Chapter 4 (Miller and Spoolman,
2010)

Largest reptile in North America and plays a number
of roles in the ecosystem.
•
•
•
•
•
Role is ecosystem is called a niche.
Gator holes
Nesting mounds
Predator
Keeps areas of open water free of invading vegetation

1930s: Hunters and poachers

1967: endangered species

1977: comeback, reclassified as threatened species

Highlights how interactions between species affect the
structure and function of ecosystems.
 Concept
4-1 The biodiversity found in
genes, species, ecosystems, and
ecosystem processes is vital to sustaining
life on earth.


Biological diversity, or biodiversity – the
variety of the earth’s species, the genes they
contain, the ecosystems in which they live, and
the ecosystem processes such as energy flow
and nutrient cycling that sustain all life.
Biodiversity is vital renewable resource
important to sustainability.
• Natural capital and natural services
 Food, wood, fibers, energy, and medicines—hundreds of
billions in natural services.
 Preserved air and water quality and maintains fertility of soils.
 Helps to dispose of wastes and control pest populations.
 Species
diversity
 Genetic
diversity
 Ecosystem diversity
• The variety of ecosystems are the storehouses of
genetic and species diversity.
 Functional diversity
• The variety of processes such as matter cycling and
energy flow in ecosystems as species interact with
one another in food webs.
 Concept
4-2A The scientific theory of
evolution explains how life on earth
changes over time through changes in
the genes of populations.
 Concept
4-2B Populations evolve when
genes mutate and give some individuals
genetic traits that enhance their abilities
to survive and to produce offspring with
these traits (natural selection).
 Biological
evolution – process whereby
earth’s life changes over time through
changes in the genes of populations.
 That life on earth had gone though changes
had been around since the time of the ancient
Greeks.
 Not until 1858 when a mechanism was
proposed independently by
• Charles Darwin (1809-1882)
 On the Origin of Species by Means of Natural Selection (1859)
• Alfred Russel Wallace (1823-1913)
 Natural
selection – occurs when some
individuals of a population have genetically
based traits that enhance their ability to
survive and produce offspring with the
same traits.
• A change in the genetic characteristics of a
population from one generation to another is known
as biological evolution, or simply evolution.
 Life
has evolved into six major groups of
organisms—kingdoms .
• Result is viewed as an ever branching tree of species
diversity called the tree of life.
 Fossils
– mineralized or petrified
replicas of skeletons, bones, teeth, shells,
leaves, and seeds, or impressions of such
items found in rocks.
• Physical evidence of ancient organisms
• Reveal what their internal structures looked like
 Fossil
record is the world’s cumulative
body of fossils.
• Incomplete, why?


Populations—not individuals—evolve by becoming
genetically different.
Genetic variability
• First step in biological evolution
• Occurs through mutations—random changes in the
structure or number of DNA molecules in a cell that can
be inherited by offspring, i.e. in reproductive cells.

Most mutations are caused by random errors
while DNA is copying, but others are cause by
mutagens.
 Second
step in biological evolution is
natural selection which acts on individuals.
• Natural selection occurs when some individuals of a
population have genetically based traits (resulting
from mutations) that enhance their ability to survive
and produce offspring with these traits.
• Adaptation – a heritable trait that enables a
individual organism to survive through natural
selection and reproduce more than other individuals
under the prevailing environmental conditions.
 Leads to differential reproduction
 Examples:
 Fur color and thickness in mammals and
 Genetic resistance in bacteria
 Summary
• Genes mutate, individuals are selected, and
populations evolve that are better adapted to survive
and reproduce under existing environmental
conditions.
 When
environmental conditions change,
populations
• Adapt
• Migrate
• Become extinct
 Like
many species, humans have survived
and thrived because we have certain traits
that allow us to adapt to and modify parts
of the environment to increase our survival
chances.
 Three human adaptations
• Strong opposable thumbs
• Walk upright
• Complex brain
 Would
adaptations evolve by natural
selection to cope with increasing UV light
levels (skin), air pollutants (lungs), and
other toxins (liver)?
 The answer is no for two reasons:
• Genetic change must precede change in the
environmental conditions.
• Reproductive capacity
 Humans and other long-lived species do not reproduce
rapidly. Thus, significant changes in populations
genetic make-up takes long period of time (thousands
to millions of years).

Myth 1: “Survival of the fittest” means “survival of
the strongest”
• Fitness is a measure of reproductive success, not strength.


Myth 2: Organisms develop traits out of need or
want.
Myth 3: There is a grand plan of nature for
perfect adaptation.
• Evolutionary process by all accounts, appears to be a
random, branching process that results in a great variety
of species.

Concept 4-3 Tectonic
plate movements,
volcanic eruptions,
earthquakes, and
climate change have
shifted wildlife
habitats, wiped out
large numbers of
species, and created
opportunities for the
evolution of new
species.

Tectonic plates affect evolution and the location
of life on earth.
• Location of continents and oceans influence climate
influences where plants and animals can live.
• Allows species physically move, adapt to new
environments, and form new species through natural
selection

Earthquakes
• Fissure can separate and isolate populations.

Volcanic eruptions
• Destroys habitat, and reduces or wipes out populations.
 Glacial
and interglacial periods: Ice ages
followed by warming temperatures.
• Ice sheets and sea levels.
• Long-term climate changes have a major effect on
biological evolution by determining where different
types of organisms can survive and by changing the
locations of ecosystems such as deserts, grasslands
and forests.
 Collisions
asteroids.
between the earth and large
• New species
• Extinction

Life can thrive only within a certain temperature
range.

Dependence on water

Average distance of orbit

Rotation on its axis and revolution around the sun

Enough gravitational mass

Oxygen and CO2 levels.
 Concept
4-4A As environmental conditions
change, the balance between formation of
new species and extinction of existing
species determines the earth’s biodiversity.
 Concept
4-4B Human activities can
decrease biodiversity by causing the
premature extinction of species and by
destroying or degrading habitats needed
for the development of new species.
 Speciation
– process by which natural
selection causes the formation of two new
species from one.
 Mechanisms of Speciation
• Geographic isolation
• Reproductive isolation
 Humans
are playing an increasing role in
the process of speciation.
• Selective breeding/artificial selection
• Genetic engineering
 Extinction
 Endemic
species
• Particularly vulnerable
 All
species eventually become extinct.
• Background extinction rate - low rate at which
species have become extinct.
• Annually: 1-5 species per million species.
 Drastic
changes in environmental
conditions.
• Mass extinction rate – catastrophic, widespread
extinction of large groups of species.
 Perhaps 25–70 % are wiped out in a geological
periods lasting up to 5 years.

There have been five
mass extinctions.
• Most recent was 65 mya.
• 250 mya, 95 % of species
disappeared.


A mass extinction
provides an opportunity
for the evolution of new
species that can fill
vacant ecological niches,
or newly created ones
Humans have become a
major force in the
premature extinction of a
growing list of species.
 Artificial
selection
 Genetic
engineering, gene
splicing
Figure 4-A An example of genetic
engineering. The 6-month-old mouse on
the left is normal; the same-age mouse on
the right has a human growth hormone
gene inserted in its cells. Question: How
do you think the creation of such species
might change the process of evolution by
natural selection.
 Consider
• Ethics
• Morals
• Privacy issues
• Harmful effects
 Concept
4-5 Species diversity is a major
component of biodiversity and tends to
increase the sustainability of ecosystems.
 Species diversity
• Species richness – number of species
• Species evenness – relative abundance
 Diversity varies with geographical location.
• In terrestrial ecosystems, highest in the tropics and
declines as we move from equator toward poles.
• Most species-rich communities




Tropical rain forests
Coral reefs
Ocean bottom zone
Large tropical lakes

Species equilibrium model, or theory of island
biogeography
• Species richness of an island reaches and equilibrium and
depends on:
 Rate of new species immigrating
 Rate of species extinction

Two features of an island affect immigration and
extinction rates.
• Island size
• Distance from the mainland

Theory is applied to habitat fragments and can be
used to make management decisions.

How does species richness affect ecosystems?
1.
2.

Is productivity higher in species-rich ecosystems?
Does species richness enhance stability, or
sustainability.
Most studies seem to support that species
richness seems to increase productivity and
stability or sustainability
• More research is needed before these observations
become accepted as theory.
• One question new question: Just how much species
richness is needed?
 Evidence suggest that anything greater than between 10-40
producer species does not necessarily increase productivity.
 Concept
4-6A Each species plays a
specific ecological role called its niche.
 Concept
4-6B Any given species may
play one or more of five important
roles—native, nonnative, indicator,
keystone, or foundation roles—in a
particular ecosystem.

Ecological niche, or simply niche
• Pattern of living, a roles in an ecosystem
• Includes everything that affects a species’ survival

Generalist species
• Broad niche
• Can live in many different places, eat many things tolerate a wide range
of environmental conditions.
• Examples: Flies, rats, mice, rats, white-tailed deer, raccoons, and humans

Specialist species
• Narrow niche
• Can live in only certain habitats, use only few types of food, and tolerate a
narrow range of environmental factors.
• Example: Tiger salamander, giant panda

Better to be a generalist or a specialist?

Cockroaches
Generalists
Been around for 350 my
3500 species
25 species are
considered pests and
can carry pathogenic
viruses and bacteria
• Play a role in natures
food web: detritivores
and food items for other
species
• High reproductive rates
•
•
•
•
 Native
species
 Nonnative
species, also referred to as
invasive, alien, or exotic species
• May spread rapidly
• Not all are villains
 Indicator
species – species that can
provide early warnings of damage to a
community or an ecosystem.
• Trout need clean water with high O2 levels.
• Birds
• Butterflies
• Amphibians
 Populations
are declining throughout the
world, at least 1/3 of all species.
 First vertebrates to set foot on land, but
having trouble adapting to some rapid
changes in the environment these past
few decades.
 Particularly vulnerable to environmental
disruption at various points in their life
cycle.









Habitat loss and fragmentation – draining wetlands,
deforestation, and urbanization
Prolonged drought – dries up breeding ponds
Pollution – esp. exposure to pesticides
Increase in UV radiation – by way of anthropogenic compounds
released into the atmosphere.
Parasites
Viral and fungal diseases – e.g., chytrid fungus which attacks
skin
Climate change – links to GW not clear, still being studied
Overhunting – esp. in Asia and France, where frog legs are a
delicacy.
Nonnative predators and competitors – such as fish and other
predators.
 Importance of amphibians
• Sensitive biological indicators of environmental
changes
• Adult amphibians and larvae
 Important ecological roles in biological communities
 Predators of insects and other animals
 Prey for other animals
• Genetic storehouse of pharmaceutical products
waiting to be discovered
 Compounds isolated from skin secretions have be used to
make painkillers an antibiotics and as treatment for burns
and heat disease.

Keystone species have a
large effect on the types
and abundances of
species in an ecosystem.
• Pollinators
• Top predator

Foundation species
create or enhance their
habitats, which benefit
others.
• Elephants
• Beavers
 Keystone
species
• Eat dead and dying
fish in the ocean
 Strong
immune
systems
 Wounds do not get
infected
 Almost never get cancer
 Could help humans if we
understood their immune
system