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

Nu

mb

er o

f in

div

idu

als

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

ozo

ic

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

Nu

mb

er o

f fa

mil

ies

Millions of years ago

Qu

ater

nar

y

Ter

tiar

y

Pre

-cam

bri

an

Cam

bri

an

Ord

ovi

cian

Sil

uri

an

Dev

on

ian

Car

bo

nif

ero

us

Jura

ssic

Dev

on

ian

Per

mia

n

Cre

tace

ou

s

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.