1

Interactions: Environments and Interactions: Environments and OrganismsOrganismsChapter 5Chapter 5

2

Ecological ConceptsEcological Concepts

• Ecology Ecology - Study of ways organisms - Study of ways organisms interact with each other and with their non-interact with each other and with their non-living surroundings.living surroundings.

• Environment Environment - Everything that affects an - Everything that affects an organism during its lifetime.organism during its lifetime.– Biotic Biotic - Living components- Living components– AbioticAbiotic - Non-living components - Non-living components

3

Levels of Organization in EcologyLevels of Organization in Ecology

4

Ecological ConceptsEcological Concepts

• Limiting FactorsLimiting Factors - Any factor whose shortage or - Any factor whose shortage or absence restricts species success.absence restricts species success.– Range of ToleranceRange of Tolerance - Range of conditions an - Range of conditions an

organism can survive in.organism can survive in. TemperatureTemperature pHpH DODO

5

Habitat and NicheHabitat and Niche

• Habitat Habitat - Space an organism inhabits; defined by - Space an organism inhabits; defined by biological requirements of each particular biological requirements of each particular organism.organism.– Usually highlighted by prominent physical or Usually highlighted by prominent physical or

biological features.biological features.• NicheNiche - Functional role an organism has in its - Functional role an organism has in its

surroundings. surroundings. – Includes all ways an organism affects Includes all ways an organism affects

organisms with which it interacts as well as organisms with which it interacts as well as how it modifies its physical surroundings.how it modifies its physical surroundings.

• Fig. 5.3Fig. 5.3

6

Ecological NicheEcological Niche

7

Genes Population and SpeciesGenes Population and Species

• GenesGenes - Distinct pieces of DNA that - Distinct pieces of DNA that determine the characteristics an organism determine the characteristics an organism displays.displays.

• PopulationPopulation - All organisms of the same - All organisms of the same kind found within a specific geographic kind found within a specific geographic region.region.– Contains more kinds of genes than any Contains more kinds of genes than any

single individual within the population.single individual within the population.

8

Genes Population and SpeciesGenes Population and Species

• Species Species - Population of all organisms - Population of all organisms potentially capable of reproducing potentially capable of reproducing naturally among themselves(Interbreed), naturally among themselves(Interbreed), and producing viable offspring.and producing viable offspring.– Working definition that only applies to Working definition that only applies to

organisms that sexually reproduce.organisms that sexually reproduce.Some species are easy to recognize, Some species are easy to recognize,

while others are more difficult.while others are more difficult.

9

• Natural SelectionNatural Selection - Process that - Process that determines which individuals within a determines which individuals within a species will reproduce and pass their species will reproduce and pass their genes to the next generation. genes to the next generation.

• Conditions:Conditions:– Individuals within a species show Individuals within a species show

genetically determined variation.genetically determined variation.– Organisms within a species typically Organisms within a species typically

produce huge numbers of offspring, produce huge numbers of offspring, most of which die.most of which die.

Natural SelectionNatural Selection

10

Natural Selection ConditionsNatural Selection Conditions

– Excess number of individuals results in Excess number of individuals results in a shortage of specific resources.a shortage of specific resources.

– Due to individual variation, some Due to individual variation, some individuals have a greater chance of individuals have a greater chance of obtaining needed resources and thus obtaining needed resources and thus have a greater likelihood of survival and have a greater likelihood of survival and reproduction.reproduction.

– As time passes, percentage of As time passes, percentage of individuals showing favorable variations individuals showing favorable variations will increase while percentage showing will increase while percentage showing unfavorable variations will decrease.unfavorable variations will decrease.

11

Evolutionary PatternsEvolutionary Patterns

• EvolutionEvolution - A change in the kinds of - A change in the kinds of organisms that exist and in their organisms that exist and in their characteristics.characteristics.– Ex. Building tolerance to pesticides.Ex. Building tolerance to pesticides.

• SpeciationSpeciation - Production of new species - Production of new species from previously existing species.from previously existing species.– Thought to occur as a result of a species Thought to occur as a result of a species

dividing into two reproductively isolated dividing into two reproductively isolated subpopulations.subpopulations.

12

Evolutionary PatternsEvolutionary Patterns

• ExtinctionExtinction - Loss of entire species. - Loss of entire species.– Of estimated 500 million species Of estimated 500 million species

believed to have ever existed on earth, believed to have ever existed on earth, 98-99% have gone extinct.98-99% have gone extinct.

• Co-EvolutionCo-Evolution - Two or more species can - Two or more species can reciprocally influence the evolutionary reciprocally influence the evolutionary direction of the other.direction of the other.– Grazing animals and grass species.Grazing animals and grass species.

13

Kinds of Organism InteractionsKinds of Organism Interactions

• Predation Predation - One animal kills/eats another.- One animal kills/eats another.– Predator benefits from food.Predator benefits from food.

Prey adaptation is manifested in a Prey adaptation is manifested in a higher reproduction rate.higher reproduction rate.

Fig. 5.7Fig. 5.7

14

Kinds of Organism InteractionsKinds of Organism Interactions

– Prey species benefits by eliminating Prey species benefits by eliminating non-adaptive genes from the gene pool.non-adaptive genes from the gene pool.Poorly adapted predators are less Poorly adapted predators are less

likely to obtain food and thus pass on likely to obtain food and thus pass on non-adaptive genes.non-adaptive genes.

15

CompetitionCompetition

• CompetitionCompetition - Two organisms strive to obtain the - Two organisms strive to obtain the same limited resource, and both are harmed to same limited resource, and both are harmed to some extinct.some extinct.– IntraspecificIntraspecific - Members of same species - Members of same species

competing for resources. competing for resources. (Mice for Cheese)(Mice for Cheese)– InterspecificInterspecific - Members of different species - Members of different species

competing for resources. competing for resources. (Fox & Hawk for Mice)(Fox & Hawk for Mice)

• The more similar the competing species, the The more similar the competing species, the more intense the competition.more intense the competition.

• Fig. 5.8Fig. 5.8

16

CompetitionCompetition

• Competitive Exclusion Principle Competitive Exclusion Principle - No two - No two species can occupy the same ecological species can occupy the same ecological niche in the same place at the same time.niche in the same place at the same time.– Less fit species must evolve into a Less fit species must evolve into a

slightly different niche.slightly different niche.

17

Symbiotic RelationshipsSymbiotic Relationships• SymbiosisSymbiosis - Close, physical relationship - Close, physical relationship

between two different species. At least one between two different species. At least one species derives benefit from the interaction.species derives benefit from the interaction.– ParasitismParasitism - One organism ( - One organism (parasiteparasite) lives in ) lives in

or on another organism (or on another organism (hosthost), from which it ), from which it derives nourishment. derives nourishment.

EctoparasitesEctoparasites - Live on host’s surface. - Live on host’s surface. FleasFleas

EndoparasitesEndoparasites - Live inside host. - Live inside host. TapewormsTapeworms

18

Symbiotic RelationshipsSymbiotic Relationships• Commensalism Commensalism - One organism benefits while the - One organism benefits while the

other is not affected. other is not affected. – Remoras and SharksRemoras and Sharks

• MutualismMutualism - Both species benefit. Obligatory in - Both species benefit. Obligatory in many cases as neither can exist without the many cases as neither can exist without the other. other. – MycorrhizaeMycorrhizae

19

Community and Ecosystem Community and Ecosystem InteractionsInteractions

• CommunityCommunity - Assemblage of all interacting - Assemblage of all interacting species of organisms in an area.species of organisms in an area.

• Ecosystem Ecosystem - Defined space in which - Defined space in which interactions take place between a interactions take place between a community, with all its complex community, with all its complex interrelationships, and the physical interrelationships, and the physical environment.environment.

20

Major Roles of Organisms in Major Roles of Organisms in EcosystemsEcosystems

• Producers Producers - Organisms able to use - Organisms able to use sources of energy to make complex sources of energy to make complex organic molecules from simple inorganic organic molecules from simple inorganic molecules in the environment.molecules in the environment.– Ex. Grasses, Trees, Moss, FernsEx. Grasses, Trees, Moss, Ferns

21

Roles of OrganismsRoles of Organisms

• ConsumersConsumers - Consume organic matter to - Consume organic matter to provide themselves with energy and provide themselves with energy and organic matter necessary for growth and organic matter necessary for growth and survival.survival.– Primary ConsumersPrimary Consumers

HerbivoresHerbivores (plants) (plants)– Secondary ConsumersSecondary Consumers

CarnivoresCarnivores (animals) (animals)OmnivoresOmnivores (plants and animals) (plants and animals)

– ScavengersScavengers (dead animals) (dead animals)

22

Roles of OrganismsRoles of Organisms

• DecomposersDecomposers– Digest organic molecules in detritus into Digest organic molecules in detritus into

simpler organic compounds, and absorb simpler organic compounds, and absorb soluble nutrients. (Bacteria and Fungi)soluble nutrients. (Bacteria and Fungi)Use non-living organic matter as Use non-living organic matter as

source of energy.source of energy.• Keystone SpeciesKeystone Species

– Play critical role in maintenance of Play critical role in maintenance of specific ecosystems.specific ecosystems.Bison in American Tall Grass PrairieBison in American Tall Grass Prairie

23

Energy Flow Through EcosystemsEnergy Flow Through Ecosystems

• Each step in the flow of energy through an Each step in the flow of energy through an ecosystem is known as a ecosystem is known as a trophic leveltrophic level..– As energy moves from one trophic level As energy moves from one trophic level

to the next, most of the useful energy to the next, most of the useful energy (90%) is lost as heat (2(90%) is lost as heat (2ndnd Law of Law of Thermodynamics).Thermodynamics).Because energy is difficult to track, Because energy is difficult to track,

biomassbiomass (weight of living material) is (weight of living material) is often used as a proxy.often used as a proxy.

24

Energy Flow Through an EcosystemEnergy Flow Through an Ecosystem

25

Food Chains and Food WebsFood Chains and Food Webs

• Food ChainFood Chain - Passage of energy from one - Passage of energy from one trophic level to the next due to one trophic level to the next due to one organism consuming another.organism consuming another.– Some chains rely on detritus.Some chains rely on detritus.

• Food WebFood Web - Series of multiple, overlapping - Series of multiple, overlapping food chains. food chains. – A single predator can have multiple prey A single predator can have multiple prey

species at the same time.species at the same time.– Fig. 5.15Fig. 5.15

26

Food ChainFood Chain

27

Nutrient Cycles in EcosystemsNutrient Cycles in Ecosystems

• Organisms are composed of molecules Organisms are composed of molecules and atoms that are cycled between living and atoms that are cycled between living and non-living portions of an ecosystem.and non-living portions of an ecosystem.– Biogeochemical Cycles - Biogeochemical Cycles - another name another name

for nutrient cycles.for nutrient cycles.

28

Carbon CycleCarbon Cycle

• Carbon and oxygen combine to form Carbon and oxygen combine to form carbon dioxide.carbon dioxide.– Plants use carbon dioxide during Plants use carbon dioxide during

photosynthesis to produce sugars.photosynthesis to produce sugars.Plants use sugars for plant growth.Plants use sugars for plant growth.

Herbivores eat plants, and Herbivores eat plants, and incorporate molecules into their incorporate molecules into their structure.structure.

Respiration breaks down sugars Respiration breaks down sugars releasing COreleasing CO22 and water back and water back into the atmosphere.into the atmosphere.

29

Carbon CycleCarbon Cycle

30

Nitrogen CycleNitrogen Cycle• Cycling of nitrogen atoms between abiotic and Cycling of nitrogen atoms between abiotic and

biotic ecosystem components.biotic ecosystem components.– Producers unable to use atmospheric N.Producers unable to use atmospheric N.

Must get nitrate NOMust get nitrate NO33 or ammonia NH or ammonia NH3.3.

– Nitrogen-fixing bacteriaNitrogen-fixing bacteria converts nitrogen gas converts nitrogen gas NN22 into ammonia. into ammonia. Legumes (Roots)Legumes (Roots)

Plants construct organic molecules.Plants construct organic molecules. Eaten by animals.Eaten by animals. Drains soil of Nitrogen.Drains soil of Nitrogen.

– Decomposers also break down nitrogen-Decomposers also break down nitrogen-containing molecules releasing ammonia.containing molecules releasing ammonia.

31

Nitrogen CycleNitrogen Cycle• Nitrifying bacteriaNitrifying bacteria are able to convert are able to convert

ammonia to nitrite, which can be ammonia to nitrite, which can be converted to nitrate.converted to nitrate.

• Denitrifying bacteriaDenitrifying bacteria are able to (under are able to (under anaerobic conditions) covert nitrite to anaerobic conditions) covert nitrite to nitrogen gas (Nnitrogen gas (N22) which is ultimately ) which is ultimately

released into the atmosphere.released into the atmosphere.

32

Nitrogen CycleNitrogen Cycle

33

Phosphorus CyclePhosphorus Cycle

• Phosphorus is not present in the Phosphorus is not present in the atmosphere as a gas.atmosphere as a gas.– Phosphorus compounds released by Phosphorus compounds released by

erosion and become dissolved in water.erosion and become dissolved in water.Plants use phosphorus to construct Plants use phosphorus to construct

necessary molecules.necessary molecules. Animals gain necessary P via Animals gain necessary P via

herbivory.herbivory. Decomposers recycle into soil. Decomposers recycle into soil.

34

Phosphorus CyclePhosphorus Cycle

35

Human Impact on Nutrient CyclesHuman Impact on Nutrient Cycles

• Two activities caused significant changes Two activities caused significant changes in carbon cycle:in carbon cycle:– Burning of fossil fuels. Burning of fossil fuels. (2001 – IPCC (2001 – IPCC

Report)Report)– Converting forests to agricultural land.Converting forests to agricultural land.

• Fossil fuel burning also increased amount Fossil fuel burning also increased amount of nitrogen available to plants.of nitrogen available to plants.

• Fertilizer carried into aquatic ecosystems.Fertilizer carried into aquatic ecosystems. Increase aquatic plant growth rate.Increase aquatic plant growth rate.

Lowered oxygen concentrations.Lowered oxygen concentrations.

36

ReviewReview

• Ecological ConceptsEcological Concepts– Habitat and NicheHabitat and Niche

• Natural Selection and EvolutionNatural Selection and Evolution• Organism InteractionsOrganism Interactions

– PredationPredation– CompetitionCompetition

• Community and Ecosystem InteractionsCommunity and Ecosystem Interactions– Roles of OrganismsRoles of Organisms– Energy Flow Through EcosystemsEnergy Flow Through Ecosystems– Nutrient Cycles in EcosystemsNutrient Cycles in Ecosystems

37