ECOLOGY - EXAM 2

diversity indices

indices used to assess diversity in an ecosystem

Simpson’s Index

likelihood that 2 individuals sampled from an area are not the same
sensitive to changes in the abundance of species

Shannon’s Index

likelihood that one cannot predict to which species the next individual collected in an area belongs
sensitive to changes in the number of rare species

evenness index

help deal with a few dominant species and many rare species
large index values imply the species are equally represented
small index values imply few species that are highly abundant and many that are rare

ecosystem services

services that support humans in non-monetary forms

4 types of ecosystem services

provisioning, cultural, supporting, regulating

provisioning

food, freshwater, timber, medicines

cultural

recreation, aesthetics, education

regulating

pollination, climate regulation, flood control

supporting

soil formation, nutrient cycling, primary production

threats to biodiversity

habitat loss, invasive species, overharvesting, climate change

habitat loss

deforestation, development, dams, and other disturbances remove or fragment habitats

overharvesting (tragedy of the commons)

hunting and fishing can remove organisms faster than populations can recover

invasive species (snake in Guam)

introduced predators, competitors, or pathogens can disrupt native communities

climate change (geese migration)

range shifts, timing mismatches, sea-level rise, and warming can increase extinction risk

ecological succession

an orderly process of community development that is reasonably directional, and therefore predictable

disturbance

any relatively discrete event in time that disrupts ecosystem, community, or population structure

anthropogenic disturbance

a discrete event that removes biomass (creates heterogeneity or patchiness) [not natural]

natural disturbance

a discrete event that creates patchiness (not man-made)

primary succession

development of an ecosystem on a newly formed surface (glaciation, volcanic eruption, massive landslide)

primary succession characteristics

stress-tolerant species, soil development, increasing diversity and structural complexity

secondary succession

occurs when a patch of vegetation suffers a severe disturbance such that many or all of the individual plants are killed

secondary succession characteristics

quick growth of pioneer plants whose existence has been tolerated in the earlier ecosystem, diversity rises then falls, biomass increase, rate of change depends on disturbance, move towards long-lived species)

characteristics of early successional species

small size, rapid growth rate, high seed production, readily dispersed, short life span

characteristics of late successional species

large size, slow growth rate, low seed production, poorly dispersed, long life span

5 phases of succession

amelioration, dispersion, colonization, establishment, ecosystem development/species assembly

amelioration

recovery, improve fertility, reduce toxicity

dispersal

add to depleted seeds, formation of bird perches, landscape permeability

colonization

few large seeded plants, competition, seedling protection

establishment

allow seedlings to grow fast enough, stable surfaces, reduce toxicity

species assembly/ecosystem development

system formed, species developed

Clement’s view of succession

waves of plant population, change was orderly and predictable, community as an organism

Gleason’s view of succession

existence of plant association due to individual response of plants to environment, chance dispersal, constant migration, and disturbance

vegetational dynamics

any change in plant communities over time (seasonal, successional, or post-glacial) where the emphasis on the process rather than the end point

3 types of vegetational dynamics

facilitation, tolerance, inhibition

faciliation

one plant species improves environmental conditions, buffers physical extremes, or provide resources that help another plant species survive

tolerance

how plant species survive, grow, and replace one another under changing abiotic conditions and biotic pressures

inhibition

the biological, environmental, and physical mechanisms that restrict, slow down, or alter plant growth, community succession, and pattern formation

what influences fires

fuels, weather, topography

three types of fires

surface, ground, crown

three types of crown fires

active, passive, independent

what happens to an ecosystem when there is a severe fire

soil becomes hydrophobic, which affects nutrients and availability

prescribed burn

planned and carefully managed application of fire to a specific land area by trained experts

Western fires

driven by droughts, low humidity, heavy conifer fuel

Midwestern fires

driven by higher humidity, precipitation, and hydroclimate whiplash

autotrophic zone

primary production, nutrients are lost

heterotrophic zone

respiration is dominant, decomposition takes place, nutrients in abiotic pool

nutrient cycling in temperate forest

when cleared, soil preserves its structure and retains relatively effective nutrients because carbon in mainly stored in soil an

nutrient cycling in tropical forest

nutrient cycling is tight and mineralization speed is fast because dead animals and plants decompose quickly

hardwood trees

better able to compete and grow on deeper, heavier, more productive soils

conifer trees

better able to compete and grow on poorer, lighter textured soils

climax of a forest

a point in succession where the overstory trees and are replaced by younger trees of the same species and have reached equilibrium

humus

organic matter decomposition are typically a vareity of organic molecules

humus absorption

organic molecules are characterized by being negatively charged, but can absorb positive ions up to 50 times greater in charge

formation of humus

crucial for the ability of soil to retain essential nutrients

scientists of evolution

Charles Darwin, Alfred Russel Wallace, Gregor Mendel, Thomas Hunt Morgan, Ronald Risher, JBS Haldane, and Sewall Wright

Charles Darwin and Alfred Russel Wallace

deduced there was a common ancestor based on their respective research

Gregor Mendel

contributed the fact that traits were inherited as discrete traits by different numbers of offspring

Thomas Morgan Hunt

contributed the idea of mutation in evolution

Ronald Fisher and JBS Haldane

contributed the fact that natural selection acted slowly

Sewall Wright

contributed the fact that genetic drift can occur