Ecology: Communities Part 1

Patterns of biodiversity

True or false: The species composition of communities changes as we move across the landscape

true

True or false: The species diversity of communities changes as we move across the landscape

true

how can boundaries between communities be gradual and blurry?

often species ranges overlap and some patches have blended community types

ecotone

sharp boundary in environmental conditions that is accompanied by major change in the composition of species in the community

give an example of a natural ecotone

forests transitions into a grassland

give an example of a human made ecotone

where a agricultural field meets a forest

Seprintine soils contains toxic metals where many plants can’t survive. How is this an example of an ecotone?

transition area where soil conditions change causing changes in which plant species can survive

zonation

a pattern where different species dominate different areas along an environmental gradient because each species has different environmental preferences

how is an intertidal zone an example of zonation?

species that tolerate drying out are on the upper shore while species that need to stay underwater are on the lower shore

what is frederic clements interdependent community concept?

communities are cohesive, interdependent groups of species that all have similar responses to the environment

what is henry gleason’s independent community concept?

species have highly individualized environmental responses and communities emerge when these overlap

Each plant species responds independently to changes in sunlight, moisture, and soil. Oak trees may disappear first, while certain shrubs remain farther into the grassland. Species gradually replace one another. This is an example of clementsian or gleasonian?

gleasonian

Oak trees, shrubs, and other plants tend to occur together as a predictable community. As environmental conditions change, the entire plant community changes together, creating a distinct boundary between forest and grassland. This is an example of clementsian or gleasonian?

clementsian

which concept best describes communities, interdependence or dependence?

both

Researchers removed neighboring plants to see how plants responded at different elevations. How are the results of their experiment evidence of interdependence?

at low elevation fruit production increased and at high elevation more plants died because at high elevations environmental conditions are harsher so neighboring plants can’t help protect them

How is the moisture level of tree species evidence for independence?

tree species have different preferred moisture levels where some thrive in drier conditions while others thrive in wetter conditions so their abundance peaks at different times

qualitative measurements of a community

describes a community using general categories such as forest or desert

quantitative measurements of a community

use numerical data to measure specific properties of a community such as species richness

species richness

the number of species in a community that does not account for the abundance of each species

what is the species richness in both communities?

they’re both 4

latitudinal diversity gradient

tropical biomes tend to have higher species richness than temperate and polar biomes

what are the 3 hypothesis for why species richness is high in the tropics?

1) long term climate stability

2) stronger species interactions

3) weaker species interactions

long term climate stability hypothesis

species were killed off by ice near the poles but species persisted and speciation continued in tropics

stronger species interactions hypothesis

stronger competition, predation, herbivory and parasitism prevent any one species from taking over

weaker species interactions hypothesis

longer growing seasons in tropics allow species to spread out their life cycle processes throughout the year reducing competition for resources

Predators eating the most abundant prey species, preventing it from dominating the community is an example of the weak or strong interactions hypothesis?

strong interactions

Different plant species may flower or grow at different times throughout the year so there’s less competition so more species can coexist. Is this an example of the weak or strong interactions hypothesis?

weak interactions