15.1 Notes

Ozark Forest vs Tropical Forest
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Terms in this set (49)
Ozark Forest vs Tropical Forest
-Ozark Forest: 50-60 species of woody plants.
-Tropical Forest: 500-600 species of woody plants.
Biological Community
Consists of all the populations of interacting species living within a defined area. Interactions may be within or between trophic levels.
2 Main Outcomes of Species Interactions
1. They influence the distribution and abundance of the interacting species.

2. They are agents of natural selection which therefore influence the fitness of individuals within populations of species within the community.
4 Main Types of Species Interactions
Species A Species B

1. Commensalism + 0
2. Competition - -
3. Consumption + -
4. Mutualism + +
Commensalism (+/0 interaction)
One species benefits and the other is neither harmed nor helped. Commensalism is challenging to demonstrate likely because it is hard to demonstrate an absence of effect on fitness.
Commensalism (+/0 interaction) Example:
Epiphytes and their hostess trees: Epiphytes benefit from being held up by the host plant. The host plant does not suffer any harm from the epiphyte.

However, if too many epiphytes live in a tree, the interaction becomes competitive: The tree and epiphytes fight for access to sunlight.
Commensalism
A type of relationship between two living organisms in which one organisms benefits from the other without harming it.

Ex: 1. Tree frogs use plants as protection , 2. Golden jackals, once they have been expelled from a pack, will trail a tiger to feed on the remains of its kills.
Competition is -/- interaction
The Act of competing uses resources, so those resources are not available for foraging, mating, or other activities to increase fitness. Some individuals lose more than others.
Intraspecific competition
Competition among members of the same species. Leads to drought due to higher competition.
Interspecific competition
Competition between members of different species.
ResourceA substance or factor that an organism consumes or occupies, and that leads to increased population growth.Limiting ResourceWhen a resource, or combination of resources, leads to competition.Because infraspecific completion for resources intensifies as a population's densityIt is a major cause of density-dependent growth.Poor competitorsOften are unable to effectively acquire and retain nutrients versus others in the food. Sometimes driven to extinction. Carrying Capacity of P.Aureola alone is higher alone, leading to higher survivorship - making them better to be alone.The Ecological Niche ConceptExplains how so many species can coexist. The range of resources that a species can use and the range of conditions it can tolerate.Specialist Species-Narrow Niche. -Less Adaptable because of specialized need. -More likely to become extinct. -Use a specific set of resources. -Easily affected by changing conditions. -Have an Advantage when conditions are more constant.Generalist Species-Broad Niche. -Adaptable to many environments. -Less likely to become extinct. -Use a variety of resources. -High range of tolerance. -Have an Advantage when conditions change.Niche OverlapWhen generalist and specialist species overlap. Leads to Competition, where number of seeds consumed different based on the seed size. Ex: Low number of seeds consumed at small size and Large size, but largest number of seeds consumed at middle size seed. This leads to competition for intermediate size seeds.2 Outcomes of Competition1. Coexistence via symmetric competition (if fitness costs are equal for each competitor and competitive overlap is low). Causes the probability of coexistence to decrease as the competition overlap approaches 1. 2. Competitive exclusion via asymmetric competition. Meaning that the carrying capacity of one is greater than species alone is greater than another species.Fundamental NicheThe total theoretical range of environmental conditions that a species can tolerate. Unshaded left side of weak competitor.Realized NicheThe portion of the fundamental niche that a species actually occupies, given limiting factors such as competition with other resources. Shaded right side of weak competitor. The weak competitor cannot occupy all of its potential niche space.Niche differentiation/resource partitioningEvolutionary change in resource use caused by competition over generations. In Niche Differentiation, Natural Selection selects against individuals that compete, causing the two species to no longer overlap in the number of individuals using resources —> Making them separate.Character displacementTendency of characteristics to be more divergent in sympatric populations than allopatric populations.Consumption / Predation is +/- interactionOccurs when one organism eats another. -3 Types of Consumption: 1. Herbivory 2. Predation 3. Parasitism1. HerbivoryThe consumption of plant or algal tissues by herbivores.2. PredationThe killing and consumption of most or all of another individual (the prey) by a predator. Often refers to carnivores, but can also refer to herbivores.3. ParasitismThe consumption of small amounts of tissues from another organism, or host, by a parasite.Evolutionary Arms RaceCoevolution can occur in competitive relationships.Predation and PopulationThe hare-lynx populations cycle every 10 years, on average, changes in lynx density lag behind changes in hare density. More hares per km^2 than lynx 100 per km^2.Constitutive or Standing Defenses are Defenses that are always present and include:-Cryptic Coloration and Object Resemblance. -Escape Behavior. -Toxins and other chemicals. -Schooling and flocking. -Defense armor and weapons. -MimicryConstitutive or Standing Defenses are Defenses that are always present and include Mimicry - Two Types of Mimicry:1. Batesian Mimicry 2. Mullerian Mimicry1. Bastesian MimicryWhen nontoxic prey species resemble dangerous prey species. The mimic benefits from the unpalatable species. Look Dangerous, are not dangerous.2. Mulleran MimicryWhen two harmful prey species resemble each other. Both species benefit. Look Dangerous, are dangerous.Inducible DefensesAre efficient energetically, but they are slow - it takes time to produce them. Many prey species have inducible defenses - physical, chemical, or behavioral traits produced in response to the presence of a predator. -Ex: Hyper-sensitive response and systematic acquired resistance.Constitutive DefensesCan be effective, but they require a lot of energy and resources to produce and maintain. -Ex: Mussels develop thick shells when crabs are present.Mutualism (+/+ interaction)Interaction that benefits both species. Needs 2 players. -Ex: Pollination by Animals - The hummingbird gets a meal of nectar, the plant gets to sexually reproduce. -Ex: Seed dispersal by animals.The Empty ForestMany large animals are already ecologically extinct in vast areas of neotropical forest where vegetation still appears intact.A species _______niche compromises the full range of climate conditions and food resources that permit the individuals in a species to live.Fundamental.Epiphytic orchids grow harmlessly on their host trees, and derive their resources from the air and from rain, rather than from their host plant. Which of the following is the best description of this species interaction?Commensalism.What is the term used to describe the process of 2 species going from overlapping and having low fitness at the overlap point to being separated completely?Niche Differentiation.In general, a species' ______ niche will be smaller than its _______ niche due to interactions with other organisms in the community.Realized, Fundamental.Measuring its costs and benefits in terms of energy spent and/or gained, competition among individuals:Results in a loss for both individuals.Overlap of niches can be minimized through:Resource partitioning.Some birds follow moving swarms of army ants in the tropics. As the ants march along the forest floor hunting insects and small vertebrates, birds follow and pick off any insects or small vertebrates that fly or jump out of the way of the ants. This situation is an example of what kind of species interaction between the birds and the ants?Commensalism.Which factors contribute most to infraspecific competition?A species rate of reproduction and the carrying capacity of the environment.Which of the following is true of species interactions?They can act as agents of natural selection.Which of the following statements is consistent with the principle of competitive exclusion?Even a slight reproductive advantage will eventually lead to the elimination of the less well adapted of two competing species.Competitive Exclusion Principle states thatIt is not possible for two species with the same niche to coexist in the same region.Density Dependent Fecundity is a result of which type of interaction?Competition.