Chapter 50 ecology: interaction between organisms and their environment from Greek oikos, meaning...

Chapter 50

• ecology: interaction between organisms and their environment• from Greek oikos, meaning ‘home,’ and logos, meaning to study • rapidly growing and exciting science

•distribution: geographic range•abundance: number of organisms

• abiotic components: nonliving chemical and physical factors• biotic components: all organisms that are pare of an

environment

organism

population

community

ecosystem

landscape• several different ecosystems linked by exchanges of energy,

material, and organisms

biosphere

sum of Earth’s ecosystems

precautionary principle• “Look before you leap”• “An ounce of protection is worth a pound of cure”• “To keep every cog and wheel is the first precaution to

intelligent tinkering”

biogeography

• study of the past and present distribution of individual species

exotic specieszebra mussel

exotic specieszebra mussels

• feed on phytoplankton• phytoplankton population• water becomes more clear• in light levels in water• more plants with roots along bottom• loss of habitat for benthic organisms

biotic factors affect the distribution of organisms• Ex. predators

• can be studied with “removal and addition” experiments• Ex. sea urchins and kelp

abiotic factors affect the distribution of organisms• temperature• water• sunlight• wind• rocks and soil

CLIMATE• determined by four main abiotic factors:

• temperature• water• light• wind

BIOMES

solar radiation and latitude

seasons

affect of mountains on rainfall

lake stratification and turnover

microclimate• variation in climate along a fine scale

• Ex. forest floor• Ex. under a rock or log

impact of climate change

• conformers: allow some conditions within their bodies to vary with external changes

• Ex. spider crabs

• principle of allocation: each organism had a limited amount of energy that can be allocated for obtaining nutrients , escaping from predators, coping with environmental fluctuations, growth and reproduction

• therefore, energy required for maintaining homeostasis is not available for other functions

• acclimation: involves substantial but reversible changes that shift an organism’s tolerance curve in the direction of the environmental change

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aquatic biomes• make up the largest portion of the biosphere• divided into

• freshwater biomes (less than 1% saltwater)• marine biomes (~3% saltwater)

• marine biomes cover 75% of Earth’s surface• evaporation is main source of rain water• water temperatures have major influence on climate• algae and bacteria near surface provide substantial

portion of O2 and consume large amounts of CO2

• photic zone: receives light• aphotic zone (profundal): little light• benthic zone: bottom

• littoral zone: rooted and floating aquatic plants• limnetic zone: floating phytoplankton

(high rate of photosynthesis)

lakes: classification based on quantity of organic matter• oligotrophic (Ex. Lake Michigan)

• deep • nutrient-poor• sparse phytoplankton

• mesotrophic• eutrophic (Ex. golf course pond)

• more shallow• nutrient-rich• abundant phytoplankton

other aquatic biomes• wetlands

• area covered with water that supports aquatic plants• can be periodically flooded or permanently saturated• includes marshes, swamps, and bogs

• estuaries• area where a freshwater stream or river merges with the ocean

marine zones

• intertidal zone: where land meets water(parts are not always covered by water)

• neritic zone: shallow regions over continental shelf(always underwater)

• oceanic zone: water past the continental shelf• pelagic zone: open water• abyssal zone: very deep; continuous cold (3 C),

high water pressure, near absence of light, low nutrient concentrations

terrestrial biomes

• classification is based on abiotic factors (especially climate)• often names for physical or climatic feature, along with

predominant vegetation• vertical layers:

• canopy• permafrost

tropical forest

savanna

desert

chaparral

temperate grassland

temperate deciduous forest

coniferous forest

tundra

behavior: what an animal does and how it does it• influenced by both genetic and environmental factors• includes nonmotor components such as learning and memory• deals with two types of questions:

• proximate…mechanisms (environmental stimuli, triggers, physiological mechanisms)

• ultimate…evolutionary significance

Example:• magnolia warbler breeds in spring and early summer• P = triggered by increase in daylength (mating can be triggered

experimentally by increasing light exposure)• U = Why did natural selection favor spring/summer?

(maximize fitness…)

•most behavioral traits are polygenic

•behavior is a product of genes and environment• phenotype (expression of genes)

depends on both genetic and environmental components

•behavioral traits evolve in order to maximize fitness

fixed action pattern (FAP)

• sequence of behavioral acts that is essentially unchangeable and usually carried to completion once initiated

• triggered by external sensory stimulus(often involves another species as sign stimulus)

fixed action pattern (FAP)

• Ex. Tinbergen study• Ex. moths fold wings and drop to ground in response to

ultrasonic signals of predatory bats• Ex. three-spined stickleback fish

• attack other males that invade territory• stimulus = red belly

• won’t attack individuals without red belly• will attack many red-bellied shapes

behavioral ecology emphasizes evolutionary hypotheses

• Ex. cost-benefit analysis of foraging• foraging: food-obtaining behavior

• crows & mollusks: choose height that provides most food / energy expended

• bluegill sunfish: feed on Daphnia• low density less selective• high density more selective

• smallmouth bass and minnows vs. crayfish: tradeoff between quantity and quality

foraging behavior is not just about calories

• must minimize risk of predation• must involve obtaining essential nutrients

learning = modification of behavior resulting from specific experiences• most innate behaviors improve with performance as animals

learn to carry them out more efficiently

• Ex. alarm calls of vervet monkeys (improve performance by learning)

• distinct calls when the see different animals• leopard loud barking run up tree• eagle short, double syllable cough look up• snake “chutter” look down

• young are indiscriminate• Ex. Give eagle call for all birds

• accuracy of calls improves with age• positive reinforcement

• if infants give correct call, adult immediately follows

learning vs. maturation

•maturation = ongoing developmental changes in neuromuscular system

•Ex. birds learning to fly•Ex. herring gull feeding behavior

habituation•loss of responsiveness to stimuli that convey little or no information

•Ex. Hydra response to initial touch•Ex. response to alarm calls•may allow nervous system to focus on important stimuli

imprinting

•learning that is limited to specific time period

•Ex. Lorenz and geese

sensitive period

•limited time in development when learning of particular behaviors can take place

•Ex. sensitive period for sexual identity in finches

bird song as model for understanding development of behavior

• isolated bird can learn song of another species after sensitive period through live interaction with individual

• exception to white-crowned sparrow learning scenario• deafened birds still able to learn song

• region of canary brain for song varied dramatically according to season and complexity of song• region is largest during breeding• must somehow increase fitness

associative learning = associate one stimulus with another• classical conditioning = associate one event with

another • Ex. Pavlov’s dog

• operant conditioning = trial and error learning• associate behavior with reward or punishment• Ex. coyote learns to avoid porcupine• Ex. Skinner box

play• no apparent external goal, but involves movements

associated with goal-directed behaviors• consumes energy + potential costs• play used to perfect behaviors needed in functional

circumstances

social biology • at times, social behavior can appear inefficient or even

counterproductive to reproductive success

competitive social behaviors• because members of a population share a niche, potential for

conflict exists

•agnostic• contest involving both threatening and submissive behavior

determines which competitor gains access to resource (I.e. food or mate)

• Ex. test of strength• dogs• ground squirrels

competitive social behaviors•dominancy hierarchy

•alpha individual, who is assured resources, controls the behavior of the others

•beta is second in command•omega is last in the chain

competitive social behaviors•territoriality

• individual defends area for feeding, mating, rearing young

• defended through agnostic behavior• defense is usually only directed at

members of the same species

•natural selection favors mating behavior that maximizes quantity or quality of mating partners

•courtship• behavior patterns that lead up to

copulation (or gamete release)• helps identify mates of same species

• impact of parental investment• eggs are more energetically

expensive to produce for females• females often invest large amounts

of time to carry and nourish offspring • male reproductive success is

proportional to # of partners• example of sexual selection

• stalk-eyed flies

mating systems

•promiscuous•monogamous•polygamous

•needs of young are ultimate factor

•certainty of paternity is another

signal

•behavior that causes change in behavior in another animal

phermones

•chemical signals that are detected by odor

altruistic behavior

•behavior that reduces fitness of individual while increasing fitness of recipient of behavior• Ex. alarm call of Belding ground squirrel• Ex. worker bees• Ex. mole rats

Chapter 52Population Ecology• population: group of individuals of a single

species that simultaneously occupy the same area• rely on same resources• influenced by same environmental factors• high likelihood of breeding with one another

population density• density: number of individuals per unit area

or volume• In most cases, it is impractical or impossible

to count all individuals in a population• Sampling allows scientists to estimate

densities and total population sizes• Ex. mark-recapture method• Animals within a study area are tagged then

released• After a period of time, second round of animals is

caught (recaptured) # marked in 1st catch x total # in 2nd catch

N = # of recaptures in 2nd catch

population dispersion• dispersion: pattern of spacing among

individuals within the geographic boundaries of the population

• clumped: individuals aggregate in patches • Ex. butterfly fish in schools

• uniform: individuals are evenly spaced• Ex. nesting penguins exhibiting territoriality

• random: position of one individual is independent of others• Ex. trees in a forest

demography• studies changes in populations

• increase (+)• birth• immigration

• decrease (-)• death• emigration

survivorship curves• plots proportion of individuals in a cohort

still alive at each age• Type I = low deaths rates until late in life

• Ex. humans

• Type II = constant death rate throughout life span• Ex. squirrel

• Type III = very high death rates early in life• Ex. oyster

life histories• includes traits that affect an organism’s schedule

of reproduction and survival (from birth through reproduction to death)

• big-bang reproduction (semelparity)• all resources devoted to one reproduction event• Ex. Pacific salmon, agave plant

• repeated reproduction (iteroparity)

limited resources mandate trade-offs between investments in reproduction and survival• Darwinian fitness is measured not by how many

offspring are produced but by how many survive to produce their own offspring• heritable characteristics of life history that result in

the most reproductively successful descendants will become more common within the population

population growth

• change in population size during time interval = births – deaths

• N = B - D t

• zero population growth occurs when the per capita birth rates and death rates are equal

carrying capacity

• maximum population size that a particular environment can support with no degradation of the habitat

• logistic growth

• K-selection• density-dependent

(sensitive to population density)• population thrives near carrying capacity• Ex. Drosophila

• r-selection• density-independent

(successful in uncrowded environments)• well below carrying capacity

population-limiting factors• If death rate increases (or birth rate decreases) as population

density increases, population density is DENSITY DEPENDENT• If birth and death rates do not change, population density is

DENSITY INDEPENDENT

factors leading to negative feedback in populations• 1. resource limitation

• competition for food and nutrients• 2. territoriality

• Ex. limited suitable nesting sites• 3. health

• Ex. plants• Ex. cannibalism among beetles

factors leading to negative feedback in populations• 4. predations

• Ex. trout focus on emerging larvae• 5. accumulation of toxic wastes• 6. disease• 7. intrinsic factors

• Ex. aggression among mice

Chapter 53Community Ecology• community: all species living in an area

Communities differ dramatically in…• species richness

• number of different species• Ex. Pond A = 17 species / Pond B = 18 species

• relative abundance• number of each species• Ex. Pond A = (1) toads=7; (2) crayfish=36; …. • Pond B = (1) toad=78; (2) crayfish=367

interspecific interactions—relationships between the species of a community• competition (- / -)

– can occur when resources are in short supply– Ex. grasshoppers and bison compete for grass– competitive exclusion

• two species that are so similar that they compete for the same limiting resources cannot coexist in the same place; one will use the resources more efficiently

– niche• sum total of a species’ use of biotic and abiotic resources in its environment

• competition (- / -)– niche

• sum total of a species’ use of biotic and abiotic resources in its environment– resource partitioning

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

– character displacement• tendency for characteristics to be more divergent in sympatric populations

than in allopatric populations of the same species• Ex. Galapagos finches (together on same island evolution of great

variety in beak shape and other features over time)

• predation (+ / -)– interaction includes herbivores and parasites– potent factor in adaptive evolution– predator adaptations

• acute senses• weapons such as claws, teeth, stingers, poison

– plant defenses• chemical toxins, thorns

– animal defenses• hiding, camouflage (cryptic coloration)• escape (energy intensive)• alarm calls• aposematic coloring warns of potential chemical defenses• Batesian mimicry: palatable or harmless species mimics unpalatable or harmful model• Mullerian mimicry: two or more unpalatable species resemble each other

• predation (+ / -)• parasites derive nourishment from another organism (host, which is

harmed by interaction)• endoparasites live within their hosts

• Ex. Tapeworm

• ectoparasites feed on an external surface• Ex. mosquitoes

• mutualism (+ / +)• interaction benefits both species

• Ex. nitrogen fixation by bacteria in legume root nodules• Ex. digestion of cellulose by bacteria in termite digestive system• Ex. ants and acacia trees

• commensalism (+ / 0)• benefits one species and has no known effect on other species• Ex. cowbirds and grazing cattle

• coevolution• reciprocal evolutionary adaptations of two species• change in one species acts as selective force on first species

food chains

food webs

dominant species• biomass: sum weight of all individuals in a population• dominant species are those in a community that have the

highest abundance or biomass• exert control over the occurrence and distribution of other

species (Ex. sugar maple)• Why do some species become dominant in an ecosystem?

dominant species• Ex. American chestnut

• dominant tree in deciduous forest before 1910• wiped out by fungal disease after Asian trees were introduced to

botanical garden in NYC• impact:

• oaks, hickories, beech, and maples have filled in• however, 7 (of 56) species that fed on chestnut trees went extinct• no mammals or birds seem to be affected

keystone species• exert control on community structure based on their ecological

Ex. Pisaster ochraceous• sea star is keystone predator of mussels in rocky intertidal

communities of western North America (promotes diverse community with 15 – 20 species)

• once removed by Robert Paine, mussel Mytilus californianus was able to monopolize space and exclude other invertebrates and algae (leads to community with less than 5 species)

• predation by Pisaster allows other species to occupy space

The structure of a community may be controlled bottom-up by nutrients or top-down by predators.

•N V H P• N = nutrients• V = vegetation• H = herbivores• P = predators

ecological succession• transition in species composition over ecological time

• primary succession: begins in virtually lifeless area where soil has not yet formed

• Ex. new volcanic island, glacial moraine• bacteria lichens, mosses grasses shrubstrees

• secondary succession: occurs where existing community has been cleared by some disturbance that leaves the soil intact

• Ex. fire, abandoned farms

biodiversity• number of species in ecological community• two key factors:

• size • small islands tend to have fewer species than large islands

• geographic location• Ex. plant and animal life more abundant and varied in tropics than in

other parts of the Earth

• species richness• total number of different species in the community

• relative abundance

Chapter 54Ecosystems• ecosystem: consists of all the organisms living in a community,

along with all the abiotic factors with which they interact• like populations and communities, boundaries are usually not

discrete

• trophic levels of feeding relationships allows us to follow the transformation of energy in ecosystems

• primary producers = autotrophs• primary consumers = herbivores• secondary consumers = eat herbivores• tertiary consumers = eat other carnivores

• detritovores (decomposers) = consumers that get their energy from detritus (nonliving organic material)

an ecosystem’s energy budget depends on primary production• primary production: amount of light energy converted to

chemical energy by an ecosystem’s autotrophs during a given time

• the amount of solar radiation reaching the surface of the globe ultimately limits the photosynthetic output of ecosystems

• 1-2% of visible light that reaches producers is converted to chemical energy

• gross primary productivity (GPP): amount of light energy that is converted to chemical energy by photosynthesis per unit time

• net primary productivity (NPP): equal to gross primary productivity minus the energy used by producers for respiration– represents storage of chemical energy available to consumers in an

ecosystem– can be expressed in energy per unit area per unit time (J/m2/yr) or biomass

of vegetation added to the ecosystem per unit time (g/m2/yr)• standing crop measures existing biomass; primary productivity measures

new biomass

in aquatic ecosystems, nutrients (and light) limit primary production• nitrogen and phosphorus are the nutrients that most often

limit marine production

eutrophication• Process where lakes with phytoplankton communities

dominated by diatoms and green algae change to host mainly cyanobacteria

• Mostly a result of fertilizer and sewage runoff (rich in nutrients)

• nutrients bacteria respiration = dissolved oxygen diversity