Transcript Ecology

Ecology
Introduction: A Tale of Two Fishes
• Population ecology is concerned with
– Changes in population size
– Factors that regulate populations over time
• It helps explain the biodiversity of an
environment
Copyright © 2009 Pearson Education, Inc.
Introduction: A Tale of Two Fishes
• Ecologists learn the structure and dynamics of
natural populations
• With this information they are better equipped to
– Develop sustainable food sources
– Assess the impact of human activities
– Balance human needs with the conservation of
biodiversity and resources
Copyright © 2009 Pearson Education, Inc.
36.4 Idealized models predict patterns of population
growth
• Exponential growth model
– The rate of population increases under ideal
conditions
– Calculated using the equation G = rN
– G is the growth rate of the population
– N is the population size
– r is the per capita rate of increase
Copyright © 2009 Pearson Education, Inc.
500
450
400
Population size (N)
350
300
250
200
150
100
50
0
0
1
2
3
4
5
6
7
Time (months)
8
9 10 11 12
36.4 Idealized models predict patterns of population
growth
• Logistic growth model
– This growth model takes into account limiting
factors
– Limiting factors are environmental factors that
restrict population growth
– Formula
(K  N)
G = rN
K
Copyright © 2009 Pearson Education, Inc.
Breeding male fur seals
(thousands)
10
8
6
4
2
0
1915
1925
1935
Year
1945
Number of individuals (N)
G = rN
K
G = rN
0
Time
(K – N)
K
10
Population increase
80
8
60
6
40
4
Total population size
20
2
0
1500
1550 1600
1650 1700
1750
1800
Year
1850
1900
1950
2000
2050
Total population (in billions)
Annual increase (in millions)
100
37.1 A community includes all the organisms inhabiting a
particular area
– Biological community
– An assemblage of populations living close enough together
for potential interaction
– Described by its species composition
– Boundaries of the community vary with research
questions
– Can be a pond
– Can be the intestinal microbes of a pond organism
Copyright © 2009 Pearson Education, Inc.
37.2 Interspecific interactions are fundamental to
community structure
– Interspecific interactions
– Relationships with other species in the community
– Interspecific competition
– Two different species compete for the same limited resource
–
–
Squirrels and black bears
Compete for acorns
Copyright © 2009 Pearson Education, Inc.
37.3 Competition may occur when a shared resource is
limited
– Ecological niche
– Sum of an organism’s use of biotic and abiotic resources
– Interspecific competition occurs when the niches of two
populations overlap
– Competition lowers the carrying capacity of competing
populations
Copyright © 2009 Pearson Education, Inc.
37.4 Mutualism benefits both partners
– Reef-building corals require mutualism
– Photosynthetic dinoflagellates
– Live in the cells of each coral polyp
– Produce sugars used by the polyps
– Provide at least half of the energy used by the coral animals
Video: Clownfish and Anemone
Copyright © 2009 Pearson Education, Inc.
37.7 Parasites and pathogens can affect community
composition
• A parasite lives on or in a host from which it
obtains nourishment
– Internal parasites include nematodes and
tapeworms
– External parasites include mosquitoes and ticks
• Pathogens are disease-causing parasites
– Pathogens can be bacteria, viruses, fungi, or protists
Copyright © 2009 Pearson Education, Inc.
37.11 Keystone species have a disproportionate impact
on diversity
• Keystone species
– A species whose impact on its community is larger
than its biomass or abundance indicates
– Occupies a niche that holds the rest of its
community in place
Copyright © 2009 Pearson Education, Inc.
Keystone
Keystone
absent
37.12 Disturbance is a prominent feature of most
communities
• Disturbances
– Events that damage biological communities
– Storms, fire, floods, droughts, overgrazing, or
human activity
– The types, frequency, and severity of disturbances
vary from community to community
Copyright © 2009 Pearson Education, Inc.
37.12 Disturbance is a prominent feature of most
communities
• Communities change drastically following a
severe disturbance
• Ecological succession
– Colonization by a variety of species
– A success of change gradually replaces other species
Copyright © 2009 Pearson Education, Inc.
37.12 Disturbance is a prominent feature of most
communities
• Primary succession
– Begins in a virtually lifeless area with no soil
• Secondary succession
– When a disturbance destroyed an existing
community but left the soil intact
Copyright © 2009 Pearson Education, Inc.
Annual
plants
Perennial
plants and
grasses
Shrubs
Softwood trees
such as pines
Time
Hardwood
trees