Download Lecture 1-Order in Nature

Food web shifts along
the Oldman River continuum
Particulate organic matter (POM)
And benthic algae
Epiphytic invertebrates
Epiphytic algae & POM
Particulate organic matter (POM)
And benthic algae
Mountain headwaters
Coldwater community
Epiphytic invertebrates
Epiphytic algae & POM
Particulate organic
Benthicmatter (POM)
And benthic algae
Invertebrates
Prairie River
Coolwater community
Particulate organic matter (POM)
And benthic algae
Daily fluctuations in O2 provides and integrated measure of
community metabolism over a reach.
Community Metabolism along the Oldman River
15
Below the Oldman Dam
gO2/m2/d
10
5
GPP
Resp
0
-5
-10
850
1050
1250
Elevation (m)
1450
1650
What is a system?
What do we mean by connectedness?
The biosphere is composed of a
hierarchy of complex systems:
•subsystems embedded within
systems—levels of organization
•ecological systems can be as small
as individual organisms and as large
and inclusive as the whole biosphere
What is ecology about?
•from the Greek “Oikos” which
means household
What is Ecology?
•
By ecology, we mean the body of knowledge concerning the
economy of nature -- the investigation of the total relations of the
animal both to its organic and to its inorganic environment; including
above all, its friendly and inimical relation with those animals and
plants with which it comes directly or indirectly into contact -- in a
word, ecology is the study of all the complex interrelationships
referred to by Darwin as the conditions of the struggle for existence.
Ernst Haeckel, 1870.
• The struggle for existence. Charles Darwin 1859
• The scientific study of the natural environment and the
relationships of organisms to one another and their
surroundings—Ricklefs 2001.
Functional connections: who eats who?
Throughout the history of life, plants, animals and microorganisms have evolved to
carry out different functions in natural systems
Eukaryotes arose when
some prokaryotes evolved
the ability to live inside
other cells and function as
organelles within them
Absorb and process dissolved organic matter
Some eubacteria became autotrophs
Protozoa feed on tiny bacteria and other
organic particles
Algae became “green” through bacterial
symbionts which evolved into chloroplasts
Some algae evolved roots, a vascular system
and a cuticle –bacame terrestrial autotrophs
Some protists evolved “hyphae” for the
absorption of organic matter, became
decomposers and pathogens
Some protists evolved into active ingestive
heterotrophs that eat other organisms
Environments influence organisms and organisms change their environment
Over millions of years the activities of organisms have profoundly changed
the global environment
Living systems are constantly evolving:
Evolutionary adaptation helps organisms survive in a harsh world
Evolution is usually thought of as a longterm process that occurs gradually over
millions of years.
However, it can also occur rapidly when
the environment changes and natural
selection is very strong.
In some cases we’ve been able to observe
it directly—some examples.
The industrial
heart of England
Industrial melanism and the British peppered moth—Biston betularia
•In 1849, a coal-black mutant was found near Manchester,
England. Within a century, this black form had increased to 90%
of the population in this region.
•Offspring of the black mutant were also black (heritable)
•The moth flies at night and rests by day on tree trunks.
•In areas far from industrial activity, the trunks of trees are
encrusted with lichens
•As the photos show, the light form (circled in red) is practically
invisible against this background.
•In areas where air pollution is severe, the combination of toxic
gases and soot has killed the lichens and blackened the trunks.
•Against such a background, the light form stands out sharply.
•The moth is preyed upon by birds that pluck it from its resting
place by day.
•In polluted woods, the dark form has a much better chance of
surviving undetected.
•When the English geneticist H. B. D. Kettlewell released moths
of both types in the woods, he observed that birds did, indeed, eat
a much higher fraction of the light moths he released than of the
dark.
•Since pollution abatement programs were put in place after World
War II, the light form has been making a comeback in the
Liverpool and Manchester areas.
•
•
Modern day examples of how natural selection can operate to
produce evolutionary adaptation to a changing environment
For example, the bent grass (Argrostis tenuis) in this photo is
growing on the tailings of an abandoned mine, rich in toxic
heavy metals.
•Only plants with genes for
metal tolerance survive.
•Individual plants do not
evolve to become more
metal tolerant during their
lifetimes.
Fig. 23.1
Ecologists study the natural world by observation and experiment
Testing hypotheses by experiment: here bird predators that eat
caterpillars are being excluded from an oak sapling in order to test for their effect.
Microcosm experiments:
•Real ecosystems are often huge and hard to replicate and control.
•Microcosms allow us to test hypotheses on scaled down systems that can be replicated.
Humans have long been a prominent part of the environment
Species introductions beyond their
native range:
•both intentional and accidental
Eg the Nile perch
Humans influence ecosystems through exploitation which can
have very complex effects, because of the interconnections in natural systems
Sea otters have a huge effect on west coast kelp forests