2. Human Ecology
• The relationship between humans and their
environment

3. Characteristics of Populations

4. • Location
• Density
• Growth Rate
• What causes a population’s size to change?
– Number of births
– Number of deaths
– Number of individuals that move in or out of population

5. Population Growth
• Under ideal conditions
populations grow
exponentially
– As population grows larger,
it grows faster

6. Population Growth
• In the natural world,
populations show “logistic
growth”
– Population's growth slows
or stops after a period of
exponential growth
– Population reaches a
carrying capacity

7. Limiting Factors!!!
• Density Independent • Density Dependent
Limits limits
– Limits that affect a – Limits that increase as
population regardless of population size
population size increases
– temperature, storms, – disease, parasites,
flood competition, predators

8. What about human populations?
• World wide human
population growth =
exponential!
• Why?
– Humans can eliminate
competition, increase food
production, control disease,
etc.

9. Biodiversity

10. Biodiversity
• The variety of
species in an area

11. high biodiversity
Marine
coral reef= lots of light
benthos= deep ocean
intertidal= lots of nutrients

12. high biodiversity
Tropical rainforest
lots of rain, lots of sunlight, always warm
many plants & animals

13. mid biodiversity
Grasslands dry season/wet season, always warm
frequent fires in dry season
many herbivores

14. low biodiversity
Desert
very dry, hot in day & cold at night
very few plants & only small animals:
reptiles, insects, rodents, birds

15. low biodiversity
Tundra
cold year round, dry, permafrost
only lichens & mosses & mostly migrating animals

16. Why is Biodiversity Important?
• Stability
• Food source - removing organisms from the food
chain will cause problems for its predator
• Pharmaceutical drug development
– Taxol – from Pacific Yew tree, breast cancer treatment
– Periwinkle – flower used to treat leukemia
– Willow bark – natural source for aspirin
– Penicillium – mold that makes the antibiotic penicillin
• Provides the world with beauty

17. What happens when biodiversity is threatened?
• Threatened species
– Population whose #’s are declining rapidly
– sea otter, sea turtles
• Endangered species
– Population with very low numbers
– ~ 1214 animals & ~750 plants
– manatees, elephants
• Extinction
– ~ 905 species are extinct

18. Humans and the Ecosystem

19. • Disrupting ecosystems can threaten
biodiversity.
• Hunting & gathering
• Agriculture
• Animal domestication
• Urbanization

20. What happens?
1. Urbanization – movement to cities
– Outcome
• Increased runoff causing flooding & erosion
• Use of nonrenewable natural resources

21. What happens?
2. Deforestation
– Human destruction of
forests
– building of malls,
homes, farming
– Outcome
• Loss of biodiversity
• Soil erosion – loss of
topsoil

22. 3. Overfarming
– When plants are harvested soil
becomes less fertile
– Outcome
• Abandoned fields
• Erosion of topsoil

23. 4. Overgrazing
– Herds of cattle &
sheep overgraze
grasslands
– Outcome
• Land has no cover &
topsoil is eroded

24. 5. Misuse of Pesticides
– Contaminate air, water
& soil
– Kill many organisms
that aren’t pests
– “Safe” pesticides have
been found to be
dangerous
• DDT

25. 6. Biomagnification
– Process where chemical becomes highly concentrated in
the bodies of upper level consumers
– How does this happen?
– E.g. DDT became concentrated
in bald eagles causing
thin-shelled eggs that did
not survive

26. 7. Invasive species
– Introduction of organisms that
are not native (natural) to an
area
• E.g. Purple loosestrife
• E.g. Zebra mussels
• E.g. Japanese beetles
– Outcompete native species &
take over
• No predators
• Able to use available resources
better

27. Pollution
You Stink

28. • Adding anything to the
environment or affecting the
environment in a way that makes it
less fit for living

29. 1. Land Pollution
• Tons of solid waste (refuse) are
produced everyday
• Sanitary Landfill
• Incineration

30. 2. Water Pollution
• Organic wastes
– fertilizer runoff, sewage, waste from factories
– Waste acts as food for algae, algae become
overpopulated and lead to death of other
organisms
– Causes “eutrophication”
• accelerated aging process/ succession

31. Water Pollution
• Inorganic chemicals
– Poisonous wastes dumped into waterways
from cities, farms & industry
– Biological Magnification
• Mercury poisoning in Japan

32. Water Pollution
• Thermal Pollution.
– Warm water can’t hold as
much oxygen as cool
water. Organisms will
suffocate & die

33. 3. Air Pollution
• Burning Fossil Fuels
– Burning of coal & gas
– Cars, factories, electrical plants
– Release CO2, sulfur, & nitrogen into the atmosphere
– Cause health problems, acid rain, etc.

34. Air Pollution
• Acid Rain
– Occurs when sulfur &
nitrogen combine with water
– Forms in the rain, snow, & sleet
– Lowers the pH of the water
– Kills many producers
Did you know that non-
polluted rain is slightly
acidic? The CO2 in the air
forms carbonic acid when
it rains…

35. Air Pollution
• Smog
– Produced from auto exhaust & industrial processes
– Results in toxins that can be inhaled
– Occurs when pollutants combine with sunlight

36. Air Pollution
• Climate Change
– Change in the climate
(temp, precipitation,
wind) last for an
extended period of
time.
– Can occur naturally
– Human activity &
pollution can add to the
effect

37. Air Pollution
• Greenhouse effect
Greenhouse effect
– Occurs when sunlight passes
through atmosphere gases
• CO 2 , methane, H 2 O
vapor
– Gases trap & absorbs the
sunlight resulting in an overall
warming effect
– Pollution can increase this
effect
The greenhouse
effect is a natural
and good process.
Without it, the
earth would be
30ºC cooler…

38. Air Pollution
• Ozone Depletion (not global warming)
– The ozone layer is made of ozone gas (O3) and is found
between 20-50km above the Earth’s surface.
– Absorbs harmful ultraviolet (UV) radiation from sunlight

39. • Ozone Depletion
– CFCs (chlorofluorocarbons) cause ozone to break down
• Found in aerosols, refrigerators, & air conditioners
– Ozone holes form
• UV light can enter atmosphere
• Kills producers
• Cause cancer
Remember, ozone
depletion does not
cause the Earth’s
temperature to
increase!!!!

40. Natural Resources

41. Restoring the Environment – What can we do?
• Nonrenewable natural • Renewable natural
resource resources
– coal, oil, natural gas, – air, water, soil, sunlight,
metals, minerals
living things
– Can be taken from earth
– Resources that are
only once
naturally replaced
– Human activity can disrupt
the natural events that
replace the resources

42. Natural Resources
• Conserving both renewable & nonrenewable natural
resources is important
– Sustainable use – use natural resources at a rate that
does not deplete them.
1. Recycling
– Newspaper, glass, metal, plastic

43. 2. Conserving Soil
• Soil is renewable, but the process is very slow,
therefore it is important to conserve
• Cover crops
– Crops planted to cover a field to prevents erosion
• Can also plant in between rows

44. Conserving Soil - HOW???
• Crop rotation
• Fertilizer
• Strip cropping
• Terracing
• Contour Farming
• Windbreaks

45. 3. Conserving Forests - WHY and HOW???
• Sustained-yield tree farming
– Cutting down trees only in certain
areas so surrounding areas are
untouched.
• Reforestation
– Replace lost trees by planting
new ones
WHY????
• Forests provide wood, paper.
• Soil holds large amts of water,
prevent erosion.
• Destruction takes a long time to
replace

46. 4. Restoring the Environment - Conserving Wildlife
• Cities & suburbs destroy natural habitats
• Protection
– Hunting/fishing laws
– Game & bird preserves
– Fish hatcheries breed fish & are restocked in heavily fished lakes
– Pesticide & herbicide restrictions

47. Controlling Pests Biologically
• More specific than chemical pesticides
• Fewer adverse environmental effects
• How ?
– Import natural enemies
• E.g. Ladybugs control aphids
– Bacteria or virus that infect insect larvae
• Gypsy moth caterpillars, mosquito larvae

48. Controlling Pests Biologically
• Crop rotation
– Remove favored food source…
• Pheromones
– Lure insect to trap & kill
• Sterilization & release of male insects
– Males become sterile by exposure to radiation
– E.g. the screwworm fly only gets to mate once, so she is
out of luck if she mates with a sterile males

49. 5. Controlling Pollution
• Emission Controls for cars
• Ban aerosol sprays
• Control Industrial waste
– Gas treated before
released
– Ban on dumping waste in
water & land
• Sewage treatment plants
– Use bacteria to treat water
before released
• Reclaim strip mined land
• Special sites for toxic
waste

50. Restoring the Environment
• Individual Actions
– People can choose:
• Not to pollute
• Not to burn garbage
• Change products that they
use
• Drive energy efficient cars
– Car pool, use public
transportation
• Reduce, Reuse, Recycle

51. Restoring the Environment
• Societal Actions
– Cities, States, &
governments can:
• Pass laws against
pollution
• Fine or jail polluters
• Hold public meetings &
hearings about pollution
• Give incentives - $$