Biological Evolution

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 4-4

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 million years ago Present 65 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 4-6

Fig. 4-6, p. 89 Land above sea level 18,000 years before present Northern Hemisphere Ice coverage Modern day (August) Note: Modern sea ice coverage represents summer months Legend Continental 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 4-7

Fig. 4-7, p. 91 Generalist species with a broad niche Number of individuals Resource use Specialist species with a narrow niche Niche separation Niche breadth Region of niche overlap

SPOTLIGHT Cockroaches: 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-A

Specialized Feeding Niches Resource partitioning reduces competition and allows sharing of limited resources. Figure 4-8

Fig. 4-8, pp Piping plover feeds on insects and tiny crustaceans on sandy beaches (Birds not drawn to scale) Black skimmer seizes small fish at water surface Flamingo feeds on minute organisms in mud Scaup and other diving ducks feed on mollusks, crustaceans,and aquatic vegetation Brown pelican dives for fish, which it locates from the air Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds Louisiana heron wades into water to seize small fish Oystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beak Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans Knot (a sandpiper) picks up worms and small crustaceans left by receding tide Herring gull is a tireless 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 4-9

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 4-10

Fig. 4-10, p. 92 Different environmental conditions lead to different selective pressures and evolution into two different species. Southern Population Northern population Adapted to heat through lightweight fur and long ears, legs, and nose, which give 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 Spreads northward and southward and separates Early fox Population

Extinction: 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

Fig. 4-12, p. 93 Tertiary Bar width represents relative number of living species EraPeriod Species and families experiencing mass extinction Millions of years ago Ordovician: 50% of animal families, including many trilobites. Devonian: 30% of animal families, including agnathan and placoderm fishes and many trilobites Cambrian Ordovician Silurian Devonian Extinction Paleozoic Mesozoic Cenozoic 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 caused by human activities. Many species are expected to become extinct within the next 50–100 years. Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Extinction Triassic Jurassic Cretaceous Extinction QuaternaryToday

Effects of Humans on Biodiversity The scientific consensus is that human activities are decreasing the earth’s biodiversity. Figure 4-13

Fig. 4-13, p. 94 Marine organisms Terrestrial organisms Number of families Millions of years ago Quaternary Tertiary Pre-cambrian Cambrian Ordovician Silurian Devonian Carboniferous Jurassic Devonian Permian Cretaceous

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 4-15

Genetic Engineering: Genetically Modified Organisms (GMO) GMOs use recombinant DNA –genes or portions of genes from different organisms. Figure 4-14

Fig. 4-14, p. 95 Insert modified plasmid into E. coli Phase 1 Make Modified Gene Cell Extract DNA E. coli Gene of interest DNA Identify and extract gene with desired trait Genetically modified plasmid Identify and remove portion of DNA with desired trait Remove plasmid from DNA of E. coli Plasmid Extract Plasmid Grow in tissue culture to make copies Insert extracted (step 2) into plasmid (step 3)

Fig. 4-14, p. 95 Plant cell Phase 2 Make Transgenic Cell Transfer plasmid to surface of microscopic metal particle Use gene gun to inject DNA 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 of transgenic cells Phase 3 Grow Genetically Engineered Plant Transfer to soil Transgenic plants with new traits Transgenic cell from Phase 2 Culture cells to form plantlets

Fig. 4-14, p. 95 Phase 3 Grow Genetically Engineered Plant Transgenic cell from Phase 2 Cell division of transgenic cells Culture cells to form plantlets Transgenic plants with 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).

Symbiosis Living 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  enhances fitness 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 prolonged attack.

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) camouflage aposematic colors mimicry

Camouflage – blending in

Aposematic colors – warning

Is he crazy???

Mimicry – look like something that is dangerous or tastes bad

Mimicry – look like something that is dangerous or tastes bad Mullerian mimicry – convergence of several unpalatable species

Mimicry – look like something that is dangerous or 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 dN prey /dt = rN prey change in prey population per capita rate of growth without predation deaths due to predation – pN prey N predator

Predator-prey population dynamics are connected Predators kill prey  affects prey death rate dN prey /dt = rN prey – pN predator N prey 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 dN predator /dt = cpN prey N predator – dN predator births due to predation change in predator population death rate

Predator-prey population dynamics are connected Predators eat prey  affects predator birth rate dN predator /dt = cpN prey N predator – dN predator predation rate conversion rate of 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 dN predator /dt = cpN prey N predator – dN predator 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 dN prey /dt = rN prey – pN predator N prey N time

Lotka-Volterra models describe predator and prey population cycling. Real world predator and prey populations can cycle in size.

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 Mussels BalanusMytilus (Paine 1966)

Keystone species affect community structure Predators can allow coexistence of competing prey Starfish competitors predator Pisaster Barnacles Mussels BalanusMytilus (Paine 1966)

Barnacles Mussels Balanus Mytilus How can we test the effect of a predator on community structure? Experiment - Remove the predator Starfish Pisaster

Removal experiment time starfish removed % of inter- tidal zone mussels - mussels are the dominant competitor - competitive exclusion of barnacles barnacles

time starfish removed % of inter- tidal zone mussels barnacles What is the effect of the predator on the structure of this community? - starfish allow coexistence of competitors

Barnacles Mussels Starfish Pisaster Starfish are picky – they prefer mussels (dominant competitor), which allows barnacles (weaker competitor) to coexist. How do starfish promote coexistence? BalanusMytilus

Keystone species affect community structure disproportionately to their abundance. Picky predators can promote coexistence among competing prey species. Competitive exclusion is prevented when the dominant 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.