Biodiversity and Evolution

Chapter 4

Core Case Study: Why Should We Care about the American Alligator?

Largest reptile in North America1930s: Hunters and poachers Importance of gator holes and nesting mounds1967: endangered species1977: comeback, threatened species

Alligator’s nicheFish, insects, snakes, turtles, birds, etc. live in gator holes

during dry weatherOld gator nests are used for nesting and feeding sites for

herons, egrets, red-bellied turtlesAlligators eat gar (fish that eats game fish - bass and

bream)Alligators move around and keep open water available

and free of vegetation.Keystone species

4-1 What Is Biodiversity and Why Is It Important?

Concept 4-1 The biodiversity found in genes, species, ecosystems, and ecosystem processes is vital to sustaining life on earth.

The more biodiverse a place is, the more likely its life is to survive changes. Most important thing you’ll see all semester.

Biodiversity Is a Crucial Part of the Earth’s Natural Capital

Vital renewable resource Species diversity – number and abundance of speciesEcosystem diversity – variety of ecosystems availableFunctional diversity – variety of bio and chem processes

in ecosystemsGenetic diversity – variety of genes and alleles among

all species (alleles are versions of genes, remember?)

Natural Capital: Major Components of the Earth’s Biodiversity

Evolution pop quizDon’t worry, you’ll get an A.

Some student comments about evolution:“I think it is interesting.”“I believe that God made the world to adapt to it’s

surroundings.”“It takes a lot of words to get the whole thought.”“It is based in solid science. I do not believe that religion

and evolution are mutually exclusive, as I am both religious and supportive of evolution.”

“I was raised religiously so evolution is practically a swear word in my house. However, I really enjoy learning about it because it makes sense to me that things change and adapt over time.”

More student comments: “I think that evolution happens to a point but I don’t agree

that humans evolved from nothing.” “I don’t like some parts of the study of evolution like people

saying we evolved from apes because we didn’t.” “I have a hard time believing we came from monkeys.” “It is interesting, but I don’t believe it. I believe God created

all animals and plants.” “I don’t necessarily believe this is how life happened. There

have been many ideas contrary to the study.” “It doesn’t answer all of the questions about how the world

came about.”

4-2 Where Do Species Come From?

Concept 4-2A The scientific theory of evolution explains how life on earth changes over time through changes in the genes of populations.

Concept 4-2B Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection).

Biological Evolution by Natural Selection Explains How Life Changes over Time

Biological evolutionNatural selection- (watch on your own time, if you’re

interested in who Darwin was.)Charles Darwin Alfred Russel Wallace

Tree of Life

(By the way, what’s a theory, again??)

Fig. 4-3, p. 81

CenozoicMesozoic

Paleozoic

Precambrian

Mil

lio

ns

of

ye

ars

ag

oFirst humansExtinction of dinosaurs

Plantscolonize land

Origin ofmulticellularorganisms

Oldesteukaryotic fossils

Accumulation ofO2 in atmospherefrom photosyntheticcyanobacterium

Prokaryotes Eukaryotes

Origin of Earth

Earth cool enoughfor crust to solidify

Oldest prokaryoticfossils

AnimalsFungiPlantsProtistsArchaebacteriaEubacteria

0

500

4,500

4,000

3,500

3,000

2,500

2,000

1,500

1,000

Six Major Kingdom

s of Species

Click here!

The Fossil Record Tells Much of the Story of Evolution

FossilsPhysical evidence of ancient organismsReveal what their internal structures looked like

Fossil record is incomplete: why?

Fossilized Skeleton of an Herbivore that Lived during the Cenozoic Era

Lots of evo this summer: read and watch videos.

What can you learn from fossils, really? http://kernfamilysite.com/blog/2014/06/14/ashfall/ What about dinosaur fossils?

http://kernfamilysite.com/blog/2014/06/21/stop-3-dinosaur/ Evolution driven by geographic isolation in the Ice Age: http://kernfamilysite.com/blog/2014/07/19/stop-9-yosemite

-part-3/

Evolution of really weird trees: http://kernfamilysite.com/blog/2014/07/08/stop-8-ancient-b

ristlecone-pines-national-forest/

The Genetic Makeup of Population Can Change

Populations evolve by becoming genetically differentGenetic variations

In a population, there is variation among individualsOccurs through mutations in reproductive cells

Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring Natural selection: acts on individuals

Individuals with traits that are beneficial to the conditions are more likely to survive and reproduce (differential reproduction)

Over time there is a shift in the most common traits, such that beneficial traits become more common within the population (Populations evolve, individuals don’t!)

Genetic resistance – good example When environmental conditions change, populations must:

Adapt – have traits which allow survival in new conditions Migrate – move somewhere where conditions are better Or…become extinct http://

www.unr.edu/nevada-today/news/2014/devils-hole-pupfish

Fig. 4-5, p. 83

Most of the normal bacteria die

The genetically resistant bacteriastart multiplying

Eventually the resistant strainreplaces the strain affected bythe antibiotic

A group of bacteria, including genetically resistant ones, areexposed to an antibiotic

Normal bacterium

Resistant bacterium

Stepped Art

Evolution by Natural Selection

Case Study: How Did Humans Become Such a Powerful Species?

Three human adaptationsStrong opposable thumbsWalk uprightComplex brain

Adaptation through Natural Selection Has Limits

Genetic change must precede change in the environmental conditions. The alleles that are beneficial in the new environmental conditions must already be found within the population before the conditions change.

(Populations don’t suddenly sprout new traits as a result of environmental changes.)

Reproductive capacity – populations with high genetic diversity and fast reproduction rates are most able to adapt to changes (mosquitos, weeds, rats, bacteria, etc.)

Three Common Myths about Evolution through Natural Selection

“Survival of the fittest” is not “survival of the strongest”Fittest = better adapted to the ENVIRONMENT Traits that confer “fitness” in one biome may be

detrimental in another (gills are great for aquatic biomes, but useless in deserts!)

Organisms do not develop traits out of need or wantThere is no grand plan in nature for “perfect” adaptation

Don’t assume all species are headed in a specific evolutionary direction!

Five Fingers of Evolutionhttps://www.youtube.com/watch?v=5NdMnlt2keE

4-3 How Do Geological Processes and Climate Change Affect Evolution?

Concept 4-3 Tectonic plate movements, volcanic eruptions, earthquakes, and climate change have shifted wildlife habitats, wiped out large numbers of species, and created opportunities for the evolution of new species.

Geologic Processes Affect Natural Selection

Tectonic plates affect evolution and the location of life on earthLocation of continents and oceansSpecies physically move, or adapt, or form new species

through natural selectionEarthquakes – fissures can isolate species and cause

speciation (geographic isolation)Volcanic eruptions – destroy habitats

Movement of the Earth’s Continents over Millions of Years

Climate Change and Catastrophes Affect Natural Selection

Ice ages followed by warming temperaturesCollisions between the earth and large asteroids

ExtinctionNew ecological roles become available for species that

don’t become extinct

Go back a slide – when did dinosaurs become extinct? Why? If you’re interested in how we know, read T. Rex and the Crater of Doom!

Changes in Ice Coverage in the N. Hemisphere during the last 18,000 Yrs

Science Focus: Earth Is Just Right for Life to Thrive

Certain temperature range H2O = s, l, AND g!!Dependence on waterRotation on its axis – no “dark side/bright side” temp

issuesRevolution around the sun – not too close or too farEnough gravitational mass to keep atmosphere

(why? Well, where else could humans evolve?)

4-4 How Do Speciation, Extinction, and Human Activities Affect Biodiversity?

Concept 4-4A As environmental conditions change, the balance between formation of new species and extinction of existing species determines the earth’s biodiversity.

Concept 4-4B Human activities can decrease biodiversity by causing the premature extinction of species and by destroying or degrading habitats needed for the development of new species.

How Do New Species Evolve?

Geographic isolationReproductive isolation

Geographic Isolation Can Lead to Reproductive Isolation

Extinction is Forever

ExtinctionEndemic species – species found in only one area, such

as on islandsParticularly vulnerable – difficult to migrate when changes

occur

Extinction Can Affect One Species or Many Species at a Time

Background extinction – happens all the time through out history

Mass extinction – significant rise above background rateHas happened five times (about once per 20-60 million

years). Why? We’re not sure.250mya 95% of all species became extinct!(OK maybe only 3 times – debated … should we define mass

extinction by many species going extinct plus low speciation rate?)

Extinctions will happen, but do we have a responsibility to make sure we aren’t causing premature extinctions?

Science Focus: We Have 2 Ways to Change the Genetic Traits of Populations

Artificial selection – we’ve been doing this since the dawn of agriculture.

Genetic engineering, gene splicingConsider

EthicsMoralsPrivacy issuesHarmful effects

4-5 What Is Species Diversity and Why Is It Important?

Concept 4-5 Species diversity is a major component of biodiversity and tends to increase the sustainability of ecosystems.

Species Diversity: Variety, Abundance of Species in a Particular Place

Species diversitySpecies richness - Species evenness -

Diversity varies with geographical locationMost species-rich communities

Tropical rain forests Coral reefs Ocean bottom zone Large tropical lakes

Science Focus: Species Richness on Islands

Species equilibrium model, theory of island biogeographyRate of new species immigrating should balance with the

rate of species extinction

Island size and distance from the mainland need to be considered

Species-Rich Ecosystems Tend to Be Productive and Sustainable

Species richness seems to increase productivity and stability or sustainability

How much species richness is needed is debatable

4-6 What Roles Do Species Play in Ecosystems?

Concept 4-6A Each species plays a specific ecological role called its niche.

Concept 4-6B Any given species may play one or more of five important roles—native, nonnative, indicator, keystone, or foundation roles—in a particular ecosystem.

Each Species Plays a Unique Role in Its Ecosystem

Ecological niche, nichePattern of living – how much space? Water? Sunlight?

Temp range? What food source?

Generalist speciesBroad niche

Specialist species Narrow niche

Specialist Species

and Generalist

Species Niches

Case Study: Cockroaches: Nature’s Ultimate Survivors

CockroachesGeneralistsHigh reproductive rates

Giant panda and tiger salamandersSpecialistsLow reproductive rates

When (where) would being a specialist be advantageous?

Fig. 4-13, p. 93

Black skimmerseizes small fishat water surfaceBlack skimmerseizes small fishat water surface

Brown pelican divesfor fish, which itlocates from the air

Avocet sweeps billthrough mud andsurface water in searchof small crustaceans,insects, and seeds

Dowitcher probesdeeply into mud insearch of snails,marine worms, andsmall crustaceans Herring gull

is a tirelessscavenger

Ruddy turnstonesearches undershells and pebblesfor smallinvertebrates

Flamingo feeds on minute organisms in mud

Scaup and other diving ducks feed on mollusks, crustaceans, and aquatic vegetation

Louisiana heron wades into water to seize small fish

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

Knot (sandpiper)picks up wormsand small crustaceansleft by receding tide

Piping plover feeds on insects and tinycrustaceans on sandy beaches

Specialized Feeding Niches of Various Bird Species in a Coastal Wetland

Niches Can Be Occupied by Native and Nonnative Species

Native species

Nonnative species; invasive, alien, or exotic speciesMay spread rapidly – (or may not be able to

survive in the new conditions) Not all are villains, but many that are successful in

the new habitat outcompete natives.

Indicator Species Serve as Biological Smoke Alarms

Indicator speciesCan monitor environmental quality

Trout Birds Butterflies Frogs

Case Study: Why Are Amphibians Vanishing?

Habitat loss and fragmentationProlonged droughtPollution Increase in UV radiationParasitesViral and fungal diseasesClimate changeOverhuntingNonnative predators and competitors

Case Study: Why Are Amphibians Vanishing?

Importance of amphibiansSensitive biological indicators of environmental changesAdult amphibians

Important ecological roles in biological communitiesGenetic storehouse of pharmaceutical products waiting to

be discovered

Fig. 4-14, p. 94

Sexualreproduction

Adult frog(3 years) Young frog

Tadpole developsinto frog

Tadpole

Egg hatches

Organ formation

Fertilized eggdevelopment

Eggs

Sperm

Life Cycle of a Frog

Keystone, Foundation Species Determine Structure, Function of Their Ecosystems

Keystone species PollinatorsTop predator

Foundation speciesCreate or enhance their habitats, which benefit others

Elephants Beavers

Case Study: Why Should We Protect Sharks?

Keystone speciesEat dead and dying fish in the oceanStrong immune systems

Wounds do not get infected Almost never get cancer Could help humans if we understood their immune system

For every shark that injures a person, we kill 1 million sharks.