APES Notes Ch. 9

1
APES Notes Ch. 9

• Mrs. Sealy

2
Major Characteristics of populations

• size
• density
• Dispersion clumped, uniform and random
• age distribution
• Population dynamics changes in size, density,
  dispersion and age distribution of a population

3
Clumped (elephants)
Uniform (creosote bush)
Random (dandelions)
Fig. 9.2, p. 199
4
Limits on Population growth

• A. Population change (Births Immigration)
  (Deaths Emigration)
• B. Carrying capacity (k) biotic potential
  environmental resistance
• C. Biotic potential capacity for growth of a
  population. Example flies high biotic
  potential, pandas - low
• D. Environmental resistance all those things
  that limit the size of a population. Examples
  fire, predation, lack of resources, disease

5
Fig. 9.3, p. 200
6
Carrying capacity

• E. the maximum number of individuals of a given
  species that can be sustained in a given area
  indefinitely. When the carrying capacity of a
  population is exceeded, the population will have
  a dieback or crash to remove the excess animals.
  An example is
• The Reindeer of Angel Island

7
(No Transcript)
8
2,000
1,500
Number of reindeer
1,000
500
1910
1920
1930
1940
1950
Fig. 9.6, p. 201
Year
9
K
Population size (N)
Population size (N)
Time (t)
Time (t)
Exponential Growth
Logistic Growth
Fig. 9.4, p. 201
10
2.0
1.5
Number of sheep (millions)
1.0
.5
1800
1825
1850
1875
1900
1925
Fig. 9.5, p. 201
Year
11
minimum viable population

• F. minimum population that a species needs to
  have to be sustained. You need a minimum number
  of individuals to support a population because
• 1. Too few individuals causes interbreeding
• 2. They need to be able to find mates
• 3. Not enough genetic variability for the
  population to adapt

12
G. Density and population growth

• 1. Density independent population controls are
  things that affect the size of a population that
  have nothing to with the density of a population.
  For example weather, natural disasters, seasons
• 2. Density dependent population controls are
  things that affect the size of a population that
  occur only as the density of the population
  increases. For example competition, predation,
  parasitism, disease

13
H. Population fluctuation curvesGraph of
population curves stable, irruptive, cyclic,
irregular
Irregular
Stable
Number of individuals
Cyclic
Irruptive
Time
Fig. 9.7, p. 202
14
160
140
Hare
120
Lynx
100
Population size (thousands)
80
60
40
20
0
1845
1855
1865
1875
1885
1895
1905
1915
1925
1935
Year
Fig. 9.8, p. 203
15
Fig. 9.9, p. 204
16
Reproductive Patterns and Survival

• III Asexual Reproduction all offspring are exact
  genetic copies (clones) of a single parent.
  Example bacteria, fungi
• Sexual Reproduction all offspring are a result
  of combining the sperm and ovum from both
  parents. This produces offspring that have traits
  from both parents. 97 of all known organisms.

17
r-Selected Species
cockroach
dandelion
Many small offspring Little or no parental care
and protection of offspring Early reproductive
age Most offspring die before reaching
reproductive age Small adults Adapted to
unstable climate and environmental
conditions High population growth rate
(r) Population size fluctuates wildly above and
below carrying capacity (K) Generalist niche Low
ability to compete Early successional species
Fig. 9.10a, p. 205
18
K-Selected Species
elephant
saguaro
Fewer, larger offspring High parental care and
protection of offspring Later reproductive
age Most offspring survive to reproductive
age Larger adults Adapted to stable climate and
environmental conditions Lower population growth
rate (r) Population size fairly stable and
usually close to carrying capacity
(K) Specialist niche High ability to compete Late
successional species
Fig. 9.10b, p. 205
19

• survivorship curves life expectancy curve
  shows number of survivors of each age group for a
  particular species
• Graph Survivorship curve

20
Fig. 9.11, p. 206
21
(No Transcript)
22
Conservation Biology

• Multidisciplinary science of that uses the best
  information available to determine how to best
  protect species from extinction.
• Determine which species are in danger of
  extinction, what the status of ecosystems is,
  what measures can be taken to preserve species.

23
Human Impacts on Ecosystems

• fragmenting and degrading habitats
• simplifying ecosystems
• strengthening some populations of pest species
  and disease causing bacteria
• eliminating predators
• introducing alien species
• over harvesting resources
• interfering with normal chemical cycling

24
Environmental Stress
Organism Level
Population Level
Population Level
Disruption of energy flow through food chains
and webs Disruption of biogeochemical
cycles Lower species diversity Habitat loss or
degradation Less complex food webs Lower
stability Ecosystem collapse
Physiological changes Psychological
changes Behavior changes Fewer or no
offspring Genetic defects Birth
defects Cancers Death
Change in population size Change in age
structure (old, young, and weak may
die) Survival of strains genetically resistant
to stress Loss of genetic diversity and
adaptability Extinction
Fig. 9.12, p. 208