Ecology Chapter 54 (AP Bio)
How is this different from the notion of a climax community?
A climax community is one that has only one stable equilibrium, it is controlled by the climate. A climax community is described as a superorganism in that it is many organisms working together. This is different from the non-equilibrium model because of the nature of the superorganism, they cannot be constantly changing.
What is a community? What are the key traits that characterize a biological community?
A community is a collection of populations of different species interacting in a specific area. Species diversity (both richness and relative abundance), growth, form, structure, dominant species, development history, and trophic structure.
What is a parasite?
A parasite is an organism that lives either in or on another organism and feeds off of its host, therefore benefitting from it. However, this is at the expense of the host as the parasite takes away its nutrients. +/- symbiotic interaction There are endo and ectoparasites Endoparasites are inside the body of the host whereas ectoparasites are outside the body of the host. Parasites significantly affect survival, reproduction and density of host, directly or indirectly.
Sometimes a single species that is not very common can be so important that removing it from an ecosystems causes that ecosystem to drastically change, or even collapse. Speculate on what ecological role such a species would play and how its removal could cause such big changes.
A species, even of minor importance, can play a monumental role in something like the food web. It provides food for an organism who preys on it, and in turn, that organism also provides food for an animal above it. If this minor species is removed from the ecosystem, all of the organisms above it may struggle because that one organism is the base for each species' food. Known as keystone species, or a species that is depended on by the rest of the ecosystem. The removal of this species could cause catastrophic changes to the ecosystem. It is disproportionately more important to the ecosystem than other species.
What is the difference between bottom-up and top-down model of community organizations?
Bottom up model: V-->H shows a bottom up model were vegetation will increase the number of biomass of herbivores, this means herbivores are limited by vegetation. Top down model: N<--V<--H<--P shows a top down model where nutrients (N) limit plants (P), plants limit herbivores (H) and herbivores limit predators (P). This is also known as the trophic cascade structure and it has +/- effects.
What is facilitation?
Facilitation is indirect mutualism and commensalism: both organisms can have positive effects from the survival of the other without necessarily living in the direct and intimate contact of symbiosis.
What traits make a predator a good predator? How can prey avoid predation? What are some strategies it might employ.
Good predators have acute senses that help them identify and locate good prey. Many also have claws, fangs, or poison, which help them kill their food. It also helps to be fast and agile. Prey are able to avoid being eaten by hiding, fleeing, or forming herds or schools. Some species also use alarm calls, and mechanical and chemical defenses, and mimicry. The two types of mimicry are Batesian mimicry (a harmless organism mimics a harmful organism) and Mullerian mimicry (a harmful organism mimics a harmful organism to increase its perceived population size).
What are some adaptations associated with herbivory? What are some key adaptations plants have to being preyed upon?
Herbivorous adaptations: Insects have chemical sensors on their feet that allow them to distinguish between plants based on toxicity or nutritional value Malian herbivores, such as goats, use their sense of smell to examine plants Many herbivores have specialized teeth or digestive systems for processing vegetation Plant adaptations: Chemical toxins used as a defense mechanism (e.g. nicotine from the tobacco plant) Compounds that are distasteful to many herbivores are used by plants (e.g. namon, cloves, and peppermint) Structures such as spines and thorns
What is species diversity, and what are its two components?
How many different species live in a community. It's two components are species richness and species evenness.
What are some key traits associated with being a predator or prey? Explain the following associated concepts: And if you could choose one as your superpower which one would you choose and why?
Predators have adapted certain characteristics which help them hunt their prey, and prey have some adaptations which protect themselves from their predators. Cryptic coloration/camouflage: prey can blend in with their environment, so it is more difficult for their predators to see them. Ex: Canyon tree frog Aposematic coloration: When prey are very vibrant or have warning coloring, to look intimidating and protect themselves. Ex: Poison dart frog Batesian mimicry: This is when a harmless species mimics the appearance/behavior of a harmful one, to ward off predators. Ex: non venomous hawkmoth larva Mullerian mimicry: When two unpleasant species mimic each other as a shared protective mechanism. Ex: Yellow jacket & Cuckoo bee
What is symbiosis? Define and give some examples of parasitism, mutualism, commensalism.
Symbiosis is the interaction between two different organisms living in close physical association. The interactions are classified into different categories by how they benefit and/or harm or do not affect both or either organisms. Parasitism is when one organism benefits and the other is harmed. An example is a leech sucking the blood from another animal. Mutualism is when both organisms benefit from the interaction, such as when a human milks a cow. Commensalism is when one organism benefits while the other organism is neither benefitted nor harmed. An example of such an interaction is how bull give egrets protection from by predators and food.
What are the 2 hypotheses that explain the length of food chains? Which one is better supported by the evidence?
The energetic hypothesis predicts that food chains should be longer in habitats of higher photosynthetic production because only 10% of energy stored in the organic matter of each trophic level is converted to organic matter at the next trophic level Another factor that limits food chain length may be that carnivores in a food chain tend to be larger at successive trophic levels, and therefore harder to eat The energetic hypothesis is supported by an experiment in which trees holes supplied with more leaf litter (greater food supply at the producer level) supported the longest food chains.
Describe the intermediate disturbance model of community diversity.
The intermediate disturbance hypothesis states that moderate levels of disturbance foster greater species diversity than high or low levels. High levels kill off certain organisms or prevent slow colonizing organisms from establishing in the area, thus lowering the species diversity. Low levels of disturbance allow for competitively dominant species to exclude other species, forcing them to leave or starve, which lowers species diversity. On the other hand, intermediate levels of disturbance can allow greater species diversity by opening up habitats for occupation by less competitive species. Intermediate levels of disturbance rarely create conditions too severe as they exceed the environmental tolerances or recovery rates of potential community members.
What is an ecological niche?
The sum of a species use of the biotic and abiotic resources in its environment. The place or function of a given organism within its ecosystem Aka its job
What is a trophic structure? As you explain this concept, include both food chains and food webs.
A trophic structure is a line of organisms that live in an ecosystem. At the top of the trophic structure is a top predator, and at the bottom is a primary producer. Trophic structures are also called food chains. If one combines all trophic structures in a community, a food web will be formed.
What is the relationship between a community's diversity and its resilience?
As the diversity of a community becomes greater, its resilience also increases. This is because it becomes more stable and the species use their resources in a more efficient way.
Define/describe interspecific competition. Also describe the following concepts associated with competition.
Competitive exclusion: The concept that when two similar species compete for the same limited resources, one population will use the resource more efficiently and have a reproductive advantage that will eventually lead to the elimination of the other species. Resource partitioning: The division of environmental resources by coexisting such that the niche of each species differs by one or more significant factors from the niches of all coexisting species. Character displacement: The tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species.
What is the non-equilibrium model of communities?
Describes most communities as constantly changing after disturbances such as storms, fires, floods, etc.
Imagine a forest. A huge fire sweeps through, reducing the forest to ashes. If nature is allowed to take its course, describe how you imagine what will happen in this area over the next few hundred years.
Directly after a forest fire occurs, there is a temporary loss in food and shelter. This causes animals to relocate, some might shift to cooler more moist conditions. Where, others might prefer warm, dry conditions. Depending on the vegetation type, burning can increase or improve forage for wildlife from a few years to as long as 100 years. Secondary succession will occur because the soil of the forest is still intact. The forest may eventually return to its original state.
Compare and contrast dominant species, keystone species and ecosystem engineers.
Dominant species in a community are the most abundant or have, collectively, the highest biomass In contrast with dominant species, keystone species often make up a very small portion of the total ecosystem, yet have a significant effect by exerting strong control on community structure through pivotal ecological roles. For example, without the presence of Pisaster, Muscles will monopolize the available rackspace and species diversity will plummet. Ecosystem engineers don't influence a community through trophic interactions as a dominant or keystone species do, but rather through changing their physical environment. Ecosystem engineers provide necessary resources for an ecosystem to thrive, removal of such could dramatically alter the environment. They all affect the community in unique ways.
Describe ecological succession. What is the difference between primary and secondary succession?
Ecological succession: the rebuilding/reestablishment of species in a community following a moderate disturbance, such as a glacier, volcano, or wildfire. Primary succession: ecological succession taking place in a lifeless, soil-less area due to a large disturbance. This type of succession often results in new species filling the community because the old ones have completely been removed. It generally begins with only protists and basic plants the like mosses and lichens which grow from wind-blown spores. Secondary succession: ecological succession following a disturbance that leaves the soil intact. This often allows the original species in that area to reform due to the same basic soil resources being available. Vegetation is usually able to regrow in time for herbivores to survive and keep the trophic structure somewhat sound.
What causes competition between different populations; what might be the consequences of competition?
When individuals of different species compete for limited resources that limit their growth and survival. Competition may cause some species to die off, and others to increase since some species are able to use resources more efficiently and reproduce more often. Competition may be the result of a newly added invasive species.
