Evolution and Biodiversity

1
Chapter 4

• Evolution and Biodiversity

2
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?

3
Chapter Overview Questions (contd)

• 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?

4
Chapter Overview Questions (contd)

• What is an ecological niche, and how does it help
  a population adapt to changing environmental
  conditions?
• How do extinction of species and formation of new
  species affect biodiversity?

5
Review4 Principles of Sustainability?
1. 2. 3. 4.
6
Core Case StudyWhy Should We Care about the
American Alligator?

• Hunters wiped out population to the point of near
  extinction.
• 1967- classified as endangered
• 1975- numbers had rebounded
• 1977- reclassified as threatened

Figure 7-1
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Core Case StudyWhy Should We Care about the
American Alligator?

• Alligators have important ecological role.
• Alligators are a keystone species
• Influence on ecosystem is much greater than their
  numbers would suggest

Figure 7-1
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Core Case StudyAmerican Alligator as Keystone
Species

• Dig deep depressions (gator holes).
• Hold water during dry spells, serve as refuges
  for aquatic life.
• Build nesting mounds.
• provide nesting and feeding sites for birds.
• Keeps areas of open water free of vegetation
  (swimming paths)
• Keep gar populations in check

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Gator Holes
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Nesting Mounds
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Keep Waterways Clear
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Longnose Gar
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Alligator Gar
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Core Case StudyEarth The Just-Right, Adaptable
Planet

• Distance from sun
• Spins
• Size- molten mantle, retain atmosphere
• Stratospheric Ozone
• (2 billion years)
• 21 Oxygen
• (several hundred million years)
• Biodiversity Sustainability
• Temp

Figure 4-1
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Core Case StudyEarth The Just-Right, Adaptable
Planet

• During the 3.7 billion years since life arose,
  the average surface temperature of the earth has
  remained within the range of 10-20oC.

Figure 4-1
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Biological Evolution

• This has led to the variety of species we find on
  the earth today.

Figure 4-2
17
Modern humans (Homo sapiens sapiens) appear about
2 seconds before midnight
Recorded human history begins about 1/4 second
before midnight
Age of mammals
Age of reptiles
Insects and amphibians invade the land
Origin of life (3.6-3.8 billion years ago)
First fossil record of animals
Plants begin invading land
Evolution and expansion of life
Fig. 4-3, p. 84
18
How Do We Know Which Organisms Lived in the Past?

• Our knowledge about past life comes from
• fossils
• cores drilled out of buried ice
• analysis of protein similarities
• DNA RNA analysis.

Figure 4-4
19
EVOLUTION, NATURAL SELECTION, AND ADAPTATION

• Evolution in Seven Words
• Genes Mutate, Individuals are Selected,
  Populations Evolve

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Natural selection acts on individuals, but
evolution occurs in populations

• Three conditions are necessary for biological
  evolution
• 1. Genetic variability 2. traits must be
  heritable
• 3. 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.

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EVOLUTION, NATURAL SELECTION, AND ADAPTATION

• Biological evolution by natural selection
  involves the change in a populations genetic
  makeup through successive generations.
• With positive selection pressure, advantageous
  traits help individuals to survive long enough to
  have and raise their young.
• With negative selection pressure, individuals die
  before they can reproduce.

22
EVOLUTION, NATURAL SELECTION, AND ADAPTATION

• Advantageous traits originate from genetic
  variability.
• Genetic variability occurs through
• mutations random changes in the structure or
  number of DNA molecules in a cell that can be
  inherited by offspring.
• Exposure to mutagens radioactivity, x rays,
  certain chemicals
• Random mistakes in DNA duplication, or during RNA
  transcription and translation.

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Limits on Adaptation through Natural Selection

• A populations 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.

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Common Myths about Evolution through Natural
Selection

• Yes Biological evolution through natural
  selection is about the most descendants.
• No (Misunderstandings)
• Survival of the fittest means survival of the
  biggest, fastest, or strongest.
• Organisms develop certain traits because they
  need them.
• Species evolve towards genetic perfection.

25
New Species Hybridization

• New species can arise through hybridization.
• Occurs when individuals to two distinct species
  crossbreed to produce a fertile offspring.

The red wolf is thought to be a coyote/wolf hybrid
There are also non-fertile hybrids, such as mules.
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New Species Gene Swapping

• Some species (mostly microorganisms) can exchange
  genes without sexual reproduction.
• Horizontal gene transfer

27
BIODIVERSITY
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Why Should We Care About Biodiversity?

• Some consider it ethical to care about nature.
• Biodiversity provides us with
• Natural Resources (food, water, wood, energy, and
  medicines)
• Natural Services (air and water purification,
  soil fertility, waste disposal, pest control)
• Aesthetic pleasure

29
Biodiversity Loss and Species Extinction
Remember HIPPO

• These are in order
• H for habitat destruction and degradation
• I for invasive species
• P for pollution
• P for human population growth
• O for overexploitation

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ECOLOGICAL NICHES AND ADAPTATION Coastal Georgia
Smooth cordgrass, Spartina alterniflora
Can grow in fresh water
but it doesnt in the wild.
Why not?
31
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.

32
Species Diversity and Niche Structure Different
Species Playing Different Roles

• Biological communities differ in the types and
  numbers of species they contain and the
  ecological roles those species play.
• Species diversity has 2 components
• species richness the number of different species
  the ecosystem contains
• species evenness the abundance of individuals
  within each of those species.

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Species Diversity and Niche Structure

• Niche structure how many potential ecological
  niches occur, how they resemble or differ, and
  how the species occupying different niches
  interact.
• Geographic location species diversity is highest
  in the tropics and declines as we move from the
  equator toward the poles.

34
TYPES OF SPECIES

• Native, nonnative, indicator, keystone, and
  foundation species play different ecological
  roles in communities.
• Native those that normally live and thrive in a
  particular community.
• Nonnative species a.k.a. invasive species those
  that migrate, deliberately or accidentally
  introduced into a community.

35
Indicator Species Biological Smoke Alarms

• Species that serve as early warnings of damage to
  a community or an ecosystem.
• Canary in a coal mine
• Presence or absence of trout species because they
  are sensitive to temperature and oxygen levels.
• Birds- require a range of habitat
• Lichens- stay in one place and absorb from the
  environment
• Amphibians- vulnerable at any part of life cycle

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Case Study Why are Amphibians Vanishing?

• Frogs serve as indicator species because
  different parts of their life cycles can be
  easily disturbed.

Next
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Adult frog(3 years)
Young frog
Sperm
Tadpole develops into frog
Sexual Reproduction
Tadpole
Eggs
Fertilized egg development
Egg hatches
Organ formation
Fig. 7-3, p. 147
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Case Study Why are Amphibians Vanishing?

• Habitat loss and fragmentation.
• Prolonged drought.
• Increases in ultraviolet radiation.
• Parasites.
• Viral and Fungal diseases.
• Overhunting.
• Air OR water pollution
• Natural immigration or deliberate introduction of
  nonnative predators and competitors.

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Keystone Species Major Players

• Keystone species help determine the types and
  numbers of other species in a community thereby
  helping to sustain it.

Figures 7-4 and 7-5
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Foundation Species Other Major Players

• Subset of keystone species category.
• Foundation species can create and enhance the
  physical habitats to benefit other species in a
  community.
• Elephants push over, break, or uproot trees,
  creating forest openings promoting grass growth
  for other species to utilize.
• Alligators making gator holes

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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. Exp tiger salamander, giant
  panda

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

• 350 million year old genus
• 3,500 different species
• Ultimate generalist
• Can eat almost anything.
• Can live and breed almost anywhere.
• Can withstand massive doses of radiation.

Figure 4-A
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Specialized Feeding Niches

• Resource partitioning reduces competition and
  allows sharing of limited resources.

Figure 4-8
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Resource Partitioning
Avocet sweeps bill through mud and surface water
in search of small crustaceans, insects, and
seeds
Ruddy turnstone searches under shells and
pebbles for small invertebrates
Herring gull is a tireless scavenger
Brown pelican dives for fish, which it locates
from the air
Dowitcher probes deeply into mud in search
of snails, marine worms, and small crustaceans
Black skimmer seizes small fish at water surface
Louisiana heron wades into water to seize small
fish
Piping plover feeds on insects and
tiny crustaceans on sandy beaches
Oystercatcher feeds on clams, mussels, and other
shellfish into which it pries its narrow beak
Flamingo feeds on minute organisms in mud
Scaup and other diving ducks feed on mollusks,
crustaceans,and aquatic vegetation
Knot (a sandpiper) picks up worms and small
crustaceans left by receding tide
(Birds not drawn to scale)
Fig. 4-8, pp. 90-91
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Evolutionary Divergence Darwins Finches

• Each species has a beak specialized to take
  advantage of certain types of food resource.

Next
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Insect and nectar eaters
Fruit and seed eaters
Greater Koa-finch
Kuai Akialaoa
Amakihi
Kona Grosbeak
Crested Honeycreeper
Akiapolaau
Maui Parrotbill
Apapane
Unknown finch ancestor
Fig. 4-9, p. 91
48
NATURAL SELECTION DRIVEN BY GEOLOGIC PROCESSES,
CLIMATE CHANGE, CATASTROPHES

• The movement of solid tectonic plates making up
  the earths 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.

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225 million years ago
225 million years ago
135 million years ago
65 million years ago
Present
Fig. 4-5, p. 88
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Climate Change and Natural Selection

• Changes in climate throughout the earths history
  have shifted where plants and animals can live.

Next
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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
Land above sea level
Fig. 4-6, p. 89
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SPECIATION, EXTINCTION, AND BIODIVERSITY

• Speciation A new species can arise when member
  of a population become isolated for a long period
  of time.
• Due to natural selection over time, the genetic
  makeup changes, preventing them from producing
  fertile offspring with the original population if
  reunited.

53
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.

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Geographic Isolation

• can lead to reproductive isolation, which leads
  to divergence of gene pools and speciation.

Figure 4-10
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Adapted to cold through heavier fur,short ears,
short legs,short nose. White fur matches snow for
camouflage.
Arctic Fox
Northern population
Different environmental conditions lead to
different selective pressures and evolution into
two different species.
Spreads northward and southward and separates
Early fox Population
Adapted to heat through lightweight fur and long
ears, legs, and nose, which give off more heat.
Southern Population
Gray Fox
Fig. 4-10, p. 92
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Extinction Lights Out

• Extinction occurs when the population cannot
  adapt to changing environmental conditions.

• The golden toad of Costa Ricas Monteverde cloud
  forest has become extinct because of changes in
  climate.

Figure 4-11
57
Categorizing Extinction Rates

• Biologists estimate that 99.9 of all the species
  that ever existed are now extinct.
• Background extinction- a certain number of
  species disappearing at a slow rate due to
  changes of local environmental conditions
• Estimate 1-5 species per million per year
• Mass depletion- rates of extinction above
  background level but not high enough to be
  considered a mass extinction.
• Mass extinction- a significant rise in extinction
  rate above background level 20-70

58
Effects of Humans on Biodiversity

• The scientific consensus is that human activities
  are decreasing the earths biodiversity.

Figure 4-13
59
Terrestrial organisms
Silurian
Permian
Jurassic
Devonian
Devonian
Cambrian
Ordovician
Cretaceous
Marine organisms
Pre-cambrian
Carboniferous
Number of families
Quaternary
Tertiary
Millions of years ago
Fig. 4-13, p. 94
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Species and families experiencing mass
extinction
Bar width represents relative number of living
species
Millions of years ago
Era
Period
Current extinction crisis caused by human
activities. Many species are expected to become
extinct within the next 50100 years.
Extinction
Quaternary
Today
Cenozoic
Tertiary
Extinction
65
Cretaceous up to 80 of ruling reptiles
(dinosaurs) many marine species including
many foraminiferans and mollusks.
Cretaceous
Mesozoic
Jurassic
Triassic 35 of animal families, including many
reptiles and marine mollusks.
Extinction
180
Triassic
Permian 90 of animal families, including over
95 of marine species many trees, amphibians,
most bryozoans and brachiopods, all trilobites.
Extinction
250
Permian
Carboniferous
Extinction
345
Devonian 30 of animal families, including
agnathan and placoderm fishes and many trilobites.
Devonian
Paleozoic
Silurian
Ordovician
Extinction
Ordovician 50 of animal families, including
many trilobites.
500
Cambrian
Fig. 4-12, p. 93
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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 (gene splicing)
• Takes half the time and costs less than
  crossbreeding.

Figure 4-15
62
Genetic Engineering Genetically Modified
Organisms (GMO)

• GMOs use recombinant DNA
• genes or portions of genes from different
  organisms.

Figure 4-14
63
Case StudySpecies Diversity on Islands

• MacArthur and Wilson proposed the species
  equilibrium model a.k.a. theory of island
  biogeography in the 1960s.
• Model projects that at some point the rates of
  immigration and extinction should reach an
  equilibrium based on
• Island size
• Distance to nearest mainland

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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.
• Currently We do not know where the new gene will
  be located in the DNA molecules structure and
  how that will affect the organism.

65
Biopharming

• Biopharming is when humans use genetically
  engineered organisms for the production of
  consumables such as
• Drugs
• Chemicals
• Human body parts
• Which one of these have we not yet mastered?

66
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?

67
Case StudyHow Did We Become Such a Powerful
Species so Quickly?

• Compared to other species, 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).

68
Ch 4 Final Thoughts

• Microevolution- Traits changing in a species
  (e.g.color, fur type, etc.)
• Industrial Melanism
• in pepper moths
• Macroevolution- The development of new species

69
Ch 4 Final Thoughts

• Gradualism- species change slowly over time at a
  steady rate of change (Darwin was wrong about
  this)
• Punctuated Equilibrium- Long periods of stability
  punctuated by periods of rapid change, initiated
  by changes in the environment (evolutionary
  biologist Stephen Jay Gould)

70
Ch 4 Final Thoughts

• Natural Selection happens to individuals, and
  leads to differential reproduction (think about
  the wooly worms lab)
• Evolution happens to a population over time, and
  is ultimately understood as changes in gene
  frequencies within that population.
• Leads to microevolution in the short term
• Leads to macroevolution in the long term

71
Genetic Engineering Genetically Modified
Organisms (GMO)

• GMOs use recombinant DNA
• genes or portions of genes from different
  organisms.

Figure 4-14
72
Phase 1 Make Modified Gene
E. coli
Insert modified plasmid into E. coli
Genetically modified plasmid
Cell
Extract Plasmid
Extract DNA
Plasmid
Gene of interest
DNA
Remove plasmid from DNA of E. coli
Identify and remove portion of DNA with desired
trait
Insert extracted (step 2) into plasmid (step 3)
Identify and extract gene with desired trait
Grow in tissue culture to make copies
Fig. 4-14, p. 95
73
Phase 2 Make Transgenic Cell
A. tumefaciens (agrobacterium)
Foreign DNA
E. Coli
Host DNA
Plant cell
Nucleus
Agrobacterium inserts foreign DNA into plant cell
to yield transgenic cell
Transfer plasmid copies to a carrier agrobacterium
Transfer plasmid to surface of microscopic metal
particle
Use gene gun to inject DNA into plant cell
Fig. 4-14, p. 95
74
Phase 3 Grow Genetically Engineered Plant
Transgenic cell from Phase 2
Cell division of transgenic cells
Culture cells to form plantlets
Transfer to soil
Transgenic plants with new traits
Fig. 4-14, p. 95
75
Phase 3 Grow Genetically Engineered Plant
Stepped Art
Fig. 4-14, p. 95