Exam 2 Study guide Part 2
Putting it all together: Ecology and ecosystems
Overview: The Scope of Ecology
Ecology is the scientific study of the interactions between organisms and the
environment
These interactions determine distribution of organisms and their abundance
Ecology reveals the richness of the biosphere
The Scope of Ecological Research
Ecologists work at levels ranging from individual organisms to the planet
Organismal ecology studies how an organism’s structure, physiology, and (for
animals) behavior meet environmental challenges
Population ecology focuses on factors affecting how many individuals of a
species live in an area
Community ecology deals with the whole array of interacting species in a
community
An ecosystem is the community of organisms in an area and the physical factors
with which they interact
Landscape ecology deals with arrays of ecosystems and how they are arranged in
a geographic region
Global ecology examines the influence of energy and materials on organisms
across the biosphere
Example of an ecosystem: Puget Sound
A glacial fjord
Examples of animals living in Puget sound
Porifera
Cnidaria
Ctenophora
Molluska
Example of an ecosystem: Deep sea vent
Alvin submarine
Animals live on chemicals from the vent, not sunlight
Temperature may explain zonation at deep sea vents
Chapter 53
Population Ecology
Population ecology is the study of populations in relation to environment, including
environmental influences on density and distribution, age structure, and population size
In most cases, it is impractical or impossible to count all individuals in a population
Sampling techniques can be used to estimate densities and total population sizes
Population size can be estimated by extrapolation from the mark-recapture
method
Survivorship curves can be classified into three general types:
Type I: low death rates during early and middle life, then an increase among older
age groups
Type II: the death rate is constant over the organism’s life span
Type III: high death rates for the young, then a slower death rate for survivors
Zero population growth occurs when the birth rate equals the death rate
Exponential Growth
Exponential population growth is population increase under idealized conditions
Under these conditions, the rate of reproduction is at its maximum
Exponential growth cannot be sustained for long in any population
A more realistic population model limits growth by incorporating carrying
capacity
Carrying capacity (K) is the maximum population size the environment can
support
The Global Human Population
The human population increased relatively slowly until about 1650 and then began to
grow exponentially
Food From the Sea
Worldwide Marine Catch and Mariculture
Atlantic bluefin tuna Thunnus thynnus
Optimal Yield and Overfishing
Ecology and the Biosphere
Chapter 50
What factors govern the distribution of organisms?
The interactions between organisms and their environments determine their distributions
and abundances
environmental factors
abiotic - non-living chemical and physical factors
biotic - living factors like other organisms
Factors affecting the distribution of organisms
dispersal
behavior and habitat selection
biotic factors
abiotic factors
Dispersal
Example: Kangaroos may not be in North America because they historically had
no way of getting there.
To test this: species transplant experiments
Figure 50.6 Set of transplant experiments for a hypothetical species
Transplant successful - distribution limited because of dispersal problems
inaccessible, not enough time to reach area, not recognized as suitable living
space
transplant unsuccessful - distribution limited by biotic or abiotic factors, I.e., for
some reason cannot survive there.
Invasive species
In modern times, normal restrictions on dispersal are lifted and invasive species
can proliferate
Biotic factors affect the distribution of organisms
Competition
interspecific
intraspecific
Predation
Mutualism - species helping each other
Figure 50.9 Predator-removal experiments
Limpet and urchin removal experiments
Results show that the herbivores limit the distribution and abundance of seaweed
limpets appear to be the main herbivores
but why is there more seaweed when both limpets and urchins are removed?
Extra credit: question on the movie Blade Runner