Transcript Chapter 4 - SchoolRack

Evolution and
Biodiversity
Biological Evolution
Has led to the variety of species we find on Earth today
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
Natural Selection
• Biological evolution by natural selection involves the change
in a population’s genetic makeup through successive
generations.
– genetic variability
– Mutations: random changes in the structure or number of
DNA molecules in a cell that can be inherited by
offspring.
Three conditions are necessary for
biological evolution by natural selection
Genetic variability, traits must be heritable, trait
must lead to differential reproduction
Zebra mussels on native mussel
Adaptation
An adaptive trait is any heritable trait that enables an
organism to survive through natural selection and reproduce
better under prevailing environmental conditions
Flying fish
Loach
Fish
Adaptations
Sun fish
Tri-pod fish
Coevolution: A Biological Arms Race
Interacting species can engage
in a back and forth genetic
contest in which each gains a
temporary genetic advantage
over the other
– This often happens between
predators and prey species
The Japanese hornet feeds on
Japanese honeybees
Japanese honeybees defend
their nests and their young by
surrounding the Japanese hornet
and fluttering their wings
increasing the body temperature
of the hornet and exposing the
hornet to increased carbon
dioxide levels
Limits on Adaptation through
Natural Selection
• A population’s 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.
Gestation period is 22
months for an elephant
Common Myths 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.
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.
225 million years ago
65 million years ago
135 million years ago
Present
Fig. 4-5, p. 88
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.
Meteor Crater,
Arizona
SPECIATION, EXTINCTION, AND BIODIVERSITY
• Speciation: A new species can arise when member of a
population become isolated for a long period of time.
– Genetic makeup changes, preventing them from producing fertile
offspring with the original population if reunited.
Geographic Isolation
• …can lead to reproductive isolation,
divergence of gene pools and speciation.
Figure 4-10
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.
Specialized Feeding Niches
• Resource partitioning reduces competition
and allows sharing of limited resources.
Figure 4-8
Avocet sweeps bill through
mud and surface water in
search of small crustaceans,
insects, and seeds
Ruddy
turnstone
Herring gull is a
searches
tireless scavenger
under shells
and pebbles
Dowitcher probes deeply
for small
into mud in search of
invertebrates
snails, marine worms,
and small crustaceans
Brown pelican
dives for fish,
which it locates
from the air
Black skimmer
seizes small fish
at water surface
Louisiana heron wades into
water to seize small fish
Flamingo
feeds on
minute
organisms
in mud
Scaup and other
diving ducks feed
on mollusks,
crustaceans,and
aquatic vegetation
(Birds not drawn to scale)
Oystercatcher feeds on
clams, mussels, and
other shellfish into which
it pries its narrow beak
Piping plover feeds
on insects and tiny
crustaceans on
sandy beaches
Knot (a sandpiper)
picks up worms and
small crustaceans left
by receding tide
Fig. 4-8, pp. 90-91
Evolutionary Divergence
• Each species has a
beak specialized to
take advantage of
certain types of
food resource.
Figure 4-9
Ecological Roles
Generalist species
•
•
•
•
Broad niche
Live in many different areas
Eat variety of foods
Tolerate wide range
environmental conditions
Specialist species
• Narrow niche
• May only live in one type of
habitat
• Few types of food
• Tolerate narrow range of
environmental conditions
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 because of
changes in climate.
Figure 4-11
SPOTLIGHT
Cockroaches: Nature’s Ultimate
Survivors
• 350 million years old
• 3,500 different species
• Ultimate generalist
– Can eat almost anything.
– Can live and breed almost
anywhere.
– Can withstand massive
radiation.
Figure 4-A
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
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
Using biotechnology to develop blight-resistant
American Chestnut
Before 1900 the American Chestnut made up 25% of
the standing trees in the Appalachian forest
These trees grew to 100 ft rapidly and their trunks
were more than 6 ft in diameter
The chestnut blight was introduced into the U.S. and
now the tree rarely reaches 30 ft before dying
Scientists have created transgenic American
Chestnut resistant to the chestnut blight
Transgenic trout with
six-pack abs = more
muscle mass which is
more profit
Transgenic fish which glow were
originally developed to detect
pollution – but developers can
make more money in the
aquarium trade
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?
Case Study:
How Did We Become Such a Powerful
Species so Quickly?
• 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).
The End