Ecology is the study of organisms and their interactions with other organisms and their environment. Evolutionary biology is the study of the evolution of living things. Combined, the two areas of study relate to each other. Like a detective, the evolutionary biologists are able to examine an ecosystem and propose various relationships and causes, and ecology can place specific examples to possible scenarios in evolutionary biology.

Clumped resources can lead to clumped dispersion of some organism population. For example, humans traditionally colonized areas near rivers and streams because that was where the water was most plentiful. Uniform dispersion can be triggered by social interactions or by competitive motives, such as plants that secrete chemical inhibitors of plant germination and growth of nearby fellows (perhaps to allow for larger leafs of sunlight not hindered by neighboring leafs). Unpredictable dispersion occurs when there are very few forces of attraction or repulsion that affect the reproductive viability of individual organisms.

Populations exhibiting Type I survivorship curves have a higher survival rate of the young, live out most of the years of the expected life span, and die at an old age. Many human populations show signs of Type I survivorship curves.

Populations that have a fairly constant death rate throughout the expected life span of the member organisms are said to show Type II survivorship curves.

Populations consisting of organisms that reproduce rapidly and care very little (and very rarely) for young are said to have a Type III survivorship curve. Examples include sea urchins, plants, and oysters.

The human mother invests time and resources into her children that may lead her to lose her job or ability to provide for herself (food, etc.).

On the island of Rhum, in Scotland, older female red deer tend to increase their chances of mortality in the winter by reproducing in the previous summer.

Population density refers to the number of organisms per some quantified amount of area. Density-dependent factors are those that change with respect to the population density of the area. The density-independent factors are those that are not directly connected to the population density of the area. An example of a density-independent factor is a river or a stream that provides a `continuous' source of water. A density-dependent factor may be something more like the amount of grass in an area. The stream of water could help to control the population's growth by first managing the water available to the grass and then the energy that the organisms get from the grass. These factors all contribute to the self-regulation of an ecosystem / habitat.

Predation kills prey and thus puts an end to some particular organism's life history meaning they no longer eat, reproduce, participate, etc.

The competition between members of the same species can affect the community structure. Evolutionary biology suggests to us that the genomes that survive are the ones that promote the survival of themselves and those that are similar to them. This shows that there is a gradient of support in community structures, it also lends to the idea of family units in communities (even though not all organisms are social in that manner). The structure of the relationships between organisms within a community determines where resources are obtained (various abiotic and biotic factors).

Batesian mimicry is where one species mimics another (“the model”) that is usually safe or has some sort of favorable trait that leads to greater reproductive success in the mimicking species. Mullerian mimicry is slightly more complicated in that many species share the same warning signs not following any particular `model' in the ecosystem.

Species richness is the number of different species in some region. Relative abundance is the number of members of species in some region. Although there may be twenty different species in my backyard, they do not all have the same population count.

Species richness generally declines along an equatorial-polar gradient. As resulting from the climate, tropical habitats tend to support more species richness.

He corresponded with Alfred Wallace who worked in the East Indies. They wrote many letters back and forth. In 1858, Darwin's true character came forth. By this time he had developed quite an ego, because, remember, in England Darwin was the biological man. Alfred Wallace describes to Darwin his theory of natural selection and in response to this, Darwin published his book rapidly, using Alfred Wallace's ideas.

Lyell's understanding of gradualism influenced Darwin's particular likening of the idea of species changing gradually with respect to time.

One of the commonly cited examples is the change in allele frequency in London's moths. Although this example is rather dated (dating back to the industrial revolution), it is still `contemporary' in comparison to the billions of years of biological natural selection. The birds (the predators) fed on moths, and the moths that were not able to blend into their environment were eaten more frequently. Over time, a separation in the gene pools appeared—first, the moths around the new industrial sectors of England (or maybe it was just London) became darker (since those were the ones that survived long enough to reproduce) and the moths from the other side of the `island' (not necessarily `continent') remained their “original” color (at least the color that they had before the industrial revolution).

Homologous structures are those that have similar functions and occasionally similar functions. This suggests that different organisms are able to develop different systems, tools, organs, parts, and so on even with ancestral separation of the genome. Darwin's theory of natural selection suggests that in some cases there may be only a limited number of possible ways of being fit enough for an environment.

Fossilized biological data can be found throughout geographical regions which supports phylogenetic trees based on deduction of similar homologies, or functions of organs across two seemingly unrelated species (fore example, the bones in fish and the bones in whales).

The “modern synthesis” refers to the combined works of Darwin and Mendel. Darwin provided massive amounts of observations on specimen morphology and Mendel provided experimental data on plant breeding and genetics. Established in the 1930s, the modern synthesis is a product of the efforts of Thomas Hunt Morgan, R. A. Fisher, Theodosius Dobzhansky, J.B.S. Haldane, Sewall Wright, Julian Huxley, Ernst Mayr, George Gaylord Simpson, and G. Ledyard Stebbins.

Hardy and Weinberg worked on their theorem that would theoretically show a situation where no evolution is occurring. The premises must be met to show that no natural selection is acting, thus also showing, in a sense, that natural selection is the mechanism of evolution. Historically, Hardy-Weinberg offered another strong supporting component of the modern synthesis (developed in the 1930s).

Microevolution refers to the changes on the small scale, such as changes in gene frequencies within a population. Genetic drift refers to the drifting alleles as they pass across the geography of the environment. Genetic drift results in intermixing of the allele frequencies. Gene flow is especially visible when there is, say, a new influx of the same species with different sets of genes from some other area. Mutation is rare (unless there is significant electromagnetic radiation from the sun and cosmic rays), although it usually switches around nucleotide sequences, replaces, inserts, and do various other things with the codes. Mutation is a direct change to the genome. Nonrandom mating is where there are some certain selective pressures, such as sexual selection, that does not cause random mating. Natural selection then refers to the fact that things die, and that those that do not reproduce before dieing, are “out of the game” (the genome is lost). By definition, any change to the genome is an example of microevolution, however, visible morphological microevolutionary developments are easy to spot—for example, look at the face of a human father and his son and spot the differences.

The variation in the genetic composition of organisms is caused by the combination of genomes between two parents resulting in offspring—achieved through meiosis. The allele-based variations are caused by DNA mutations (addition, subtraction, relocation, and one other). Organisms that reproduce alone, through mitosis, are less likely to immediately produce any sort of variation in their genomes, however, over long periods of time (think thousands of generations) variations add up to larger variations from the original organism under consideration.