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Species Species InteractionInteraction

Species Interact in Five Major WaysSpecies Interact in Five Major Ways

• Interspecific Competition

• Predation

• Parasitism

• Mutualism

• Commensalism

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Interspecific CompetitionInterspecific Competition

• Occurs when members of two or more species interact to gain access to the same limited resources such as food, light, or space

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PredationPredation

• Occurs when a member of one species (the predator) feeds directly on all or part of a member of another species (the prey)

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ParasitismParasitism

• Occurs when one organism (the parasite) feeds on the body of, or the energy used by another organism (the host), usually by living on or in the host

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MutualismMutualism

• Is an interaction that benefits both species by providing each with food, shelter, or some other resource.

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CommensalismCommensalism

• Is an interaction that benefits one species but has little, if any, effect on the other.

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These interaction:These interaction:• have significant effects on the

resource use and population sizes of the species in an ecosystem.

• also influence the abilities of the interacting species to survive and reproduce, thus serve as agents of natural selection

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CompetitionCompetition

• The most common interaction

• The niches of two species overlap when they are competing for the same resources.

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Competitive exclusion principleCompetitive exclusion principle

• Two species can’t occupy exactly the same ecological niche for very long.

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If one species can take over the largest share If one species can take over the largest share of one or more key resources, the other of one or more key resources, the other

competing species must:competing species must:

• Migrate to another area (if possible)

• Shift its feeding habits or behavior through natural selection

• Suffer a sharp population decline

• Become extinct in that area

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PREDATION

PredatorsPredators

• Herbivores

• Carnivores

• Omnivores

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Methods to capture preysMethods to capture preys

• Herbivores: just walk, swim, fly

• Carnivores: –pursuit,

–ambush,

–camouflage,

–chemical warfare14

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Prey AdaptationsPrey Adaptations• Avoid detection

– camouflage, mimics,

– diurnal/nocturnal

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Prey AdaptationsPrey Adaptations• Avoid detection

– camouflage, mimics,

– diurnal/nocturnal

• Avoid capture– flee

– resist

– escape

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Prey AdaptationsPrey Adaptations• Avoid detection

– camouflage, mimics, – diurnal/nocturnal

• Avoid capture– Protective shells– Thick bark– Spines and thorns– Chemical warfare

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• At the individual level, members of the predator species benefit and members of the pray species are harmed.

• At the population level, predation plays a role in evolution by natural selection.

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CoevolutionCoevolution

• Evolution in which two or more species interact and exert selective pressures on each other that can lead each species to undergo adaptations.

• Ex. Predator-prey, parasite-host27

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Symbiosis: Symbiosis: Mutualists, Mutualists,

Commensalists Commensalists and Parasitesand Parasites

ParasitismParasitism• Occurs when one species (the

parasite) feeds on the body of, or the energy used by, another organism (the host), usually by living on or in the host.

• The parasite benefits and the host is harmed but not immediately killed

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ParasitismParasitism

• Parasite usually is smaller than host

• Live on

• Live in

• Little contact

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MutualismMutualismDEFINITION:

An interaction between two individuals of different species that benefits both partners in this interaction

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PollinationPollination

• Animals visit flowers to collect nectar and incidentally carry pollen from one flower to another

• Animals get food and the plant get a pollination service

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• Yucca’s only pollinator is the yucca moth. Hence entirely dependent on it for dispersal.

• Yucca moth caterpillar’s only food is yucca seeds.

• Yucca moth lives in yucca and receives shelter from plant.

Yucca and Yucca Moth Yucca and Yucca Moth

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Lichen (Fungi-Algae)Lichen (Fungi-Algae)• Symbiotic relationship of algae and

fungae…results in very different growth formas with and without symbiont.

• What are the benefits to the fungus?

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CommensalistsCommensalists• Benefit from the

host at almost no cost to the host

• Birds nesting in trees

• Eyelash mite and humans

• Sharks and remora

To avoid or reduce CompetitionTo avoid or reduce Competition

• Some species develop adaptations that allow them to reduce or avoid competition with other species for resources. In other words, some species evolve to reduce niche overlap.

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Resource PartitioningResource Partitioning

• Process of dividing up resources in an ecosystem so that species with similar needs (overlapping ecological niches) use the same scarce resources at different times, in different ways, or in different places.

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Population GrowthPopulation Growth

• No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.

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Populations Have Certain Populations Have Certain CharacteristicsCharacteristics

• Populations differ in–Distribution

–Numbers

–Age structure

–Density

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Population dynamicsPopulation dynamics

• Is a study of how these characteristics of populations change in response to changes in environment conditions.

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Changes in population Changes in population characteristics due to:characteristics due to:

–Temperature

–Presence of disease organisms or harmful chemicals

–Resource availability

–Arrival or disappearance of competing species

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Most Populations Live Together Most Populations Live Together in Clumps or Patchesin Clumps or Patches

• Population distribution –Clumping (Ex. Wolf packs, desert

vegetation around springs,…)

–Uniform dispersion ( Ex.Creosote bushes in a dessert)

–Random dispersion (Ex. Dandelions) 42

Why clumping?Why clumping?

– Species tend to cluster where resources are available

– Groups have a better chance of finding clumped resources

– Protects some animals from predators

– Packs allow some to get prey

– Temporary groups for mating and caring for young 43

•The living world is mostly clumpy and patchy

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Populations Can Grow, Populations Can Grow, Shrink, or Remain StableShrink, or Remain Stable

• Population size governed by

– Births

– Deaths

– Immigration

– Emigration

• Population change =

(births + immigration) – (deaths + emigration)45

Age structureAge structure

–Pre-reproductive age

–Reproductive age

–Post-reproductive age

• The size of a population with a fairly even distribution among these three age groups tends to remain stable. 46

No Population Can Grow Indefinitely: No Population Can Grow Indefinitely: J-Curves and S-CurvesJ-Curves and S-Curves

• Biotic potential: capacity for population growth under ideal conditions.– Low – High

• Intrinsic rate of increase (r): is the rate at which the population of a species would grow if it had unlimited resources.

• Individuals in populations with high r – Reproduce early in life– Have short generation times– Can reproduce many times– Have many offspring each time they reproduce

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No Population Can Grow Indefinitely: No Population Can Grow Indefinitely: J-Curves and S-CurvesJ-Curves and S-Curves

• Size of populations limited by–Light–Water–Space–Nutrients–Exposure to too many competitors,

predators or infectious diseases48

• Environmental resistance: Is the combination of all factors that act to limit the growth of a population.

• Carrying capacity (K): The maximum population of a given species that a particular habitat can sustain indefinitely without being degraded.

• The growth rate of a population decreases as its size nears the carrying capacity of its environment.

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Exponential or geometric growthExponential or geometric growth

• Exponential growth: starts slowly but then accelerates as the population increases, because the base size of the population is increasing (J-shaped growth curve)

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Logistic growthLogistic growth

• Involves rapid exponential population growth followed by a steady decrease in population growth until the population size levels off.

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Why logistic growth?Why logistic growth?

• This slowdown occurs as the population encounters environmental resistance from declining resources and other environmental factors and approaches the carrying capacity of its environment.

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• After leveling off, a population fluctuates slightly above and below the carrying capacity.

• The size of such population may also change as the carrying capacity does.

• Read page 11053

When a Population Exceeds Its Habitat’s Carrying When a Population Exceeds Its Habitat’s Carrying Capacity, Its Population Can CrashCapacity, Its Population Can Crash

• Carrying capacity: not fixed

• Reproductive time lag may lead to overshoot

– Dieback (crash)

• Damage may reduce area’s carrying capacity

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Reproductive PatternsReproductive Patterns

• r-selected species:– Have many, usually small, offspring

– Little or no parental care or protection

– Massive losses of offspring.

– Ex. Algae, bacteria, rodents, frogs,..

– Tend to be opportunists

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Reproductive PatternsReproductive Patterns

• k- selected species:– Tend to reproduce later in live

– Have a small number of offspring with fairly long life spans

– For k-selected mammals, the offspring develop inside their mothers, are born fairly large, mature slowly and are cared

– They do well in competitive conditions56

Genetic Diversity and small Genetic Diversity and small populationspopulations

• Several genetic factors can play a role in the loss of genetic diversity and the survival of small, isolated populations.

– Founder effect

– Demographic bottleneck

– Genetic drift

– Inbreeding57

Founder effectFounder effect

• Can occur when a few individuals in a population colonize a new habitat that is geographically isolated from other members of the population. In such a cases, limited genetic diversity may threaten the survival of the colonizing population

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Demographic bottleneckDemographic bottleneck

• It occurs when only a few individuals in a population survive a catastrophe such as a fire. Lack of genetic diversity may limit the ability of these individuals to rebuild the population (increase in the frequency of harmful genetic deseases)

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Genetic driftGenetic drift

• It involves random changes in the gene frequencies in a population that can lead to unequal reproductive success. The founder effect is one cause of genetic drift.

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InbreedingInbreeding

• It occurs when individuals in a small population mate with one another.

• This can occur when a population passes through a demographic bottleneck

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Minimum viable population sizeMinimum viable population size

• Conservation biologists use these concepts to estimate the minimum viable population size or rare and endangered species: the number of individuals such populations need for long-term survival.

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Density-dependent population controlsDensity-dependent population controls

• Population density is the number of individuals in a population found in a particular area or volume.

• Density-dependent population controls

– Predation

– Parasitism

– Infectious disease

– Competition for resources (mates, food, sunlight,…)

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Density independent Density independent

• Some factors (mostly abiotic) that can kill members of a population are density independent.

• Ex. Severe freeze, flood, pollution, fire,…

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Several Different Types of Population Several Different Types of Population Change Occur in NatureChange Occur in Nature

• Stable

• Irruptive

• Cyclic fluctuations, boom-and-bust cycles

– Top-down population regulation

– Bottom-up population regulation

• Irregular

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Humans Are Not Exempt from Humans Are Not Exempt from Nature’s Population ControlsNature’s Population Controls

• Ireland

– Potato crop in 1845

• Bubonic plague

– Fourteenth century

• AIDS

– Global epidemic66

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Ecological Ecological ProcessesProcesses

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Ecological SuccessionEcological Succession

Primary and Secondary SuccessionPrimary and Secondary Succession

gradual & fairly predictable change in species composition with time

•some species colonize & become more abundant;

•other species decline or even disappear.

Primary SuccessionPrimary Succession• Involves the gradual

establishment of biotic communities in lifeless areas where there is no soil in a terrestrial ecosystem or no bottom sediment in an aquatic ecosystem.

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Secondary SuccessionSecondary Succession

• A series of communities or ecosystems with different species develop in places containing soil or bottom sediment

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Primary SuccessionPrimary Succession• Bare rock weathers release nutrients for soil

formation.• The slow process of soil formation begins when early

successional plant species or pioneer arrive and attach themselves to inhospitable patches of rock. Such as lichens, mosses,..

• After hundreds to thousands of years, the soil may be deep and fertile enough to store the moisture and nutrients needed to support the growth of midsuccessional plant species, such as herbs, grasses,.. 71

Primary SuccessionPrimary Succession

• Late successional plant species (mostly trees) that can tolerate shade are going to replace the midsuccessional plant species.

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Secondary SuccesionSecondary Succesion

• Candidates for secondary succession include abandoned farmland, burned or cut forests, heavily polluted streams, and land that has been flooded.

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Succession Doesn’t Follow a Succession Doesn’t Follow a Predictable PathPredictable Path

• Traditional view

– Balance of nature and a climax community

• Current view

– Ever-changing mosaic of patches of vegetation

– Mature late-successional ecosystems

• State of continual disturbance and change74

Living Systems Are Sustained Living Systems Are Sustained through Constant Changethrough Constant Change

• Inertia, persistence– Ability of a living system to survive moderate

disturbances

• Resilience – Ability of a living system to be restored through

secondary succession after a moderate disturbance

• Tipping point75

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Ecological SuccessionEcological SuccessionGradual changing environment in

favor of new / different species / communities

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Primary Primary SuccessionSuccession

Glacier Glacier RetreatRetreat

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DisturbanceDisturbanceEvent that disrupts an ecosystem or community;

• Natural disturbance

•tree falls, fires, hurricanes, tornadoes, droughts, & floods

• Human–caused disturbance

•deforestation, erosion, overgrazing, plowing, pollution,mining

• Disturbance can initiate primary and/or secondary succession

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Ecological StabilityEcological StabilityCarrying Capacity – maximum number of

individuals the environment can support

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Ecological Stability - StressEcological Stability - Stress1. Drop in Primary Productivity2. Increased Nutrient Losses3. Decline or extinction of indicator

species4. Increased populations of insect

pests or disease organisms5. Decline in Species diversity6. Presence of Contaminants

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Which law directed the Secretary of the Which law directed the Secretary of the Interior to review every roadless area of Interior to review every roadless area of 5,000 or more acres and every roadless 5,000 or more acres and every roadless island within National Wildlife Refuge and island within National Wildlife Refuge and National Park Systems?National Park Systems?

A. Endangered Species ActA. Endangered Species ActB. Wilderness Act B. Wilderness Act C. Lacey ActC. Lacey ActD. National Park ActD. National Park ActE. Wild and Scenic Rivers ActE. Wild and Scenic Rivers Act

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What are keystone species?What are keystone species?

A. A. existing in such small numbers that it is in existing in such small numbers that it is in danger of becoming extinctdanger of becoming extinct

B. introduced to an environment where it is not B. introduced to an environment where it is not native, and that has since become a nuisance native, and that has since become a nuisance

C. likely to become an endangered species within C. likely to become an endangered species within the foreseeable future throughout all or a the foreseeable future throughout all or a significant portion of its rangesignificant portion of its range

D. serve as early warnings of damage to a D. serve as early warnings of damage to a communitycommunity

E. presence and role within an ecosystem has a E. presence and role within an ecosystem has a disproportionate effect on other organisms within disproportionate effect on other organisms within the system the system

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Who did Roosevelt appoint to head Who did Roosevelt appoint to head the newly created US Forest the newly created US Forest Service to protect and manage the Service to protect and manage the world’s forests?world’s forests?A. E.O. Wilson A. E.O. Wilson B. Aldo LeopoldB. Aldo LeopoldC. Robert MacArthurC. Robert MacArthurD. Stephen MatherD. Stephen MatherE. Gifford PinchotE. Gifford Pinchot

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Mutualism benefits:Mutualism benefits:

A) one of the organisms & hurts A) one of the organisms & hurts the otherthe other

B) neither of the organismsB) neither of the organismsC) both of the organismsC) both of the organismsD) benefits one & doesn’t hurt the D) benefits one & doesn’t hurt the

otherotherE) only one of the organismsE) only one of the organisms

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CommensalismCommensalism::

A) benefits only one of the organismsA) benefits only one of the organisms

B) benefits both organismsB) benefits both organisms

C) benefits one, doesn’t harm the otherC) benefits one, doesn’t harm the other

D) benefits neither of the organismsD) benefits neither of the organisms

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Biodiversity:Biodiversity:

A) decreases with speciation and A) decreases with speciation and extinction extinction

B) decreases with speciation and B) decreases with speciation and increases with extinctionincreases with extinction

C) increases with speciation and C) increases with speciation and extinctionextinction

D) increases with speciation and D) increases with speciation and decreases with extinctiondecreases with extinction

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What is not a pre-zygotic barriers?What is not a pre-zygotic barriers?

A) behavioral isolationA) behavioral isolation

B) habitat isolationB) habitat isolation

C) mechanical isolationC) mechanical isolation

D) hybrid isolationD) hybrid isolation

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Which of the following does Which of the following does species richness not depend on?species richness not depend on?

A) rate of immigrationA) rate of immigration

B) island sizeB) island size

C) distance from mainlandC) distance from mainland

D) types of speciesD) types of species

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Which is a species on which the Which is a species on which the persistence of a large number of other persistence of a large number of other species in the ecosystem depends?species in the ecosystem depends?

A) r-strategistsA) r-strategists

B) k-strategistsB) k-strategists

C) nonnative C) nonnative

D) keystoneD) keystone

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What is not characteristic of a What is not characteristic of a k-strategists?k-strategists?

A) long lifeA) long life

B) bigger bodiesB) bigger bodies

C) produce a lot of offspringC) produce a lot of offspring

D) produce late in lifeD) produce late in life

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What is not a predator What is not a predator adaptation?adaptation?

A) prey detectionA) prey detection

B) prey captureB) prey capture

C) eating preyC) eating prey

D) avoid detectionD) avoid detection

E) mass numbersE) mass numbers

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