Biodiversity and Evolution Chapter 4 Part 1 Introductions

Biodiversity and Evolution

Chapter 4Part 1 Introductions

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

Largest reptile in North America

Importance of gator holes and nesting mounds• Gator holes hold

freshwater during dry spells and serve as habitats for many aquatic species

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

1930s: Hunters and poachers

1967: endangered species; protected from poaching

1977: comeback, threatened species

Types of Diversity

Species diversity Genetic diversity Ecosystem

diversity

Functional diversity – variety of processes such as matter cycling and energy flow

Natural Capital: Major Components of the Earth’s Biodiversity

What is classification?

Classification • a systematic

arrangement of organisms into groups or categories

Taxonomy • science of

classifying organisms

Why Classify?

Set up an organized system so scientists can communicate

Study similarities and propose relationships between organisms

Show evolutionary linkages between organisms

Why Classify?

Prevents misnomers such as starfish and jellyfish

Prevents duplicated names• International

Naming Congress

Common Names

One species can have many different names• Example:

Mountain lion, puma, cougar, or panther?

•Vary among languages and regions

Keys to Binomial Nomenclature

Felis domesticus

Must be in Latin Must be in italics or underlined Genus (1st word) must be

capitalized Species (2nd word) must be

lowercase

Correct or Incorrect?

Triticum Aestivum - wheat Felis domesticus - cat canis lupus - wolf Canis familiaris - dog Populus deltoides -

cottonwood

DICHOTOMOUS KEY

Identification tool Uses paired statements to assist a person

in learning the identity of an object.• Characteristics such as structure and

behavior

Think of a dichotomous key as a type of scavenger hunt!

DICHOTOMOUS KEY EXAMPLE

1. a. tail fins are horizontal—whale………………….go to 2 b. tail fins are vertical—fish……………………….go to 32. a. has teeth or tusk—toothed whale………………..go to 4 b. has no teeth………………………...BALEEN WHALE3. a. has gill slits behind mouth—shark…….………...go to 4 b. has no gill slits……………………..NONSHARK FISH4. a. black with white underside………….KILLER WHALE b. tusk, gray with dark spots………………....NARWHAL5. a. head is hammershaped……..HAMMERHEAD SHARK b. tail is half the body length……….THRESHER SHARK

Hierarchy of Classification

Domain Kingdom Phylum Class Order Family Genus Species

Dear King Philip Came Over For Good Soup

Inclusive: broad or general in scopeExclusive: limited and restricted; specific

Inclusive: broad or general in scope

Exclusive: limited

and restricted;

specific

Your Turn!

Leaf and Seed Identification Kits


Chapter 4Part 2: Natural Selection

Six Major Kingdoms of Species as a Result of Natural Selection

Evolution by Natural Selection

The Struggle for Existence • Darwin realized that

high birth rates and a shortage of life's basic needs would force organisms to compete for resources.

Evolution by Natural Selection

Fitness • Ability of an

individual to survive and reproduce in its specific environment

• Result of adaptations.

Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring

Natural selection: acts on individuals

Differential reproduction – individuals with a certain desirable trait leave more offspring than other members

The Genetic Makeup of a Population Can Change

Populations (not individuals) evolve by becoming genetically different

Genetic variations• First step in biological evolution• Occurs through mutations in reproductive

cells

Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring

When environmental conditions change, populations• Adapt• Migrate• Become extinct

Genetic resistance – ability of one or more organisms in a population to tolerate a chemical designed to kill it

• Malaria

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

What do you think…

Will human adaptations allow our skin to become more resistant to the harmful effects of UV radiation, our lungs to cope with air pollutants, and our livers to better detoxify pollutants?

Adaptation through Natural Selection Has Limits

Genetic change must precede change in the environmental conditions• If the genes aren’t there,

the change won’t take place!

Reproductive capacity – species that reproduce in greater numbers at a higher frequency adapt more quickly

Things to remember:

“Survival of the fittest” is not “survival of the strongest”

Organisms do not develop traits out of need or want

Classification Systems

Taxonomy – science of classifying organisms• Assigns each organism a universally

accepted name that has biological significance

Classification Systems

Taxonomic classification may change with expanding knowledge about new and known organisms

How do scientists classify new organisms?

They study their characteristics.

They try to see if they are similar to other already known organisms.

They group a new organism with others that have similar characteristics.

The Fossil Record Tells Much of the Story of Evolution

Fossils• Physical evidence of ancient organisms• Reveal what their internal structures

looked like• Represents only 1% of all species that

have ever lived

Fossil record is incomplete: why?

Fossilized Skeleton of an Herbivore that Lived during the Cenozoic Era

Scientists need to study organisms COMPLETELY

Whale’s closest relative?

Whale’s closest living relative!

What characteristics are important?

Similarities in DNA and RNA• Genes show similarities at

the molecular level

• More similar the DNA, the more recently they shared a common ancestor

• Myosin: Humans and Yeast?

Your Turn!

Lords of the Wild• Panda Bears• 29:30 – 33:00

Computer Lab Phylogenetic

Analysis Using Molecular Data Sets • PART A ONLY


Chapter 4Part 3: Species Richness

vs. Evenness

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

Species diversity• Species richness

– number of different species in a community

• Species evenness – abundance of organisms within each type of species


Most species-rich communities• Tropical rain forests• Coral reefs• Ocean bottom zone• Large tropical lakes


1,700 different species of beetles in a SINGLE tree • Tropical Rainforest

– Panama• Species

Richness?• Species

Evenness?

Worldwide Richness?

Diversity varies with geographical location• Richness is highest at tropics• Lowest at the poles

Science Focus: Species Richness on Islands (Ease of Study)

Species equilibrium model, theory of island biogeography• Rate 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

Organisms more resilient; greater genetic diversity

Species-Rich Ecosystems Tend to Be Productive and Sustainable

Research suggests annual net primary productivity reaches its peak with 10-40 primary producer species

Your Turn!

Species Diversity Index


Chapter 4Part 4: Speciation

Geologic Processes Affect Natural Selection

Tectonic plates affect evolution and the location of life on earth• Location of continents and oceans• Species physically move, or adapt, or form

new species through natural selection

Earthquakes

Volcanic eruptions

225 million years ago 135 million years ago

65 million years ago Present

Changes in Ice Coverage in the Northern Hemisphere During the last 18,000 Years

Speciation

Speciation is the formation of new species.• Group of organisms

that breed with one another and produce fertile offspring.

What factors are involved in the formation of new species?

The gene pools of two populations must become separated for them to become new species.

As new species evolve, populations become reproductively isolated from each other.

Geographic Isolation

Geographic isolation occurs when two populations are separated by geographic barriers such as rivers, mountains, bodies of water.

Geographic Isolation

Does not guarantee the formation of new species• May separate

certain types of organisms (small rodents) but not others (birds).

Genetic Drift

Individuals may carry alleles in different relative frequencies than did the larger population from which they came.

The Founder Effect

Situation in which allele frequencies change as a result of the migration of a small subgroup

Reproductive Isolation

When the members of two populations cannot interbreed and produce fertile offspring, reproductive isolation has occurred.

Reproductive Isolation

Each population will respond to natural selection as separate units

Geographic Isolation Can Lead to Reproductive Isolation

Extinction is Forever

Extinction

Endemic species • Species found only

in one area• Particularly

vulnerable• Golden Toad (Costa

Rica) died out when habitat dried up

Extinction Can Affect One Species or Many Species at a Time

Background extinction – throughout most of history species have disappeared at a low rate• Average annual extinction = 1 to 5

species for every million on earth

Mass extinction• Significant rise in extinction rates• Scientists estimate between 3 and 5 mass

extinctions during the history of the Earth

Video Clip

Endangered Animals• Echo 25:44 – 31:30

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

Artificial selection

Genetic engineering, gene splicing

Consider• Ethics• Morals• Privacy issues• Harmful effects

Natural Selection on Polygenic Traits

How does natural selection affect polygenic traits?

1. Directional Selection2. Stabilizing Selection3. Disruptive Selection

Directional Selection

When individuals at one end of the curve have higher fitness than others

Range of phenotypes shifts as some individuals survive and reproduce while others fail

Stabilizing Selection

When individuals near the center of the curve have higher fitness than at either end• Keeps the center of

the curve at its current position

• Narrows the overall graph

Stabilizing Selection

Example • Human babies born

at an average mass are more likely to survive than babies born either much smaller or much larger than average

Disruptive Selection

When individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle

If the pressure of natural selection is strong enough and long enough, the curve will split, creating two distinct phenotypes

Disruptive Selection

Example• If average-sized

seeds become scarce, a bird population will split into two groups:

• One that eats small seeds and one that eats large seeds

Your Turn…Seed Lab!

Step 1 – Sort your pile of sunflower seeds according to number of stripes • Only count ONE

side

Step 2 – Place your seeds in appropriate tubes

Step 3 – Create a paragraph describing a situation which lead to EACH of the following types of selection• Directional• Stabilizing• Disruptive


Chapter 4Part 5: Ecological Roles

Each Species Plays a Unique Role in Its Ecosystem

Ecological niche• Role a species plays

in an ecosystem• Pattern of living

(reproduction, amount of sunlight, space, temperature, etc.)

Habitat• Location organism

lives

Keystone, Foundation Species Determine Structure, Function of Their Ecosystems

Keystone species – have a large effect on the types and abundances of other species in an ecosystem• Pollinators• Top predator

Keystone, Foundation Species Determine Structure, Function of Their Ecosystems

Foundation species• Create or enhance

their habitats, which benefit others • Elephants• Beavers

Case Study: Why Should We Protect Sharks?

Keystone species• Eat dead and dying

fish in the ocean• Strong immune

systems • Wounds do not get

infected• Almost never get

cancer• Could help humans if

we understood their immune system

Each Species Plays a Unique Role in Its Ecosystem

Generalist species• Broad niche• Live in different places,

eat different food, high range of tolerance

• Examples?

Specialist species • Narrow niche• More prone to

extinction• Examples?

Specialist Species and Generalist Species Niches

Niches Can Be Occupied by Native and Nonnative Species

Native species – organisms that normally live and thrive in a particular ecosystem

Nonnative species - invasive, alien, or exotic species• May spread

rapidly• Not all are villains

Indicator Species Serve as Biological Smoke Alarms

Indicator species – species that provide early warnings of damage to a community or ecosystem• Can monitor environmental quality • Trout• Birds• Butterflies• Frogs

Coal Canaries: 1800s – 1900s

Coal miners took caged canaries into mines to act as early warning sentinels

If birds stopped singing and appeared to be distressed miners knew there were poisons being released

Case Study: Why Are Amphibians Vanishing?

Sensitive biological indicators of environmental changes

Adult amphibians• Eat more

mosquitoes than birds

Genetic storehouse of pharmaceutical products

Case Study: Why Are Amphibians Vanishing?

Habitat loss and fragmentation

Prolonged drought

Pollution

Increase in UV radiation (no protection for eggs)

Parasites, viral and fungal diseases

Climate change

Nonnative predators and competitors

Strange Days on Planet Earth Video Clip

Troubled Waters: Frogs and Atrazine

Documents

Biodiversity and Evolution Chapter 4 Part 1 Introductions