Biological Evolution
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Transcript of Biological Evolution
Biological EvolutionBiological Evolution
Biological Biological EvolutionEvolution
How Do We Know Which Organisms Lived in the Past?
• Our knowledge about past life comes from fossils, chemical analysis, cores drilled out of buried ice, and DNA analysis.
Figure 4-4Figure 4-4
EVOLUTION, NATURAL SELECTION, AND ADAPTATION
• Biological evolution by natural selection involves the change in a population’s genetic makeup through successive generations.– genetic variability– Mutations: random changes in the structure or
number of DNA molecules in a cell that can be inherited by offspring.
Natural Selection and Adaptation: Leaving More Offspring With
Beneficial Traits
• Three conditions are necessary for biological evolution:– Genetic variability, traits must be heritable, trait must
lead to differential reproduction.
• An adaptive trait is any heritable trait that enables an organism to survive through natural selection and reproduce better under prevailing environmental conditions.
Coevolution: A Biological Arms Race
• Interacting species can engage in a back and forth genetic contest in which each gains a temporary genetic advantage over the other.– This often happens between predators and prey
species.
Hybridization and Gene Swapping: other Ways to Exchange Genes
• New species can arise through hybridization.– Occurs when individuals to two distinct species
crossbreed to produce an fertile offspring.
• Some species (mostly microorganisms) can exchange genes without sexual reproduction.– Horizontal gene transfer
Limits on Adaptation through Natural Selection
• A population’s ability to adapt to new environmental conditions through natural selection is limited by its gene pool and how fast it can reproduce.– Humans have a relatively slow generation time
(decades) and output (# of young) versus some other species.
Common Myths about Evolution through Natural Selection
• Evolution through natural selection is about the most descendants.– Organisms do not develop certain traits because
they need them.– There is no such thing as genetic perfection.
GEOLOGIC PROCESSES, CLIMATE CHANGE,
CATASTROPHES, AND EVOLUTION
• The movement of solid (tectonic) plates making up the earth’s surface, volcanic eruptions, and earthquakes can wipe out existing species and help form new ones.– The locations of continents and oceanic basins
influence climate.– The movement of continents have allowed species to
move.
Fig. 4-5, p. 88
135 million years ago
Present65 million years ago
225 million years ago
Climate Change and Natural Selection
• Changes in climate throughout the earth’s history have shifted where plants and animals can live.
Figure 4-6Figure 4-6
Fig. 4-6, p. 89
Land above sea level
18,000years before present
Northern HemisphereIce coverage
Modern day(August)
Note:Modern sea ice
coveragerepresents
summer months
LegendContinental ice
Sea ice
Catastrophes and Natural Selection
• Asteroids and meteorites hitting the earth and upheavals of the earth from geologic processes have wiped out large numbers of species and created evolutionary opportunities by natural selection of new species.
ECOLOGICAL NICHES AND ADAPTATION
• Each species in an ecosystem has a specific role or way of life.– Fundamental niche: the full potential range of
physical, chemical, and biological conditions and resources a species could theoretically use.
– Realized niche: to survive and avoid competition, a species usually occupies only part of its fundamental niche.
Generalist and Specialist Species: Broad and Narrow Niches
• Generalist species tolerate a wide range of conditions.
• Specialist species can only tolerate a narrow range of conditions.
Figure 4-7Figure 4-7
Fig. 4-7, p. 91
Generalist specieswith a broad niche
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Resource use
Specialist specieswith a narrow niche
Nicheseparation
Nichebreadth
Region of niche overlap
SPOTLIGHTCockroaches: Nature’s Ultimate
Survivors
• 350 million years old• 3,500 different species• Ultimate generalist
– Can eat almost anything.– Can live and breed almost
anywhere.– Can withstand massive
radiation.
Figure 4-AFigure 4-A
Specialized Feeding Niches
• Resource partitioning reduces competition and allows sharing of limited resources.
Figure 4-8Figure 4-8
Fig. 4-8, pp. 90-91
Piping plover feedson insects and tinycrustaceans on sandy beaches
(Birds not drawn to scale)
Black skimmerseizes small fishat water surface
Flamingofeeds on minuteorganismsin mud
Scaup and otherdiving ducks feed on mollusks, 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 up worms andsmall crustaceans leftby receding tide
Herring gull is atireless scavenger
Ruddy turnstone searches
under shells and pebbles
for small invertebrates
Evolutionary Divergence
• Each species has a beak specialized to take advantage of certain types of food resource.
Figure 4-9Figure 4-9
Fig. 4-9, p. 91
Maui Parrotbill
Fruit and seed eaters Insect and nectar eaters
Kuai Akialaoa
Amakihi
Crested Honeycreeper
Apapane
Akiapolaau
Unknown finch ancestor
Greater Koa-finch
Kona Grosbeak
SPECIATION, EXTINCTION, AND BIODIVERSITY
• Speciation: A new species can arise when member of a population become isolated for a long period of time.– Genetic makeup changes, preventing them from
producing fertile offspring with the original population if reunited.
Geographic Isolation
• …can lead to reproductive isolation, divergence of gene pools and speciation.
Figure 4-10Figure 4-10
Fig. 4-10, p. 92
Different environmentalconditions lead to different selective pressures and evolution into two different species.
SouthernPopulation
Northernpopulation
Adapted to heat through lightweightfur and long ears, legs, and nose, which give off more heat.
Adapted to cold through heavier fur,short ears, short legs,short nose. White furmatches snow for camouflage.
Gray Fox
Arctic Fox
Spreadsnorthward
and southwardand separates
Early foxPopulation
Extinction: Lights Out
• Extinction occurs when the population cannot adapt to changing environmental conditions.The golden toad of Costa Rica’s The golden toad of Costa Rica’s
Monteverde cloud forest has Monteverde cloud forest has become extinct because of become extinct because of changes in climate.changes in climate.
Figure 4-11Figure 4-11
Fig. 4-12, p. 93
Tertiary
Bar width represents relative number of living speciesEra Period
Species and families experiencing
mass extinction
Millions ofyears ago
Ordovician: 50% of animal families, including many trilobites.
Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites.
500
345
Cambrian
Ordovician
Silurian
Devonian
Extinction
Extinction
Pal
eozo
icM
eso
zoic
Cen
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Triassic: 35% of animal families, including many reptiles and marine mollusks.
Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites.Carboniferous
Permian
Current extinction crisis causedby human activities. Many speciesare expected to become extinctwithin the next 50–100 years.Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including manyforaminiferans and mollusks.
Extinction
Extinction
Triassic
Jurassic
Cretaceous
250
180
65Extinction
ExtinctionQuaternary Today
Effects of Humans on Biodiversity
• The scientific consensus is that human activities are decreasing the earth’s biodiversity.
Figure 4-13Figure 4-13
Fig. 4-13, p. 94
Marineorganisms
Terrestrialorganisms
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Millions of years ago
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GENETIC ENGINEERING AND THE FUTURE OF EVOLUTION
• We have used artificial selection to change the genetic characteristics of populations with similar genes through selective breeding.
• We have used genetic engineering to transfer genes from one species to another.
Figure 4-15Figure 4-15
Genetic Engineering: Genetically Modified Organisms (GMO)
• GMOs use recombinant DNA – genes or portions
of genes from different organisms.
Figure 4-14Figure 4-14
Fig. 4-14, p. 95
Insert modifiedplasmid into E. coli
Phase 1Make Modified Gene
Cell
Extract DNA
E. coli
Gene ofinterest
DNA
Identify and extract gene with desired trait
Geneticallymodifiedplasmid
Identify and remove portion of DNA withdesired trait
Remove plasmidfrom DNA of E. coli
Plasmid
ExtractPlasmid
Grow in tissueculture to
make copies
Insert extracted(step 2) into plasmid
(step 3)
Fig. 4-14, p. 95
Plant cell
Phase 2Make Transgenic Cell
Transfer plasmid to surface of microscopic metal particle
Use gene gun to injectDNA into plant cell
Agrobacterium inserts foreign DNA into plant cell to yield transgenic cell
Transfer plasmid copies to a carrier agrobacterium
Nucleus
E. Coli A. tumefaciens(agrobacterium)
Foreign DNA
Host DNA
Fig. 4-14, p. 95
Cell division oftransgenic cells
Phase 3Grow Genetically Engineered Plant
Transfer to soil
Transgenic plantswith new traits
Transgenic cell from Phase 2
Culture cells to form plantlets
Fig. 4-14, p. 95
Phase 3Grow Genetically Engineered Plant
Transgenic cell from Phase 2
Cell division oftransgenic cells
Culture cells to form plantlets
Transgenic plantswith new traits
Transfer to soil
Stepped Art
How Would You Vote?
To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living In the Environment.
• Should we legalize the production of human clones if a reasonably safe technology for doing so becomes available?– a. No. Human cloning will lead to widespread human
rights abuses and further overpopulation.– b. Yes. People would benefit with longer and healthier
lives.
THE FUTURE OF EVOLUTION
• Biologists are learning to rebuild organisms from their cell components and to clone organisms.– Cloning has lead to high miscarriage rates, rapid aging,
organ defects.
• Genetic engineering can help improve human condition, but results are not always predictable.– Do not know where the new gene will be located in the
DNA molecule’s structure and how that will affect the organism.
Controversy Over Genetic Engineering
• There are a number of privacy, ethical, legal and environmental issues.
• Should genetic engineering and development be regulated?
• What are the long-term environmental consequences?
Case Study:How Did We Become Such a Powerful
Species so Quickly?
• We lack:– strength, speed, agility.– weapons (claws, fangs), protection (shell).– poor hearing and vision.
• We have thrived as a species because of our:– opposable thumbs, ability to walk upright, complex
brains (problem solving).
SymbiosisLiving Together
Three Types of Symbiosis
• Mutualism
• both species benefit
• Commensalism
• one species benefits, the other is unaffected
• Parasitism
• one species benefits, the other is harmed
Mutualism• Both organisms benefit from the relationship
The otters help the kelp by eating the sea urchins which endanger it. The kelp provides and anchor for the otters while they sleep.
Otters and Kelp
Lichen
• Lichen is really two organisms: algae and fungus. The fungus needs food but cannot make it. The algae makes food but needs some way to keep moist. The fungus forms a crust around the algae which holds in moisture. Both organisms benefit.
The Chital and the Tree-pie• The tree-pies help
the chital by stripping the dead velvet from the antlers. This provides them with nourishment Therefore both species are benefiting from this symbiotic behavior.
Cleaner Fish and the Moray Eel• The cleaner fish eats
parasites and food bits out of the inside of this moray eel. It gets a meal and is protected from predators by the fierce eel.
Yucca Plants and Yucca Moths• Each type of Yucca plant can
only be pollinated by a specific kind of Yucca moth.
• That moth can only live on that kind of Yucca.
Swollen Thorn Acacia Tree and Ants
• The tree provides a nursery for the ants in the thorns and makes special food for the ant babies.
• In return the ants sting and attack any other plants or insects that try to invade the tree.
Commensalism• One species benefits while the other is uneffected
The cattle help the egret who look for grasshoppers and beetles that are raised by the cows. Now and then they sit on the back of a cow, looking for ticks and flies. This does not effect the cattle in any way.
The cattle egret and cows
Barnacles and Whales• Barnacles need a
place to anchor. They must wait for food to come their way. Some barnacles hitch a ride on unsuspecting whales who deliver them to a food source. This does not effect the whale in any way.
Oak Gall Wasps and Oak Trees• The oak gall wasp
stings the oak tree.
• the tree then grows a GALL which is a nest for the wasp’s babies.
• When the larva hatch, they eat their way out of the gall.
• Does not help or hurt the oak tree
Parasitism• One species benefits while the other is harmed
Mistletoe is an aerial parasite that has no roots of its own and lives off the tree that it attaches itself to. Without that tree it would die. It slowly chokes out the life of the host tree.
Bedbugs• Bedbugs are small,
nocturnal parasites that come out of hiding at night to feed on unsuspecting humans. They feed exclusively on blood! Their bites often result in an allergic reaction.
Tapeworms• The definitive host of the
cucumber tapeworm is a dog or a cat (occasionally a human). Fleas and lice are the intermediate host. the dog or cat becomes contaminated when the eggs are passed in the feces, and the flea or louse ingests the eggs. The dog or cat (or human) is infected when they ingest a flea or louse. Hence the importance of controlling fleas on your pet!
Which type of symbiosis is it?• Mutualism, commensalism, parasitism
Fleas/dogs
Lice/humans
Clownfish/sea anemone
Crocodile bird/crocodile
Joshua tree/pronuba moth
Predation – one species feeds on another enhancesfitness of predator but reduces fitness of prey
(+/– interaction)
Types of predators
Carnivores – kill the prey during attack
Herbivores – remove parts of many prey, rarely lethal.
Parasites – consume parts of one or few prey,rarely lethal.
Parasitoids – kill one prey during prolongedattack.
Diet breadth
consumes only one prey type
consumes many prey types
broad diet
narrow diet
specialist
generalist
Why are ecological interactions important?
Interactions can affect distribution and abundance.
Interactions can influence evolution.
How has predation influenced evolution?
Adaptations to avoid being eaten:
spines (cactii, porcupines)hard shells (clams, turtles)toxins (milkweeds, some newts)bad taste (monarch butterflies)
camouflageaposematic colorsmimicry
Camouflage – blending in
Aposematic colors – warning
Is he crazy???
Mimicry – look like something that is dangerousor tastes bad
Mimicry – look like something that is dangerousor tastes bad
Mullerian mimicry – convergence of several unpalatable species
Mimicry – look like something that is dangerousor tastes bad
Batesian mimicry – palatable species mimics an unpalatable species
model
mimic
model
mimics
Why are ecological interactions important?
Interactions can affect distribution and abundance.
Interactions can influence evolution.
Predator-prey population dynamics are connected
Predators kill prey affects prey death rate
dNprey/dt = rNprey
change in prey population
per capita rate of growth without predation
deaths due to predation
– pNpreyNpredator
Predator-prey population dynamics are connected
Predators kill prey affects prey death rate
dNprey/dt = rNprey – pNpredatorNprey
predation rate
• prey population size depends on number of predators
• with few predators, prey population grows• with many predators, prey population shrinks
Predator-prey population dynamics are connected
Predators eat prey affects predator birth rate
dNpredator/dt = cpNpreyNpredator – dNpredator
births due to predation
change inpredator population
death rate
Predator-prey population dynamics are connected
Predators eat prey affects predator birth rate
dNpredator/dt = cpNpreyNpredator – dNpredator
predation rate
conversion rateof prey to baby
predators
• predator population size depends on number of prey
• with many prey, predator population grows• with few prey, predator population shrinks
Predator-prey population dynamics are connected
Predators kill and eat prey
dNpredator/dt = cpNpreyNpredator – dNpredator
• with few predators, prey population grows• with many prey, predator population grows• with many predators, prey population shrinks• with few prey, predator population shrinks
affects prey death rate affects predator birth rate
dNprey/dt = rNprey – pNpredatorNprey
N
time
Lotka-Volterra models describe predator and preypopulation cycling.
Real world predator and prey populations can cyclein size.
http://phet.colorado.edu/en/simulation/natural-selection
Why are ecological interactions important?
Interactions can affect distribution and abundance.
Interactions can influence evolution.
Keystone species affect community structure
Predators can allow coexistence of competing prey
competitors
Barnacles MusselsBalanus Mytilus (Paine 1966)
Keystone species affect community structure
Predators can allow coexistence of competing prey
Starfish
competitors
predator Pisaster
Barnacles MusselsBalanus Mytilus (Paine 1966)
Barnacles MusselsBalanus Mytilus
How can we test the effect of apredator on community structure?
Experiment - Remove the predator
StarfishPisaster
Removal experiment
time
starfishremoved
%of
inter-tidalzone
mussels
- mussels are the dominant competitor- competitive exclusion of barnacles
barnacles
time
starfishremoved
%of
inter-tidalzone
mussels
barnacles
What is the effect of the predatoron the structure of this community?
- starfish allow coexistence of competitors
Barnacles Mussels
StarfishPisaster
Starfish are picky – they prefer mussels (dominant competitor),which allows barnacles (weaker competitor) to coexist.
How do starfish promote coexistence?
Balanus Mytilus
Keystone species affect community structuredisproportionately to their abundance.
Picky predators can promote coexistence amongcompeting prey species.
Competitive exclusion is prevented when thedominant competitor is the preferred prey.
Competiton
• is a contest between individuals, groups, nations, animals, etc. for territory, a niche, or a location of resources. It arises whenever two or more parties strive for a goal which cannot be shared. Competition occurs naturally between living organisms which co-exist in the same environment.
• Intraspecific:
A form of competition in which members of the same species vie for the same resources in an ecosystem (e.g. food, light, nutrients, space).
Example: two same species trees growing beside each other competing for the same water, sun, nutrients.
• Interspecific:
A form of competition in which members of the different species vie for the same resources in an ecosystem (e.g. food, light, nutrients, space).
Ex: A taller tree in a forest out competing a smaller tree underneath it.