Chapter 4Chapter 4

Ecosystems and Living OrganismsEcosystems and Living Organisms

EvolutionEvolution

A process of change through A process of change through timetime

Theory of EvolutionTheory of Evolution1.1. Suggests that existing forms of life Suggests that existing forms of life

on earth have evolved from earlier on earth have evolved from earlier life forms over long periods of timelife forms over long periods of time

2.2. Evolution accounts for the Evolution accounts for the differences in structures, function, differences in structures, function, and behavior among life forms as and behavior among life forms as well as changes that occur in well as changes that occur in populations over many generationspopulations over many generations

Charles Charles DarwinDarwin

DarwinDarwin Charles Darwin devised a theory of evolution Charles Darwin devised a theory of evolution

based on variation and natural selection as seen based on variation and natural selection as seen in the Galapagos islands. in the Galapagos islands.

Included in his theory were five main ideas:Included in his theory were five main ideas:

1. Overpopulation1. Overpopulation

2. Competition2. Competition

3. Survival of the fittest/Natural selection3. Survival of the fittest/Natural selection

4. Reproduction4. Reproduction

5. Speciation5. Speciation

1. 1. OverpopulationOverpopulation

Within a population, there are Within a population, there are more offspring produced in more offspring produced in

each generation than can each generation than can possibly survivepossibly survive

2. Competition2. Competition Natural resources; like food, water, Natural resources; like food, water,

and space available to a population and space available to a population is limitedis limited

Because there are many organisms Because there are many organisms with similar nutritional with similar nutritional

requirements, there must be requirements, there must be competion between them for the competion between them for the

resources needed to surviveresources needed to survive

Variations among members of a population make some of Variations among members of a population make some of them better adapted to the environment than othersthem better adapted to the environment than others

It is generally the best-adapted individuals that will It is generally the best-adapted individuals that will survivesurvive

The environment is the agent of The environment is the agent of natural selectionnatural selection determining which species will survive.determining which species will survive.

3. Survival of the Fittest3. Survival of the Fittest

Survival of the FittestSurvival of the Fittest

Survival of the FittestSurvival of the Fittest

Survival of the FittestSurvival of the Fittest

Natural SelectionNatural Selection1.1. Natural selection involves the struggle of organisms to Natural selection involves the struggle of organisms to

survive and reproduce in a given environmentsurvive and reproduce in a given environment2.2. Traits which are Traits which are beneficial to the survivalbeneficial to the survival of an of an

organism in a particular environment tend to be organism in a particular environment tend to be retained andretained and passed onpassed on, and therefore, increase in , and therefore, increase in frequency within a population frequency within a population

3.3. Traits which have Traits which have low survival valuelow survival value to an organism to an organism tend to decrease in frequency from generation to tend to decrease in frequency from generation to generationgeneration

4.4. If environmental conditions change, traits that have If environmental conditions change, traits that have low survival value may now have a greater survival low survival value may now have a greater survival value. Therefore, traits that prove to be favorable value. Therefore, traits that prove to be favorable under new environmental conditions will increase in under new environmental conditions will increase in frequencyfrequency

ExEx: Insects resistant to insecticides: Insects resistant to insecticides1.1. Genetic make-up of some insects make them resistant Genetic make-up of some insects make them resistant

to the effects of insecticidesto the effects of insecticides2.2. Before the widespread use of insecticides, this trait was Before the widespread use of insecticides, this trait was

of no particular survival valueof no particular survival value3.3. With the increased use of insecticides, this trait With the increased use of insecticides, this trait

developed a very high survival valuedeveloped a very high survival value4.4. Therefore, insects with resistance to insecticides Therefore, insects with resistance to insecticides

survived and reproduced much more successfully than survived and reproduced much more successfully than those lacking the traitthose lacking the trait

5.5. As a result, the frequency of insecticide resistance has As a result, the frequency of insecticide resistance has increased greatly in insect populationsincreased greatly in insect populations

Important! The trait already exists within Important! The trait already exists within the genetic make-up of the organism.the genetic make-up of the organism.

4. Reproduction4. Reproduction

Individuals that survive and Individuals that survive and then reproduce, transmit these then reproduce, transmit these

variations to their offspringvariations to their offspring

5. Speciation5. Speciation

The development of a new species The development of a new species occurs as variations or adaptations occurs as variations or adaptations

accumulate in a population over accumulate in a population over many generationsmany generations

Ex: caveman Ex: caveman present man present man

Speciation: “Bigfoot? Sasquatch?Speciation: “Bigfoot? Sasquatch?

Evidence which supports the Evidence which supports the Theory of EvolutionTheory of Evolution

1. Fossil record1. Fossil record2. Comparative anatomy of organisms2. Comparative anatomy of organisms

3. Biogeography (Study of species distribution)3. Biogeography (Study of species distribution)4. Molecular Similarities4. Molecular Similarities

Diversity and classificationDiversity and classificationThe 5 Major KingdomsThe 5 Major Kingdoms

1. Monera-1. Monera-(Bacteria)(Bacteria)

2. Protista2. Protista

3. Fungi 3. Fungi

4. Plant4. Plant

5. Animal5. Animal

Six Kingdom Taxonomic System Six Kingdom Taxonomic System

Rotting Log Community: Rotting Log Community: An Ecosystem An Ecosystem

Ecosystem Formation-Ecosystem Formation-

Ecosystems tend to change over a Ecosystems tend to change over a long period of time until a stable long period of time until a stable

ecosystem is formed.ecosystem is formed.Both the living and nonliving Both the living and nonliving

parts of an ecosystem change.parts of an ecosystem change.

(A) (A) Ecological SuccessionEcological Succession The replacement of one kind of community with The replacement of one kind of community with

another is called another is called ecological succession.ecological succession. The kind of stable ecosystem that develops in a The kind of stable ecosystem that develops in a

particular geographical area depends on climate.particular geographical area depends on climate. Pioneer organismsPioneer organisms- are the first plants to - are the first plants to

populate an area. Lichens and algae may be populate an area. Lichens and algae may be pioneer organisms on bare rock. (Create soil)pioneer organisms on bare rock. (Create soil)

Climax CommunitiesClimax Communities- Succession ends with the - Succession ends with the development of a climax community in which the development of a climax community in which the populations of plants and animals exist in populations of plants and animals exist in balance with each other and the environment.balance with each other and the environment.

Ecological Succession Ecological Succession

Secondary SuccessionSecondary Succession

When a previously inhabited environment is When a previously inhabited environment is disturbed, and must undergo a new round of disturbed, and must undergo a new round of succession.succession.

Examples- Mt. St. Helens,Yellowstone firesExamples- Mt. St. Helens,Yellowstone fires

Keystone speciesKeystone species These determine the These determine the

nature and structure of nature and structure of an entire ecosystem. an entire ecosystem. Usually found in Usually found in small numbers but small numbers but have a key influence.have a key influence.

Examples: Examples:

Wolves, Fig Trees Wolves, Fig Trees

CoevolutionCoevolution

Interdependent Interdependent evolutionevolution of two of two speciesspecies

Results in symbiotic relationshipsResults in symbiotic relationships

Coevolution Coevolution

SymbiosisSymbiosis

An intimate relationship An intimate relationship between two or more speciesbetween two or more species

MutualismMutualism (+ , +)(+ , +)

In this relationship both organisms In this relationship both organisms benefit from each other.benefit from each other.

ExEx: Anenome and clown fish: Anenome and clown fish

MutualismMutualism

CommensalismCommensalism

(+ , o)(+ , o)

One benefits, one not affectedOne benefits, one not affected Epiphytes (mosses, orchids, ferns) attach Epiphytes (mosses, orchids, ferns) attach

themselves to tree bark and obtain their themselves to tree bark and obtain their nutrients without harm to the trees.nutrients without harm to the trees.

ParasitismParasitism (+ , - )(+ , - )

One helped, one harmedOne helped, one harmed PathogensPathogens (disease causing (disease causing agents) agents) are parasite that harm a are parasite that harm a

host organism.host organism. Crown gall disease in plants., TICKSCrown gall disease in plants., TICKS

PredationPredation

Predators exert strong selective Predators exert strong selective pressures upon their prey. pressures upon their prey.

Both prey and predator Both prey and predator evolveevolve in an in an attempt to be more successful and attempt to be more successful and survive.survive.

Predator/Prey RelationshipsPredator/Prey Relationships Data collected from fur pelts from the Hudson Bay CompanyData collected from fur pelts from the Hudson Bay Company

Studies have shown that Endocrine changes Studies have shown that Endocrine changes in populations may produce behavioral in populations may produce behavioral changes which tend to limit population changes which tend to limit population

growth. Therefore all population changes growth. Therefore all population changes may not be duemay not be due to predator/prey relationships to predator/prey relationships

alone.alone.

Defensive Adaptations in AnimalsDefensive Adaptations in Animals

Chemical defenses: Sprays, stinging cellsChemical defenses: Sprays, stinging cells Warning ColorationWarning Coloration: avoidance of predators by : avoidance of predators by

unpalatable animals. Ex: Poison Dart Frog.unpalatable animals. Ex: Poison Dart Frog.

Defensive Adaptations in AnimalsDefensive Adaptations in Animals

Cryptic coloration (Camouflage): Cryptic coloration (Camouflage): Blending into the Blending into the surroundings for avoidance of predators by surroundings for avoidance of predators by palatable animals.palatable animals.

Ex: Argentinean Horned FrogEx: Argentinean Horned Frog

Defensive Adaptations in Defensive Adaptations in AnimalsAnimalsMimicry:Mimicry: resemblance to another species. resemblance to another species. Ex: Io moth, Monarch and Viceroy Ex: Io moth, Monarch and Viceroy

butterfliesbutterflies

CompetitionCompetition1.1. Different species living in the same Different species living in the same

environment, or environment, or habitathabitat, may require the same , may require the same resources. When the resources are limited, resources. When the resources are limited, competition occurs among the species. competition occurs among the species.

2.2. Intraspecific:Intraspecific: competition within a population competition within a population

Interspecific:Interspecific: competition between species competition between species

CompetitionCompetition2.2.CompetitionCompetition- is the struggle between different - is the struggle between different

species for the same limited resources. The species for the same limited resources. The more similar the needs of the species, the more more similar the needs of the species, the more intense the competition. intense the competition.

CompetitionCompetition

3.Each species occupies a specific niche in the 3.Each species occupies a specific niche in the community. A niche is the role the species plays, community. A niche is the role the species plays, and includes the type of food it eats, where it and includes the type of food it eats, where it lives, where it reproduces, and its relationships lives, where it reproduces, and its relationships with other species.with other species.

Limiting FactorsLimiting Factors

Are those resources that are scarce!Are those resources that are scarce!Cause population size to be limited.Cause population size to be limited.Results in Results in resource partitioningresource partitioning and and

competitive exclusioncompetitive exclusion..

Resource PartitioningResource Partitioning: : differences in differences in resource use among species.resource use among species.

Limiting Factors Gause’s ExperimentsLimiting Factors Gause’s Experiments

Limiting Factors Gause’s ExperimentsLimiting Factors Gause’s Experiments

Which type of Competition?Which type of Competition?

Interspecific Competition!Interspecific Competition!

Competitive ExclusionCompetitive Exclusion: one species is : one species is excluded from a portion of a niche by another excluded from a portion of a niche by another

as a result of interspecific competition. as a result of interspecific competition. (Two species with identical niches can’t coexist.) (Two species with identical niches can’t coexist.)

Species RichnessSpecies Richness

Related to the # of available nichesRelated to the # of available niches Tropical rain forests- Most diversity/Low #’sTropical rain forests- Most diversity/Low #’s Mountaintops/Tundra- Low diversity/High #’sMountaintops/Tundra- Low diversity/High #’s More stressful habitats have lower diversity.More stressful habitats have lower diversity.

Community complexity and species diversity Community complexity and species diversity