Chapter 4: Biodiversity and
Evolution
Biodiversity & Evolution
Evolution and Biodiversity;
Chapter 4
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
Chapter Overview Questions
• How do extinction of species and
formation of new species affect
biodiversity?
• What is the future of evolution, and what
role should humans play in this future?
• How did we become such a powerful
species in a short time?
Chapter Overview Questions
How do scientists account for the development
of life on earth?
What is biological evolution by natural selection,
and how can it account for the current diversity
of organisms on the earth?
How can geologic processes, climate change and
catastrophes affect biological evolution?
What is an ecological niche, and how does it help
a population adapt to changing the
environmental conditions?
CASE STUDY: Conserving Shark Species
• 400 known species
• 6 Human deaths per year from shark attacks
• 79-97 million sharks killed every year
– Fins
– Organs, meat, hides
– Fear
– 32% shark species threatened with extinction
• Keystone species
• Rarely get cancer/infections
Endangered Scalloped
Hammerhead Shark
Threatened Whale
Shark- Harmless
Species to Humans
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.
Biodiversity Is a Crucial Part of the
Earth’s Natural Capital (1)
• Species: set of individuals who can mate and
produce fertile offspring
• ESTIMATED: 8 million to 100 million species
– Best guess ~10-14 million
• 1.9 million identified
• Up to half of earth’s species are mostly in rain
forests and oceans
Encyclopedia of Life
• Scientists are working on a website devoted to
summarizing all the basic info on the world’s
known and named species
• Continually updated as more species are
discovered
• www.eol.org
Biodiversity Is a Crucial Part of the
Earth’s Natural Capital (2)
4 Components of Biodiversity
• Species diversity
– The # and abundance of different species present in different
communities
• Genetic diversity
– The Variety of Genetic Material
• Ecosystem diversity
– Biomes: terrestrial regions with distinct climates/species
– Different terrestrial and aquatic ecosystems on earh
• Functional diversity
– Different Biological and chemical processes on earth
– Ex. Energy flow, matter cycling
Biodiversity is an important part of natural capital
Functional Diversity The biological and
chemical processes such as energy flow
and matter recycling needed for the survival
of species, communities, and ecosystems.
Heat
Chemical
nutrients
(carbon dioxide,
oxygen,
nitrogen,
minerals)
Heat
Solar
energy
Heat
Decomposers
(bacteria, fungi)
Heat
Ecological Diversity The
variety of terrestrial and
aquatic ecosystems
found
in an area or on the
earth.
Producers
(plants)
Consumers
(plant eaters,
meat eaters)
Genetic Diversity The
variety
of genetic material within
Heat
Species Diversity The number
and abundance of species
present in different communities. Fig. 4-2, p. 82
Different variations of Caribbean snail.
Which component of biodiversity does this exemplify?
Fig. 4-4, p. 83
Terrestrial Biomes
Denver
San
Francisco
Coastal
mountain
ranges
Coastal
chaparral
and scrub
Las
Vegas
Sierra
Nevada
St. Louis
Great
American
Desert
Coniferous
forest
Baltimore
Rocky
Mountains
Desert
Great
Plains
Coniferous
forest
Mississippi Appalachian
River Valley
Mountains
Prairie
grassland
Deciduous
forest
Fig. 4-5, p. 84
Classifying Homo Sapiens
Supplement 5, Fig. 2, p. S19
Science Focus: Have you thanked insects
today?
• Very Important part of the earth’s natural capital
• Often classified as pests
– competition
– Spread human disease
– bite/sting
• Natural services of insects include
– Pollination
– Population control
– Loosen/renew soil
• Reproduce and develop new genetic traits rapidly
– Very resistant to extinction
– How is this good for us?
Science Focus: Insects
• Ultimate lesson to be learned:
– Although insect may not need us [humans], we
and most other land organisms need them
Individuals Matter: Edward O. Wilson:
A Champion of Biodiversity
• Loved bugs as a kid
• Specialized in ants
• Widened scope to earth’s biodiversity
• Theory of island biogeography
• First to use “biodiversity” in a scientific paper
Edward O. Wilson
Fig. 4-B, p. 85
4-2 How Does Earth’s Life Change Over
Time?
• Concept 4-2A: The scientific theory of evolution
explains how life on earth changes over time
through changes in the genes of population
• Concept 4-2B: Populations evolve when genes
mutate and give some individuals genetic traits
that enhance their abilities to survive and to
reproduce offspring with these traits (natural
selection).
Biological Evolution by Natural Selection
Explains How Life Changes over Time (1)
• Fossils- mineralized/petrified replicas of bones,
skeletons, teeth, shells, leaves, and seeds or
impressions of such items
– Found in rocks, glacial ice, different layers of earth
– Physical evidence of ancient organisms
– Reveal what their external structures looked like
• Fossil record: entire body of fossil evidence
– Uneven and incomplete
• Only have fossils of 1% of all species that lived on
earth
– Some species leave no fossil, or fossils decompose
Fossilized Skeleton of an Herbivore that Lived during the
Cenozoic Era
Fig. 4-6, p. 86
Biological Evolution by Natural Selection
Explains How Life Changes over Time (2)
• Biological evolution: how earth’s life changes over time
through changes in the genetic characteristics of populations
– Darwin: Origin of Species
• Natural selection: individuals with certain traits are more
likely to survive and reproduce under a certain set of
environmental conditions
•
• Theory of Evolution: All Species descended from
earlier ancestral species (aka- life came from life)
– Huge body of evidence
Evolution by Natural Selection Works
through Mutations and Adaptations (1)
• Populations evolve by becoming genetically
different
• Genetic variations
– First step in biological evolution
– Occurs through mutations in reproductive cells
– Mutations: random changes in DNA molecules
• From hiccups in DNA transcription
• From x-rays, radioactivity, natural & human-made
chemicals
Evolution by Natural Selection Works
through Mutations and Adaptations (2)
• Natural selection: acts on individuals
– Second step in biological evolution after mutation
– Adaptation to environment may lead to
differential reproduction
• Some species with the beneficial trait survive and
produce more offspring than other members with out
the trait
• Eventually those with out the trait diminish
• Those with the trait increase in abundance
– Genetic resistance: ability of one or more
members of a population to resist a chemical
designed to kill it
• Example: Antibiotic resistant bacteria
(a)
A group of
bacteria,
including
genetically
resistant ones,
are exposed to
an antibiotic
(b)
Most of the
normal
bacteria die
(c)
The genetically
resistant
bacteria start
multiplying
(d)
Eventually the
resistant strain
replaces all or
most of the strain
affected by the
antibiotic
Normal bacterium Resistant bacterium
Fig. 4-7, p. 87
Summary of Biological Evolution
• Evolution by natural selection in a nutshell:
1. Genes mutate
2. Individuals are selected based on possession of
successful traits
3. Populations evolve such that they are better adapted to
survive AND reproduce under existing environmental
conditions
•
It is important to understand evolution occurs over
generations- NOT within individuals
–
–
Individuals are naturally selected
Populations evolve over time (change over time)
Case Study: How Did Humans Become
Such a Powerful Species?
• Success attributed to 3 adaptations
– Strong opposable thumbs
– Walk upright
– Complex brain
• Adaptations that make a species successful
now do not ensure survival when environment
changes
– Our own environment is rapidly changing
– Will we be able to adapt to these changes?
Adaptation through Natural Selection
Has Limits
1. Adaptive genetic traits must precede change
in the environmental conditions
– Adaption can only occur when that trait is
already present in the population
1. Reproductive capacity
– Species that reproduce rapidly and in large
numbers are better able to adapt
– Unlike weeds, cockroaches, rats, etc., some
species cannot reproduce in large numbers or
rapidly
Three Common Myths about Evolution
through Natural Selection
1. “Survival of the fittest” is not “survival of the
strongest”
– Fitness= reproductive success (NOT strength)
2. Organisms do not develop traits out of need
or want
– Giraffe’s necks
3. No grand plan of nature for perfect
adaptation
– No evidence that evolution steers toward making
a super-species
Natural Selection of the Kernel
Hunters
• There are 3 types of kernel hunters hunters on
Utensiles Island
– Forkus Utensilus
– Knifus Utensilus
– Spoonus Utensilus
• Each hunter competes with the other for the
same resource to survive (corn kernels)
Island Background Info
• There are currently 3 individuals who make up the
Utensiles community on the island- one of each
species
• Depending on how many kernels each species gets, the
hunter will spontaneously reproduce a certain number
of additional members of its own species
– Each species may only gather kernels with their heritable
beak faeture
• Each hunter can only hunt for a maximum of 12
seconds per generation
Resource Benefits
• If a hunter gathers:
– >30 kernels: survives and reproduces 2
– 20-29 kernels: survives and reproduces 1
– 10-19 kernels: survives but does not
reproduce
– <10 kernels: hunter dies
Help Keep track of the island
population and diversity
• Groups of 4
– 3 hunters (one of each species)
– 1 timer
• All group members record data for 4
generations
• Copy down data Tables on your own piece of
paper
Generation 1- starts with population of
3 (1,1, and 1)
Initial
population
size
# of beans
collected
New
Population
size
SPOON
Knife
Fork
1
1
1
Generation 2 starts with ending
population from previous generation
SPOON
Initial
population
size
# of beans
collected
New
Population
size
Knife
Fork
Continue for 3 more generations
• If you don’t collect enough beans, your hunter
dies.
• If the dead hunter reproduced, the population
is now minus 1
• If population = 0- species is EXTINCT (i.e- no
longer part of community competition)
Complete your Island Report
• Formal report should include:
– Title
– Explanation of the island mechanics (brief- no
more than 1 paragraph)
– Data Tables
– 1-Graph
– Analysis (see questions on next slide)
Complete Data and Analyses
• Construct a graph of the data for the population
changes of each species over the generations
• Answer the Analysis Questions in paragraph format
– Did one species’ population size increase more than
others? Which one, and why?
– Did any species go extinct? Why
– What was the independent and dependent variable of this
simulation?
– If the simulation were to continue, what would you expect
to happen to the species diversity?
– Connect the findings of this simulation the the process of
evolution. Explain how natural selection acts on the
individual and evolution occurs over populations.
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 (giant solid plates breaking earth’s surface)
– affect evolution and the location of life on earth (2) ways:
1.
2.
Shifted latitudes of continents/oceans, influencing climates
Species physically move, or adapt, or form new species
through natural selection (via movement of continents)
• Earthquakes
– Sudden movement of tectonic plates
– Cause fissures in earth’s crust- separates populations
•  speciation may occur
• Volcanic eruptions
– Occur along boundaries of tectonic plates
– Affect biological evolution by destroying habitats, reducing
populations
225 million years ago
65 million years ago
135 million years ago
Present
Stepped Art
Fig. 4-8, p. 89
Climate Change and Catastrophes
Affect Natural Selection
• Ice ages followed by warming temperatures
– Retreating ice sheets = raised seal level, reduced
land area
• Collisions between the earth and large
asteroids
– New species
– Extinctions
Cause shifts in ecosystem locations and
create opportunities for evolution of new
species
18,000 years
before
present
Northern Hemisphere
Ice coverage
Modern day
(August)
Legend
Continental ice
Sea ice
Land above sea level
Fig. 4-9, p. 89
Science Focus: Earth Is Just Right
for Life to Thrive
• Temperature range: supports life
• Orbit size: moderate temperatures
• Liquid water: necessary for life
• Rotation speed: sun doesn’t overheat surface
• Size: gravity keeps atmosphere
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 extinction of many
species and by destroying or degrading habitats
needed for the development of new species.
How Do New Species Evolve?
• Speciation: one species splits into two or more species
– For sexually reproducing species, new species forms when:
• One population of species evolved to a point where it no longer
can breed and produce fertile offspring with members of another
population who did not evolve
• Speciation happens in (2) ways:
1. Geographic isolation: happens first; physical isolation of
populations for a long period
1. Reproductive isolation: mutations and natural selection
in geographically isolated populations lead to inability to
produce viable offspring when members of two different
populations mate
Geographic Isolation
• Different groups of same population become
separated (physically)
– Migration
– Physical barriers (mountain range, stream, road)
– Volcanic eruption
– Tectonic plate movement
– Wind, flowing water
• First step in speciation
Reproductive Isolation
• After separated for long period of time
• Separated species adapt to new environment
under natural selection
• Occurs at the genetic level due to mutation
• If rejoined with separated population long
enough, cannot produce live, fertile offspring
any longer
Adapted to cold through
heavier fur, short ears,
short legs, and short
nose. White fur matches
snow for camouflage.
Arctic Fox
Northern
population
Early fox
population
Different environmental
conditions lead to different
selective pressures and
evolution into two different
species.
Spreads
northward and
southward and
separates
Gray Fox
Southern
population
Adapted to heat through
lightweight fur and long
ears, legs, and nose,
which give off more heat.
Fig. 4-10, p. 91
Extinction is Forever
• 3 possible futures for species when
environmental conditions change:
1. Adapt
2. Move (if possible)
3. Extinction
• Extinction
– Biological extinction
– Local extinction- over large region, not globally
• Endemic species
– Found only in one area
– Particularly vulnerable to extinction
– Found on islands and unique areas
• i.e- tropical rainforests, have specialized roles
– Unlikely to migrate or adapt to new environment
• Background extinction: typical low rate of
extinction
– All species go extinct eventually, however at a low
rate
– Average annual background extinction: 1-5
species for ever million species
– Drastic environmental conditions shorten this rate
Golden Toad of Costa Rica, Extinct
Lived in a
protected region,
yet still went
extinct in 1989
Fig. 4-11, p. 92
Mass Extinction
• Mass extinction: significant rise in extinction
rates above background extinction rate
– Often a global event
– Fossil record suggests 3-5 mass extinctions over
past 500 million years
– Provides opportunity for evolution of new species
• Fill unoccupied ecological roles or newly created ones
– Occurrences of mass extinctions usually followed
by increase in species diversity via speciation
***Concept 4-4A-balance of speciation and
extinction determines biodiversity
Extinction rates, before and now
• Before: speciation kept ahead of extinction
– Species diversity increased over time
• Now: evidence suggests extinction rate now
higher than any other time in past 65 million
years
– Much of loss of biodiversity due to human
(anthropogenic) activities
Science Focus: Changing the Genetic Traits
of Populations
• Artificial selection
– Use selective breeding/crossbreeding
• Genetic engineering (GMO), gene splicing
– Alter organisms DNA
– Transfer genes from 2 different species (fish and tomato)
– Create new drugs, pest-resistant plants, rapid growing
animals
• Consider
–
–
–
–
Ethics
Morals
Privacy issues
Harmful effects
• Decreased nutrition, new allergens, increased toxicity, antibiotic
resistance
Genetically Engineered Mice
Normal 6-mo old
mouse
6-mo old Genetically
modified mouse
Fig. 4-D, p. 92
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 (1)
• Species diversity- number and variety of species an
ecosystem community contains
• Species richness (R):
– The number of different species in a given area
– Does not reflect dominance
– R= s
• Species evenness (E):
– Comparative number of individuals
– Measure how similar the abundances of different species
are
– Equal/similar proportions: E=1
– Unequal/dissimilar proportions: E decreases
– E= H/[ln(R)]
Shannon-Weiner Index
• Accounts for species evenness and richness
together
• Determined by # of species and even distribution of
individuals among those species
– Accounts for relative dominance
• Ranges from 0 (community with 1-species) to over 7
(very diverse community)
• H= -Σ(Pi*ln[Pi])
– Pi= relative abundance= ni/N
– ni= # of individuals in species-i
– N= total number of individuals in all species
Species Diversity cont’d
• Most tropical forests have high species
evenness
– Also coral reefs, tropical lakes, ocean bottom zone
• Species diversity varies with geographical
location
• Islands are good areas of study for species
richness
Variations in Species Richness and Species Evenness
Fig. 4-12, p. 93
Science Focus: Species Richness
on Islands
• 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
– The smaller the island is, and further from the
mainland, more likely less species
• Edward O. Wilson
Species-Rich Ecosystems Tend to Be
Productive and Sustainable
• Species richness seems to increase productivity
and stability or sustainability, and provide
insurance against catastrophe
• How much species richness is needed is
debatable
• Ed. Wilson- “The more species you have in a food
web, the more likely you will have an insurance
policy for the whole ecosystem.”
4-6 What Roles Do Species Play in an
Ecosystem?
• 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—in a particular ecosystem.
Each Species Plays a Unique Role
in Its Ecosystem
• Ecological niche, niche
–
–
–
–
Pattern of living: everything that affects survival and reproduction
A Species’ “Role” in life
Water, space, sunlight, food, temperatures
Not to be confused with “habitat”
• Generalist species
– Broad niche: wide range of tolerance
– Eat variety of food, live in different places, etc
– Examples: mice, white-tailed deer, roaches
• Specialist species
– Narrow niche: narrow range of tolerance
– Opposite of generalist
– Example: shorebirds
Specialist Species and Generalist Species Niches
Fig. 4-13, p. 95
Specialized Feeding Niches of Various Bird Species in a
Coastal Wetland
Fig. 4-14, p. 96
Specialists vs Generalists
• Which is better?
– Depends
– Specialists usually have fewer competitors when
environmental conditions are constant
– Generalists have the option of tolerance or change
• What do you think most shark species are??
Case Study: Cockroaches: Nature’s
Ultimate Survivors
• 3500 species
• Outlived dinosaurs
• Generalists
– Eat almost anything
– Live in almost any climate
• Some survived being frozen for 48 hours
• High reproductive rates
• What’s their purpose
– Serve as food for birds/lizards
Species Can Play Five Major Roles within
Ecosystems
• Native species– Normally live and thrive in a particular area
• Nonnative species
– Invasive, alien, exotic; Introduced into an area not
normally found
• Indicator species
– Provide early warning signs of ecosystem damage
– Many bird species, butterflies
• Keystone species
– Roles have large effect on the types and abundance of
other species
• Foundation species
– Play major role in shaping their communities
Indicator Species Serve as Biological
Smoke Alarms
• Indicator species
– Provide early warning of damage to a community
– Usually vulnerable to Enviro. Change
– Can monitor environmental quality
• Trout
• Birds- found everywhere, affected quickly by
environmental change
• Butterflies-association with various plants
• Frogs
Case Study: Why Are Amphibians
Vanishing? (1)
• Habitat loss and fragmentation
• Prolonged drought
• Pollution
• Increase in UV radiation
• Parasites
• Viral and fungal diseases
• Climate change
• Overhunting
• Nonnative predators and competitors
Case Study: Why Are Amphibians
Vanishing? (2)
• Importance of amphibians
– Sensitive biological indicators of environmental
changes
– Adult amphibians
• Important ecological roles in biological communities
• Important food web interactions
– Genetic storehouse of pharmaceutical products
waiting to be discovered
• Compounds in skin secretions useful as painkillers
antibiotics, burn and heart disease treatment
Keystone Species Play Critical Roles in
Their Ecosystems
• Keystone species: roles have a large effect on
the types and abundances of other species
– Exist in limited or small numbers
– Vulnerable to extinction
• Pollinators
• Top predators
– Regulate populations
Case Study: Why Should We Care
about the American Alligator?
• Largest reptile in North America
• 1930s: Hunters and poachers
– By 1960’s : 90% wiped out
• a keystone species
– Gator holes
– Nesting mounds
– Keep shore/open water free of invading vegetation
• 1967: endangered species
• 1977: comeback, threatened species
Foundation Species Help to Form the
Bases of Ecosystems
• Create or enhance their habitats, which benefit
others
• Elephants
• Beavers
• Similar role of keystone species
– Major difference: keystone species usually do the job
of foundation species and much more additionally
Three Big Ideas
1. 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).
2. Human activities are decreasing the earth’s vital biodiversity
by causing the extinction of species and by disrupting
habitats needed for the development of new species.
1. Each species plays a specific ecological role (ecological niche)
in the ecosystem where it is found.
FRQ Practice
• Read the following statement and answer the
questions in essay style-response.
• Be sure to read the question completely and
understand exactly what it is asking
• Never let your answer deviate from the
prompt’s purpose!
FRQ Practice
• Complete in your notebook
• Write questions and answer
• Answers should be complete essay style