BIO151 UNIT 3 MISC. FROM HAZEL

interspecific interactions

refers to the interactions of an organism with individuals of other species in the community

ecological niche

the specific set of biotic & abiotic resources that an organism uses in its environment

parasitism

an exploitative (+ / -) interaction in which one organism derives its nourishment from the host, which is harmed in the process

eg: ticks that feed on moose can weaken their hosts by withdrawing blood

some change the behavior of their current host in ways that increase the likelihood that the parasite will reach its next host

endoparasites

live within the body of their host

ectoparasites

feed on the external surface of their host

predation

a + / - interaction in which an individual of one species kills & eats an individual of another species

ecological disturbance

an event such as a storm, fire, flood, drought, or human activity that changes a community by removing organisms from it or altering resource availability

trophic level

the position that an organism occupies in a food chain

food web

refers to a group of food chains linked together

a specific species may occupy more than one trophic level (such as omnivores) may be simplified in 1 of 2 ways:

species w. similar trophic relationships can be grouped into broad functional groups

isolate a portion that interacts very little w. the rest of the community

community

a group of populations of different species in an area

what are the limits on primary production in terrestrial ecosystems?

temperature & moisture are the main factors, nutrition plays a role as well

primary production is greater in wetter ecosystems

net primary production increases with temperature & amount of solar energy available to drive evaporation & transpiration

what are the limits on primary production in marine environments?

light: depth of light penetration affects primary production throughout the photic zone of an ocean or lake, however the impact is minor

nutrient limitation: most significant factor; the nutrients that most often limit marine production are nitrogen & phosphorus. concentrations of these nutrients are typically low in the photic zone, as they are taken up by phytoplankton & because detritus tends to sink

other nutrients, such as iron, can also limit primary production

symbiotic relationship between a legume & rhizobium (how do both sides benefit)

the bacteria (Rhizobium) supply the host plant (legume) with fixed nitrogen while the plant provides the bacteria w. carbohydrates & other organic compounds

the root nodules use most of the ammonium produced to make amino acids, which are then transported up the shoot through the xylem

limits on primary production in freshwater lakes

nutrient limitation is common

during the 1970s, scientists showed that sewage & fertilizer runoff adds considerable nutrients to lakes, promoting growth of primary producers. when the primary producers die, their bodies are broken down by aerobic decomposers, which depletes the water of O2, killing large amounts of fish

while nitrogen rarely limits primary production in lakes, many experiments have shown that phosphorus availability limited cyanobacterial growth

4 major components of climate

temperature

precipitation

sunlight

wind

global ecology

examines how the regional exchange of energy & materials influences the functioning & distribution of organisms across the biosphere

biosphere

the global ecosystem, sum of all the planet’s ecosystems & landscapes

secondary succession

involves the recolonization of an area after a major disturbance has removed most but not all of the organisms in a community

the area may return to something like its original state

ex: Yellowstone after 1988 fires

herbivory

an exploitative (+ / -) interaction in which an herbivore eats part of a plant or algae thereby harming it but usually not killing it

ex: cattle grazing on grass

keystone species

not usually abundant in a community

exert strong control on community structure not by numerical might but by their pivotal ecological roles

ex: the sea star maintains the diversity of an intertidal community by feeding on, thereby limiting the abundance of a competitively dominant species, the mussel

why are chains within a food web limited in length?

the “energetic hypothesis” suggests that the length of a food chain is limited by the inefficiency of energy transfer along the chain

predicts that food chains should be relatively longer in habitats characterized by higher photosynthetic production, since a greater amount of energy will be stored in primary producers

each chain within a web is usually only a few links long, there are rarely more than 7 links from the producers to any top-level predator

competitive exclusion

when individuals of two species compete for limited resources, even a slight reproductive advantage will eventually lead to local elimination of the inferior competitor

resource partitioning

refers to the differentiation of niches that enables similar species to coexist in a community

helps to prevent competitive exclusion

primary succession

when the processes of ecological succession begins in a virtually lifeless area, such as on a new volcanic island or on the rubble (moraine) left by a retreating glacier

ecological succession

changes in the composition of terrestrial communities are most apparent after a severe disturbance, such as a volcanic eruption or a glacier, strips away all the existing vegetation

the disturbed area may be colonized by a variety of species, which are gradually replaced by other species, which are in turn replaced by still other species

trophic structure

refers to the feeding relationships between organisms in a community, the transfer of chemical energy from its source in plants/other autotrophs (primary producers) through herbivores (primary consumers) to carnivores (secondary, tertiary, quaternary consumers)

mutualism

a +/+ interaction that benefits individuals of both interacting species

typically both partners incur costs as well as benefits, however the benefits to each partner must exceed the costs

in some cases, each species depends on the other for survival/reproduction, in other cases, each can survive on their own

ex: animals that pollinate flowers or disperse seeds

commonsalism

an interaction that benefits the individuals of one of the interacting species but neither harms nor helps the individuals of the other species (+/0)

ex: many wildflowers that grow best in low light levels are found only in shaded forest floor environments. they depend on trees for shade, but the survival/reproduction of trees are entirely unaffected by these wildflowers

competition

a -/- interaction that occurs when individuals of different species each use a resource that limits the survival & reproduction of both individuals

ex: lynx & foxes compete for prey such as snowshoe hares

6 types of interspecific interactions

competition

predation

herbivory

parasitism

mutualism

commensalism

6 levels of ecological study

organismal ecology

population ecology

community ecology

ecosystem ecology

landscape ecology

global ecology

organismal ecology

concerned w. how an organism’s structure, physiology, and behavior meet the challenges poses by its environment

includes the subdisciplines of physiological, evolutionary, behavioral ecology

population ecology

analyzes factors that affect population size & how/why it changes through time

population

a group of individuals of the same species living in the same area

community ecology

examines how interactions between species, such as predation & competition, affect community structure & organization

ecosystem

refers to the community of organisms in an area & the physical factors with which those organisms interact

ecosystem ecology

emphasizes energy flow & chemical cycling between organisms & the environment

landscape/seascape

a mosaic of connected ecosystems

landscape ecology

focuses on factors controlling exchanges of energy, materials, and organisms across multiple ecosystems

in the symbiosis between mycorrhizae & plants, what does each partner typically gain from the relationship?

host plant provides the fungus w. a steady supply of sugar

the fungus increases the surface area for water uptake & supplies plant w. phosphorus & other minerals absorbed from the soil

fungi of mycorrhizae also secrete growth factors that stimulate roots to grow & branch, as well as antibiotics that help protect the plant from soil pathogens

how do legumes encourage the growth & activity of nitrogen-fixing bacteria?

there is a mutualistic relationship between legume roots & rhizobium (root-living) bacteria

involves dramatic changes in root structure, along a legume’s roots are swellings called nodules, composed of cells “infected” by Rhizobium bacteria

nitrogen fixation by Rhizobium requires an anaerobic environment, which is facilitated by the location of the bacteroid inside living cells in the root cortex. the woody external layers of root nodules help limit gas exchange

each legume species is associated with a strain of Rhizobium bacteria

why are nitrogen-fixing symbiotic bacteria important to some plants?

although Earth’s atmosphere is 79% nitrogen, plant can’t use free gaseous nitrogen (N2) because there’s a triple bond between the 2 nitrogen atoms, making the molecule almost inert. it’ll have to be reduced to NH3 by a process called nitrogen fixation

all nitrogen-fixing organisms are bacteria. others are free-living in the soil, others live in the rhizosphere

rhizosphere

the soil closely surrounding plant roots

how do plants benefit from mutualistic relationships w. bacteria in the rhizosphere?

some rhizobacteria produce antibiotics that protect roots from disease

others absorb toxic metals to make nutrients more available to roots

other convert gaseous nitrogen into forms usable by the plant or produce chemicals that stimulated plant growth

inoculation of seeds w. plant-growth promoting rhizobacteria can increase crop yield & reduce need for fertilizers & pesticides

how do bacteria in the rhizosphere benefit from a mutualistic relationship w. plants?

they depend on nutrients such as sugars, amino acids, and organic acids that are secreted by plant cells

up to 20% of a plant’s photosynthetic production may be used to fuel these complex bacterial communities

what plant macronutrients are absorbed as dissolved ions in the soil?

nitrogen: a component of DNA/RNA, proteins, chlorophyll

potassium: cofactor for enzymes used throughout the cell, plays a major role in maintaining turgor

phosphorus: a component of DNA/RNA, ATP produced by mitochondria, phospholipids in cell membranes

tropical forest

occurs in equatorial & subequatorial regions

are vertically layered & competition for light is intense, however there are generally fewer layers in dry versions of this biome

animal diversity is higher here than any other terrestrial biome

temp. is high year round, little seasonal variation

may be rainy or dry

desert

occurs in bands near 30 degrees North & South latitude, or at other latitudes in the interior of continents

precipitation is low & highly variable, generally less than 30cm per year

max. temp may exceed 50 degrees C, or low as -30 degrees C

higher proportion of bare ground

dominated by low, widely scattered vegetation, many plants exhibit C4 or CAM photosynthesis

savanna

occurs in equatorial & subequatorial regions

dry season can last 8-9 months

warm year-round, but with somewhat more seasonal variation than tropical forests

fires are common in dry season, dominant plant-species are fire-adapted & tolerant of seasonal drought, grasses & small nonwoody plants called forbs grow rapidly in response to seasonal rains

scattered trees are thorny & have small leaves

dominant herbivores are actually insects

chaparal

occurs in midlatitude coastal regions on several continents

precipitation highly seasonal, rainy winters & dry summers

fall, winter, spring are cool while summers can reach 30 degrees C

dominated by shrubs & small trees, many kinds of grasses & herbs, plant diversity is high & adaptations to fire are common

temperate grassland

precipitation highly seasonal, relatively dry winters & wet summers

cold winters & hot summers

dominant plants grasses & forbs, which vary in height from a few cm to over 2m in tallgrass prairie

grazing of large mammals helps prevent establishment of woody shrubs & trees

periodic drought is common

Northern Coniferous Forest

extending in a broad band across northern North America & Eurasia to the edge of the arctic tundra

largest terrestrial biome on Earth

winters are usually cold, summers may be hot

some coastal variants are temperate rain-forests

dominated by cone-bearing trees such as pine, spruce, fir, hemlock, some of which depend on fire to regenerate. conical shape prevents too much snow to accumulate & breaking branches. diversity of shrub & herb layers is lower than temperate broadleaf forests

Temperate Broadleaf Forests

found mainly at midlatitudes in the Northern Hemisphere, smaller areas in Chile, South Africa, Australia, New Zealand

significant precipitation during all seasons, including winter snow in some; summers are hot & humid

a mature forest has distinct vertical layers, including a closed canopy, one or 2 strata of understory trees, shrub layer, herb layer

few epiphytes in Northern Hemisphere, deciduous trees are dominant plants

major terrestrial biomes

tropical forest

desert

savanna

temperate grassland

northern coniferous forest

temperate broadleaf forest

tundra

tundra

covers expansive areas of the Arctic, amounting to 20% of Earth’s land surface

high winds & low temperatures produce similar plant communities (alpine tundra) on very high mountain-tops at all latitudes, including the tropics

winters are cold, summer temp. averages less than 10 degrees C

vegetation mostly herbaceous, consisting of a mixture of mosses, grasses, forbs, with some dwarf shrubs & lichens; a permanently frozen layer of soil called permafrost restricts growth of plant roots

primary producers

the trophic level that ultimately supports all others

most autotrophs are photosynthetic organisms that use light energy to synthesize sugars & other organic compounds, which they use as fuel for cellular respiration & as building material for growth (most common autotrophs are plants, algae, photosynthetic prokaryotes)

however, chemosynthetic prokaryotes are the primary producers in some ecosystems, such as deep-sea hydrothermal vents & places deep under the ground or ice

heterotrophs

“consumers”

refers to organisms in trophic levels above the primary producers

depend on the outputs of primary producers, whether directly or indirectly

primary consumers

herbivores, which eat plants & other primary producers

secondary consumers

carnivores that eat herbivores

tertiary consumers

carnivores that eat carnivores

decomposers

consumers that get their energy from detritus

although some animals fall under this category, it is mostly composed of fungi & prokaryotes

these organisms secrete enzymes that digest organic material, then absorb breakdown products

help recycle chemical elements by converting organic matter from all trophic levels to inorganic compounds usable by primary producers

detritus

nonliving organic materials, such as the remains of dead organisms, feces, or fallen leaves

eutrophication

process in which the nutrient status of an ecosystem changes from nutrient-poor to nutrient-rich

can cause primary production to increase dramatically

how does the high specific heat of water affect climates?

oceans & lakes tend to moderate the climate of nearby land

during a hot day, when land is warmer than the water, air over the land heats up & rises, drawing a cool breeze from the water across the land

because temp. drops more quickly over land than over water wat night, air over the now warmer water rises, drawing cooler air from the land back out over the water & replacing it w. warmer air from offshore

in some climates, cool & dry ocean breezes in summer are warmed when they contact the land, creating a hot arid climate just a few kilometers inland (mediterranean climate)

how do ocean currents influence climate along the coasts of continents?

by heating or cooling overlying air masses that pass across the land

coastal regions generally wetter than inland areas of same latitude

cool, misty climate produced by cold California Current supports coniferous rainforest ecosystem along Pacific coast

West coast of northwestern Europe has a mild climate because the Gulf stream carries warm water from the equator to the North Atlantic

how do mountains affect air flow over land?

when warm, moist air approaches a mountain the air rises & cools, releasing moisture on the windward side of the peak

on the leeward side, cooler, dry air descends, absorbing air & producing a “rain shadow”

such leeward rain shadows determine where many deserts are found

how do mountains affect the amount of sunlight reaching an area (and therefore local temperature & rainfall)?

south-facing slopes in the northern hemisphere receive more sunlight than north-facing slopes, therefore they’re warmer & drier

these physical differences influence species distributions locally

ex: on many mountains in western N. America, spruce & other conifers grow on cooler N.-facing slopes, but shrubby, drought-resistant plants inhabit S-facing slopes

every 1000m increase in elevation produces an average temperature drop of 6 degrees C, equivalent to that caused by an 880m increase in latitude

Why is seasonality important?

changing angle of sun affects local environments

ex: belts of wet & dry air on either side of the equator move slightly north-ward/south-ward as the sun’s angle changes; this produces wet/dry seasons around 20 degrees North & South latitude, where many tropical deciduous forests grow

seasonal changes in wind patterns alter ocean currents, sometimes causing upwelling of cold water from deep ocean layers. this nutrient-rich water stimulates the growth of surface-dwelling phytoplankton and the organisms that feed on them. these small zones are the source of more than 25% of all fish caught globally