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Unit ThreeUnit Three

Evolution, Evolution, Biodiversity, and Biodiversity, and

Community ProcessesCommunity Processes A. C. Mosley High School

Mrs. Dow

Chapter 5

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The Just-Right PlanetRead Case study on page 87.

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Origins of Life (5-1)

Chemical evolution of organic Chemical evolution of organic molecules, biopolymers & molecules, biopolymers & systems systems

Took about 1 billion years!Took about 1 billion years!

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Miller-Urey Experiment

conducted in 1953 by Stanley Miller with Harold Ureythe first experiment about the evolution of prebiotic chemicals and the origin of life on Earth

mixture of methane, ammonia, hydrogen, and water vapor introduced into a 5-liter flask (simulate the Earth's primitive, reducing atmosphere) energized by an electrical discharge apparatus to represent ultraviolet radiation from the Sunproducts were allowed to condense and collect in a lower flask which modeled a body of water on the Earth's surface

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Miller-Urey Experiment

heat supplied to this flask recycled the water vapor just as water evaporates from lakes and seas, before moving into the atmosphere and condensing again as rainafter a day of continuous operation

• a thin layer of hydrocarbons on the surface of the water

after about a week of operation• a dark brown scum had collected in

the lower flask and was found to contain several types of amino acids, including glycine and alanine, together with sugars, tars, and various other unidentified organic chemicals

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EVOLUTIONisGradual Change

EVOLUTIONisGradual Change

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Origins of Life (5-1)Next, biological evolution

Single-celled prokaryotic bacteria single-celled eukaryotes multicellular organisms

Evidence from fossils, ice-core drilling, chemical analysis & DNA

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Plants begininvadingland

Evolution and expansion of life

First fossilrecord ofanimals

Age of reptiles

Age of mammals

Insects and amphibians invade the land

Modern humans(Homo sapiens)appear about2 secondsbefore midnight

Recorded humanhistory begins1/4 secondbefore midnight

Origin of life(3.6–3.8 billionyears ago)

Page 89

noon

midnight

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FossilsOldest fossils are the approximately 3.465 billion-year-old microfossils from the Apex Chert, Australia

colonies of cyanobacteria (formerly called blue-green algae) which

built real reefs

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History of Theories of Evolution

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Old Theories of Evolution

Jean Baptiste Lamarck (early 1800’s) proposed:

“The inheritance of acquired characteristics”

He proposed that by using or not using its body parts, an individual tends to develop certain

characteristics, which it passes on to its offspring.

Lamarck's scientific theories were largely ignored or attacked during his lifetime, Today, the name of Lamarck is associated merely with a discredited theory of heredity

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“The Inheritance of Acquired Characteristics”

Example:

A giraffe acquired its long neck because its ancestor stretched higher and higher into

the trees to reach leaves, and that the animal’s increasingly lengthened neck was

passed on to its offspring.

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Charles Darwin

Darwin set sail on the H.M.S. Beagle (1831-1836) to survey the south seas (mainly South America and the Galapagos Islands) to collect plants and animals.

On the Galapagos Islands, Darwin observed species that lived no where else in the world.

These observations led Darwin to write a book

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Darwin’s Journey on the H.M.S. Beagle

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Pinta IslandIntermediate shell

Pinta

Isabela IslandDome-shaped shell

Hood IslandSaddle-backed shell

HoodFloreana

Santa Fe

Santa Cruz

James

Marchena

Fernandina

Isabela

Tower

Giant Tortoises of the Galápagos Giant Tortoises of the Galápagos IslandsIslands

17http://www.galapagosislands.com

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Charles Darwin

Wrote in 1859:

“On the Origin of Species by Means of Natural Selection”

Two main conclusions:

1. Species were not created in their present form, but evolved from ancestral species.

2. Proposed a mechanism for evolution: NATURAL SELECTION

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Darwin’s ObservationsDarwin’s Observations

1.1. 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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Natural Selection

Individuals with favorable traits are more likely to leave more offspring better suited for their environment

Also known as “Differential Reproduction”

Example:

English peppered

moth (Biston betularia)

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Evolution & Adaptation (5-2)Change in a population’s genetic makeup over timeTheory of evolution all species came from a earlier, ancestral species

Microevolution (genes mutate individuals are selected populations evolve)Small genetic changes over time (traits are passed on)

Sexual reproduction leads to diversityGene pool (all the genes in a populations offspring)Variability is created by mutations

DNA exposed to external agentsRandom mistakes

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Microevolution- Microevolution works through a combination of

four processes that change the genetic composition of a population:

Mutation – involving random changes in the structure or number of DNA molecules in a cell and is the ultimate source of genetic variability in a population.

Natural selection – occurs when some individuals of a population have genetically based traits that cause them to survive and produce more offspring than other individuals

Gene flow – which involves movement of genes between populations and can lead to changes in the genetic composition of local populations.

Genetic drift – involves changes in the genetic composition of a population by chance and is especially important for small populations.

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Natural selectionMembers of a population have favorable traits that are passed on3 necessary conditions

Must have genetic variabilityMust be heritableMust allow for further offspring

• Some mutations are harmful/some beneficial

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Adaptive traits (adaptation)Heritable traits that help organisms survive and reproduce

Helps to:Adapt to new conditionsMigrate to a new areaBecome extinct

Adaptive Radiation

Emergence of numerous species from a common ancestor introduced to new and diverse environments

Example:

Hawaiian Honeycreepers

Convergent Evolution

Species from different evolutionary branches may come to resemble one another if they live

in very similar environments

Example:

1. Ostrich (Africa) and Emu (Australia).

2. Sidewinder (Mojave Desert) and

Horned Viper (Middle East Desert)

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Three Types of Natural Selection and Co evolution

Three types of natural selection

Biologists recognize three types of natural selection – depending on environmental conditions.

1. Directional natural selection

2. Stabilizing natural selection

3. Diversifying natural selection

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Click to view animation.

Example of directional selection animation.

Animation (watch on CD)

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Animation (watch on CD)

Click to view animation.

Stabilizing selection animation.

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Animation (watch on CD)

Click to view animation.

Disruptive selection animation.

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What is co evolution?What is co evolution?

It is an evolution in which two or more It is an evolution in which two or more species interact and exert selective species interact and exert selective pressures on each other that can lead pressures on each other that can lead each species to undergo various each species to undergo various adaptations. adaptations.

Bats and Moths

Coevolution

Evolutionary changeOne species acts as a selective force on a second speciesInducing adaptations that act as selective force on the first species

Example:1. Wolf and Moose2. Acacia ants and Acacia trees2. Yucca Plants and Yucca moths3. Lichen

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Ecological Niches and Adaptation (5-3)

NicheSpecies way of life and every thing that affects it

Includes member’s adaptations

Range of tolerance

Role of energy flow

HabitatWhere an organism lives

Conditions and resources it needs

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Niche isthe species’ occupation and its

Habitat location of species

(its address)

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Niche

Realized niche:Realized niche: more restricted more restricted set of conditions under which set of conditions under which the species actually exists due to the species actually exists due to interactions with other speciesinteractions with other species

Fundamental niche:Fundamental niche: set of set of conditions under which a conditions under which a species might exist in the species might exist in the absence of interactions with absence of interactions with other speciesother species

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GeneralistsBroad ecological role

Living in many places

Eat a variety of foods

Will adapt easily

Ability to develop genetic resistance to poisons

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SpecialistsSpecialistsLive in specific environmentsLive in specific environmentsProne to extinctionProne to extinctionCompetition may cause them to Competition may cause them to evolveevolve

Panda eat mostly bamboo, are Panda eat mostly bamboo, are separated into small isolated separated into small isolated groups and have low birth rates groups and have low birth rates and litter size and litter size Organism is classified a generalist or a

specialist based on its

Range of toleranceNicheLimiting factorsResponse to changing conditions

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Region of niche overlap

Generalist specieswith a broad nicheSpecialist species

with a narrow nicheNiche

breadth

Nicheseparation

Num

ber

of in

divi

dual

s

Resource use

Overlap of the niches of two different species

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Specialized feeding niches of various birds species in a coastal wetland

Black skimmerseizes small fishat water surface

Flamingofeeds on minuteorganismsin mud

Scaup and otherdiving ducks feed onmollusks, crustaceans,and aquatic vegetation

Brown pelican dives for fish,which it locates from the air

Avocet sweeps bill throughmud and surface water in search of small crustaceans,insects, and seeds

Louisiana heron wades intowater to seize small fish

Oystercatcher feeds onclams, mussels, and other shellfish into which it pries its narrow beak

Dowitcher probes deeplyinto mud in search ofsnails, marine worms,and small crustaceans

Knot (a sandpiper) picks upworms and small crustaceansleft by receding tide

Herring gull is atireless scavenger

Ruddy turnstone searchesunder shells and pebbles for small invertebrates

Piping plover feedson insects and tinycrustaceans on sandy beaches

Resource partitioning reduces competition

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“Evolution is concerned about leaving the most descendents, not the strongest”

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MacroevolutionWhat is macroevolution?

Macroevolution is concerned with how evolution takes place above the level of species and over much longer periods than microevolution, and macro evolutionary patterns include genetic persistence, genetic divergence, and genetic loss.

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Speciation, Extinction and Biodiversity (5-4)

SpeciationTwo species arise when two species can no longer breed

• Allopatric speciation Due to geographical isolation or reproductive isolation Fox population (next slide)

• Sympatric speciation Two species live close together, can’t interbreed Example: some insects when two populations experience

different types of mutations by feeding on different types of plants

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Early foxpopulation

Spreadsnorthwardandsouthwardandseparates

How geographic isolation can lead to reproductive

isolation, divergence, and speciation.

Adapted to heatthrough lightweightfur and long ears, legs, and nose, whichgive off more heat.

Adapted to cold through heavier fur, short ears,short legs, short nose. White fur matches snow for camouflage.

Gray Fox

Arctic Fox

Different environmentalconditions lead to differentselective pressures and evolutioninto two different species.

Northernpopulation

Southernpopulation

Grey Fox

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Going, Going, Gone

Extinction Natural disasters

Introduction of new competitive species

Environmental changes

Adaptive radiationRecovery periods after mass extinction

It takes 1 to 10 million years to rebuild biological diversity of a mass extinction

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Biologist estimate that 99.9% of all the species that ever existed are extinct.

When local environmental changes, some species will disappear at a low rate: this is called background extinctionMass extinction is a significant rise in extinction rates above the background extinction (usually 25-70% species lost)Mass depletion extinction rates are higher than normal but not high enough to classify as a mass extinction

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Mass Extinctions & Depletion2 Mass extinction & 3 Mass depletions

Date of the Extinction Event

Percent Species

Lost Species Affected

65 mya

(million

years ago)

85 Dinosaurs, plants (except ferns and seed bearing plants), marine vertebrates and invertebrates. Most mammals,

birds, turtles, crocodiles, lizards, snakes, and amphibians were unaffected.

213 mya 44 Marine vertebrates and invertebrates

248 mya 75-95 Marine vertebrates and invertebrates

380 mya 70 Marine invertebrates

450 mya 50 Marine invertebrates

http://www.geog.ouc.bc.ca/physgeog/contents/9h.html

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Pangea

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EURASIA

AFRICASO

UTH

AM

ER

ICA

IND

IA

135 million years ago

Present65 million years ago

225 million years ago

120°80° 0°

120°120°

120°

80°80° 80°80°40°

40°120° 120°

120°GONDWANALANDGONDWANALAND

120°

LAURASIALAURASIA

PA

NG

AE

A

PA

NG

AE

A

ANTARCTICAANTARCTICA AUSTRALIA

AUSTRALIAMADA-

GASCARMADA-

GASCAR

Continental drift

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Natural capitalTerrestrialorganisms

Marineorganisms

Qu

ate

rna

ry

Ter

tiar

yCre

tace

ou

s

Jura

ssic

Tri

assi

c

Per

mia

n

Car

bo

nif

ero

us

Dev

on

ian

Silu

rian

Ord

ovi

cian

Cam

bri

an

Pre

-cam

bra

in

1.8 06514520525029035541044050054535000

1600

1200

800

400

Nu

mb

er o

f fa

mili

es

Millions of years ago

Change in the earth’s biodiversity over geological

time.

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Sustainability and EvolutionEarth is constantly changing, and throughout the earth’s history the atmosphere has changed, the climate has changed, the geography has changed he types and numbers of organisms have changes, and continental drift has changed the positions of the earth’s continents.

Biologists estimate that the current human-accelerated extinction rate of species is 1,000 to 10,000 times higher than natural extinction rates. (100 to 1,000 species per million species)

It has been predicted that by the end of the 21st century we may see the extinction of half of the present species now on Earth.

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Future of Evolution? (5-5)

Artificial selection by humans

Selective breeding

Genetic breeding/gene splicingCloning

Biopharming

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Genetic engineeringUnpredictable process

Ethical

Success rate is 1%

How will benefit?

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Crop

Crossbreeding

Desired trait(color)

ApplePear

Offspring

Crossbreeding

Best results

Newoffspring

Desiredresult

Figure 5-10

Page 97

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Phase 1Make Modified Gene

Identify and extractgene with desired trait

Identify and removeportion of DNAwith desired trait

Remove plasmidfrom DNA of E. coli

Insert extracted DNA(step 2) into plasmid(step3)

Insert modifiedplasmid into E. coli

Grow in tissueculture tomake copies

cell

gene

DNA

plasmid

E. coliDNA

Geneticallymodifiedplasmid

plasmid

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Phase 2Make Transgenic Cell

Transfer plasmidcopies to a carrier

agrobacterium

Agrobacteriuminserts foreignDNA into plantcell to yieldtransgenic cell

Transfer plasmidto surfacemicroscopic metalparticle

Use gene gunto inject DNAinto plant cell

A. tumefaciens(agrobacterium)

Plant cell

Nucleus

Host DNA

Foreign DNA

Figure 5-11b Page 98

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Phase 3Grow Genetically Engineered Plant

Transgenic cellfrom Phase 2

Cell division oftransgenic cells

Culture cellsto form plantlets

Transgenic plantswith new traits

Figure 5-11c Page 98

Transfer to soil

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Animation (watch on CD)

Click to view animation.

Evolutionary tree of life animation.

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Animation

Click to view animation.

Evolutionary tree diagrams interaction.