
One adaptive result of resource partitioning
Types of Interspecific Interactions
Species A Species B
Commensalism + 0
Mutualism + +
Competition - -
Predation + -
Parasitism + -
Canadian lynx (dashed line) Snowshoe hares (solid line)
Predator & Preya Mutualism?
Caulerpa taxifolia suffocating a marine ecosystem
Do not post on Internet
Number of species of ants Number of species of breeding birds
Mosses
Vascular Plants
Number of colonizing species of mosses and vascular plants recorded on Surtsey between 1965 and 1973
Keystone species
• Pisaster (Sea Star) defends tide pool from being taken over by mussels, barnacles.
Sea Otters maintain Kelp forest• Otters are a Keystone
species• Kelp are the base of the
kelp forest community• Urchins eat kelp at their
base• Otters eat urchins,
keeping their numbers low.
• Otter numbers along California are dropping.
• Alaska- Orcas starting to eat otters, because seal numbers are dropping
• No fish for seals
Succession:Community Structure changes over time
• Primary Succession: starts with no soil, just bare exposed rock– Progresses in stages until long term
climax stage
• Secondary Succession starts with the climax vegetation type– Disturbance (fire) resets timeline– Progresses in stages back to climax.
1-Glacier Retreats
2-Barren Rock
3-Moss and Lichen
4-Cottonwood and Alders
5-Spruce moves in
6-Spruce and HemlockClimax Vegetation
Fire Cycle in Chaparral
Fire poppies in burn area
Madrones sprouts from burl
Ceanothus seedlings sprout after fire
1 month post fire
Schmidts, M.J., D.A. Sims, J.A. Gamon California State University, Los Angeles, CA
http://vcsars.calstatela.edu/eas_00/miriam/miriam_esa_00.html
First spring 3 years post fire
20 and 40 years post fire
Mosaic of ages burns