Transcript evolution and biodiversity1

Evolution and Biodiversity
Chapter 4
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?
Chapter Overview Questions
(cont’d)
• 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?
Video: Creation vs. Evolution
Videos\crea
tion_evoluti
on.flv -
• From ABC News, Environmental Science in the Headlines, 2005 DVD.
Modern humans (Homo
sapiens sapiens) appear
about 2 seconds before
midnight
Age of
mammals
Age of
reptiles
Insects and
amphibians
invade the
land
Recorded human history
begins about 1/4 second
before midnight
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
How Do We Know Which
Organisms Lived in the Past?
• Our knowledge
about past life
comes from fossils,
chemical analysis,
cores drilled out of
buried ice, and
DNA analysis.
Figure 4-4
What is Evolution?
• Biological Evolution: change in a population’s
genetic makeup (gene pool) through successive
generations.
• Populations, NOT individuals, evolve by
becoming genetically different
– Microevolution: small genetic changes that occur in a
population
– Macroevolution: long-term, large-scale evolutionary
changes through which new species are formed and
other species are lost
Macroevolution
• Long-term, largescale evolutionary
changes through
which new species
form and others
become extinct.
GEOLOGIC PROCESSES, CLIMATE
CHANGE, CATASTROPHES, AND
EVOLUTION
• The movement of solid (tectonic) plates
making up the earth’s 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.
Video: Continental Drift
PLAY
VIDEO
Climate Change and Natural
Selection
• Changes in climate throughout the earth’s
history have shifted where plants and
animals can live.
Figure 4-6
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.
Microevolution
• Small, genetic
changes that occur
within a population’s
gene pool
– Sickle cell anemia
– Antibiotic resistance
– Pesticide resistance
Microevolution
• Processes by which microevolution
occurs:
– Gene pool
– Alleles
– Mutations
– Natural selection
Facts about Evolution through
Natural Selection
• Evolution through natural selection is
about the most descendants.
– Organisms do not develop certain traits
because they need them.
– There is no such thing as genetic perfection.
What are three types of natural
selection?
• Directional natural selection: changing
environmental conditions cause individuals
with traits at one end of the normal range
become more common than midrange
forms.
– Example: evolution of genetic resistance to
pesticides among insects and to antibiotics
among disease-carrying bacteria
Second type of natural selection
• Stabilizing natural selection: tends to
eliminate individuals on both ends of the
genetic spectrum and favor individuals
with an average genetic makeup.
– Occurs when an environment changes little,
and most members of the population are well
adapted to that environment
Third type of natural selection
• Diversifying natural selection: occurs
when environmental conditions favor
individuals at both extremes of the genetic
spectrum and eliminate or sharply reduce
number of individuals with normal genetic
traits.
– A population is split into two groups.
Animation: Stabilizing Selection
PLAY
ANIMATION
Animation: Diversifying Selection
PLAY
ANIMATION
Animation: Moth Populations
PLAY
ANIMATION
Animation: Adaptive Trait
PLAY
ANIMATION
Formation of New Species
• New species develop when specific traits
are selected for by environmental changes
• Organisms exchange genes by
reproduction among members of the same
species
• There are also other ways to exchange
genes besides intraspecies exchange.
Hybridization and Gene
Swapping: Other Ways to
Exchange Genes
• New species can arise through
hybridization.
– Occurs when individuals to two distinct
species crossbreed to produce a fertile
offspring.
• Some species (mostly microorganisms)
can exchange genes without sexual
reproduction.
– Horizontal gene transfer
What is Coevolution?
• Coevolution is used to describe cases
where two (or more) species reciprocally
affect each other’s evolution. So for
example, an evolutionary change in the
morphology of a plant, might affect the
morphology of an herbivore that eats the
plant, which in turn might affect the
evolution of the plant, which might affect
the evolution of the herbivore...and so on.
Ecological Niches and Adaptation
• Ecological niche: species functional role in an
ecosystem.
– Involves range of tolerance for various physical and
chemical conditions (water availability, for example)
– Types and amounts of resources it uses, such as food
or nutrients
– How it interacts with other living and nonliving
components of the ecosystem
– The role it plays in the energy flow and matter cycling
in the ecosystem
How is the niche different from a
habitat?
• The niche is like a species’ occupation,
whereas the habitat is like its address
• The niche represents the adaptations or
adaptive traits that its members have
acquired through evolution
What is the difference between a species’
fundamental niche and its realized niche?
• The fundamental niche is the full potential
range of conditions and resources it could
use if there were no competition from
other species
• The realized niche is the part of the
fundamental niche in a community or
ecosystem that the species actually
occupies
Generalist vs. Specialist Species
• Generalist species: have broad niches
– Can live in many different places
– Eat a variety of foods
– Tolerate a wide range of environmental conditions
• Rats, mice, white-tailed deer, cockroaches, flies
• Specialist species: have narrow niches
– Live in only one type of habitat
– Use only one or a few types of food
– Tolerate only a narrow range of climatic and other environmental
conditions
– Makes them more prone to extinction when conditions change
• Tiger salamander, red-cockaded woodpeckers, spotted owls
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.
Figure 4-7
Specialized Feeding Niches
• Resource partitioning reduces
competition and allows sharing of limited
resources.
Figure 4-8
Fruit and seed eaters
Insect and nectar eaters
Greater Koa-finch
Kuai Akialaoa
Amakihi
Kona Grosbeak
Crested Honeycreeper
Akiapolaau
Maui Parrotbill
Unknown finch ancestor
Apapane
Fig. 4-9, p. 91
What limits adaptation?
• A change in environmental conditions
• Reproductive capacity.
– Quickly reproducing populations adapt in a short time
– Slowly reproducing populations take a long time to
adapt through natural selection
• Most of the population has to die or become
sterile so individuals with the desirable trait
could predominate and pass the trait on.
Different species of bowerbird construct elaborate bowers and
decorate them with different colors in order to woo females. The
Satin bowerbird (left) builds a channel between upright sticks, and
decorates with bright blue objects, while the MacGregor’s Bowerbird
(right) builds a tall tower of sticks and decorates with bits of charcoal.
Evolutionary changes in mating rituals, such as bower construction,
can contribute to speciation.
http://evolution.berkeley.edu/evolibrary/article/_0_0/evo_44
Speciation, Extinction, and
Biodiversity
• Speciation: when two species arise from
one.
– Geographic isolation: groups of the same
population of a species become physically
separate for long periods
• Part of the population migrates
• Population separated by a physical barrier
• Population separated by volcanic eruption or
earthquake
• A few individuals are carried to a new location by
wind or water
Speciation
• Reproductive isolation: mutation and
natural selection operate independently in
two geographically isolated populations
and change the gene pools in different
ways (called divergent evolution).
Adapted to cold through
heavier fur,short ears, short
legs,short nose. White fur
matches snow for camouflage.
Arctic Fox
Northern
population
Early fox
Population
Spreads
northward
and southward
and separates
Southern
Population
Different environmental
conditions lead to different
selective pressures and
evolution into two different
species.
Adapted to
heat through
lightweight
fur and long
Gray Fox ears, legs,
and nose,
which give
off more
heat.
Fig. 4-10, p. 92
Extinction: Lights Out
• Extinction
occurs when
the population
cannot adapt to
changing
environmental
conditions.
The
golden toad of Costa Rica’s
Monteverde cloud forest has
become extinct. Reason?
Figure 4-11
How do species become extinct?
• Extinction is the second process affecting
the number and types of species on the
earth
• When environmental conditions change, a
species must
– Evolve, or become better adapted
– Move to a more favorable environment, if
possible
– Cease to exist (become extinct)
Cenozoic
Era
Period
Millions of
years ago
Quaternary
Today
Tertiary
65
Mesozoic
Cretaceous
Jurassic
180
Triassic
Species and families
experiencing
mass extinction
Extinction Current extinction crisis caused
by human activities. Many species
are expected to become extinct
Extinction within the next 50–100 years.
Cretaceous: up to 80% of ruling
reptiles (dinosaurs); many marine
species including many
foraminiferans and mollusks.
Extinction
Triassic: 35% of animal families,
including many reptiles and marine
mollusks.
Bar width represents relative
number of living species
250
Extinction
345
Extinction
Permian
Paleozoic
Carboniferous
Devonian
Permian: 90% of animal families,
including over 95% of marine
species; many trees, amphibians,
most bryozoans and brachiopods,
all trilobites.
Devonian: 30% of animal
families, including agnathan and
placoderm fishes and many
trilobites.
Silurian
Ordovician
Cambrian
500
Extinction
Ordovician: 50% of animal
families, including many
trilobites.
Fig. 4-12, p. 93
Earth’s long-term patterns of
speciation and extinction
• Affected by:
– Large-scale movements of the continents
– Gradual climate changes caused by
continental drift and slight shifts in the earth’s
orbit around the sun
– Rapid climate change caused by catastrophic
events (such as large volcanic eruptions,
huge meteorites and asteroids crashing into
earth)
Types of Extinction
•
•
•
•
Background extinction
Mass extinction
Mass depletion
Adaptive radiations
Effects of Humans on
Biodiversity
• The scientific consensus is that human
activities are decreasing the earth’s
biodiversity.
Figure 4-13
How do speciation and extinction
affect biodiversity
• Speciation minus extinction equals biodiversity
• Mass extinction and mass depletions temporarily
reduce biodiversity
• Also create evolutionary opportunities
• Much evidence indicates that humans have
become a major force in premature extinction of
species
– During the 20th century, extinction rates increased by
100-1000 times the natural background rate
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.
Figure 4-15
Genetic Engineering:
Genetically Modified Organisms (GMO)
• GMOs use
recombinant
DNA
– genes or portions
of genes from
different
organisms.
Figure 4-14
Animation: Transgenic Plants
PLAY
ANIMATION
• From ABC News, Biology in the Headlines, 2005 DVD.
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.
– Do not know where the new gene will be
located in the DNA molecule’s structure and
how that will affect the organism.
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?