Terms in this set (14)
1. Be able to define communities and describe four interactions among species including both short term and long term effects
a. A community is an interacting population of different species
i. Interrelationships between species govern the flow of energy and nutrient cycling
ii. There interactions can often lead to coevolution of interacting species
b. In a community you have competition, commensalism, parasitism, mutualism, and a predator and prey relationship.
2. Explain the two contrasting concepts of communities
a. There are two different views of what a biological community is
i. Interactive approach- Communities are interactive units
1. Communities are discrete units with unique organization. A species functions are interconnected and evolve to enhance their interdependent functioning.
2. Species work together and their survival is dependent on each other. They have evolved to depend on each other.
ii. Individualistic approach- Communities are fortuitous associations of species
1. A communities adaptations and requirements produce their coexistence. The gain or loss of a species within a community is unimportant and the numerous amounts of species within the community are redundant.
3. Explain the difference between dominant and
a. Keystone species- A species that has a much greater impact on the surrounding species than its abundance would suggest
i. A sea star would be an example
4. Describe the competitive exclusion principle and
discuss how it may lead to niche, differentiation, resource partitioning and character displacement
a. The competitive exclusion principle- It is not possible for species within the same niche to coexist.
i. This was tested using Paramecium. Both species were grown in separate cultures, as they were grown in separate cultures they exhibited logistic growth. When the two species grew in the same culture together, only one species exhibited logistic growth; the other species was driven to extinction.
b. Niche differentiation-
i. Because competition has a negative outcome for both species natural selection on both species tends to avoid it. What usually will happen is an evolutionary change in traits that reduces the amount of niche overlap and the amount of competition.
ii. Niche differentiation/ resource partitioning- The change in a species resources
iii. Character displacement- The change in a species traits.
1. An example of this would be with Galapagos finches. Finches on the island have evolved different morphologies that reduces their competition.
5. What happens when one species is a better competitor than the other?
a. Asymmetric competition- When one species suffers a much greater fitness decline than the other.
b. Symmetric competition- When each species experiences a roughly equal decrease in fitness.
c. If asymmetric competition occurs and the two species have completely overlapping niches, the stronger competitor is likely to drive the weaker competitor to extinction.
6. Explain the difference between fundamental and realized niches and be able to determine using experimental data
i. Fundamental niche- the resources a species uses or conditions it tolerates in the absence of competitors
ii. Realized niche- the resources a species uses or conditions it tolerates when competition occurs
iii. If asymmetric competition occurs and the niches of the two species do not overlap completely the weaker competitor will move from its fundamental niche to a realized niche, ceding some resources to the stronger competitor
7. What is consumption?
a. Consumption is a +/- interaction that occurs when one organism eats another. There are three major types of consumption:
i. Herbivory- The consumption of plant tissues by herbivores
ii. Parasitism- The consumption of small amounts of tissues from another organism, or host, by a parasite.
iii. Predation- The killing and consumption of most or all of another individual (the prey) by the predator.
8. What are consecutive defenses?
a. We know that natural selection favors traits that allow individuals to avoid being eaten. Consecutive defenses are defenses that are always present and include:
i. Avoidance- hiding, with or without camouflage, or running, flying or swimming away
ii. Poison- Many plants lace their tissues with compounds that are toxic to consumers
iii. Schooling and flocking behaviors that confuse predators
iv. Fighting back, with the use of weaponry or toxins
9. What is mimicry and what are the two forms?
a. Mimicry- A consecutive defense that closely resembles another species
b. Mullerian- Resemblance of two harmful prey species (harmful and is harmful)
c. Batesian- Resemblance of an innocuous prey species to a dangerous prey species (Not harmful but looks harmful)
10. What are inducible defenses?
a. Defensive traits produced only in response to the presence of a predator.
i. They are more efficient energetically, but they are slow and take time to be produced.
ii. Example: Mussels have thicker shells and attach more strongly to a substrate only in the presence of crabs.
11. What is mutualism?
a. This is a +/+ interaction that involves a wide variety of organisms and rewards a few examples would be:
i. Flowering plants and their pollinators
ii. Farmers ants and fungi
iii. Cleaner shrimp and fish
12. What is the role of Natural Selection in Mutualism?
a. The benefits received in a mutualism relationship are byproduct of each individual pursuing its own self-interest by maximizing its ability to survive and reproduce
13. What is succession and what are the two types?
a. Succession- the recovery, the development of communities, that follows a severe disturbance
b. Primary succession- occurs when a disturbance removes the soil and its organisms, as well as organisms that love above the surface
c. Secondary succession- occurs when a disturbance removes some or all of the organisms from an area but leaves the soil intact
14. What are the Global patterns in species richness?
a. High Productivity Hypothesis: There is a high productivity in the tropics, there is an increase in speciation rates and this reduces extinction rates. Due to the climate there is a high plant biomass that supports more herbivores, predators, ect. High population sizes promote evolution of niche specialization.
b. The area and age hypothesis:
i. Age- Repeated glaciations in temperate and artic latitudes
1. The tropics have been more stable over evolutionary time scales
ii. Area- Species area relationship- tropics have had larger land mass historically. They have more time and more space for speciation.
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