Environmental Science - Lecture notes - Chapter 4 PDF

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Chapter 4 – Species Interactions and Community Ecology Community: - Set of populations of different species living together in a particular area - Community ecology studies 1. Species interactions 2. Good webs 3. Response to disturbance 4. Invasive species 5. Biomes Species Interactions

Competition: multiple organisms seeking same limited resource 1. Competitive exclusion (one takes over resources) 2. Resource partitioning( use slightly different resources or in different ways )

Resource Partitioning

Predation: one species hunts, tracks, kills, prey species - Can lead to cycles in numbers of predators and prey - Adaptations to avoid predators

Avoiding Predation

Parasitism: one species depends on, but also harms, host species - Does not usually kill host Ex: Lamprey, tapeworms, cowbirds, insects

Herbivory: animals consuming plants - Usually does not kill plant, but affects its growth and reproduction - Plant defenses Ex: Thorns, spines, hairs, toxic chemicals

Mutualism: both species benefit from interaction Ex: pollination, plant roots and fungi, intestines Ant- Acacia Mutualism

Feeding Hierarchy - Trophic level: rank in feeding hierarchy - Producers - Consumers - Decomposers and Detritivores: - Organisms that break down leaf litter, waste, dead bodies, and other non-living matter - Bacteria, fungi, millipedes, soil insects

Food Chain

Food Chain

Energy Loss at Trophic Levels - Most energy is lost as heat - Only about 10% of energy passes from one trophic level to next - Makes “ Energy Pyramid”

- Pyramid also applies to numbers and biomass - Key implication: eating at lower trophic levels

Food Webs - Visual map of feeding relationships and energy flow among trophic levels - More realistic than food chain (though still not ALL interactions)

Species Impacts - Some species have a stronger impact on communications than others - Beavers and prairie dogs physically modify - Decomposers recycle matter - Keystone species: have wide impact even though not abundant

Community Disturbance - Flood, landslide, climate change, human impact - Communities respond in different ways - Succession: 1. Predictable series of changes following disturbance 2. Primary succession- no life (volcano, glacier) 3. Secondary- some life remains (fire, hurricane, logging, farming)

Primary Succession

Secondary Succession Invasive Species: spreads widely and rapidly becomes dominant - Interferes with community’s normal functioning - Usually non-native (alien, exotic ) Ex: Zebra mussels from ship ballast water - Native to southern Russia

Zebra Mussel Impacts

Effect of 1991 Zebra Mussel Invasion on Fish Populations

Futher Zebra Mussel Effects on Fish

Solutions to Invasive - Sometimes they are beneficial Ex: European honeybee, ornamental plants, pest control - National Invasive Species Act 1996: 1. Regulate ballast water release 2. Funding for control and eradication Preventing Invasive - environmental model can help predict where a species might spread - This area could then be closely monitored - Increase ground surveys and satellite observations Restoration Ecology - Study of historical conditions of communities before human alteration - Devise ways to return to earlier condition - Goal can be functionality - Or “pre- settlement” Ex: Tall-grass prairie

Florida Everglades

Biomes: major regional complex of similar communities - Recognized by characteristic plants - Determined by temperature and rain

Temperate Deciduous Forest...