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BIOL 313


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Competition
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-interaction between individuals for limited resources -reduces survival, growth and fertility -(-/-) -inevitable consequence of increased population size and limited resources

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Competition
-interaction between individuals for limited resources -reduces survival, growth and fertility -(-/-) -inevitable consequence of increased population size and limited resources
Intraspecific Competition
Competition between individuals of same species
Interspecific Competition
Competition between individuals of different species
Which type of competition is most common?
Intraspecific --because similar resources, space and reproduction
What is interspecific competition important for?
1. Natural Selection 2. Fixation of adaptive traits in species 3. Phenotypic divergence of species (all above increase differences between species) 4. abundance and distribution of species
What is Interference Competition?
-direct interaction of individuals -aggressive behaviour ,defending territory, fighting after food -each individual has a negative impact on the other
Avoidance of Competition leads to...
(-/-) -Interspecific competition decreases overtime -traits in 1 or both species evolve (character displacement) -effectively decreases 2 species from competing for limited resources -harder for intraspecific competition because it would lead to speciation (need to be similar enough to mate)
What is Exploitative Competition?
(-/-) -indirect interaction -harmed by taking up resources -one individual more negatively impacted than the other, but still a cost to both
What are the 6 mechanisms of interspecific competition?
1. Consumption 2. Pre-emption 3. Over-growth 4. Chemical Interactions (Allelopathy) 5. Territoriality 6. Encounter Competition
What is Consumption?
One species inhibits another by consuming a shared resource
What is Pre-emption?
Primarily sessile organism occupies physical resource ex. barnacles
What is Over-growth?
One organism grows directly over another, with or without contact ex. plants competing for light
What are Chemical Interactions (Allelopathy)?
Chemical growth inhibitors or toxins produced to inhibit competitors growth
What is Territoriality ?
Aggressive behaviour to exclude others from units of space
What is Encounter Competition ?
Non-territorial encounters between foraging individuals ex. going for same prey
What are the differences in competition of plants and animals?
1. Biological Differences 2. Wide size variation in plants 3. Competition for same resources in plants
What are the biological differences of competition between plants and animals?
Plants are sedentary so generally a smaller scale / immediate neighbour most important
What is the Competitive Exclusion Principle?
-exclusion often occurs between related species -Gause says no 2 species can co exist "Complete Competitors Cannot Coexist"
What did Gause do/find?
**limited resources increase competitive intensity ** -alone and together -full and half resources intraspecific competition determines K -with one species both survive at half and full resources -with both species, one species goes extinct in half and full resources -one species --> lower K with half resources -both species --> extinct quicker with half resources
Why do we use models?
Models yield important predictions about conditions promoting coexistence and exclusion
Competition Coefficients ?
Alpha - effects of species 2 on growth rates of species 1 beta - effect of species 1 on growth rate of species 2 alpha and beta are not always equal to each other
If alpha/beta = 1
Species have same effect one each other
If alpha/beta =4
Effect of species 2/1 is same effect on growth rate of species 1/2 as adding 4 of species 1/2
If alpha/beta > 1
Per capita effect of interspecific competition is greater than intraspecific competition
If alpha/beta < 1
Intraspecific competition is greater than interspecific competition
If alpha/beta = 0
No competitive exclusion
State Space Graphs
Plots abundance of species 1 on x axis and species 2 on y axis
DN1/dt=
RN1(K1-N1-alphaN2/K1)
DN2/dt =
RN2(K2-N2-betaN1/K2)
When is coexistence possible?
When per capita rates of inter comp are weaker than the per capita rates of intra comp
3 factors that determine distribution?
-environments -competition -predation
What are 4 ways to see coexistence ?
1. Spatial Heterogeneity 2. Variation in Competition Ability 3. Competitive Equivalence 4. Non Equilibrium Conditions
What is Spatial Heterogeneity?
-Caused by varying resources -many resources leads to little competition and coexistence -few resources leads to strong competition and competitive exclusion
What is Variation in Competitive Ability?
-caused by genetic variation at species level and environmental conditions
What is Competitive Equivalence
When 2 species are competitively equal species A will out compete Species B and vice versa at equal rates
What does Non-Equilibrium Conditions mean?
Competitive exclusion is not instantaneous exclusion can be in progress but appears like coexistence because so slow
Predator Mediated Coexistence
Species can be equal in resources if predator keeps them both at low densities because resources will become limiting at a slower rate
2 Outcomes of Competitive Interactions?
1. Character Displacement 2. Niches
What is Character Displacement?
-evolutionary outcome that leads to competitive coexistence -characteristics continue to become more and more different until the are not the same or so far apart the don't overlap.
What are Niches?
1. needs that allow species to exist (Grinnell) 2. biological interaction and abiotic factors. "role a species plays in a community" (Elton) 3. more quantitative developed Fundamental niche and realized niche (Hutchinson)
What is the Fundamental Niche?
Physical conditions a given specie requires
What is the Realized niche?
Fundamental niche with restrictions recognizes interactions between species in presence of competitor
Predation
-(+/-) -one organism feeds on another -killing and consuming part or all of it
Prey/Victim
Organism that gets killed
Predator Prey Relationship
- # of predators is effected by # of prey (vice versa) -prey # is negatively impacted by predation -prey adapt to decrease predation
Lynx/hare cycles explanation
1. food availability 2. predation
Process of Prey Capture?
1. Encounter - in the same place? 2. Detection - see it 3. Identification - is it food 4. Approach - sneaking up 5. Subduing Prey - immobilizing/killing it 6. Consumption - eating it
Describe Encounter and how a prey can avoid it
Predators have to be physically close to prey to consume it Avoid by: go to different area enter refuge be active at different time of day/night
Describe Detection and how a prey can avoid it
Predators need to be able to detect their prey To avoid: decrease conspicuousness move unpredictably or abnormally confuse pred by being in groups ex is masting of seeds
What is masting?
Synchronous production of seeds over long intervals by a population of plants
What is identification and how can a prey avoid it
Predators need to be able to identify if the detected organism is in fact prey and is edible to Avoid: crypsis aposematism mimicry
What is crypsis?
Ability of prey to avoid detection or identification by being able to blend into the background
What is Aposematism ?
-opposite of crypsis -advertising a warning 1. synthesis of toxins that makes an organism unpalatable 2. honest advertising of toxic condition. typically via bright colors
What is mimicry?
2 forms 1. Batesian- one species is palatable (mimic) and the other is not (model) rely on previous encounters of poisonous model predator associates bad experience with color 2. Mullerian Mimicry - dangerous species all look similar (ex, bees, wasps and stinging flies) share same superficial body plan so pred only has to experience one to dislike all
Describe Approach and how a prey can avoid it
A predator needs to get close enough to the prey To Avoid; outrun predator or retreat to refuge
What is the life dinner principle?
The difference between running for your life and running for dinner prey trying to escape death predator just trying to catch a meal
Process of subduing prey and how prey can avoid it
Predator must gain control of or kill the prey To avoid: be strong enough to fight slimy/mucus covered detach a body part (autotomy)
Process of consumption and how a prey can avoid it
Can help relatives if consumption of prey allows predator to become sick. May not eat prey in future. Does not help current prey.
Herbivory?
- does not always result in death of plant -effects plant species/community -leads to counter adaptations -herbivores are primary consumers (+/-) interaction
Herbivory Can...(4 things)
1. negatively affect plant fitness OR 2. promote growth due to overcompensation (plants respond to herbivory with increased productivity) OR 3. Control the distribution of and abundance of plant species OR 4. Alter plant community structure and composition (where and which species are found)
Altering species dominance
Herbivores can preferentially feed on dominate species this alters species composition in community ex. bison--> tall grass --> increased light at ground level
Specialists
Target a few plant species ex. koala and eucalyptus
Generalist
Forage on many species ex. deer
Biological Control of Invasive Species
Herbivores used to control plants species -ex. prickly pear cactus and cactus moth not always successful: sometimes herbivores can eat anything or not have any predators itself
Predator Release
Add predator to environment that previously did not have that predator
Why is the Earth Green? Why don't herbivore eat more plants?
1. predators and parasites control plant abundance 2. plants defend against herbivory
Green World Hypothesis
Predator or Top down hypothesis We have three trophic levels 1. plants - limited by resource availability 2. Herbivores- limited by predators and parasites 3. Carnivores- food limited HYP: herbivores don't consume all plants because predators keeps their numbers in check density is controlled by predators.
Plants Fight Back! (defenses)
Bottom up effect, arms race, co adaptation Plants have defenses: 1. Mechanical - structures on plants (passion vines have cones to trap pred) 2. Biotic - animal "gaurds" (Acacia trees and ant guards) 3. Biochemical - synthesis of toxins
Symbiosis
Long term, close interaction between at least two species Mutualism(+/+)--> Commensalism (+/0)--> Parasitism (+/-)
Parasites
Spends all/part of life cycle in/on another organism, which suffers some reduction in fitness parasite typically have some extreme specialization to successfully stay on host coevolution between host and parasite
Types of Parasites
MICRO- small, short generation, reproduces with host, usually diseases (malaria) MACRO- long/large generation, does not complete life cycle in host (tick/ flatworm) ENDO- found inside hosts body ECTO- found outside hosts body
Parasite Specializations (4)
1. mechanism of attaching to host 2. withstand host's defensive response (animals-immune system, plants-chemical response) 3. contend with natural enemies 4. reproduction and dissemination difficulty (offspring right next to them)
Brood Parasitism
Female finds nest of 'host', lays eggs when host is gone, host raises offspring eggs must look similar to hosts real eggs
Host-Parasite Coevolution
Change in one may initiate change in other 1. Reciprocal Speciation : when host speciation leads to parasite speciation 2. Niche Partitioning: different parts of host body leads to speciation
Parasitoids
Similar to parasites that live in/on a host, one big difference -larvae develop in/on host -development of larvae eventually kills or consumes host -usually hymenopterans (bees/wasps)
Direct Transmission
-directly from one host to another -definitive/primary host (DH)-organism the parasite matures and reproduces in -Intermediate Host (IH) - organism required for developmental stages of parasite, allows parasite to get back to DH -parasites can also have accidental hosts
Vector Transmission
-vector usually not harmed -facilitates transfer to host ex. malaria and mosquitoes
Commensalism
Interaction between two species in which one benefits, one is unaffected hard to demonstrate that one is actually unaffected
Mutualism
Mutually beneficial interactions between members of different species also known as reciprocal exploitation or controlled parasitism benefits outweigh the costs
Facultative Mutualism
Two species provide fitness benefits to each other but the interaction is not necessary to the persistence of either specie ex. ants and aphids
Obligate Mutualism
Two species provide fitness benefits to each other and require interaction to persist ex lichen and fungus
Resource -Resource Relationships
One type of food resource traded for another nutritional mutualism (AKA) ex. legumes and nitrogen fixing bacteria
Service - Resource Relationships
Ex. pollination where nectar and pollen are traded for pollen dispersal can lead to reciprocal selection and coevolution of plant and pollinator
Zoochory
Dispersal of seeds by animals plant dispersal by animals often associated with traits that are presumably adaptive like color
Service - Service Relationships
Rare to find cases of this maybe clownfish in anemones
Exploiting of Mutualism
Exploiters gain benefits of mutualism without any costs involves cheating at low levels cheating is sustainable excessive exploitation causes mutualism to break down
What is a Community?
Assemblage of interaction species inhabiting a defined area at a given time typically consists of many species effected by competition, parasitism, herbivory, predation
Factors that influence community structure
Number of indiv. in species number of species abundance of species
Biodiversity
Diversity in genotype structure of communities, species diversity, ecosystem diversity and organization Two components 1. Species Richness 2. Species Evenness
Species Richness
Number of species found within a community hard to determine because some species are rare
Species Evenness
Relative abundance of different species within a community more even communities are more diverse opposite of dominance, a species with high evenness has low dominance
Rank Abundance Curves
Assess both species richness and evenness number of different species (r) on x axis abundance of each species on y axis
Lognormal Distribution
Few rare species, many moderate species, few abundant species (creates parabola ) found it was common across all taxon if you didn't get parabola shape then you didn't do enough sampling
Preston's Veil Line
As you sample more you will unveil more species if you sample enough Preston's line should disappear if you have a Preston's line you didn't sample enough
Distribution - Abundance Model
1. widespread species are likely to occur at high densities locally 2. species restricted in their distribution tend to be scarce
Why does the distribution - abundance relationship appear?
1. Meta-Population Approach - positive feedback between local abundance and regional distribution of species larger populations produce more offspring, increasing the chance they disperse to other locations 2. Niche Differences Among Species- density assumed to reflect species tolerance to environment condition at that location better tolerance means better range
Biological Resources
Products we harvest from nature
Ecosystem Functions
Ecological processes that control fluxes of energy, nutrients and organic matter through the environment
Ecosystem Services
Process provided by nature that support human life ex. decomposition of waster, water purification
Natural causes of Biodiversity decline
Small population size competition predation parasitism natural selection environmental stochasticity habitat loss