Chapter 1 Environmental Problems_ Their Causes_ and Sustainability

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Chapter 1 Environmental Problems_ Their Causes_ and Sustainability Powered By Docstoc
					Chapter 5 Biodiversity, species interactions, and population control

Core case study: Southern sea otters: Are they back from the brink of extinction?
Core case study: Southern sea otters
1. Background:
     (1) 1 million otters before European settlers arrived in Pacific coast, North
     (2) 1900s, over hunting
     (3) 1938-2007, population increased from 50 to 3,026
2. Keystone species: sea otter help control the population of sea urchins and other
kelp-eating species.

5-1 How do species interact?
5-2 How can natural selection reduce competition between species?
5-3 What limits the growth of population?
5-4 How do communities and ecosystems respond to changing environmental

5-1 How do species interact?
1. Species interact in five major ways:
     (1) interspecific competition:
     (2) predation:
     (3) parasitism:
     (4) mutualism: benefits both species (互利共生)
     (5) commensalism: benefits one species but has little effect on the other. (片利共
2. Competition: for limited resources
     competitive exclusion principle
3. Predation: predation-prey relationship
     (1) camouflage: (偽裝)(fig. 5-2)
     (2) chemical warfare: (生化戰劑)
     (3) waning coloration: (示警)
     (4) mimics: (擬態)
     (5) deceptive looks: (虛偽的外表)
     (6) deceptive behavior: (虛偽的行為)
4. Coevolution: predator and prey species can drive each other’s evolution. (fig. 5-3)
5. Parasitism: parasite vs. host, killing host.
     (1) inside: (pathogens)
     (2) outsides: (fig. 5-4)
6. Mutualism: two species behave in ways that benefit both, including nutrition and
protection. (fig. 5-5)
7. Commensalism: one species benefits and the other is not harmed. Ex: air plants (fig.

5-2 How can natural selection reduce competition between species?
1. Resource partitioning: some species evolve ways to share resources (fig. 5-7, 8)
2. Specialization: specialist species (fig. 5-9)

5-3 What limits the growth of population?
1. Population dynamics: distribution, numbers, age structure, and density.
2. Populations distribution: (fig. 5-10)
     (1) clumping: most populations
     (2) uniform:
     (3) random
3. Reasons for clump:
     (1) resources for population vary greatly from place to place
     (2) better protection from predators. Ex. deer
     (3) better chance of getting a meal
     (4) temporary groups for mating and caring for their young
4. Changes in population size: entrances and exits
     (1) four variables: births, deaths, immigration, and emigration
     (2) population = births + immigration – deaths – emigration
5. Age structure: young populations can grow fast
     (1) age structure: proportions of individuals at various ages
      (2) three age groups
            a. prereproductive ages
            b. reproductive ages
            c. postreproductive ages
      (3) stable: fairly even distribution of three age groups
6. Intrinsic rate of increase (r): population would grow if it had unlimited resources
      (1) reproduce early in life
      (2) have short generation times
      (3) can reproduce many times
     (4) have many offspring each time
      no population can grow indefinitely
7. Limiting factors: light, water, living space, nutrients, many competitors, predators,
infectious diseases, …
8. Environmental resistance: consists of all factors that act to limit the growth of a
     Carrying capacity (K): a species can be sustained in a given space.
     Intrinsic rate of increase (r) or biotic potential vs. Carrying capacity (K) or
environmental resistance
9. Exponential growth or geometric growth: starts slowly but then accelerates.
J-shaped (fig. 5-11)
     Logistic growth: rapid exponential population growth followed by a steady
decrease in population growth with time until the population size levels off. S-shaped
(fig. 5-12)
10. Exceeding carrying capacity: move, change habits, or decline in size
      (1) overshooting and population dieback or crash: to maintain carrying capacity
(fig. 5-13)
     (2) human population crash: Ireland in 1845, Polynesians on Easter Island, …
11. Types of reproductive patterns: (fig. 5-14)
     (1) r-selected species: opportunist
     (2) K-selected species: competitor
12. Loss of genetic diversity:
     (1) founder effect:(奠基者效應)colonize a new habitat
     (2) bottleneck effect:(瓶頸效應)survive under a catastrophe
     (3) genetic drift: unequal reproductive success
     (4) inbreeding: in a small population mate with one another
13. Minimum vialbe population size: founder effect, bottleneck effect, genetic drift,
inbreeding, island biogeography
14. Population density: number of individuals in a population found in a particular
      (1) density-dependent population controls:
      (2) density-independent population controls: affect a population’s size regardless
of its density.
15. Density-dependent population controls
      (1) competition for resources
      (2) predation
      (3) parasitism
      (4) infectious disease
16. Density-independent population controls: (1) floods
     (2) fires
     (3) hurricanes
     (4) unseasonable weather
     (5) habitat destruction
     (6) pesticide spraying
     (7) pollution
17. Populations change:
     (1) stable: stable temperature and rainfall
     (2) irruptive: high peak and crash
     (3) irregular: chaotic behavior
     (4) cyclic: boom-and-bust cycle
18. Do predators control population size?
     Lynx-Hare cycle (fig. 5-15)
     (1) Top-down control hypothesis: based on predators
     (2) 10-year boom-and-bust for Hare
     (3) Bottom-up control hypothesis: based on food supplement
19. Case study: white-tailed deer
     (1) 500,000 deer population in 1900
     (2) 1920-30s, laws were passed to protect deer
     (3) 25-30 million now
     (4) disadvantages:
          a. over-consuming native plants
          b. spread disease to human
          c. 1.5 million/ y traffic accidents (14,000 people injured, 200 people
          d. cause more than $1.1 billion in damages

5-4 How do communities and ecosystems respond to changing environmental
1. Ecological succession: gradual change in species composition in a given area
     (1) primary succession
     (2) secondary succession: disturb or destroy
2. Primary succession: (fig. 5-16)
     (1) weather
     (2) pioneer or early successional species
     (3) midsuccessional species
     (4) late successional species
3. Secondary succession: (fig. 5-17)
     (1) abandoned farmland
     (2) burned or cut forest
     (3) heavily polluted stream
     (4) land that has been flooded
4. Climax community: stable type, balance of nature
5. Succession doesn’t follow a predictable path
6. Living systems are sustained through constant change: resilience