Transcript Ch 4 - Evolution and Biodiversity

Chapter 4
Evolution and
Biodiversity
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?
Chapter Overview Questions (cont’d)
 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?
LIFE!!!
1
billion years of chemical change to form the
first cells, followed by about 3.7 billion years of
biological change.
 Biological evolution – a “life-changing”
experience!
 Darwin and Wallace – natural selection
Figure 4-2
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
Past life
 Our
knowledge about past life comes from
fossils, chemical analysis, cores drilled out of
buried ice, and DNA analysis.
 Fossil record – what species lived when?
 Very incomplete
Figure 4-4
Mutations!
 Biological
evolution by natural selection
involves the change in a population’s genetic
makeup through successive generations.



genetic variability – happens through…
Mutations: random changes in the structure or
number of DNA molecules in a cell that can be
inherited by offspring.
Happen through mutagens or random mistakes
 Populations
evolve by becoming genetically
different, not individuals
Natural Selection and Adaptation

Three conditions are necessary for biological evolution:
 Genetic variability, traits must be heritable, 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.
 When things get bad, an organism can:
 Adapt
 Migrate
 Go extinct
 Simplified process: mutations  natural selection 
populations evolve
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.
http://www.youtube.com/watch?v=CCYvPUChnIo
Hybridization and Gene Swapping
 New


species can arise through hybridization.
Occurs when individuals to two distinct species
crossbreed to produce a fertile offspring.
Killer bees! (Africanized bees = European
honeybee + African honeybee)
 Some
species (mostly microorganisms) can
exchange genes without sexual reproduction.


Horizontal gene transfer
Can happen with infection, interaction, or
consumption
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.
 We also do not have unique beneficial mutations
arise often.
 Viruses (though not “living”) adapt quickly because
of their quick and numerous “reproduction” and
quick mutation rate (in some viruses)
 Evolution
through natural selection is about the
most descendants.



Organisms do not develop certain traits because
they need/want them.
There is no such thing as genetic perfection.
Fittest ≠ Strongest
Plate tectonics
 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.
Volcanic eruptions and earthquakes disrupt
environment
225 million years ago
65 million years ago
135 million years ago
Present
Fig. 4-5, p. 88
Climate Change
 Changes
in climate throughout the earth’s
history have shifted where plants and
animals can live.
Figure 4-6
ASTEROIDS!
 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.
 The four basic
principles of
sustainability
have helped
earth to adapt!
Niches
 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.
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.
 Specialists have less competition, but
generalists survive better under rapidly
changing environmental conditions.
 Natural selection can lead to an increase in
specialized species.
Number of individuals
Specialist species
with a narrow niche
Niche
separation
Generalist species
with a broad niche
Niche
breadth
Region of
niche overlap
Resource use
Fig. 4-7, p. 91
Evolutionary Divergence
 Each
species has a
beak specialized to
take advantage of
certain types of
food resource.
Figure 4-9
Resource partitioning reduces competition and allows
sharing of limited resources.
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
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
Speciation

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: different groups of same
population of species becoming geographically
isolated for a long time.
 Reproductive isolation: mutation and change by
natural selection occurs independently in each
isolated population.
 Can take different amounts of time depending on the
species
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
 Extinction
occurs when
the population cannot
adapt to changing
environmental conditions.
 Endemic species: only
lives in one area
The
golden toad of
Costa Rica’s Monteverde
cloud forest has become
extinct because of
changes in climate.
Figure 4-11
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
More extinction!
 Background
extinction: a certain number of
species disappear at a low rate as local
environmental conditions change.

Scientists estimate average background extinction
is 1-5 species per million species.
 Mass
extinction: significant rise in extinction
rates above background level.


Usually catastrophic and widespread, with 25-70%
of existing species wiped out in up to 5 million
years.
We have had 5 mass extinctions
 Mass
depletion: somewhere in between.
Effects of Humans on Biodiversity
 The
scientific consensus is that human
activities are decreasing the earth’s
biodiversity.
Figure 4-13
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)
AKA Transgenic Organisms
 GMOs
use
recombinant
DNA

genes or portions
of genes from
different
organisms.
Figure 4-14
Phase 1
Make Modified Gene
E. coli
Cell
Extract DNA
Gene of
interest
DNA
Identify and
Identify and
remove portion
extract gene
of DNA with
with desired trait
desired trait
Extract
Plasmid
Genetically
modified
plasmid
Insert modified
plasmid into E. coli
Plasmid
Remove
Insert extracted
plasmid
(step 2) into plasmid
from DNA of
(step 3)
E. coli
Grow in tissue
culture to
make copies
Fig. 4-14, p. 95
Phase 2
Make Transgenic Cell
E. Coli A. tumefaciens
(agrobacterium)
Foreign DNA
Plant cell
Host DNA
Nucleus
Transfer plasmid
copies to a carrier
agrobacterium
Transfer plasmid to
surface of microscopic
metal particle
Agrobacterium inserts
foreign DNA into plant cell
to yield transgenic cell
Use gene gun to inject
DNA into plant cell
Fig. 4-14, p. 95
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
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?
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).