Adaptation,
Biodiversity and
Population Ecology
Chapter 5
QUESTION: Review
Which group contains the most species on Earth?
a. Mushrooms
b. Orchids
c. Spiders
d. Beetles
e. Oak trees
QUESTION: Review
Which of these pairs of terms is included as
causes of biodiversity loss?
a. Pollution and Indicator species
b. Harvesting and Population decline
c. Habitat alteration and Invasive species
d. Overexploitation and Pollination
e. Indicator species and Population growth
QUESTION: Review
Which is NOT a benefit to humans of biodiversity?
a. Economic benefits through ecotourism
b. New potential sources of food
c. New potential sources of drugs
d. Ecosystem services
e. All of the above are benefits of biodiversity.
QUESTION: Review
Which has NOT been an approach of conservation
biologists?
a. Identifying and mapping areas with large numbers of
endemic species.
b. Applying island biogeography theory to habitat
fragments.
c. Breeding animals in captivity.
d. Requiring landowners to give up their land.
e. Working with local communities to get them invested
in conservation.
QUESTION: Weighing the
Issues
When North American pharmaceutical companies go
“bioprospecting” in developing countries for compounds for
new drugs and medicines, should they be required to pay the
host country for its biodiversity?
a.
Yes; the biodiversity is a natural resource of the host country, and
it should be paid a fee up front.
b. Yes; the biodiversity is a natural resource of the host country, and
it should share in any eventual profits from any medicines
developed.
c. No; the company is the one doing all the work, so all profits should
go to the company.
QUESTION: Interpreting
Graphs and Data
Arachnid species comprise what percentage of ALL species?
a. 5.7%
b. 75%
c. 4.3%
d. It cannot be
calculated
from the
information
given.
QUESTION: Interpreting
Graphs and Data
Extinction rates are…?
a. Greater than immigration
rates on small islands
b. Greater on large islands
than small islands
c. Greater when number of
species are smaller
d. Greater on small islands
than large islands
QUESTION: Viewpoints
Are parks and protected areas the best strategy
for protecting biodiversity?
a. Yes; it is absolutely necessary to preserve
untrammeled habitat for species to persist.
b. No; parks won’t matter because climate change will
force the biota out of them.
c. No; it is more effective to work with local people and
give them economic incentives to conserve nature.
d. Both parks and other strategies are necessary.
QUESTION: Review
Which is a K-selected species?
a.
A dragonfly that lays 300 eggs and flies away
b.
An oak tree that drops its acorns each year
c.
A bamboo plant that flowers only once every 20
years
d.
A human who raises three children
e.
A fish on the second trophic level
QUESTION: Review
What is the average time for a species on Earth?
a.
b.
c.
d.
1000 years
5000 years
1 million years
~1-10 million years
Question: Review
Which of the following attributes does NOT help
predict population dynamics (changes in
population):
a.
b.
c.
d.
Population size
Population distribution
Age structure
Sex ratio
QUESTION: Weighing the Issues
Can we continue raising the Earth’s carrying
capacity for humans by developing technology
and using resources more efficiently?
a. Yes, our growth can continue indefinitely.
b. Our growth can continue some more, but will
eventually be halted by limiting factors.
c. No, we cannot raise Earth’s carrying capacity
for ourselves any longer.
QUESTION: Weighing the Issues
Are national parks and preserves the best way to
conserve biodiversity?
a.
Yes, because species depend on their habitats and intact
communities being protected.
b.
No, because climate change can ruin conservation efforts
if it changes conditions inside preserves.
c.
Ecotourism and encouraging local interest in conservation
is more important than establishing parks.
QUESTION: Interpreting Graphs and
Data
You would expect this population to be…?
a. Growing rapidly
b. Shrinking rapidly
c. Stable in size
d. Oscillating in size
QUESTION: Interpreting Graphs and
Data
How can you tell that this population growth curve shows
exponential growth?
a. Population is increasing.
b. Data points match curve
closely.
c. Population is rising by the
same number during each
interval.
d. Population is rising by the
same percentage during
each interval.
QUESTION: Interpreting Graphs and
Data
This shows
growth ending at a(n)
a. exponential… carrying
capacity
b. intrinsic… equilibrium
c. logistic… carrying
capacity
d. runaway… equilibrium
e. logistic… extinction
QUESTION: Viewpoints
What is the most important lesson we can learn from the
Monteverde preserve?
a. Preserves do little good if species can become
extinct inside them.
b. Climate change means that we will need more than
preserves to save all species.
c. Ecotourism and local participation can make for
successful conservation.
Evolution and natural
selection

Evolution = genetic change across generations

Natural selection = process by which traits that
enhance survival are passed on to future generations
more than those that do not

This alters the genetic makeup of populations over time.
Natural selection shapes
diversity

Charles Darwin and Alfred Russell Wallace each proposed natural
selection as a mechanism for evolution and a way to explain the
variety of living things.

A trait that promotes success in natural selection is called an
adaptive trait or an adaptation.

A trait that reduces success is maladaptive.

A trait that is adaptive in one location or season may prove
maladaptive in another.
Natural selection and genetic
variation

For a trait to be heritable, genes in an organism’s DNA
must code for the trait.

Mutations are accidental changes in DNA.

Mutations that are not lethal provide the genetic
variation on which natural selections act.

In these ways, variable genes and variable
environments interact in adapting to environmental
conditions.
Biodiversity
•
Biodiversity, or biological diversity, is the sum of an
area’s organisms, considering the diversity of species,
their genes, their populations, and their communities.
•
A species is a particular type of organism; a
population or group of populations whose members
share certain characteristics and can freely breed with
one another and produce fertile offspring.
•
A population is a group of individuals of a particular
species that live in the same area.
Biodiversity
Costa Rica’s Monteverde cloud forest is home to
many species and possesses great biodiversity.
Speciation

Speciation: The process by which new species come
into being

It is an evolutionary process that has given Earth its
current species richness—more than 1.5 million
described species and likely many million more not yet
described by science.

Allopatric speciation is considered the dominant
mode of speciation, and sympatric speciation also
occurs.
Allopatric speciation
1. Single interbreeding
population
2. Population
divided by a barrier;
subpopulations
isolated
Allopatric speciation
3. The two populations
evolve independently,
diverge in their traits.
4. Populations reunited
when barrier removed,
but are now different
enough that they
don’t interbreed.
Allopatric speciation
Many geological and climatic events can serve as
barriers separating populations and causing
speciation.
Phylogenetic trees

Life’s diversification results from countless
speciation events over vast spans of time.

Evolutionary history of divergence is shown
with diagrams called phylogenetic trees.

Similar to family genealogies, these show
relationships among organisms.
Phylogenetic trees
These trees are constructed by analyzing patterns
of similarity among present-day organisms.
This tree shows all of life’s major groups.
Phylogenetic trees
Within the group Animals in the previous slide,
one can infer a tree of the major animal groups.
Phylogenetic trees
And within the group Vertebrates in the previous
slide, one can infer relationships of the major
vertebrate groups, and so on…
Extinction

Evolution has not
always progressed in a
straight-forward
manner, or from simple
to complex.

The Burgess Shale
fauna were complex
and bizarre marine
animals from 530
million years ago that
vanished completely.
Extinction
•
Extinction is the disappearance of an entire
species from the face of the Earth.
•
Average time for a species on Earth is ~1–10
million years.
•
Species currently on Earth = the number
formed by speciation minus the number
removed by extinction
Extinction


Some species are more vulnerable to extinction
than others:
•
Species in small populations
•
Species adapted to a narrowly specialized resource or
way of life
Monteverde’s golden toad was apparently such
a specialist, and lived in small numbers in a
small area. It was endemic to the forest,
occurring nowhere else.
Extinction


Until 10,000 years ago, North America teemed with
camels, mammoths, giant sloths, lions, horses, sabertoothed cats, and other large mammals.
Many scientists think their extinction was brought on by
hunting after human arrival.
Mass extinctions
Earth has seen five mass extinction events: 50%+
of species were wiped out.
An asteroid
impact doomed
the dinosaurs
65 million
years ago.
Today we are
beginning a
sixth mass
extinction as
humans alter
the planet.
From The Science behind the Stories
Life’s hierarchy of levels
Ecology deals with these
levels of life:





Organismal
Population
Community
Ecosystem
Biosphere
Ecology





Communities are made up of multiple interacting
species that live in the same area.
Ecosystems encompass communities and the
nonliving material with which their members interact.
Population ecology investigates how individuals
within a species interact with one another.
Community ecology studies interactions among
species.
Ecosystem ecology reveals patterns by studying
living and nonliving components of systems in
conjunction.
Habitat and niche

Habitat = the specific environment where an organism
lives (including living and nonliving elements: rocks,
soil, plants, etc.)

Habitat selection = the process by which organisms
choose habitats among the options encountered

Niche = an organism’s functional role in a community
(feeding, flow of energy and matter, interactions with
other organisms, etc.)

Specialists = organisms with narrow breadth and thus
very specific requirements
Population ecology

Population = a group of individuals of a
species that live in a particular area

Several attributes help predict population
dynamics (changes in population):
•
•
•
•
•
•
Population size
Population density
Population distribution
Sex ratio
Age structure
Birth and death rates
Population size
Number of individuals present at a given time
The passenger pigeon was once North America’s most
numerous bird, but is now extinct.
Population density
Number of individuals per unit area
In the 19th century, the flocks of passenger
pigeons showed high population density.
Population distribution
Spatial arrangement of individuals
Age structure

Or age distribution =
relative numbers of
individuals of each age
or age class in a
population

Age structure
diagrams, or age
pyramids, show this
information.
Age structure
Pyramid weighted
toward young:
population growing
Pyramid weighted
toward old: population
declining
Sex ratio

Ratio of males to
females in a population

Even ratios (near 50/50)
are most common.
Fewer females causes
slower population
growth.

Note human sex ratio
biased toward females at
oldest ages.
Population growth
Populations grow, shrink, or remain stable,
depending on rates of birth, death,
immigration,
and emigration.
(crude birth rate + immigration rate) –
(crude death rate + emigration rate)
= growth rate
Survivorship curves



Type I: survival rates are high when organisms are
young and decrease sharply when organisms are old.
Type II: survival rates are equivalent regardless of an
organism’s age.
Type III: most mortality takes place at young ages, and
survival rates are greater at older ages.
Exponential growth

Unregulated populations increase by
exponential growth:

Growth by a fixed
percentage, rather
than a fixed amount.

Similar to growth
of money in a
savings account
Exponential growth in a
growth curve

Population
growth
curves show
change in
population
size over
time.

Scots pine
shows
exponential
growth
Limits on growth

Limiting factors restrain exponential population
growth, slowing the growth rate down.

Population growth levels off at a carrying capacity—
the maximum population size of a given species an
environment can sustain.

Initial exponential growth, slowing, and stabilizing at
carrying capacity is shown by a logistic growth
curve.
Logistic growth curve
Population growth: Logistic
growth
Logistic growth (shown here in yeast from the lab)
is only one type of growth curve, however.
Population growth:
Oscillations
Some populations fluctuate continually above and
below carrying capacity, as with this mite.
Population growth: Dampening
oscillations
In some populations, oscillations dampen, as
population size settles toward carrying capacity,
as with this beetle.
Population growth: Crashes
Some populations that rise too fast and deplete
resources may then crash, as with reindeer on St.
Paul Island.
Density dependence

Often, survival or reproduction lessens as
populations become more dense.

Density-dependent factors (disease, predation,
etc.) account for the logistic growth curve.

Other factors (e.g., catastrophic weather events)
occur regardless of density, and are densityindependent factors.
Biotic potential and
reproductive strategies
•
Species differ in strategies for producing young.
•
Species producing lots of young (insects, fish, frogs,
plants) have high biotic potential.
•
Others, such as mammals and birds, produce few
young.
•
However, those with few young give them more care,
resulting in better survival.
r and K-selected species
r-selected species
•
Many offspring
•
Fast growing
•
No parental care
K-selected species
•
Few offspring
•
Slow growing
•
Parental care
Terms come from:
r = intrinsic rate of
population increase.
(Populations can
potentially grow fast,
have high r.)
K = symbol for carrying
capacity. (Populations
tend to stabilize near K.)
Conservation of Biodiversity


Ecotourism = tourism focused on visiting natural
areas.
It provides economic incentive to local communities for
conservation of nature
Canopy walkway in Costa Rican rainforest
Conclusion

The golden toad and other Monteverde organisms have
helped illuminate the fundamentals of evolution and
population ecology.

Natural selection, speciation, and extinction help
determine Earth’s biodiversity.

Understanding ecological processes at the population
level is crucial to protecting biodiversity.