Creative Community Ecology Ch 54 notes

I. Introductory Vocabulary Community group of populations in an area or habitat

II. Interspecific Interactions Relationships between the species of a community Types include: Competition -/- Predation +/- Mutualism +/+ Commensalism +/0

A. Competition Detrimental to both species Organisms compete for available resources such as food, water, shelter, sunlight

1. Competitive exclusion principle Two species so similar that they compete for the same limiting resource cannot coexist in the same place

2. Ecological niche sum total of a species’ use of biotic and abiotic resources – how an organism fits into it’s ecosystems (it’s role) two species cannot coexist in a community if they occupy the same niche

3. Resource partitioning if two species have the same niche, the less competitive one will either be driven from the area, or will evolve through natural selection to use a different set of resources

4. Character displacement The tendency for characteristics to be more divergent in sympatric (geographically overlapping) populations of two species than in allopatric (geographically separate) populations of the same two species

B. Predation beneficial to one organism but not the other one organism eats another includes herbivory (eating part of a plant), parasitism (parasite living on host)

1. Predator adaptations acute senses to locate prey many have claws, teeth, fangs, stingers, poison generally fast and agile if they have to pursue prey

2. Animal defenses against predators Passive defenses: hiding, chemical toxins Active defenses: escaping, defending themselves, warning calls

Animal defenses against predators Adaptive coloration camoflauge – cryptic coloration to blend with environment aposematic coloration – bright coloration of animals that have chemical toxins dangerous to predators Can you see me?

Animal defenses against predators Mimicry – “copycat” adaptation Batesian mimicry – harmless species mimics a harmful model (ex. larvae puffs up and resembles cobra) I’m Harmless!!!

Animal defenses against predators Mullerian mimicry two unpalatable species resemble each other predators learn more quickly about danger of the appearance

3. Parasites and Pathogens as predators host harmed in the process endoparasites – live within their host (tapeworm) ectoparasites – feed on external surface of host (mosquito) parasitoidism – insects lay eggs on living host

4. Herbivory Organism eats part of a plant or alga ex. Cattle, many invertebrates, manatee Herbivores may have adaptations such as chemical sensors to detect toxins, specialized teeth

5. Plant defenses against herbivores Chemical toxins Spines Thorns Used since plants cannot run from predator

C. Mutualism interspecific interaction that is beneficial to both species often requires coevolution of adaptations in both species if one is harmed, the other is usually harmed as well

There’s bacteria in my belly Examples of Mutualism microorganisms in digestive system of termites and ruminants (help digest cellulose) Photosynthesis by algae in tissue of coral There’s bacteria in my belly Who knew!!!

4. Commensalism interaction between species that benefits only one of the species but no harm to the other ex. algae growing on shell, birds eating insects flushed up by cows Yummy Bugs MOOOO

III. Biodiversity Species diversity in a community

Species Diversity The variety of different kinds of organisms that make up the community

Species Diversity Species Richness Relative Abundance number of species that a community can contain Relative Abundance The proportion of each species represents of all individuals in the community

Which community is more diverse???

Community 1 and 2 are equal in their species richness (both have 4 different species) Community 1 is more diverse because there is equal representation of all 4 Community 2 has a large amount of Species A Community 1 has greatest heterogeneity (looks at species number and relative abundance

IV. Trophic structures feeding relationships between organisms

A. Food Chain Transfer of food energy from it’s source in plants through herbivores to carnivores and eventually to decomposers Each link makes a trophic level Each food chain has only four or five links due to inefficient energy transfer as you move up the chain Longer food chains may not be able to recover as quickly from environmental change

B. Food Web more than one food chain hooked together

Dominant species have the highest abundance or the highest biomass exert control over occurrence and distribution of other species

Keystone species exert control on community structure by their ecological role (niche) may help to maintain diversity and balance in community ex. sea otter eats sea urchin eats algae remove sea otter (keystone) and algae population goes down add sea otter – algae population increases

Example of Keystone Species Removal experiment Robert Paine and Sea Star – Pisaster is a keystone predator of mussels With Pisaster – many species able to coexist Without Pisaster – mussels able to overtake area eliminating many other species

Foundation Species Exert influence on a community by causing physical changes in the environment ex. Beaver building a dam can transform the landscape on both sides Can be positive or negative on other species

V. Disturbances storms, fires, floods, drought, overgrazing, human activities may upset balance or equilibrium in community

Ecological succession transition in the biological species composition of a community usually following a disturbance

Primary succession succession that begins in a virtually lifeless area where soil has not yet formed (like Hawaii) Autotropic bacteria  lichens/mosses soilother plants animals

Secondary succession existing community has been cleared by a disturbance that leaves soil intact Often these areas return to something like the original state