I. What is ecology?

A. Definitions

- The scientific study of the relationships between organisms and their environments.1865 by combining greek 'logos' and 'oikos' (house)

- Haeckle's definition: the body of knowledge concerned with the total relations between organisms and their inorganic and organic environments.

- Mulkey's definitions: (1) The study of carbon - how you get it, what to do with it after you get it, and where it goes after you are done with it. (2) The study of biotic and abiotic factors in the acquisition, utilization, transfer and storage of carbon. Note that these definitions are incomplete because carbon is but one component of life. Is it not the most important component?

B. Two modern terms for house:

1. Environment: all external physical and biological factors that directly influence the survival, growth, development, and reproduction of organisms.

2. Habitat: the place where organisms occur and the environmental factors that exist there.

C. Current academic debate:

"Much of the work that is done under the name of ecology is not ecology at all, but either pure physiology --- i.e., finding out how animals work internally--or pure geology or meterology, or some other science concerned primarily with the outer world. In solving ecological problems we are concerned with what animals do in their capacity as whole, living animals, [neither] as dead animals [nor] as a series of parts of animals. We have ... to study the circumstances under which they do these things, and, most important of all, the limiting factors [that] prevent them from doing ... other things. By solving these questions it is possible to discover the reasons for the distribution and numbers of ... animals in nature." 1927 Charles Elton Animal Ecology, p.33-34

Ecologists see themselves very differently, depending on the practice of their science. Please read this editorial by C. S. Holling, the Editor-in-Chief of Conservation Ecology about the Two Cultures of Ecology.

II. Origins

Please see the history provided by the chronology in Characters in Ecology (Revised from Calow, P. ed., T, 1999., The Encyclopedia of Ecology and Environmental Management, Blackwell Science, Oxford. Pp. 122-123.) Capitalized words are key terms found in Calow (1999). If you are not sure, check them out in your general ecology textbook.

A. John Graunt (1662) -

British haberdasher - published a catalog of statistics on births, deaths, etc.

B. Malthus (1830s) -

formulated the principles of exponential population growth. - inspired Darwin and Wallace

C. Darwin

and Wallace (1840s) -

Only two of many biologists studying the natural history around the world who noticed the direct link to Malthus because they tried to explain the causes of population control

"In October 1838, that is, fifteen months after I had begun my systematic inquiry, I happened to read for amusement Malthus on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long- continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The results of this would be the formation of a new species. Here, then I had at last got a theory by which to work".

Charles Darwin, from his autobiography. (1876)

"Something led me to think of the positive checks described by Malthus in his essay on population. These checks --war, disease, famine, and the like -- must act on animals as well as on man. While pondering vaguely on this fact there suddenly flashed upon me the idea of the survival of the fittest -- that the individuals removed by these checks must be on the whole inferior to those that survived.

In the two hours that elapsed, I had thought out almost the whole of the theory, and I sketched a draft of my paper. In two succeeding evenings I wrote it out in full, and sent it by the next post to Mr. Darwin."

Wallace on an island in Malaysia (c. 1875)

Questions:

• - still the same questions we ask today
• - why are so many species extinct?
• - why does a given species occur in one location and not another
• - what are the differences between narrowly restricted and widely distributed species?
• - why are there more species in the tropics?
  

E. Leibig (1840): "Father of physiological ecology"

studied mineral elements added to plant soil :

Law of the Minimum: When a process is conditioned as to its rate by a number of separate factors, the rate is limited by the pace of the 'slowest' or most limiting factor.

F. Overview:

Malthus - populations, Darwin - evolutionary theory, Many - natural history of populations and communities, Leibig - natural economics or physiological ecology; Erhlich, Carson - Environmental Issues.

Conclusion: Ecology has a very diverse history, and remains a diverse science today.

III. Levels of ecological organization:

Note the role of carbon in each:

A. Individuals: the fundamental functional unit because (1) interact directly with the environment and with each other, and (2) breeding unit.

B. Populations: groups of genetically similar individuals co- occurring in space and time. Not necessarily interbreeding.

C. Guild: groups of populations that exploit the same class of resources in a similar way. May be of different species: lizard and bird.

D. Communities: groups of populations co-occurring in space and time. All living things in an ecosystem, or restrict only to one class such as birds.

E. Biomes: regional ecosystem types with similar communities - tall grass biome, arctic biome, tropical forest biome.

IV. Conceptual levels and time scales:

A. Biological hypotheses may be developed at two levels:

proximate causes (Example: The developmental environment of a leaf acts as a cue for the plant to produce a large or a small leaf)

ultimate (The economics of support for leaves of different size)

B. Time is referenced at two levels:

ecological - typically corresponds to proximate causation

evolutionary - typically corresponds to ultimate causation

C. Perspective of the organism?

Habitat: place or physical setting in which an organism lives

Niche: representation of the range of conditions that an organism can tolerate and the ways of life that an organism can pursue - ie, its role in the ecological system.

V. Organization of course: four primary subdisciplines.

A. Ecosystem Ecology

- Large-scale acquisition, transfer, and storage of materials and energy between biotic and abiotic components of the biosphere.

B. Physiological Ecology and Behavioral Ecology (Autecology)

- How organisms acquire carbon and how it is allocated to the competing functions of growth, reproduction and maintenance.

C. Population Ecology

- What to do with carbon after it is acquired - i.e., make babies. Another level of organization at which to study the allocation of carbon to growth, reproduction and maintenance.

D. Community Ecology

- The distribution of carbon among species through time and space.

E. Human Ecology and Conservation

- How to make a planet less inhabitable by profoundly altering the processes of carbon acquisition, transfer and storage.

VI. Evolution and adaptation

Note that all of Darwin and Wallace's work was contemporary with Mendel, but prior to the recognition of the significance of Mendel's results.

A. Necessary conditions:

1. genetic variability

2. inheritance of traits

3. environmental variation influencing which traits are passed on

=> Given these necessary and sufficient conditions, organic evolution will proceed as an algorithmic, inexorable consequence of natural selection acting on variation in phenotypes. See Darwin's Origin of Species.

=> Darwin concluded The Origin of Species: "There is grandeur in this view of life, ...[that] from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved."

=> Ernst Mayr is the last living biologist to have experienced the development of the Modern Synthesis of Evolution. This article describes is life and times.

B. Definition of biological evolution:

"a change in the gene (allelic) frequency in a population with time."

Fig. from Univ. of Minn. Intro. Biology.

1. phenotype

2. genotype

C. Factors that can cause changes in allelic frequencies:

1.Genetic Drift in Small Populations- results in Genetic Drift, random fluctuations in the frequency of alleles due to chance events.

Founder Effect - the establishment of a new population based upon a small random sample from a parental population.

Evolutionary Bottleneck - a process where a population decreases in size, resulting in an increase in sampling error. Reduces genetic variability, produces a population that is more monomorphic.

Fig. from Univ. of Minn. Intro. Biology.

 

2.Mutations - mutation pressure from natural sources.

3.Gene flow (Migration; see Genetic Drift above)

4.Nonrandom reproduction - sexual selection

5. Selection - mean and normal distribution

i. directional

ii. stabilizing

iii. disruptive

6. Human disturbance and evolutionary change

-> Industrial melanism. Note that the British example of industrial melanism has been replicated in a parallel natural experiment near Detroit.  

7. Artificial selection

VII. The nature of adapation

A. adaptations are integrated

- it is the phenotype that is selected.

B. Natural selection acts in the present,

but adaptations reflect the past

C. Natural selection is opportunistic

D. All species are not well adapted.

Neutral characters may exist for which selective pressure is negligible.

E. There is no such thing as "progress" in evolution

-However, there may be "progression" to phenotypes with fewer evolutionary "options". For example, a genetic bottleneck may cause variation to be lost within a population, thus limiting the possible phenotypes that can be selected in future generations. Some researchers argue that this process causes an increase in the probability of extinction.

- Note that we (Homo sapiens) share a very large part of our genome (98% or more) with the Bonobo, a species of chimpanzee. This has two important implications: (1) natural selection can generate speciation by affecting a very small portion (percentage-wise) of a species' genome. (2) Humans and the Bonobo share a very recent common ancestor; perhaps as recent as 2 million years ago.

Fig. from Univ. of Minn. Intro. Biology.

F. Interaction of cultural evolution and genetic evolution

meme, gene concept - see Richard Dawkins: The Selfish Gene.

VIII. Examples of the explanatory power of natural selection

• Drug resistance in bacteria.
• Pesticide resistance in insects.
• Sickle cell anemia
• Rabbits and myxomatosis.
• Industrial melanism
  

A. Sickle cell anemia and malaria --- how can something bad be good?

Sickle-cell allele (S ) is a defect in the beta hemoglobin chain resulting from a single animo acid

change.hemoglobins have two pairs of chains , alpha and beta

Sickle allele, S, is a change in the beta chain (146 aa)

glutamic acid at position 6 in normal beta replaced by valine

S S homozygotes die, yet the sickle-cell allele is widespread throughout the world

Key: the sickle-cell heterozygote is resistant to malaria

The frequency of the S allele closely matches the world-wide distribution of malaria.

B. Rabbits and myxomatosis

• In 1859, 12 rabbits brought to Australia.
• by 1886, the army of rabbits was advancing at over 66 miles a year, smashing through "rabbit-proof" barriers. They spanned Australia by 1907.
• Myxomatosis introduced in 1950, with an initial mortality rate of 99.9%
• Mortality rate today is about 40%, The rabbits have adapted through selection.

IX. Debate about Darwin's theory

A. Search for a mechanism for Punctuated Equilibrium has failed

Punctuated Equilibrium of Gould & Eldredge is a theory without a mechanism. The resolution of the geographical record is consistent with gradual evolutionary change.

B. Creationism

Talk Origins Archive for review of the Creationism debate.

Some Darwinian Answers to Creationism. from Cornell's on-line magazine

The Pope Issues Statement on Evolution (1997)

See also Darwin's Dangerous Idea by Daniel C. Dennett.

So....Does Darwin have anything to say about our emotions?

Charles Darwin

About The Tropics:

"It must be remembered that within the tropics, the wild luxuriance of nature is not lost.....Epithet after epithet was found too weak to convey to those who have not visited the intertropical regions, the sensation of delight which the mind experiences.....The land is one great wild, untidy, luxuriant hothouse, made by Nature for herself."

1845. Voyage of the Beagle.

About Himself:

"I have no great quickness of apprehension or wit which is so remarkable in some clever men, for instance Huxley. I am therefore a poor critic; a paper or book, when first read, generally excites my admiration, and it is only after considerable reflection that I perceive the weak points. My power to follow a long and purely abstract train of thought is very limited; I should, moreover, never have succeeded with metaphysics or mathematics. . . . On the favourable side of the balance, I think that I am superior to the common run of men in noticing things which easily escape attention, and in observing them carefully. My industry has been nearly as great as it could have been in the observation and collection of facts. What is far more important, my love of natural science has been steady and ardent. This pure love has, however, been much aided by the ambition to be esteemed by my fellow naturalists. From my early youth I have had the strongest desire to understand or explain whatever I observed, that is, to group all facts under some general laws. These causes combined have given me the patience to reflect or ponder for any number of years over any unexplained problem."

Charles Darwin, 'The Autobiography'

Time-line of evolutionary theory. Note that Darwin and Wallace were important players, but they were also far from the only contributors.