1. What is ecology about? What is a system? from the Greek “Oikos” which
means household
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

2. What is Ecology?
The total relationship of organisms to environment, and to each other, Ernst Haeckel 1870
The struggle for existence. Charles Darwin 1859
The study of the factors affecting the distribution and abundance of organisms, Charles Krebs 1970.
The scientific study of the natural environment and the relationships of organisms to one another and their surroundings—Ricklefs 2001.

3. There are different ways of looking at the relationships of organisms to their environment
Some ecologists classify habitats and examine the relationship between organisms and the habitats they occupy
Others are more concerned with functional roles of different types of organisms within food webs and ecosystems—the ecological niche

4. Populations of living organisms are constantly evolving and adapting to change:
Evolution as a long, slow process of change tracking the global environment
Evolution can be a complex arms race, predators are constantly evolving better tactics and prey are constantly evolving better defence—coevolution can be rapid.
Evolution is constantly producing new “variants” –diversification
Evolution is constantly changing and diversifying organisms, which in turn changes the “systems” that they are a part of, and in the long-term can change even the global environment itself.

5. Functional connections: who eats who?
Throughout the history of life, plants, animals and microorganisms have evolved to carry out different and complimentary 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

6. Environments influence organisms but organisms also change their environment
Over millions of years the activities of organisms have profoundly changed the global environment

7. Evolution can occur rapidly when the environment changes and natural selection is very strong—especially where there are strong interactions among species.
In some cases we’ve been able to observe it directly—some examples.

8. The industrial
heart of England

9. Industrial melanism and the British peppered moth—Biston betularia

10. In 1849, a coal-black mutant was found near Manchester, England
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.

11. 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.

13. Only plants with genes for metal tolerance survive.
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 become more metal tolerant during their lifetimes.
Populations transplanted back to “clean” soil, lose their metal tolerance over a few generations. Why?
Fig. 23.1

14. 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.

15. 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.

16. Humans have long been a prominent part of the environment
Species introductions beyond their native range:
both intentional and accidental
Eg the Nile perch

17. Ecologically, we are victims of our own enormous success
Humans influence ecosystems through exploitation which can have very complex effects, because of the interconnections in natural systems
Ecologically, we are victims of our own enormous success
at exploiting, manipulating and substituting resources

18. Sea otters have a huge effect on west coast kelp forests