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BiodiversityBiodiversity

BiodiversityBiodiversity

• Biological Diversity or Biodiversity, is the variety of the earth’s species, the genes they contain, the ecosystems in which they live, and the ecosystems processes such as energy flow and nutrient cycling.

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BiodiversityBiodiversity

• Biodiversity – increases with speciation– decreases with extinction

• Give-and-take between speciation and extinction changes in biodiversity

Why Biodiversity is important?Why Biodiversity is important?

• It supplies us with food, wood, energy, medicines,…

• It preserves the air and water quality and maintains the fertility of soils.

• It helps us to dispose of wastes and to control populations of pests

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• In carrying out these free ecological services, which are also part of the earth’s natural capital, biodiversity helps to sustain life on the Earth.

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Biological Evolution Biological Evolution by Natural by Natural

SELECTIONSELECTION

IdeaIdea• Early Greek philosophers

• Wallace and Darwin (1858) independently proposed the concept of natural selection as a mechanism for biological evolution’

• But Darwin gathered evidence and publish it in 1859 in his book, On the Origin of Species by Means of Natural Selection

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Charles DarwinCharles Darwin• 1809-1882

• British naturalist

• Proposed the idea of evolution by natural selection

• Collected clear evidence to support his ideas

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Darwin’s ObservationsDarwin’s Observations1.1. Most species produce more offspring Most species produce more offspring

than can be supported by the than can be supported by the environmentenvironment

2.2. Environmental resources are limitedEnvironmental resources are limited3.3. Most populations are stable in sizeMost populations are stable in size4.4. Individuals vary greatly in their Individuals vary greatly in their

characteristics (phenotypes)characteristics (phenotypes)5.5. Variation is heritable (genotypes)Variation is heritable (genotypes)

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Darwin’s finchesDarwin’s finches• 13 species of finches in the Galápagos

Islands• Was puzzling since only 1 species of this

bird on the mainland of South America, 600 miles to the east, where they had all presumably originated

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Darwin’s finchesDarwin’s finches

• Differences in beaks – associated with eating different foods– adaptations to the foods available on their home

islands

• Darwin concluded that when the original South American finches reached the islands, they adapted to available food in different environments

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What did Darwin say?What did Darwin say?• Organisms reproduce more than the

environment can support– some offspring survive– some offspring don’t survive– competition

• for food• for mates• for nesting spots• to get away

from predators

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Survival of the fittestSurvival of the fittest• Who is the fittest?

–traits fit the environment

–the environment can change, so who is fit can change

Peppered moth

• According to this theory, life has evolved into six major groups of species, called Kingdoms.

• Tree of life (development of life)

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At any given moment (e.g. the At any given moment (e.g. the ‘present’), all we see is ‘present’), all we see is current current

diversitydiversity……all all extinctextinct forms are gone (99.9%) forms are gone (99.9%)

At any given moment (e.g. the At any given moment (e.g. the ‘present’), all we see is ‘present’), all we see is current current

diversitydiversity……all all extinctextinct forms are gone (99.9%) forms are gone (99.9%)

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LamarckLamarck• Lamarck’s theory stated that organisms

evolve over time due to the environmental factors that act upon that organism

• If they began to use an organ more than they had in the past, it would increase in its lifetime.

• Meanwhile organs that organisms stopped using would shrink.

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Fossil Record:Fossil Record:• The world’s cumulative body of fossils The world’s cumulative body of fossils

found.found.

• Fossils: Mineralized or petrified replicas of Fossils: Mineralized or petrified replicas of skeletons, bones,… or impressions found in skeletons, bones,… or impressions found in rocksrocks

• Strongest evidence for evolutionStrongest evidence for evolution

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Main cause of evolutionary change:Main cause of evolutionary change: Main cause of evolutionary change:Main cause of evolutionary change:

• MutationMutation: random changes in the : random changes in the structure or number DNA molecules in a structure or number DNA molecules in a cell that can be inherited by offspring.cell that can be inherited by offspring.

• Mutations can occur in any cell, but only Mutations can occur in any cell, but only those taking place in reproductive cells are those taking place in reproductive cells are passed on to offspring.passed on to offspring.

• New genetic traits that give better chances New genetic traits that give better chances for survival (now or in the future)for survival (now or in the future)

• MutationMutation: random changes in the : random changes in the structure or number DNA molecules in a structure or number DNA molecules in a cell that can be inherited by offspring.cell that can be inherited by offspring.

• Mutations can occur in any cell, but only Mutations can occur in any cell, but only those taking place in reproductive cells are those taking place in reproductive cells are passed on to offspring.passed on to offspring.

• New genetic traits that give better chances New genetic traits that give better chances for survival (now or in the future)for survival (now or in the future)

• Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with theses traits (natural selection)

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AdaptationAdaptation

• An adaptation or adaptive trait, is any heritable trait that enables and individual organism to survive through natural selection and to reproduce more than other individuals under prevailing environmental conditions

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For natural selection to occur,…For natural selection to occur,…

• The trait must be heritable.

• The trait must lead to differential reproduction, which enables individuals with the trait to leave more offspring than other members of the population.

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Genetic ResistanceGenetic Resistance

• Genetic resistance is the ability of one or more organisms in a population to tolerate a chemical design to kill it. (Ex. Bacteria)

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Natural Selection acts in Natural Selection acts in individuals, but evolution individuals, but evolution

occurs in populationsoccurs in populations

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When environmental When environmental conditions change:conditions change:

• A population of a species faces 3 possible futures:–Adapt

–Migrate

–Become extinct

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HumansHumans

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How long does it takes?How long does it takes?

• Populations of genetically diverse species that reproduce quickly often adapt to a change in short time.

• Species that cannot reproduce large numbers of offspring rapidly, take long time to adapt.28

3 Common myths3 Common myths

• Survival of the fittest means survival of the strongest.

• Organisms develop certain traits because they need or want them.

• Evolution by natural selection involves some grand plan of nature in which species become more perfectly adapted.

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SpeciationSpeciation

• Tectonic plate movements, volcanic eruptions, earthquakes, and climate change have shifted wildlife habitats, wiped out large number of species, and created opportunities for the evolution of new species.

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SpeciationSpeciation• One species can evolve into two or

more species

• 2 step process– Geographical isolation

– Reproductive isolation

When a group becomes geographically isolated over time

it will become reproductively isolated = new species formed.

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Geographic isolationGeographic isolation•When a population becomes divided by a natural barrier.

•Mountains, river, body of water, landslides•Groups can’t interbreed or intermix•Become adapted to a different environment

Harris’s antelope squirrel inhabits the canyon’s south rim (L). Just a few miles away on the north rim (R) lives the closely related white-tailed antelope squirrel

Harris’s antelope squirrel inhabits the canyon’s south rim (L). Just a few miles away on the north rim (R) lives the closely related white-tailed antelope squirrel

Ammospermophilus spp

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Reproductive IsolationReproductive Isolation• Differences in isolated groups become so

great, they can no longer interbreed– Physical changes

– Behavioral changes

– Biochemical changes

How long does it takes the How long does it takes the speciation?speciation?

• For some rapidly reproducing organisms, this may occur within hundreds of years.

• For most species, it takes from tens of thousands to millions of years.

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ExtinctionExtinction• Extinction of a species occurs when it

ceases to exist; may follow environmental change - if the species does not evolve

• Evolution and extinction are affected by:– large scale movements of continents– gradual climate changes due to continental

drift or orbit changes– rapid climate changes due to catastrophic

events

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Extinction: Lights OutExtinction: Lights Out

•Extinction occurs when the population cannot adapt to changing environmental conditions.

•The golden toad of Costa Rica’s Monteverde cloud forest has become extinct because of changes in climate.

Figure 4-11

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ExtinctionExtinction• Background extinctionBackground extinction - species disappear - species disappear

at a low rate as local conditions changeat a low rate as local conditions change

• Mass extinctionMass extinction - catastrophic, wide- - catastrophic, wide-spread events --> abrupt increase in spread events --> abrupt increase in extinction rateextinction rate

• Five mass extinctions in past 500 million Five mass extinctions in past 500 million yearsyears

How many mass extintions?How many mass extintions?

• Some biologists argue that a mass extintions should be distinguished by a low speciation rate as well as by a high rate of extintion.

• Under this: only 3 mass extintions.

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• A mass extintion provides an opportunity for the evolution of new species that can fill unoccupied ecological roles or newly created ones.

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Species Diversity: Richness vs. Evenness

Species Richness: measurement of the number of species in a given area

Species Evenness: measurement of how evenly distributed organisms are among species

Community A Community Bspecies 1 25 1species 2 0 1species 3 25 1species 4 25 1species 5 25 96

• Species richness appears to increase the productivity and stability or sustainability of an ecosystem.

• While there may be some exceptions to this, most ecologists now accept this as a useful hypothesis

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Niche isthe species’ occupation

and its

Habitat location of species

(its address)

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NicheNicheA species’ functional role in its ecosystem; includes anything affecting species survival and reproduction

1. Range of tolerance for various physical and chemical conditions

2. Types of resources used

3. Interactions with living and nonliving components of ecosystems

4. Role played in flow of energy and matter cycling

Scientists use the niches of Scientists use the niches of species to classify them species to classify them

broadly as:broadly as:Generalist speciesGeneralist speciesSpecialists speciesSpecialists species

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Types of SpeciesTypes of Species•Generalist

–large niches–Live in many places–Eat a variety of food–tolerate wide range of environmental variations–do better during changing environmental

conditions–Such as flies, cockroaches, mice, rats, humans,

…

Types of SpeciesTypes of Species• Specialist

–narrow niches–May be able to live in only one type of habitat–Use one or a few types of food–Tolerate a narrow range of climatic and other

environmental conditions– more likely to become endangered– do better under consistent environmental

conditions–Such as tiger salamanders, China´s giant panda

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Fig. 4-7, p. 91Fig. 4-7, p. 91

Fig. 4-7, p. 91

Generalist specieswith a broad niche

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f in

div

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Resource use

Specialist specieswith a narrow niche

Nicheseparation

Nichebreadth

Region of niche overlap

Generalist SpeciesGeneralist Species

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• Any given species may play one or more of five important roles- native, nonnative, indicator, keystone, or fundation roles – in a particular ecosystem.

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Types of SpeciesTypes of Species• Native speciesNative species normally live and thrive in a

particular ecosystem• Nonnative speciesNonnative species are introduced - can be

called exotic or alien• Indicator speciesIndicator species serve as early warnings of

danger to ecosystem- birds & amphibians• Keystone speciesKeystone species are considered of most

importance in maintaining their ecosystem• Foundation species help to create habitats

and ecosystems

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Nonnative Nonnative SpeciesSpecies• Nonnative plant species are invading the Nonnative plant species are invading the

nation's parks at an alarming rate, nation's parks at an alarming rate, displacing native vegetation and displacing native vegetation and threatening the wildlife that depend on threatening the wildlife that depend on themthem

• At some, such as Sleeping Bear Dunes At some, such as Sleeping Bear Dunes National Lakeshore in Michigan, as much National Lakeshore in Michigan, as much as 23 percent of the ground is covered with as 23 percent of the ground is covered with alien species, and the rate of expansion is alien species, and the rate of expansion is increasing dramaticallyincreasing dramatically..

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Indicator Indicator SpeciesSpecies

• a species whose status provides information on the overall condition of the ecosystem and of other species in that ecosystem

• reflect the quality and changes in environmental conditions as well as aspects of community composition

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Keystone SpeciesKeystone Species• A keystone is the stone at the top of an arch that supports the

other stones and keeps the whole arch from falling– a species on which the persistence of a large number of other species in

the ecosystem depends.

• If a keystone species is removed from a system– the species it supported will also disappear

– other dependent species will also disappear

• Examples– top carnivores that keep prey in check

– large herbivores that shape the habitat in which other species live

– important plants that support particular insect species that are prey for birds

– bats that disperse the seeds of plants