Week 3 Evolution of the Biosphere

Midterm Exam Notice

(FINAL IS SCHEDULED FOR TUES MARCH 20TH AT 8:45)

I omitted a picture of a statigraphic column from the last lecture.   plese refer to last week notes for details!

Who are we?

• We are living beings, with a range of characteristics that we share with other living things

• We are one of 10-30 million species that each have their own unique histories.

• We are primates and share with them the biological traits that typify that group

• We are a unique species with a sophisticated culture, unlike anything seen in other organisms. This culture was an adaptation that permitted us to withstand the rigors of the Pleistocene. It is also that attribute that allowed us to step outside the confines of local ecosystems and become a global species.

"The most basic definition of life might involve the ability to ingest nutrients, to give off waste products, and to grow and reproduce"

Bruce Jakosky

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alternatively

Life is:

"a deal struck between nucleic acids and proteins"

P C W Davies

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Evolution – Some precursors

The idea of the transmutation of biological types (Species) is an old one. Here are some of the authors who reflected upon these  themes:

John Ray 1628-1705 http://www.ucmp.berkeley.edu/history/ray.html
Erasmus Darwin 1731-1802 http://www.ucmp.berkeley.edu/history/Edarwin.html
Jean-Baptiste Lamarck (1744-1829) --"inheritance of acquired
characteristics"http://www.ucmp.berkeley.edu/history/lamarck.html
Thomas Malthus 1766-1834 it’s him again! http://www.ucmp.berkeley.edu/history/malthus.html



Darwin and Wallace

Alfred Russel Wallace 1823-1913 http://www.iol.ie/~spice/alfred.htm

In which, Wallace, a working class British lad, set sail for South America with the naturalist Henry Bates, collected biological  specimens, lost them in a fire at sea, returned to Britain, wrote, and headed to Malaysia. There, while in a malarial delirium, he dreams up his theory of natural selection. He communicates the theory to Charles Darwin.

Charles Darwin 1809-1882
http://www.nyu.edu/projects/fitch/courses/evolution/html/darwin.html
http://www.csuchico.edu/~curban/Darwin/DarwinSem-S95.html
Son of a wealthy Shrewsbury physician, studies medicine in Edinburgh University (but dropped out), went to Cambridge with the idea that he would become a clergyman. He obtained his BA (1831). He forgoes becoming the man of the cloth that his family had anticipated and instead went to sea on the H.M.S. Beagle (1831-1836) as a naturalist and companion to Captain Robert Fitzroy.  After his travels he married and lived an essentially retiring life (which included a 7-year study of barnacle systematics). For reasons that have been endlessly debated in the literature he never published his thoughts on natural selection until he received the communication from Wallace that he had also uncovered the principle of natural selection. The ideas of both men were presented at a meeting of the Linnean Society in a co-authored paper (1858).

 

Evolution through natural selection

Conditions for evolution

As has been stressed in recent lectures one of the most distinctive features of life has been it's diversity. This diversity is a reflection of the most prevalent type of speciation events (creation of new species), namely the splitting of one population of a species into a two reproductively isolated populations. This usually happens when a physical barrier is created which isolates a small potion of the original population. In this small population genetic changes can spread rapidly and distinctive new anatomies and behaviors become established.  In the example above, from the Sierra Nevada, Ca. range local populations of the plant Achillea have developed.   Altough these popualtions are not new species that have strong genetically determined differences in heights.  Even when grown in a common plot they retain these differences (i.e the differences are not environmental, not a consequence of them growing in different soils or climatic conditions).  If these populations develop to they point where they cannot  interbreed they are, by definition, distinct species.

So, the hallmark of a speciation event is that when the populations later overlap (as they may when the new species range expands) there is no sucessful reproduction between the two populations. This mode of speciation of call allopatric speciation. There are circumstances under which speciation may occur with the physical seperation of species occuring (this is called sympatric speciation).

This leads to the definition:

Species concept:

"A species is a population whose members are able to interbreed freely under natural conditions"

 

How many species?

(we discussed this last week - but here are some additional notes on the Terry Erwin work).

Terry Erwin estimated 30 million arthropods alone, though Nigel Stork has suggested 5-10.

Panamanian forest

Fogged tree canopies

One species, Luehea seemania, had 163 specialists.

50,000 tropical trees in all = 8,150,000 tropical beetles

Beetles are 40% of all species of arthropods,

Total tropical arthropods (in canopy) 20 million….

 

In conclusion the evolutionary process changes both the form of organisms over time.  It also results in a process of splitting, the emergence of new species.   We are still unsure about the magnitude of the diversity of life on Earth.

 

Who are we - how did we get this way?

The argument of this section of the course is that humankind is an evolutionary product of a
lineage of animals that evolved in trees. Our distinctive features: reliance on stereoscopic eyesight
at the expense of diminished sense of smell (hence the configuration of the human face), hind-limb
dominated locomotion, and increased intelligence; are features that have their genesis in the
primordial INSECT consuming habits of the earliest Primates. These characteristics became
refined as humans adapted to a variety of ecological circumstances. These changes were
accompanied by closely associated ecological changes that have a large bearing on our Life
History Strategy (our way of going about the business of reproduction).

Could humankind have emerged from a lineage of grazing animals that flourished on the earliest
savannahs? In thinking about the origins of humans, what do you regard as the primary biological
characteristics of our species? Intelligence, upright walking, sociality, consciousness? Are these traits
represented in other primates?

"We have reached our present precarious position as an outcome of an ecological evolutionary course on which our ancestors embarked at least 2.5 million years ago. And our deep evolutionary history - hence our deep evolutionary future - is a story of shifting positions vis-à-vis our approach to the natural world and its component ecosystems."

Niles Eldredge, Dominion 1995

 

"Of course, our ancestors were affected not just by great - indeed cataclysmic - geological and environmental changes; they lived virtually every day of their lives very much at the mercy of nature. Even small changes in the physical conditions, we know, the kind of experience every day without notice, could have deadly consequences… What evolved as a superior energy-extracting system for human groups in the marginal habitats of the Pleistocene was a machine that over-produced in times of plenty. Culture in the hands of the first agriculturists 10,000 years ago increased population densities, created diseases unknown to earlier hominids, built the first villages and temples, and gave humans that pervasive misconception that they were above the laws of nature even as they rushed headlong into a despoilment of their habitat unknown in any other species."

Noel Boaz, Eco Homo, 1997

 

Our evolutionary limb on the tree of life – vertebrates, Placental mammals, Primates (Old World Monkeys, Gibbons and Great Apes)

http://phylogeny.arizona.edu/tree/eukaryotes/animals/chordata/mammalia/eutheria.html

http://www.indiana.edu/~primate/primates.html

Primates

• 4 groups:

Strepsirhines (Lemurs, lorises and bushbabies), http://www.thewildones.org/Animals/lemur.html ,

New World Monkeys New World Monkeys (marmosets, spider monkeys and howler monkeys),
http://www.foxhome.com/dunston/Shock/Content/dontCallMe/newworld.html
http://www.umanitoba.ca/anthropology/courses/121/neworld.html,

Old World Monkeys (macaques, baboons, and colobus monkeys) http://www.umanitoba.ca/anthropology/courses/121/oldworld.html,

Homonoids (apes and humans)
http://arrs.envirolink.org/gap/gaphome.html (Great Ape Project)

• Mainly tropical in distribution

• Distinctive features of Man: uprightness, intelligence, extreme sociality, are extensions of the primate condition

• Hind-limbed dominated locmotion

• Increased encephalization -- some ecological and reproductive consequencesThere are 4 groups of

  Required Reading

  Up from the Apes

  MICHAEL D. LEMONICK AND ANDREA DORFMAN

  http://www.pathfinder.com/time/magazine/articles/0,3266,29513-1,00.html