Download Biological Communities and Species Interaction

 Biotic component
 Definitions
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Biological Communities and Species Interaction
Organism
Species
Population
Community
Populations
 All members of a single species that live together in a specific geographic range
 Range from a small pond to a continent
Communities
 All species living in a specified geographic region or all species that potentially interact with
one another in a given region
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Ecosystems
Communities of living things and their nonliving environment
Small as a field
Large as a half continent
Have varied characteristics
Variation
Change over time, evolve
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Evolution
Changes at the population level, organisms don’t evolve
Survival of the fittest—producing the most offspring
No direction
Natural selection—interplay of organisms and environmental conditions
Natural Selection
Some have adaptations that allow them to survive
Next generation will have greater frequency of those adaptations
“In tune” with the environment as it exists at the present time
Future is not known
Critical Factors and Tolerance Levels
Limits to what can be endured
“comfort zone”
Temperature
Amount moisture and form—fog vs. rain (California redwoods)
Seasonal variation—length, temp. extremes, etc.
Soil types
Range of tolerance
Used to be big thing—id limiting factors
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Tolerance
Gradient or continuum
Optimum range—species do best, most numerous
Range (or zone) of stress—can exist, but smaller population size
Range of intolerance (or zone)—species are absent
Remember—in each population, variation exists
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Tolerance
Keystone Species
Species or group of species with impacts larger than by mere abundance
Usually considered to be top predator
May be less conspicuous
Keystone Species
Fungi: recycle, mineral mobilization and absorption
Kelp: provides food, shelter, structure
Sea otter: eat shellfish, hunted, no shellfish predation
Figure 6.12a
Figure 6.12b
Foundation Species
 Play major role in shaping communities by creating or enhancing habitat that benefits other
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species
Elephants: knock over trees
Birds: distribute seed
Mosses: breakdown rock
Prairie dogs: prevent soil compaction
Environmental Indicators
 Species that are indicators of certain, relatively specific, environmental conditions
 If you see species X, then you know that:……….
 If you see alpine lotus, then you know that you are above tree level, precipitation is snow, etc.
Indicator Species
 Tied to specific biotic communities or
 Success ional stage (lodgepole pines), or
 Environmental condition
 Certain plants found only salt marshes
 Alpine plants only above tree line
Umbrella species
 Require large blocks of relatively undisturbed territory to maintain viable populations
 Consequence—other species are maintained or saved
 Caribou or other migratory animals—not isolated large areas (islands) but large areas
connected by “migratory freeways”
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People react to emotionally
“Bambi” effect
“Shamu”
Increase public awareness
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Productivity
Diversity
Complexity
Resilience
Stability
Structure
 Rate of biomass production
Flagship Species
Community Properties
Productivity
Biodiversity
 Measure of number of
 species
 niches
 genetic variation
Complexity
 Number of species at each trophic level
 Number of trophic levels in a community
 Tropical rainforests
Resilience and Stability
Tendency to remain stable and constant over time
Constancy
Inertia
Renewal
Biodiversity
 Complexity of species composition
 3 factors determine richness (or lack of it)
 Variety of species (we tend to decrease biodiversity)
 So. Cal.: problems with Caulerpa used in hobby aquaria, dumped into ocean, takes
over
 Sparrows: “Aggressive” cavity nesters
Biodiversity
 Species distribution and population size—geographic
 Development in So. Cal.: loss of wetlands and desert oases
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 Genetic variety
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(gmo): food and ornamental crops
 Habitat
Types of Interaction
 Address
 Physical surroundings
 Niche
 Mode of living and resource acquisition
 occupation
Niche
 Fundamental Niche--full range of resources that could be exploited if no competition
 Realized Niche—resources that are actually exploited
Figure 6.2a
Figure 6.2b
Ways to Exploit
 Generalists—cockroaches, opossums, humans (?)—wide range of niches
 Specialists—pandas—narrow range
 Entrepreneurs—elephants, chimps, humans (?)—learn new ways in new situations
Competition
 Seen in species (closely related) occupying niches that overlap to some degree
 Long term competition between species with same niche is rare
Competition
 Usually results in elimination of one—extinction, migration, change behavior, etc
 Problem with introduced species—alien and invasive--kudzu, tumbleweed, rats, cats
Resource Partitioning and Niche Specialization
Resource Partitioning
 Share habitat—exploit resources in slightly different ways
 Temporal
 Location
 Creosote bush in Southern California deserts
Figure 6.3
Resource Exploitation
 Predation—one freestanding organism feeding on parts or all of a second organism (prey)
 Complex relationships
 Populations are linked
 Cyclical change in abundance or decline of populations, populations held in check
Figure 6.4
Resource Exploitation
 Parasitism—type of predation
 Predator feeds on prey but does not immediately kill it
 Complex life cycles
 One host, different tissues--Dracuncula
 Different hosts at stages of life cycle—malarial parasite
Figure 6.7
Resource Exploitation
 Most efficient parasites don’t kill off
 With time, effect on predator may not be as severe
 Predator and prey develop mechanisms to “deal” with each other
 Toxins (salamanders and garter snakes)
 Coevolution
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Resource Partitioning
Culling of less capable “weaker” members of population
Adaptive “arms race”
 Promotes species diversity
 Frees up space
 Competition
Resource Exploitation
 Intraspecific—among members of same species
 Intense—same resource requirements
 Jackals fighting over carcasses
Resource Exploitation
 Seedlings and light in forests
 Production of toxins to prevent germination
 Territoriality
 Different life stage, different foods
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Immature caterpillar—eats leaves, adult butterfly sucks nectar
 Interspecific
Resource Exploitation
 Different species
 Seed production
 Avoidance
 Mimicry—avoid predation
Adaptations to
predator-prey relationships
 Batesian—one species copies the form of another to gain superior protective capability—
syrphid fly and bees
 Mullerian—several species that have protection against predators come to resemble one
another, collectively provides a “learning” experience—fewer individuals are killed
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Adaptations to
predator-prey relationships
Commensalism: interaction that does not harm either partner and may be beneficial to one,
Finding Nemo—clownfish and anemones
Mutualism-both partners benefit—fungi and roots—orchids can’t live without fungi on and in
their roots, remora and sharks
Mutualism
 Coevolution—interdependent evolution
 Extensive in flowering plants and insects
 Orchids and wasps
 Yucca and moths
 UV only landing patterns on certain flowers
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Community Properties
Primary productivity—biomass production
Abundance—total number of organisms
Diversity—measure of the different species
Many variations—dependent on all components of the area being discussed
Such as….
Community Properties
 Complexity—number of species at each trophic level and the number of tophic levels
 Connectedness—lots of trophic levels with lots of interactions within in a trophic level and
between trophic levels
 Few straight lines—a complex food web
Resilience and Stability
Some communities appear to remain stable for a long time
Constancy—lack of fluctuation
Inertia—resistance to change
Renewal—ability to repair after change
Stability
 Rule of thumb—more diverse, more resilient
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 If one species is lost, another one there
 Removal of keystone species may destroy the community—destruction of certain trees and
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removal of dead trees has decimated western bluebird
Community Properties
Edge effect—boundary between one community and its neighbor(s)
Dramatic or gradual--forest bordering prairie or grassland into sagebrush
Ecotones—boundaries between adjacent communities
Ecotones
Open community—gradual or indistinct boundaries
Closed community—sharply divided from neighbors
Edges may be shallow—grazed vs. ungrazed land or deep—forest edge with blowdown,
erosion, etc
Succession
Change in a community—water availability, soil deposition, change of plants
Primary succession—sequence that occurs on previously unoccupied land
Secondary succession—sequence occurs when existing community is altered by human
activities or natural occurrences
Primary Succession
Starting state—little or no life, exposed rock, mud, ash (Mt. St. Helens)
1-windborne plants
2-increase in biomass (stops, may reverse in time
3-longer-lived plants more prevalent than ephemerals
Primary Succession (cont’d)
4-increased species diversity
5-facilitation of growth for later species through action of preceding species—break down soil,
build up soil layers, provide habitat
6-late arriving species drive out earlier species—compete for sunlight, soil, etc
Secondary Succession
 Occurs when existing community is disrupted, natural or human activity
 Occurs when habitat is left alone following a major disturbance of original final-state
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community—woods that grow into abandoned farm fields
Climax Community
Stable end product of any process of succession
May be shifts inn some animal and plant components but grassland stay grassland
Post climax community-lodgepole pine forests appear to die off, what follows
Disclimax—adapted to cycle of destruction and regeneration—fires in Western US, Southern
California chapparal
Increasing Problems
Alien and invasive species—plant and animal
Discontinuous tracts of land