Species Interactions Community Ecology
Ecology
The study of:
the distribution and abundance of organisms,
the interactions among them,
and the interactions between organisms and their abiotic environments
Levels :
Biosphere - sum of total living things on earth
Ecosystem - living and non living - interaction between them
Community - different type same area
Population - same type same area
Organismal - individual living
Species Interaction
Natural species interactions:
Competition = relationship in which both species are harmed
Exploitative = one species benefits and the other is harmed
Predation, herbivory
parasitism - rarely kill their host but predators do
Symbiosis - one participant is benefited and the other may be benefited, harmed or unaffected
Commensalism= relationship in which one member benefits and the other is not helped or harmed
- Mutualism = relationship in which both species benefit
Parasitism- one is benifited and the other is harmed
Competition can occur when resources are limited - In competition, multiple organisms seek the same limited resources and all competitors suffer (/ interaction)
Food, space, water, shelter, mates, sunlight
Intraspecific competition **= occurs between members of the same** species
High population density leads to increased competition
Interspecific competition = occurs between members of two or more species Strongly affects community composition Leads to competitive exclusion or species coexistence
Competition can occur when resources are limited
Competitive exclusion = one species completely excludes another species from using a resource - Zebra mussels displaced native mussels in the Great Lakes
Species coexistence = neither species fully excludes the other from resources, so both live side by side - This produces a stable point of equilibrium, with stable population sizes - Species minimize competition by using only a part of the available resource (niche)
Niche 
Fundamental niche = the full niche of a species (what they would occupy if there were no interspecies competition)
Realized niche = the portion of the fundamental niche that is actually filled Due to competition or other species’ interactions
Resource partitioning = process by which species use different resources or use shared resources in different ways
Character displacement = competing species diverge in their physical characteristics due to the evolution of traits best suited to the resources they use- Results from resource partitioning , Birds that eat larger seeds evolve larger bills, Birds that eat smaller seeds evolve smaller bills. Competition is reduced when two species become more different
What Happens with Extreme Character Displacement?
Sympatric Speciation: one ancestral population splits and exploits resources differently until they become so different they can’t reproduce with each other anymore
Energy passes among trophic levels - who eats whom
Trophic level = rank in the feeding hierarchy
Producers (autotrophs) - Producers, or autotrophs (“self-feeders”) = organisms that capture solar energy for photosynthesis to produce sugars
Has the largest Biomass
Consumers
Detritivores and decomposers : Organisms that consume nonliving organic matter enrich soils and/or recycle nutrients found in dead organisms
Primary consumers Herbivores = second trophic level, Organisms that consume producers, Herbivores consume plants, Deer, grasshoppers
Tertiary consumers Predators = fourth trophic level , Predators at the highest trophic level , Consume secondary consumers, Are also carnivores ,Hawks, owls
Omnivores = consumers that eat both producers (plants) and consumers (animals)
Secondary consumers Carnivores = third trophic level, Organisms that prey on primary consumers, Carnivores consume meat, Wolves, rodents (that eat insects)
Detritivores = scavenge waste products or dead bodies ,Millipedes, soil insects
Decomposers = break down leaf litter and other nonliving material into simpler chemicals that can be used by plants , Fungi, bacteria , Enhance topsoil and recycle nutrients
Food chain = a linear series of feeding relationships
Food web = a visual map of feeding relationships and energy flow
Includes many different organisms at all various levels
Greatly simplified; leaves out most species
Contains many food chains
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Community dynamics are complex - Species interactions differ in strength
Keystone species Usually Large Bodied, higer lever consumers = a species that has a strong or wide-reaching impact far out of proportion to its abundance
- Removal of a keystone species has substantial ripple effects - Significantly alters the food web
Trophic cascade = a phenomenon in which predators at high trophic levels indirectly affect populations at low trophic levels
Ex- Extermination of wolves led to increased deer populations, which overgrazed vegetation and changed forest structure
Disturbance = event that causes rapid changes in the environment that alters the community or ecosystem
Tree falling, opening space in a forest
Removal of keystone species, spread of invasive species
Natural disturbances like tornadoes, hurricanes
Human impacts cause major community changes
Communities have different ways of maintaining themselves when disturbed
Resistance = when a community of organisms resists change and remains stable despite the disturbance
Resilience = when a community changes in response to a disturbance, but later returns to its original state
A disturbed community may never return to its original state
Succession follows severe disturbance
Succession = the predictable series of changes in a community following a disturbance
Primary succession = disturbance removes all vegetation and soil life. - Community is built from scratch / Glaciers, drying lakes, volcanic lava
Pioneer species = the first species to arrive in a primary succession area (e.g., lichens, mosses)
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Secondary succession = a disturbance dramatically alters, but does not destroy, all local organisms - The remaining organisms and soil form “building blocks” that help shape the process of succession. Fires, hurricanes, farming, logging
Climax community = community that remains in place with few changes until another disturbance restarts succession
Introduced Species vs Invasive Species
10,000 kcal of producer could support approximately 10 kcal of tertiary consumer.
What moves through the community from one trophic level to another as organisms feed on one another? Matter and Energy- Matter is continuously recycled while energy is captured from the sun by plants and progressively lost at higher trophic levels.
Tundra- This cold, dry biome is populated by lichens and shrubs that can survive great seasonal variations in sunlight and temperature
Savanah- In this hot, dry biome, populations of zebras, gazelles, and giraffes are concentrated around widely spaced watering holes
Temperate Grassland- Also called steppe or prairie, this biome has been extensively developed for agricultural use due to its nutrient-rich soils
Tropical Rainforest- Despite having lush vegetation and diverse biological communities, the soil in this biome has low nutrient content and cannot support long-term agriculture.
Desert- This is the driest biome, where many plants have water-conserving features such as thick leaves and needles.
Temperate Deciduous Forest- This biome is characterized by broad-leaved trees that lose their leaves each fall and remain dormant during winter