All interactions between biotic factors that can impact an ecosystem Community Ecology All interactions between biotic factors that can impact an ecosystem

Community Ecology Basics Population: One species in a specific area Community: All biotic factors in a specific area Ecosystem: All biotic and abiotic factors in an area

Community Members Producers: organisms that produce their own food through photosynthesis or chemosynthesis Autotrophs

Community Members Consumers: Organisms that consume their food Heterotrophs, Detritivores Carnivores, Omnivores, herbivores Primary, secondary, tertiary, etc...

Can be organized into TROPHIC LEVELS Community Members Can be organized into TROPHIC LEVELS Trends of survivorship can be found in Trophic levels

BIG IDEA Community Ecology is the study of interactions between Community Members

Types of Interactions - Competition

Types of Interactions - Competition Organisms attempting to use the same resource Mates, food, territory (any need that must be filled for life) Intraspecific Competition: between same species Sexual selection Interspecific Competition: between different species Weeds vs garden plants

Types of Interactions - Competition Competitive Exclusion Principle: no two species can occupy the same niche Niche: organism’s role in an ecosystem Includes habitat, food source, behavior (the sum of all biotic and abiotic interactions of an organism)

Types of Interactions - Competition Result of Competition and CEP: Population control Extinction Behavioral shift of one species Long term evolutionary shift of one species Character Displacement If two similar species geographically overlap (sympatric populations), they will look more different than those than don’t overlap

Types of Interactions - Competition Result of Competition and CEP: Population control Extinction Behavioral shift of one species Long term evolutionary shift of one species Character Displacement If two similar species geographically overlap (sympatric populations), they will look more different than those than don’t overlap

Types of Interactions - Predation

Types of Interactions - Predation One organism hunts and eats another Population growth can be affected by predation Predator / Prey Population Density Cycles One population’s growth responds to the other

Types of Interactions - Predation Apex Predator: predator at the top of a food chain on which no other predators prey upon. Mesopredator: Mid-level predator that preys upon and is preyed upon

Types of Interactions - Predation

Types of Interactions - Predation Predation causes physical adaptations to both predator and prey due to natural selection

Types of Interactions - Predation Prey Adaptation Tend to be community oriented herd animals Physical defensive and offensive adaptations Adaptations specific to prey’s environment Eye placement Coloration Cryptic Aposematic Mimicry

Types of Interactions - Predation Prey Adaptation Cryptic Coloration: Camouflage Aposematic Coloration: indicates chemical warnings and defenses (poison)

Types of Interactions - Predation Prey Adaptation Batesian Mimicry: a harmless species look like a harmful one to avoid predation Mullerian Mimicry: two or more distasteful species, mimic each other’s warning signals Do not have to be closely related

Types of Interactions - Predation Predator Adaptation: Can be pack hunters or solo hunters Acute senses Physical Adaptations Eye placement Teeth Feet Speed Cryptic Coloration

Types of Interactions - Herbivory

Types of Interactions - Herbivory Type of predation in which autotrophs are eaten Also results in defensive adaptations due to natural selection

Types of Interactions - Herbivory Adaptive Results of Herbivory Mechanical defense such as thorns and needles Masting: producing more offspring than an animal can consume Chemical defense that can include Taste Digestive absorption Toxins Repellents

Types of Interactions - Symbiosis

Types of Interactions - Symbiosis A close and often long term interaction between two different species Mutualism Commensalism Parasitism Feeding relationships do not qualify as they are not long term

Types of Interactions - Symbiosis Mutualism: Both species benefit from relationship + / + Flowers and insects Nemo and the Anemone Result can be in increase in population

Types of Interactions - Symbiosis Commensalism: one member benefits while the other is neither helped nor harmed + / 0 Egrets and Water Buffalo Result can be an increase or stabilizing effect on one population and no effect on the other

Types of Interactions - Symbiosis Parasitism: One organism lives in or on another and harms it in order to get what it needs to live + / - Ticks and mammals Result can be a limitation of one species population

Community Interactions can shape and impact an ecosystem in both positive and negative ways. A Big Idea

Impact Through Trophic Interactions

Impact Through Trophic Interactions Dominant Species Species in a community that are the most abundant in number or biomass Biomass = the total mass of all individuals in a population

Impact Through Trophic Interactions How do species become dominant? Superior in exploiting resources Successful avoidance of predators or disease Affects community by decreasing biodiversity or providing niche for other species American Chestnut Tree

Impact Through Trophic Interactions Keystone Species Species that have a strong control over an ecosystem Not based on numbers or biomass Affects community by having large impact on other species

Impact Through Trophic Interactions Keystone Species Species that have a strong control over an ecosystem Not based on numbers or biomass Affects community by having large impact on other species

Impact Through Trophic Interactions Foundation Species Ecosystem engineers that impact trophic levels by providing habitats and niches for other species Positively affect the reproduction and survival of other species

Changing Communities by changing trophic levels Top Down and Bottom Up Models

Trophic Level Manipulation Bottom Up Model: Biomass is altered at the lower trophic levels, allowing changes to move up the food web Adding minerals to vegetation to stimulate growth Top Down Model: Biomass is altered at the top trophic levels, allowing changes to move down the food web Introducing a predator to control population of lower levels

Trophic Level Manipulation

Limits on Trophic Structure and Food Chain Length Food Chain: transfer of food energy up trophic levels from source to eventually decomposers Rarely more than 7 links Most have 5 or fewer Why?

Limits on Trophic Structure and Food Chain Length Energetic Hypothesis: Inefficiency of energy transfer along trophic levels Only 10% is transferred Producer level consisting of 100 kg of plant matter can support 10 kg of herbivore biomass This model predicts longer food chains in areas of high photosynthetic capability

Limits on Trophic Structure and Food Chain Length Dynamic Stability Hypothesis: long food chains are less stable than short ones Population fluctuations at lower trophic levels are magnified at higher levels Cause potential extinction of top predators

Limits on Trophic Structure and Food Chain Length Dynamic Stability Hypothesis: long food chains are less stable than short ones Population fluctuations at lower trophic levels are magnified at higher levels Cause potential extinction of top predators