Download Ch 5 Evolution _ Biodiversity Notes

Evolution and Biodiversity
Sections 5-2 & 5-4
What is Evolution?
Core Case Study
Earth: The Just-Right, Adaptable Planet

Oxygen Level
On earth, oxygen comprises 21
percent of the atmosphere. If oxygen
were 25% fires would erupt
spontaneously, if it were 15%, human
beings would suffocate.

Water Vapor Levels. If water vapor
levels in the atmosphere were greater
than they are now, a runaway
greenhouse effect would cause
temperatures to rise too high for human
life. If they were less, an insufficient
greenhouse effect would make the
earth to cold to support human life.
Figure 4-1
Biological
Evolution
 Proposes
theories about
development of
the variety of
species we find
on the earth
today.
Figure 4-2
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,
DNA analysis.
Figure 4-4
EVOLUTION, NATURAL SELECTION,
AND ADAPTATION

Biological evolution by natural selection involves the
change in a population’s genetic makeup through
successive generations.

Natural selection: a difference in reproductive
success of certain traits due to organisms’
interactions with their environment.
 Ex.

Adaptation: an organism’s characteristics or traits
that allow it to survive and reproduce in an
environment.
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.
Natural Selection
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.
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.
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.
SPECIATION
 Speciation:
Theoretically, a new species can
arise when members of a population become
isolated for a long period of time.

Genetic makeup changes prevent 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
Evolutionary Divergence
 Each
species has a
beak specialized to
take advantage of
certain types of
food resource.
Figure 4-9
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.
Or plants and pollinators
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
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
Definition of Biodiversity
 Biodiversity
is the
variation of life forms
 within

a given ecosystem,
biome,
or on the entire Earth.
From Wikipedia: http://en.wikipedia.org/wiki/Biodiversity
Effects of Humans on Biodiversity
 The
scientific consensus is that human
activities are decreasing the earth’s
biodiversity.
Figure 4-13
HUMAN IMPACTS ON TERRESTRIAL
BIODIVERSITY
 We
have depleted
and degraded some
of the earth’s
biodiversity and these
threats are expected
to increase.
Figure 10-2
Human Population
Size and resource use
Human Activities
Agriculture, industry, economic
production and consumption, recreation
Direct Effects
Degradation and destruction Changes in number and
of natural ecosystems
distribution of species
Alteration of natural chemical Pollution of air, water,
cycles and energy flows
and soil
Climate
change
Indirect Effects
Loss of
Biodiversity
Fig. 10-2, p. 192
HIPPO+C
 H-Habitat
Loss-destruction, degradation
and fragmentation
 I-Invasive Species
 P-Population of humans increasing
 P-Pollution
 O-Overharvesting
 + C- Climate Change
Why Should We Care About Biodiversity?

Use Value: For the
usefulness in terms of
economic and
ecological services.

Nonuse Value:
existence, aesthetics,
bequest for future
generations.
The Value of Biodiversity
Figure 10-3