Chapter 5: Populations

1
Chapter 5 Populations
2
Characteristics of Populations

• Geographic distribution
• Density
• Growth Rate
• Age Structure

3
Geographic Distribution

• Describes the area inhabited by a population
• Can range from a few cubic centimeters occupied
  by bacteria in a rotting apple to millions of
  square kilometers occupied by migrating whales in
  the Pacific Ocean.

4
Population Density

• The number of individuals per unit area
• Varies based on species and its ecosystem.
• Ex 150 bullfrogs
• living in a pond that
• covers an area of
• 3 square kilometers.
• What is the density?

5
Population Growth

• Factors that affect population size
• Number of births
• Number of deaths
• Number of individuals that move into or leave the
  population

6

• Immigration
• Movement into an area
• Emigration
• Movement out of an area

• Occurs when individuals move into or out of areas
  in search of food, shelter, or mates.

7
Limits to Growth

• Competition
• Predation
• Parasitism and disease
• Climate extremes
• Human disturbances

8

• Density Dependent Factors
• Affects populations that are large and dense
• Competition, predation, parasitism/disease

• Density-Independent Factors
• Affects all population sizes
• Unusual weather, natural disasters, seasonal
  cycles, and human activities

9
Chapter 6

• Humans in the Biosphere

10
Tragedy of the Commons

• A few hundred years ago, inhabitants of English
  villages
• could graze their cattle on shared pasture land
  called
• commons. Since grazing was free of charge,
  villagers often
• put as many cattle as possible on those commons.
  
• Occasionally there were more cattle on the
  commons than
• the land could support. Even as the land became
  overused,
• people kept putting more animals on it. After
  all, those who
• didnt use that free land would sacrifice their
  own profit while
• others would continue to benefit.
• Overgrazing on village commons
• sometimes caused the pastures to
• deteriorate so badly that they could
• no longer support cattle.

11
Classifying Resources

• Renewable can regenerate or be replenished.
• Does not mean that it is unlimited
• Nonrenewable cannot be replenished by natural
  processes.
• Coal, oil, and natural gas
• Classification depends on situation.A single
  tree is renewable, but a population of trees in
  an ecosystem may not be, because the entire
  ecosystem may never be the same once those trees
  are gone.

12
Sustainable Development

• Way of using natural resources without depleting
  them, and of providing for human needs without
  causing long-term environmental harm.
• Human activities can affect the quality and
  supply of renewable resources such as land,
  forests, fisheries, air, and freshwater.

13
Biodiversity

• Sum total of the genetically based variety of all
  organisms in the biosphere.
• Earths greatest natural resource
• Studied at three different levels
• Species
• Ecosystem
• Genetic

14
Species Diversity

• Refers to all the differences between populations
  of species, as well as between different species.
• Receives the most attention

15
Ecosystem Diversity

• Refers to the variety of habitats, communities,
  and ecological processes within and between
  ecosystems.

16
Genetic Diversity

• Refers to all the different genes contained
  within all members of a population.
• A gene is a piece of DNA that codes for a
  specific trait that can be inherited by an
  organisms offspring.
• The level of genetic diversity within populations
  is a critical factor in species survival.
• Genetic variation increases the chance that some
  members of a population will survive
  environmental pressures.

• Refers to all the different genes contained
  within all members of a population.
• A gene is a piece of DNA that codes for a
  specific trait that can be inherited by an
  organisms offspring.

17
Benefits of Biodiversity
ecosystems

• Species are connected to
• Every species is either depended upon by or
  depends on at least one other species.
• When one species disappears, a strand in a food
  web is removed. Could this cause a problem?

18
Keystone Species

• Species that are critical to the functioning of
  an ecosystem
• Sea otter/kelp population

19
Benefits of Biodiversity

• Foods
• Industrial Products
• Medicines
• Painkillers
• Antibiotics
• Heart drugs
• Anticancer drugs
• Recreation/Aesthetics

20
Extinction

• Species with small populations in limited areas
  can easily become extinct
• Species at a high risk of extinction
• Those that migrate
• Those that need large or special habitats
• Those that are exploited by humans.

21
Endangered

• Endangered Species- A species that is likely to
  become extinct if protective measures are not
  taken immediately

22
Magellanic Penguin
Javan Rhinoceros
Giant Panda
Tiger
23
Leatherback Turtle
Monarch butterfly
Mountain Gorilla
Blue-fin Tuna
24
Pacific Walrus
Polar Bear
25
How do humans cause extinctions?

• Habitat destruction and fragmentation
• Invasive Exotic Species
• Harvesting, Hunting, and Poaching
• Pollution

26
Habitat Destruction and Fragmentation

• As the human population grows, we use more land
  to build homes and harvest resources.
• Habitat loss causes more than 75
• of the extinctions now occurring.
• Ex Florida panther,
• lt80 remain

27
Invasive Exotic Species

• An exotic species is a species that is not native
  to a particular region.
• Exotic species can threaten native species that
  have no natural defenses against them.

28
Harvesting, Hunting, and Poaching

• Excessive harvesting and hunting can lead to
  extinction. (pets, houseplants, wood, food, or
  medicine)
• Laws are put into place to regulate hunting,
  fishing, harvesting, and trade of wildlife.
• If these laws are broken, then it is
• considered poaching.

29
Pollution

• Pesticides, cleaning agents, drugs, and other
  chemicals are making their way into food webs
  around the globe.
• Ex. DDT/bald eagle

30
The Future of Biodiversity
31
Saving Species One at a Time

• Captive Breeding Programs
• Preserving Genetic Material
• Zoos, Aquariums, Parks, and Gardens
• More Study

32
Captive Breeding

• Involves breeding species in captivity, with the
  hopes of reintroducing populations to their
  natural habitats
• Example California condors (habitat loss,
  poaching, lead poisoning)

33
Preserving Genetic Material

• Germ plasm banks-store genetic material for
  research or species-recovery efforts
• Material is stored as seeds, sperm, eggs, or pure
  DNA

34

• The most effective way to save species is to
  protect their
• Conservation Strategies- conserve entire
  ECOSYSTEMS instead of a single species.WHY?

habitats!
35
Impact on the Future

• Ozone Depletion
• Ozone (O3) found in layer of atmosphere and
  absorbs harmful UV radiation. (GLOBAL SUNSCREEN)
• UV radiation can cause cancer, sunburn, damage to
  the eyes, and decrease resistance to disease.
• Ozone depletion is caused by CFCs
  (chlorofluorocarbons) released into the
  atmosphere.
• CFCs were used as propellants in aerosol cans
  as coolant in refrigerators, freezers, and air
  conditioners.
• Reduced in 1987, but can linger for many years.

36
Impact on the Future

• Global Climate Change
• An increase in Earths average temperature.
• Human activities are adding carbon dioxide to the
  atmosphere at a rate faster than producers can
  remove it.
• Burning fossil fuels
• Cutting down forests
• May increase the sea level enough to flood
  coastal cities
• Parts of the world may experience more droughts
  during the summer growing season.
• Changes the balance of the ecosystems.