Population growth can follow either a J curve trend or an S curve trend. A J curve represents exponential, or unrestricted growth. An S curve represents logistic, or restricted, growth and accounts for the carrying capacity of an environment.

In a J curve model, the population will continue to grow even when it has reached capacity. In an S curve model, the population will stagnate and stabilize at a maximum value when capacity is reached.

A deme is defined as a group of individuals more genetically similar to each other than to other individuals, even if spatially isolated. A group of conspecific individuals separated demographically, genetically, or spatially from other groups is a population. A set of spatially disjunct populations in which some immigration still occurs is a metapopulation. The other options are not well-defined in population ecology.

Organisms with little to no parental care typically have large amounts of offspring to compensate for high mortality rates of the young, as shown in a type III survivorship curve. These include organisms like trees, which spread large numbers of seeds because the seeds rarely find a good growing spot and mature to adulthood.

The over-browsing by the invasive jackrabbit population has resulted in harm being done to the desert plant communities with no negative impact on the rabbits, resulting in amensalism.

Coevolution is a process by which two or more species evolve in response to one another, and generally describes competing species. While the hummingbird and the flower may evolve due to this relationship, coevolution more freqeucntly describes the evolution of defense mechanisms in response to a predator-prey relationship. Parasitism is the relationship in which one species benefits at the expense of the host. This can sometimes lead to coevolution, depending on how the host reacts. Neither species is being harmed in the given scenario, so this is incorrect. Commensalism is when one species benefits, but the other species is not impacted. In this case, both the hummingbird and the flower are benefiting, so this is not our answer. Resource partitioning is when species evolve together to share resources in a sustainable way. The hummingbird is using a resource that the flower provides, but they are not "sharing" in the sense of the definition of resource partitioning. Competitive exclusion describes the phenomenon when two species share the same niche, and the stronger one forces out the weaker competitor. 

Mutualism, the correct answer, describes a relationship wherein species exploit each other mutually. In this case, the hummingbird gains nutrition from the flower, and the flower gains a reproductive advantage from the hummingbird.

Beta diversity measures the rate of change in the species composition of one habitat as compared to others. This is called the species evenness of an area. For instance, if one habitat has radically more species than a neighboring habitat, this would result in a high beta diversity. Alpha diversity is measured as the number of species in a uniform area, and gamma diversity is the species richness in a range of habitats (a mix of alpha and beta).

Autotrophs use  for their carbon source, while heterotrophs use organic compounds from other organisms. Chemotrophs use chemical bonds as their energy source, while phototrophs use light. Combining these ideas we can come up with various terms to describe an organism's nutrition. The bacterium in this question stated to rely on organic chemicals from other organisms as a carbon and energy source. This makes it a chemoheterotroph.

The phosphorus cycle does not contain an atmospheric phase, while both the sulfur and nitrogen cycles do.

Primary succession is characterized by plants establishing themselves in areas that were initially devoid of soil (usually bedrock). Grasses establishing themselves on a newly-formed island that is mostly bedrock is the best fit for this definition.

Primary succession is characterized by pioneer species establishing themselves in areas that are predominantly bedrock and devoid of organic material. The formation of organic material in these areas typically occurs with the accumulation of wind-carried soil erosion, nutrients deposited by flowing bodies of water, and erosion of bedrock. Wildlife populations are also a significant contributor of soil nutrients, with feces being rich in both nitrogen and phosphorus. In contrast, pre-existing nitrogen-fixing plants (or any pre-existing plant communities) are uncommon to nonexistent in an area with no established soil system.