Unit6

1. Unit 6/7
Notes 2:
Population Dynamics,
Pollution, Renewable
Energy Sources

2. Terminology
• A population is a collection of individual organisms
of the same species that occupy some specific area.
• The term "population dynamics" refers to how the
number of individuals in a population changes over
time
– either going up or down, or
– changing regularly (for example with seasons,
plants or animals may die off in winter, or the dry
season, etc.

3. Unstructured Populations
• Scientists describe two types of populations
• Unstructured populations
– Rates of growth, reproduction, mortality, etc. roughly
the same for all members
– No fitness (survival) advantages for size, age, etc.
(i.e. bacterial colony)

4. Structured Populations
• Structured Populations
– Rates differ for members of the
population
– Mortality may be higher for young
and old, or smaller individuals
– Reproductive rates may be best for
certain ages
– Certain groups have a different
“fitness”
Vs.

5. “Internal” Population Dynamics
• Referred to intraspecific competition (competition
between members of the SAME species)
– Generally lowers the fitness of both (or all) individuals in
competition (i.e. competing for limited food impacts all)
– May compete for
• Food
• Water
• Light
• Mates

6. “External” Population Dynamics
• Interspecific competition
(competition between
different species)
– Food, water, space
– Light nutrients, etc.
• One group may
outcompete another
• “Survival of the Fittest”

7. Carrying Capacity
• Carrying capacity of a species is the maximum
number of individuals an environment can
support indefinitely (based on food, water, space,
etc.)
• Keep in mind, other
species may compete for
the same resources,
lowering carrying
capacity for all

8. Species Strategies for Growth
• R Selected species
– Focus is on rate of increase
– Reproduce at young age
– Lots of offspring, most die
– Usually little parental care
• K Selected species
– Focus is on survival rate
– Reproduce at later age
– Few babies, but most live
– May be large amount of parental care /
investment

9. J-shaped Curves (R Selected Species)
• Dangerous scenario,
proportional growth, even as
population size increases.
Means more people = faster
growth
• Population is growing
– No real limits
– No predators
– No resource constraints
• Rate of growth increases
with time until it is
exponential

10. S-Shaped Curves (K-
Selected Species)
• More stable scenario
• Phases
– Geometric growth
– Growth slows, but
– Overshoot & Crash
– Oscillates around K
• K = carrying capacity, how many
organisms can the environment
support long term i.e. sustainable

11. The Human Population
• Humans are a K Selected species, but acting like R
• Logistic population growth assumes resources are limiting
and environmental conditions may vary over time. Thus, the
abundance of individuals may also fluctuate over time.
Some populations
“cycle” in around
K in a predictable
manner.
Human K has
been estimated at
12 billion…

12. Population Interactions
• Populations are affected by a variety of
biological and physical factors.
• For example, the abundance of a snail might
be controlled by the abundance of organisms
that have a negative effect on them, such as
competitors, predators, and diseases.
• Similarly, the snail’s abundance could be
limited by the abundance of organisms that
benefit the species of interest (for example,
algae consumed by the snails = food).

13. Keystone Species or Predators
• A species whose presence and
role within an ecosystem has a
disproportionate effect on other
organisms within the system.
• A keystone predator is a
dominant predator whose
removal allows a prey
population to explode and often
decreases overall diversity.

14. Limiting Factors
• Anything that can limit
a population’s growth
(food, light, space,
mates, etc.)
• Can be variable or
seasonal, so often see
populations hover
around K, but go over
and under through time
No limits,
population
grows
quickly
See limits at
K, population
overshoots,
too many
organisms
As a result of
overshoot,
population then
crashes.
Then cycles
above/below K
due to limiting
factors

15. Complex interactions
• The species that inhabit a
specific habitat, along with the
abiotic factors lead to extremely
complex interactions
– Trees compete for water and
light so precipitation, cloud
cover, season, humidity, wind,
temperature and more all
impact those two variables

16. Childhood Survival Rates
One answer to reducing the rate of population
growth starts with increasing childhood survival
rates and limiting family size
Big problems in Africa and India, etc.

17. Human Life Expectancy
Many people globally are living longer, leading to
population growth and major AGE issues
Big problems in Africa and India, etc.

18. Population Growth Rates
Many countries are growing at an alarming rate,
others are growing at a lower rate but still growing.
Still other countries have a 0 or even negative rate.
Big problems in Africa

19. Population Age Distribution
● An aging
population can
cause problems
● A very young
population
WILL HAVE
problems with
growth, jobs,
etc.

20. Population by Region
Regions that can’t sustain it, have the highest growth

21. Population Growth and Economics
Similarly, places
that cannot
afford it, have
growth problems

22. HSHS Example
• School opens
• Small number of students
at first
• More added and more,
and more
• School’s max capacity is
2,100
• Hits 2,500…too many
• Some reassigned, some
move, some
graduate…numbers
fluctuate 5 10 15 20 25
(Thousands)
https://www.youtube.com/watch?v=E8dkWQVFAoA

23. Human Population
• Dangerous
– 1 billion in 1800 years
– 2 billion in 130 years
– 3 billion in 30 years
– 4 billion in 15 years
– 5 billion in 12 years
– 6 billion in 12 years
– Over 7 billion now

24. Population Dynamics
• Monocultures – humans must grow crops, and like to grow others
(like grass) for food, resources, business, etc. If only one things is
growing in an area it is called a monoculture. They tend to be bad
• Biodiversity - also called biological diversity, the variety of life found
in a place on Earth or, often, the total variety of life on Earth. Can be
for a specific habitat or biome. Greater biodiversity gives and area
more resistance to challenges and provides greater flexibility

25. Human Impacted Populations
• Invasive species – species we bring to an area (on
purpose or by accident) or release into an area
where they are not native. Often no natural limiting
factors so the population explodes at the expense of
native species
• Loss of biodiversity – due to all manner of human
activity and action (on purpose and by accident) we
are losing biodiversity in most biomes and globally
http://wn.com/the_sixth_extinction_%28book%29

26. Human Impacted Populations
• Extinctions – we are in the process of another
MAJOR extinction event. However, unlike the
previous events, this one is being caused by humans.
• Overharvesting is one major reason, taking too
much too fast
– Not allowing recovery – for example fisheries
– No recovery at all – for example urbanization and
large scale habitat destruction or replacement

27. Human Population
• National Geographic – 7 Billion People (2:58)
http://www.youtube.com/watch?v=sc4HxPxNrZ
0&feature=player_embedded

28. Pollution and
Human Impact

29. The Ocean as a Dump
• Just as humans have
always taken things
out of the ocean, we
have probably always
thrown trash into it
• Problem is the same as
over harvesting
resources, we put too
much trash in the
ocean

30. The Global Ocean
•With all the ocean water on Earth interconnected,
pollution in one area can affect the ocean in other
very distant parts of the globe.

31. Non-point Source Ocean Pollution
• Most ocean pollution is non-
point source
• Hard to identify, therefore
nearly impossible to regulate
• May come from too many
sources
• Car owners
• Boat owners
• Lawn care

32. Point Source Ocean Pollution
• Point source pollution
comes from a single
identifiable source but it
is still very hard to
regulate or clean up,
especially once diluted in
the ocean

33. • People have dumped trash in
the ocean for ages legally or
illegally
• To this day some people,
businesses and countries still
take trash out into the deep
ocean and dump it, other
regions have no real trash
pickup, so it just ends up
there
The Ocean and Trash Dumping

34. Where does this pollution originate?

35. Effects of Trash Dumping
• Trash in the ocean can get caught up in animals, or be mistaken
for food and hurt or kill the animal that accidentally eats it
• Plastic is especially bad since it does not break down

36. Sludge Dumping
• When water treatment plants remove the solid material from the
waste water it is called sludge. Through the years the U.S. alone
had dumped about 38 trillion liters into the sea

37. Oil Spills
• As long as we drill for and ship oil, there will be oil spills
• Just remember, there
is a natural seepage of oil
out of the ground into the
ocean, we will never stop
it and we must be realistic

38. Effects of Oil Spills
• Actual oil spills account for very little ocean pollution and even
very little of the oil in the ocean, most comes from land sources,
but they can be devastating for the local area

39. Secondary Pollutants
• Pollutants that form when primary pollutants react
with other primary pollutants or with naturally
occurring substances, such as water vapor, are
secondary pollutants.

40. • Pollutants that are put directly into the air by human or natural
activity are primary pollutants.
• Primary pollutants from human sources include carbon monoxide,
dust, smoke, and chemicals from paint and other substances.
Industrial emissions Volcanic Ash
Vehicle
Exhaust
# 1 air pollutant
Air Pollution - Primary Pollutants

41. • Smog is a secondary
pollutant
that forms when ozone
and vehicle exhaust react with
sunlight, as shown.
• Many acids in acid rain are
secondary pollutants as well

42. Chapter 15
Indoor Air Pollution
Sometimes, the air inside a building can be more polluted than the
air outside. Above are some sources of indoor air pollution.

43. Acid
Precipitation
• Rain, sleet or snow or hail that contains a high
concentration of acids is called acid precipitation or
acid rain.

44. • Acid precipitation
can cause
the acidity of soil to
increase.
This process, called
acidification,
changes the balance
of a soil’s
chemistry and
negatively affects
plants.
Acid Precipitation and Plants

45. • If acid precipitation increases the acidity of a lake or stream,
aquatic plants, fish, and other aquatic organisms may die.
Acid Precipitation in Aquatic Systems

46. The Ozone Hole
• The Earth’s
protective ozone layer is
thinning over the Arctic
and Antarctic regions.
These ozone holes allow
more UV radiation, which
damages genes and can
cause skin cancer, to
reach the earth’s surface.

47. In 1987, many nations agreed to
reduce the use of CFCs, the
chemicals that cause ozone
depletion. Because CFCs remain
active for 60 to 120 years,
however, it will take many years
for the ozone layer to recover.
Cooperation to Reduce the
Ozone Hole

48. Reducing Pollution
• Community groups are
adopting roads cleaning up
beaches and parks, etc.
• Even simple labels can
help – paper towels come
from trees, drains lead to
rivers, etc.

49. Renewable Energy
Sources

50. Nuclear Power
• Nuclear fission
Energy comes from
breaking bonds between
subatomic particles
• Nuclear fusion
Energy is released as two
or more small atoms fuse
to form a heavier one

51. Pros and Cons of Nuclear Power
• Nuclear fission
– Pro – splitting one U-236 releases 50 million times more energy
than breaking a C bond in coal, chain reaction, very efficient,
relatively clean
– Cons – radioactive waste, accidents, U is non-renewable
resource
• Nuclear fusion
– Pro – materials for fuel are cheap and readily available, waste
is not radioactive
– Cons – we cannot do it yet…

52. Chemical Energy
• In chemical power generation you use the formation of a new
chemical to produce power
– Been around since 1830’s, many different types
– Car fuel cells combine H and O to release energy and form water
• Pros – very efficient, quiet, and clean, only waste product in this
case is water, no recharging time, can be very small
• Cons – very expensive, sensitive to temperature, hydrogen
production and storage

53. Solar Energy
• In solar energy generation light and/or
heat from the sun are harnessed for use
• Pros – inexhaustible resource,
technology is getting better and
cheaper, can be passive
• Cons – technology is still not sufficient
to provide for all needs, unpredictable,
space for solar farms

54. Wind Energy
• Wind is powered by the sun, we
use wind to turn turbines and
generate a little energy
• Pros – inexhaustible, simple, no
pollution
• Cons – space for wind farms,
unpredictable , directionality ,
limited use

55. Hydroelectric Energy
• In hydroelectric power
generation moving water drives
turbines
• Pros – clean, almost
inexhaustible, efficient
• Cons – large expensive plants,
large dams needed – land and
water issues

56. Biomass Energy
• Burning bio matter,
including wood and
charcoal, or gasohol
• Pros – can be renewable
• Cons – land lost to grow
biomass, burning, not very
efficient

57. Geothermal Energy
• Generate power or heat living
space and water with the Earth’s
heat
• Pros – inexhaustible , can be
simple, clean
• Cons – limited areas can use it,
still needs development, can
shift

58. Wave Energy
• Waves in the ocean, possibly
even large lakes move booms
which drive pistons
• Pros – inexhaustible, clean,
efficient , lots of coastline
• Cons – block ocean front, not a
lot of power, vulnerable

59. Other Alternatives
• South Carolina methane fuel