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Across 6. The process by which one species "wins" a competitive interaction by driving the other species to extinction. This can occur in either a local or a general sense. Humans are competitively excluding many species currently on the endangered species list. Nice job, us. 7. An organism that feeds on and breaks down dead or decaying matter in the process of ecological decomposition. Examples of decomposers include fungi, like mushrooms and molds; worms, like earthworms and some nematodes; and some bacteria. Decomposers are also called saprotrophs, meaning "putrid eaters." 8. The process by which some substances increase in concentration in a food chain or food web. Biomagnification occurs because certain substances, including some pesticides and heavy metals, are not easily degraded and can accumulate in organisms’ tissues or internal organs. Pregnant women are advised not to eat certain kinds of fish because of the potential for biomagnification of mercury, a heavy metal, in aquatic systems. No, you cannot use biomagnification to light ants on fire. 12. A reproductive strategy where an organism reproduces multiple times throughout its life but only produces a small number of offspring (usually just one) per reproductive event. Humans and other large mammals are iteroparous, except for mutant celebrities like the Octomom. 15. An organism on, or in, which a parasite lives or feeds. For example, dogs are known to be good hosts for fleas. Frontline Plus: it does wonders. 16. A species in a community that has an effect on the community larger than one would expect based on the population size of that species. If a keystone species were to go extinct in a given environment, such extinction might lead to drastic consequences for a large number of other species in that environment. 17. The buildup of nitrogen and phosphorous in an aquatic environment. Eutrophication usually leads to an exponential growth in bacteria and algae. These organisms quickly use all the available oxygen, which kills off all other species in the environment. Sucks to be them. 18. A symbiotic (read: long-term and partly beneficial) relationship between organisms, where one organism benefits from the relationship, and the other receives no harm or benefit. A common example is the clown fish, or anemonefish, and the sea anemone (think Finding Nemo), where the fish receives protection and other services from the anemone, but the anemone receives no measurable benefit from the fish. Sounds inappropriate. 22. Detritivore 23. A simple, direct, and trophic, or eating, relationship among a group of organisms, where one organism, like a plant, is the food source for the next organism, like a cow, which in turn is the food source for the next organism, like a human, and so on and so forth. 24. Any living organism that makes its own food by converting simple inorganic molecules into complex organic compounds like carbohydrates, fats, and proteins. Autotrophs are often the "producers" in a food chain or web. Photoautotrophs use energy from light to make food, while chemoautotrophs obtain their energy from chemical reactions. 26. An organism that cannot convert sunlight or chemicals into "food" (and by food, we mean carbohydrates). Heterotrophs must obtain their nutrients by consuming other organisms. All animals, all fungi, and some kinds of bacteria are heterotrophs. This means that all carnivores, herbivores, and omnivores are also heterotrophs. And yes, you're a member of that not-so-exclusive club, too. 29. An interaction where individuals of different species—interspecific competition—or the same species—intraspecific competition—vie for limited resources. Examples of interspecific competition include trees of different species vying for limited sunlight in a rainforest, birds of different species vying for limited prey in a prairie, and even bacteria of different species vying for limited oxygen in your large intestine. Examples of intraspecific competition include lions vying for limited antelope in the Savannah; piglets vying for limited milk from their sow, or mom-pig; and even humans vying for limited space to build a home. Move it or lose it, buddy. 30. A symbiotic (read: long-term and partly beneficial) relationship where both organisms benefit. A common example of mutualism is the relationship between pollinators, like honeybees, moths, or hummingbirds, and the plants they pollinate. In this situation, the pollinator receives the benefit of nutrition in the form of nectar, and the plant receives the benefit of having its pollen, equivalent to sperm, spread to other plants, increasing the probability of reproductive success. Honeybees are so cute; who knew that their real jobs were sperm-spreading? 31. See primary consumer, secondary consumer, and tertiary consumer below. That's right—nothing to see here. Move along. 32. A term describing all the living and nonliving things in a certain location. Ecosystem studies in ecology explore the interactions between organisms, like individuals, populations, or communities, and the abiotic components in the environment, like chemicals, landscapes, and the like. 33. A complex trophic relationship among a group of organisms, consisting of interactions among multiple food chains (see definition above). A food web describes how multiple producers and consumers directly or indirectly interact in an ecosystem.

Down 1. An increase in population size at a rate proportional to the size of the population. During exponential growth, the rate of growth constantly increases. That is, the larger the population, the faster it grows. Exponential growth will only occur when density-dependent factors (see definition) are either nonexistent or not in force. A good example of exponential growth is in certain types of bacteria, where the population doubles with every generation as long as there are enough resources, like nutrients and space. 2. A species that arrives early in the ecological succession of an environment. A little bit like the first Vikings to reach North America, except without the longboats and fuzzy hats. Colonizer species are usually able to disperse offspring quickly and over long distances, allowing more of their ilk to arrive before members of other species. However, colonizers do not often compete well with other species once a community begins to mature, and are often replaced by more stable persister species. Colonizer species are also sometimes called pioneer species. Davy Crockett-style. 3. A restriction on the growth of a population not related to or affected by the density, or number of organisms in a given space, of that population. Examples of density-independent factors in human populations include major natural disasters like earthquakes or tsunamis, where the effect on the population, or proportion of individuals killed, is not intensified by an increase in the size of the population. 4. A community of plants and animals that is considered stable, or at equilibrium, because the members of that community are the best adapted for the average conditions in their environment. The climax community is so named because it is considered the final and most stable condition in the process of ecological succession. 5. The evolution of one species in relation or response to the evolution of another closely interacting species or set of species. Examples of coevolution include the interactions of hosts and parasites, like bird lice and birds, and obligate mutualists, like bees and the flowers they pollinate. The human species has most certainly coevolved with several different species of bacteria living in the colon and other areas of the digestive system. Mmm, yummy. 9. A type of population growth characterized by initial exponential growth, with a gradual slowing in growth rate as the population nears its carrying capacity (see definition). Since biologists don’t know of any populations that grow exponentially forever, logistic growth is thought to be the most common pattern of growth in the world. 10. A chart for a species that shows, for each age, the probability that an organism will live to the next year. The period does not necessarily need to be a year, and can be any relevant generational time period. Life tables also usually include information on reproductive probabilities and other life history characteristics. Life insurance companies use massive life tables to compute insurance rates. Again, buckets of fun. 11. A characteristic of a population describing the change in the size of the population over time. In its simplest form, a growth rate is calculated as the birth rate minus the death rate of a population. It can also be thought of in terms of the following equation: the growth rate (r) equals the population size at the end of a period of time (Nt+1) minus the population size at the beginning of a period of time (Nt), all divided by the population size at the beginning of a period of time (Nt). In symbols, the equation looks like this: 13. The maximum number of individuals in a single population that a given environment can sustain at a given time. The carrying capacity for a population can change when fluctuations occur in resources, like increases in nutrients or water; habitat structure, like deforestation; biotic interactions, like the introduction of a new predator or competitor into the environment; and other local factors. The carrying capacity is a characteristic of a single population of a single species at a single time in a single place. Therefore, it is a difficult concept to measure or even fully understand. The carrying capacity of the human population is an extremely important, yet controversial, topic in ecology. 14. A triangularly shaped drawing showing how energy from the Sun moves through the biological components of an ecosystem. Producers, like plants and algae, are at the bottom of the pyramid, and tertiary consumers, like carnivores that eat carnivores, and detritivores, or decomposers, are at the top. 17. The study of interactions between organisms and their environments. Ecology includes the study of individuals, populations, communities, and ecosystems. 19. A description of a species’ vital statistics, including age at first reproduction, survival probabilities, reproduction probabilities, clutch or litter size, reproductive strategy, and longevity. Life insurance companies rely on life histories, especially survival probabilities, to calculate insurance rates for people at different ages. Calculating how much people are worth. Sounds like a fun job. 20. An organism that only eats animal tissue. Most predators and scavengers are exclusively carnivorous. Some examples of carnivores include members of the feline family, like lions, tigers, and house cats, and birds of prey, like eagles, hawks, and owls. Beef: It's what's for dinner. 21. Anything that is, or has ever been, alive. Examples of biotic factors in an environment include organisms, organic molecules, and cells. Biotic is the opposite of abiotic. 25. Anything that is not, nor has ever been, alive. Some examples of abiotic factors in an environment include precipitation, sunlight, and minerals. Abiotic is the opposite of biotic. Life or no life, that is the question. 26. An organism that only eats tissue from autotrophic organisms, like plants and algae. Some examples of herbivores include members of the bovine family, like cows, bison, antelope, and sheep; members of the deer family, like moose, reindeer, and elk; and many insects, like leaf beetles, lady bugs, and aphids. 27. The physical environment where a population of a single species lives, or inhabits. A habitat consists of all the abiotic, or nonliving, resources influencing the population. A habitat is only understood in terms of the population it describes. For instance, we say "the black bear habitat" or "the whale habitat." It doesn’t describe the entire ecosystem, or a community of organisms, or even the home of a single individual. Habitats of different species can and almost always do overlap. 28. A group of two or more populations of organisms from different species inhabiting the same location at the same time. While humans often refer to their "community" as being a part of a group of other humans who live in the same small geographic location, a human population’s true ecological community includes all of the other organisms from other species in the area as well. Communities are composed only of biotic factors, aka living organisms. Abiotic factors like sunlight, temperature, and terrain are not considered part of a community; these factors are part of the ecosystem, which can contain one or more communities of organisms.