Download Austin Brown Interactions Within Communities Definitions

Austin Brown
Interactions Within Communities
Definitions
Community: The population living in a given ecosystem at a given time.
Ecological Niche: Organism’s biological characteristics, and abiotic/biotic resources in
environment
Fundamental Niche: biological characteristics of organism, set of resources individuals could
use under ideal conditions.
Interspecific Competition: competition for same resource between different species.
Realized Niche: biological characteristics of the organism and resources individuals in a
population actually use under prevailing environmental conditions.
Symbiosis: interactions in which two species maintain a close relationship. (parasitism,
mutualism, and commensalism)
Interference: aggression between individuals of different species fighting over same resource.
Exploitative Competition: interspecific competition involving consumption of shared
resources. May limit access to resource of other species.
Resource Partitioning: avoidance/reduction in competition for same resources by different
species occupying different ecological niches
Mutualism: both species benefit
Commensalism: one specie benefits other is unharmed
Parasitism: one species benefits at the others expense
Obligatory Mutualism: symbiotic relationship where neither species could survive without the
other.
Microparasites: parasites that is too small to see with the naked eye
Macroparasites: parasites that is larger and readily visible
Endoparasites: parasites that live and feed inside of the host
Ectoparasites: parasites that live and feed outside of the host
Social Parasites: parasites that complete their life cycle by manipulating the hosts social
behaviour
Austin Brown
Notes
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Populations don’t live in isolation they interact in their community
Some species need each other to survive (insects pollinating flowers)
Ecological Niche
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Ecological niche includes what it eats/eats it, way it reproduces, temp. range, habitat
Interactions between same species (intraspecific)
Interactions between different species (interspecific)
These two types of interaction have important role on individuals in a community
Interaction
Competition
Predation
Symbiosis
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Parasitism
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Mutualism
Commensalism
Effect on population
Interactions can be detrimental to one or
both species.
Interaction beneficial to one species/lethal
to the other.
Interaction beneficial to one
species/harmful but not lethal to other
species.
Interaction beneficial to both species.
Interaction is beneficial to one
species/harmless to the other.
Interspecific Competition
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Competition between different species
Restricts pop. growth
2 ways actual fighting or consuming shared resources
Strongest competition between species that have niche overlap
More niches in common the bigger the competition
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1934 Russian ecologist found that the more niches two species shared the less they
coexist without driving one species to extinction. (Gause’s principle/principle of
competitive exclusion)
Compared Paramecium aurelia and Paramecium caudatum.
Species grown in separate test tubes then in the same test tube
P. aurelia drove P. caudatum to extinction in test tube.
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Interspecific relationships can take on several forms:
o Weaker population declines
o One species changes food source
Austin Brown
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o One species migrates to another habitat
Causes competition to decline
Resource partitioning works by using different areas for food
Interspecific relationships cause species to evolve to have new abilities for getting food
out of their environment
These evolutions have possibly resulted in much of the biodiversity we see today
Competition affects density/dispersion of populations
Predation
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When predator population increases prey population decreases
Higher prey population=higher predator population
Lower prey population=lower predator population
Some predator/prey populations move in a cyclical pattern where one population is
slightly out of synch with the other
Cycle is affected by changes in weather, presence of new prey, and changes in amount of
trapping by humans
Defence Mechanisms
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Predator/prey interactions drive prey to develop defence mechanisms
Examples in plants; thorns, hooks, spines, needles, and chemicals
When prey develops defence mechanisms predators develop counter-adaptations
Changes through coevolution
Passive defence mechanisms include hiding
Active defences mechanisms cost the prey more energy than passive defence
mechanisms (e.g. fleeing)
Alarm calls are also used to warn fellow prey that there is a predator
Some animals use camouflage to hide or bright colours to warn they are poisonous
(passive)
Some species mimic these abilities to help them out…
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Batesian Mimicry: harmless species resemble a harmful species so that they
can trick predators to not attack them (named after Henry Bates)
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Mullerian Mimicry: animal species that resemble each other and are all
dangerous or poisonous. This way predators learn faster not to eat things that
look like them (named after Fritz Muller).
Symbiosis
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Means “living together” (two different species live in close, usually physical contact)
Three types… Mutualism, Commensalism, Parasitism
Austin Brown
Mutualism:
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Bacteria live in guts of herbivores to help break down plant products (obligatory
mutualism)
Humans also bacteria in their intestines to make nutients
Oxpecker birds feed on back of grazing animals
Nectar and insects
Commensalism:
 Hard to classify some biologists argue existence
 Caribou uncover the ground helping arctic foxes find prey
 Remora and barnacles hitch a ride on sharks and whales to new food sources
Parasitism
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Parasites live/eat on most nutritious areas on earth bodies of living organisms
Parasites require host to live (have constant supply of nutrients)
Best known cause serious human disease (malaria, schistosomiasis, and African sleeping
disease)
Microparasites cause diseases
An example of social parasitism is the North American cowbird laying it’s eggs in other
birds’ nests
Symbiotic relationships show how different species interact in a community
Disruption of Community Equilibrium:
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Stability exists when resources are sustained, populations don’t exceed carrying capacity
Interspecific relations lead to biodiversity
Invasive species can harm environment
As human populations expand they affect animal habitats more