Exam 1 Chapter 4
What is a trophic cascade?
A change at the top of the trophic level can trigger a series of events going all the way down the trophic "ladder" Predators at high trophic levels can indirectly promote pops of organisms at low trophic levels by keeping species at intermediate trophic levels in check, a phenomenon ecologists refer to as a TROPHIC CASCADE.
what is biome?
A major regional complex of similar communities - a large-scale ecological unit recognized primarily by its dominant plant type and vegetation structure. Climatograph indicates "moist" conditions (green) as well as "dry" (yellow, when temp curve is above precipitaion curve.. Mean monthly TEMPERATURE and mean monthly PRECIPITATION from Jan to Dec in a year - determines different biomes.
What is a food web?
As energy is transferred from lower trophic levels to higher trophic levels, it is said to pass up a FOOD CHAIN ( a linear series of feeding relationships) EXAMPLE: Plant, grasshopper, rodent, and hawk make up a food chain. Thinking in terms of food chains is conceptually useful, but ecologic systems are far more complex than simple linear chains. A more accurate representation of the feeding relationships is a community is a FOOD WEB: a visual map of energy flow that uses arrows to show the many paths along which energy passes as organisms consume one another.
What is the purpose of the field of restoration ecology?
Attempting to restore the natural way of things. May need to find out the way things were before we tore everything down and mader the environment unrecognizable. Preserving certain areas, protecting from harm, reintroducing native flora and fauna Invasive species are adding to the transformations that people have forced on ecological systems through habitat alteration, deforestation, pollution, overharvesting, and climate change. Because ecological systems support our civilization and all of life, when degraded system cease to function, our health and well-being are threatened. This realization has given rise to the science of RESTORATION ECOLOGY. Rest ecologists research the historical conditions of ecological communities as they existed before our industrialized civilization altered them. Devise ways to restore altered areas to an earlier condition - intent primarily to restore the functionality of the system. Restoration often involves the removal of invasive species and planting native vegetation that had originally grown on site. (removing an invasive Burmese Python from the florida everglades)
What is coevolution and what role does it play in a community?
COEVOLUTION - hosts and parasites may become locked in a duel of escalating adaptations, known as a evolutionary arms race. Hosts and parasites repeatedly evolve new responses to each other's latest advance. In the long run though, it may not be in a parasite's best interest to do its host too much harm. In many cases, a parasite may leave more offspring by allowing its host to live longer.
How does a realized niche differ from a fundamental niche?
Coexisting species that use the same resources tend to adjust to their competitors to minimize competition with them. Individuals may do this by changing their behavior to use only a portion of the total array of resources they are capable of using. In such cases, individuals do not fulfill their entire niche. A species' niche reflects its functional role in a community, including resource use, habitat use, food consumption, and other attributes (it is kind of a multidimensional summary of everything an organism does). The full niche of a species is called its FUNDAMENTAL NICHE. An individual that plays only part of its role because of competition or another type of species interaction is said to display a REALIZED NICHE - the portion of its fundamental niche that is actually "realized" or fulfilled. EXAMPLE: the quagga mussel can occupy a wider range of water conditions and substrates than the zebra mussel, so it is thought to have a larger fundamental niche. The quagga mussel also appears to be reducing the zebra mussel's realized niche, as it displaces the zebra mussel in many areas.
How does inter-specific competition differ from intra-specific competition?
Competitive interactions can take place between members of the same species (INTRAspecific competition) or between members of different species (INTERspecific competition). Intraspecific comp is pop-level phenomena. Interspecific comp affects communities. If individuals of the same species are competing for limited resources, then competition become more intense when there are more individuals per unit area (denser pops). This is density dependence and it can limit the growth of a population.
Be familiar with the different biomes on the planet. You will not be tested on the details of these biomes.
From coldest to hottest in mean annual temperature: and low to high precip. Left to right Tundra (ARCTIC/ALPINE) Boreal forest (COLD TEMPERATE) Desert (cool), Temperate grassland, chaparral, temperate deciduous forest, temperate rainforest (WARM TEMPERATE) Desert (hot), Savana, Tropical dry forest, tropical rainforest (TROPICAL)
Describe the phenomenon of competitive exclusion
In interspecific competition, if one species is a very effective competitor, it may exclude other species from resource use entirely. This outcome, called COMPETITIVE EXCLUSION, occurred in parts of the Great Lakes as zebra mussels displaced native mussels - and it is happening now where quagga mussels are displacing zebra mussels. IF NO SINGLE COMPETITOR FULLY EXCLUDES OTHERS, the species may continue to live side by side. This result is called SPECIES COEXISTENCE
What is the importance of Parasitism in a community?
PARASITISM is a relationship in which one organism, the parasite, depends on another, the host, for nourishment or some other benefit while doing the host harm. Parasitism usually does not result in an organisms's immediate death. Example: tapeworms Parasites that cause disease in their hosts are called PATHOGENS - protists that cause malaria and amoebic dysentery, the bacteria that cause pneumonia and tuberculosis, and the viruses that cause hepatitis and AIDS.
Describe primary and secondary succession.
PRIMARY SUCCESSION follows a disturbance so severe that no vegetation or soil life remains from the community that had occupied that site. In primary succession, a community is essentially built from scratch. SECONDARY SUCCESSION begins when a disturbance dramatically alters an existing community but does not destroy all life and organic matter in the soil. Vestiges of the previous community remain, and these building blocks help shape the process.
Briefly describe the role of producers, consumers and detritivores/decomposers in a food web
PRODUCERS - autotrophs use photosynthesis or chemosynthesis to produce their own foods - glucose. CONSUMERS - primary consumers (herbivorous grazing animals such as deer and grasshoppers), secondary consumers (prey on primary consumers - rodents an birds that prey on grasshoppers, wolves that prey on deer), tertiary consumers (hawks and owls that eat rodents that have eaten grasshoppers) DETRITIVORES AND DECOMPOSERS - consume nonliving organic matter. DETRIT - millipedes, soil insects, scavenge the waste products or dead bodies of other community members. DECOMP - fungi and bacteria break down leaf litter and other nonliving matter into simpler constituents that can be taken up and used by plants. These organisms enhance the topmost soil layers and play essential roles as the community's recyclers, making nutrients from organic matter available for reuse by living members of the community.
What is the importance of predation in a community?
Predation is the process by which individuals of one species - the predator - hunt, capture, kill and consume individuals of another species - the prey. Interactions among predators an prey structure the food webs and help shape community composition by influencing the relative numbers of predators and prey. Predation can sometimes drive population dynamics. Increased pop of prey creates more food for predators, which may survive and reproduce more effectively as a result. As predator pop rises, intensified predation drives down the pop of prey. Diminished # of prey in turn causes some predator to starve, and the predator pop declines. This allows the prey pop to rise again, starting the cycle anew. Predation also has EVOLUTIONARY RAMIFICATIONS: individual predators that are more adept at capturing prey may live longer lives, reporduce more, and be better providrrs for their offspring. Natural selection leads to the evolution of adaptations that enhance hunting skills. Prey face an even stronger selective pressure - the risk of immediate death. Result: predation pressure has driven the evolution of an elaborate array of defenses against being eaten.
How does primary and secondary succession in a community differ from each other? How are they similar?
Primary starts from scratch and secondary already starts with some organic matter or life in soil. Both processes lead to a CLIMAX community - which remains in place until some disturbance restarts succession.
Use the example of sea otters to in detail describe the importance of key stone predators.
Sea otters are a keystone species. Sea otters consume sea urchins that eat kelp in coastal waters of the pacific. Otters keep urchin numbers down, allowing lush underwater forests of kelp to grow, providing habitat for many species. When otters are absent, urchins increase and devour the kelp, destroying habitat and depressing species diversity.
What is the importance of resource partitioning as one studies competition in ecology?
Species experience similar adjustments (fundamental and realized niches) over evolutionary time. Over many genrations, the process of natural selection may respond to competition by favoring individuals that use slightly different resources or that use shared resources in different ways. For example, if 2 bird species eat the same type of seeds, natural selection might drive one species to specialize in eating larger seeds and the other to specialize in eating smaller seeds. Or one bird might become more active in the morning and the other more active in the evening, minimizing interference. This process is called RESOURCE PARTITIONING because the species partition, or divide, the resources they use in common by specializing in different ways. This can leas to character displacement: competing species come to converge in their physical characteristics because of the evolution of traits best suited to the range of resources they use . For birds that specialize on larger seeds, natural selection may favor the evolution of larger bills that enable them to make the best use of this resource. COMPETITIVE interactions - each participant exerts a negative effect on other participants, because each takes resources the other could have used. In other types of interactions, some participants benefit while others are harmed; one species exploits the other. (include PREDATION, PARASITISM, HERBIVORY
do biomass, numbers of individuals and the energy present in a system vary between trophic levels in a food chain?
The lower trophic level of primary producers typically has the highest biomass, number of individuals, and energy present. The higher you go up through the trophic levels, the less energy, biomass and # of individuals you get. This really makes sense when you think about it, as there must be A LOT of plants to feed the less numerous grasshoppers, and grasshoppers to feed the less numerous rodents, and rodents to feed the still less numerous hawks. . . Low trophic level: High trophic level = 10:1 ratio typically
Define the field of community ecology.
The scientific study of species interactions and the dynamics of communities. Community ecologists study which species coexist, how they interact, bow communities change through time, and why these patterns occur.
What is a keystone species? What is the importance of key stone species in a community?
Usually a predator (often secondary or tertiary consumers near the top of food chains) - if you remove a keystone species from the community, there can be a harmful trophic cascade (wolf in yosemite example). Keystone species are responsible for keeping a healthy level of biodiversity. Top predators control populations of herbivores, which otherwise would multiply and greatly modify the plant community.
What is competition?
When organisms seek the same limited resource, their relationship is said to be one of competition. Competing organisms do not usually fight with one another directly and physically, as the term might imply. More subtle and indirect, taking place as organisms wie with one another to procure resources. Such resources: food, water, space, shelter, mates, sunlight. . .more
What is a pioneer species?
first species to populate an area during succession Pioneer species are well adapted for colonization, having traits such as spores or seeds that can travel long distances. In primary succession pioneers: liches, then grasses, small herbs and forbs, then shrubs In secondary succession pioneers: NO lichens, starts with grasses, small herbs, and forbs, then shrubs