Chapter 4: Species Interaction and Community Ecology

Species interactions

competition, predation, parasitism, herbivory, and mutualism

Competition

when multiple organisms seek the same limited resource/ subtle&indirect/ (-/-) each participant exerts a negative effect on other participants by taking resources that others could have used.

intraspecific competition

same species

interspecific competition

different species

resource partitioning

species partition, or divide, the resources they use in common by specializing in different ways

predation, parasitism, & herbivory

(+/-) some participants benefit while others are harmed/ one species exploits the other

predation

is the process by which individuals of one species (the predator) hunt, capture, kill, and consume individuals of another species (the prey).

Predation can sometimes drive population dynamics

more prey = more food for predators, more predators = less food (prey), some predators die off from starvation, less predators = increase in prey, cycle starts all over again

predation may also cause evolutionary ramifications

Through natural selection the evolution of adaptations will enhance hunting skills (predators). Prey face a stronger selective pressure, predation pressure has driven the evolution of defenses against being eaten.

parasitism

is a relationship in which one organism, the parasite, depends on another, the host, for nourishment or some other benefit while doing the host harm

pathogens

parasites that cause diseases in their hosts

human pathogens: malaria&amoebic dysentery(protists), pneumonia&tuberculosis(bacteria), hepatitis&AIDS(viruses)

coevolution

reciprocal process of adaptation and counter-adaptation

evolutionary arms race

hosts and parasites may become locked in a duel of escalating adaptations

mutualism

is a relationship in which two or more species benefit from interacting with one another each partner provides some resource or service that the other needs

symbiosis

occur between organisms that live in close physical contact/ close association (may be either mutualistic or parasitic)

pollination

involves free-living organisms that may encounter each other once (bees, birds, bats, & others)

community

is an assemblage of population of organisms living in the same area at the same time

community ecology

is the study of species interactions and the dynamics of communities

community ecologists

study which species coexist, how they interact, how communities change through time, and why these patterns occur

most important interactions among community members involve who _________ whom

eats

trophic level

as organisms feed on one another, matter and energy move through the community from one rank in the feeding hierarchy, to another

producers

autotrophs (self-feeders) comprise the first trophic level: green plants, cyanobacteria, &algae

consumers

organisms that consume producers are known as primary consumers & comprise the second trophic level: grazing animals, deer, & grasshoppers

secondary consumers

third trophic level prey on primary consumers: wolves, rodents, & birds

tertiary consumers

predators that feed at still higher trophic levels: hawks, sharks, & owls

detritivores

scavenge the waste products or dead bodies of other community members ex. millipedes & soil insects

decomposers

break down leaf litter and other nonliving matter into simpler constituents that can be taken up and used by plants ex. fungi & bacteria

at each trophic level, organisms use energy in ________ __________ and most of the energy ends up being given off as ______.

cellular respiration , heat

each trophic level contains how much energy of the trophic level below it?

10%

biomass

the collective mass of living matter

food chain

a linear series of feeing relationships/ as energy is transferred from lower trophic levels to higher ones it passes up the food chain

food web

more accurate representation of the feeding relationship in a community/ a visual map of energy flow that shows the many paths along which energy passes as organisms consume one another

benthic zone

bottom region (open-water region)

littoral

nearshore region (open-water region)

keystone species

a species that has strong or wide-reaching impact far out of proportion to its abundance/ removal of a keystone species will likewise have major consequences (secondary or tertiary consumers near the top of food chains are considered keystone species)

trophic cascade

predators at high trophic levels can indirectly promote populations of organisms at low trophic levels by keeping species at intermediate trophic levels in check

the removal of a keystone species can be a type of __________

disturbance

disturbance

is an event that has rapid and drastic impacts on environmental conditions, resulting in changes to the community and ecosystem.

examples of a disturbance

localized: when a tree falls in a forest, creating a gap in the canopy that lets in additional sunlight or can be severe like a hurricane, tornado, volcanic eruption, landslides, or floods. major sources of disturbance are human impacts

resistance

a community that resists change and remains stable despite disturbance

resilience

it changes in response to disturbance but later returns to its original state

Ecological succession

if a disturbance is severe enough to eliminate all or most of the species in a community, the affected site may then undergo a predictable series of changes

2 types of successions

primary & secondary successions

primary successions

a community is built from scratch

secondary successions

begins when a disturbance dramatically alters an existing community but does not destroy all life and organic matter; vestiges of previous community remain and these building blocks help shape the process (fire, storm, logging or farming)

pioneer species

species that arrive first and colonize the new substrate, have traits such as spores or seeds that can travel long distances

phase shift or regime shift

in which the character of the community fundamentally changes occurs when crucial climate threshold is passed or a keystone species is removed or lost, or a non native species invades

novel communities or no-analog communities

are composed of novel mixtures of plants animals, and have no analog or precedent

introduced species

species introduced by people, most fail to establish populations and turn invasive spreading widely to dominate communities

invasive species

often thrive in disturbed communities and in turn disturb them further

National Invasive Species Act 1996

in 1990 Congress passed legislation this law required ships to dump their freshwater ballast at sea and exchange it with salt water before entering the Great Lakes

eradication

total elimination of a population/ difficult to accomplish

restoration ecology

researchers focus on the historical conditions of ecological communities as they existed before our industrialized civilization altered them & devise ways to restore the functionality of a system

ecological restoration

the on-the-ground efforts to carry out these visions and restore communities

biome

is a major regional complex of similar communities/ a large scale ecological unit recognized primarily by its dominant plant type and vegetation structure

climate diagrams or climatographs

depict information on temperature and precipitation (greatest influence on a biome)

temperate deciduous forest

characterized by broad-leafed trees that are deciduous, meaning that they lose their leaves each fall & remain dormant during the winter. Dominates the area around the Great Lakes, Europe, eastern China, and eastern North America where precipitation is evenly throughout the year. Soils are fertile but this biome contains fewer trees than do tropical rainforest. Common trees oaks, beeches, and maples.

temperate grasslands (steppe or prairie)

temperature differences between winter and summer become more extreme, rainfall diminishes. Limited precipitation in the Great Plains supports grasses more easily than trees. Vertebrate animals include American bison, prairie dogs, pronghorn antelope, and ground nesting birds (meadowlarks & prairie chicken). Most of these lands have been converted to farming and ranching.

temperate rainforest

heavy rainfall in costal Pacific Northwest region. Coniferous trees cedars, spruces, hemlocks, and Douglas fir grow very tall here. The forest interior is shaded and damp. Moisture-loving animals reside here. Soils are fertile but are susceptible to landslides and erosions when forest are cleared.

tropical rainforest

they are closer to the equator and therefore warmer on average year-round. They hold far greater biodiversity. Found in Central America, South America, Southeast Asia, west Africa, and other tropical regions. Characterized by year-round rain and uniformly warm temperatures. They have dark, damp interiors, lush vegetation, and highly diverse communities, with more species of insects, birds, amphibians, and other animals than any other biome. Also consists of high numbers of tree species intermixed, each at a low density. Soils are poor, acidic soils that are low in organic matter. All nutrients in this biome are contained in the plants, not the soil.

tropical dry forest or tropical deciduous forest

tropical areas that are warm year-round but where rainfall is lower overall and highly seasonal. Biome widespread in India, Africa, South America, and northern Australia. Wet and dry seasons each span about half a year. Organisms that inhabit here have adapted to seasonal fluctuations in precipitation and temperature. Plants leaf grow out profusely with the rains, then drop their leaves during dry times of the year. Rains during wet season can be heavy and, coupled with erosion-prone soils, can lead to severe soil loss where people have cleared forest.

savanna

drier tropical regions, tropical grasslands interspersed with clusters of acacias or other trees. Biome is found across stretches of Africa, South America, Australia, India, and other dry tropical regions. Precipitation usually arrives during distinct rainy seasons. Grazing animals usually stay close to a water hole. Common herbivores include zebras, gazelles, and giraffes. Predators include lions and hyenas.

desert

rainfall is very sparse. Driest biome on Earth. Receive well under 10in of rain per year much of it during isolated storms months or years apart. Most are bare sand dunes. Not always hot because they are low in humidity and little vegetation to insulate them from temperature extremes, sunlight readily heats them in the daytime, but heats is quickly lost at night. Temperatures vary greatly from day to night and from season to season. Soils can be saline and are sometimes known as lithosols, or stone soils, for their high mineral and low organic-matter content. Animals and plants show many adaptation to deal with a harsh climate, birds are nomadic. Plants tend to have thick, leathery leaves to reduce water loss, or green trunks so that the plant can photosynthesize without leaves.

tundra

nearly as dry as desert occurs at very high latitudes in northern Russia, Canada, and Scandinavia. Extremely cold winters with little daylight and summers with lengthly days characterize this landscape of lichens and low, scrubby vegetation without trees. Great seasonal variation in temperature and day length results from this biome's high-latitude location, angled toward the sun in summer and away from the sun in winter. Due to cold climate underground soil remains frozen which is called permafrost. During the winter the soil freezes and when warm weather occurs the frozen topsoil produces pools of surface water, forming ideal habitat for mosquitos and other insects. Animals include polar bears and musk oxen.

boreal forest

northern coniferous forest (taiga) extends across much of Canada, Alaska, Russia, and Scandinavia. Trees include evergreens: black spruce, dominate large stretches of forest, interspersed with many bogs and lakes. They occur in cooler, drier regions and they experience long, cold winters and short cool summers. Soils are typically nutrient-poor and somewhat acidic. Animals have 3 months to feed and breed these include wolves, moose, bears, lynx, and rodents.

chaparral

limited to small patches widely flung around the globe. Consists of mostly evergreen shrubs and is densely thicketed. Biome is highly seasonal with mild wet winters and warm dry summers - climate influenced by ocean waters and often termed Mediterranean. Occur along the coasts of California, Chile, and southern Australia. Experience fires and their plants have adapted to resist fire or even to depend on it for germination of their seeds.