a checklist, or species count can measure the richness of a community

ecology usually focuses on several organisms rather than all of them because there are too many to quantify

the objectives of ecology studies can vary, one might cover species checklists, while another cover just the herbs shrubs and trees present

studies could examine tropic levels, or even alleles present in a community

region - area larger than a few square kilometers but typically much less than a continent, encompasses all members of many species, and speciation and extinction are important

biome - a large region characterized by the dominant plants present and climate. Ex. temperate grassland, temperate rainforest, tropical rainforest, desert, and salt marcsh

biogeographical region - an extremely large region that usually coincides with a continent or other very large region bounded by a geological or climatic barrier to migration barriers such as oceans and mountains prevent migration of most species #

species area relationship

whitaker proposed 3 scales: alpha for local, beta for differences between several small sites, and gamma is the number of species within a region

a checklist and species are relationships dont take abundance of each species into account, a species abundance distribution would plot the amounts of each species

diversity goes down with increase in lattitude, this may be due to harsher conditions and less rainfall or shorter growing seasons farther north

50 million years ago, most of the earth's climate was tropical. 20 million years ago the earth started to cool and ice sheets formed. so temperate plants began to evolve, this probably relates to tropic diversity - temperate plants have had less time to delineate

in nature this doesnt happen, but this model works for understanding harvesting fish, lumber or deer #

as a plant species reaches its carry capacity the herbivore and plant will cycle up and down together

the populations of both predator and prey can fall together or even both become extinct if all of the prey is consumed

the functional response includes a predator's feeding rate and the handling time to consume the prey

this functional response is prey dependent, it is faster when prey are more dense

population stability is represented by dN/dT or zero growth isocline

sometimes enriched numbers of prey result in predators overconsuming prey and losing food source. this is called the paradox of enrichment

fixed effort harvesting, setting a limit on time and style of harvest, like a 2 month long hunting season, where bag limit can vary based on population size

fixed quota harvesting - limit is a specific number no matter how long it takes.

in japan and norway they are harvesting whales even though they are endangered.

most communities have multiple plant species that are prey to herbivores

optimal foraging theory studies why herbivores choose certain plants over others

first predators evolve to prefer whichever prey yields the most energy per unit of handling time

second if high yield prey become scarce the predator will have more success with a broader diet and include prey that are less efficient but more abundant

third, some items like grasses will always be eaten even though lower in nutrients and other never eaten because of defense like cactus spines

fourth the probability a plant will be eaten is dependent on the abundance and efficiency of other plants

in exploitation competition the resource is consumed making ti less available for other organisms

in interference competition, one organism restricts another's access to resources even though the first might not be using it

invasive species have the ability to increase their population density despite competition

a resource is any substance or factor that can lead to growth

bracken fern is an intense competitor, throwing shade on shrubs below it yet able to grow in shade if something manages to grow taller than it

if all herb populations are low and one spikes, the increase in prey from its boom could result in more consumption of the lower populated species as well, endangering their survival, this is apparent competition

mutualism is when two organisms interact and both are benefitted

facilitation is when one organism helps another without benefit to themselves

these ants feed on the nectar and are protected by spines, they also keep out other insects and their wastes and decomposition enrich the soil

there are small costs for mutualism, something must be given up on each side

facilitation ex is nurse plants, who make a small habitat for other plants underneath