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Lecture 3

ENVR 101 Lecture Notes - Lecture 3: Trophic Cascade, Niche Differentiation, Coevolution


Department
Environmental Studies
Course Code
ENVR 101
Professor
Daniel Taylor Brantley
Lecture
3

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Competition:
o Multiple organisms seek the same resource
o Basic needs
o Intraspecific:
Competition between members of the same species
High population density: increased competition
o Interspecific:
Competition between different species
Coexistence
Usually subtle and indirect
One species can exclude another from resources
Resource partitioning:
Competing species coexist by specializing
Sharing resources
o Predation:
Interactions between predator and prey structure food webs
Also influence community competition
Less predators = more prey
Natural selection leads to evolutions that create better hunters/predators
Prey face strong selection pressures, forced to adapt to defensive measures
Parasitism
o Parasite depends on a host for nourishment or some other benefit
o Parasite harms but doesn't usually kill the host
o Coevolution:
Parasites and hosts are in an evolutionary race to defend and attack
accordingly
o Herbivores exploit plants
o Symbiosis: Both organisms benefit
Bees and pollination
Trophic cascade: High level predators effect low level prey by keeping the middle men in check
population wise
Disturbance: Any event that has a dramatic impact on an environment
Resistance: How much a community resists change and remains stable despite the disturbance
Resilience: how fast a community comes back to original state after being destroyed or altered.
Evolution
o Species
Population of group of populations whose members share characteristics and
breed with each other to create fertile offspring
o Population
Group of individuals of a species that live in the same area at the same time
Natural selection
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