Biodiversity and Evolution Chapter 4 Part 1 Introductions
Dec 25, 2015
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
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
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?
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
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
Species Diversity: Variety, Abundance of Species in a Particular Place
Most species-rich communities• Tropical rain forests• Coral reefs• Ocean bottom zone• Large tropical lakes
Species Diversity: Variety, Abundance of Species in a Particular Place
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
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
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.
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
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
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?
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