WEEK 1, VERTEBRATE ZOOLOGY 03051: INTRODUCTION; EVOLUTION
1/18/00 Text (7th ed.): Ch. 4; Ch. 6, pp. 138-140; Ch. 15 (aspects)
Dr. W. Crone (303 FTZ, 629-7439, cronewil@hvcc.edu, http://www.hvcc.edu/academ/faculty/crone/index.html)
possible web site: http://www.ucmp.berkeley.edu/chordata/chordata.html
(an introduction to the chordates and vertebrates that will be a resource for the semester)
http://www.ucmp.berkeley.edu/help/timeform.html
(a useful timeline for keeping geologic times in order)
http://www.talkorigins.org/origins/faqs-qa.html
(The Talk.Origins Archive: answers and links concerning the most frequently asked questions about evolution)
The focus of this course is on vertebrate animals, or those with a backbone. The course is divided up into two parts: 1) a survey of different vertebrate groups (with emphasis on comparative anatomy) and 2) aspects of animal structure and function (mostly physiology).
bilateral symmetry: arrangement of body parts so that a single midline plane divides the body into mirror images
Orientation of animals. Anterior/posterior (front [head]/back [tail]), distal/proximal (away/towards site of attachment), dorsal/ventral (back/belly), inferior/superior (below/above), median/lateral (middle/side) and transverse (cross) vs. median or midsagittal planes vs. frontal or coronal planes of section.
Levels of organization:
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cell: |
basic unit of life, with eukaryotic cells containing nucleus, cytoplasm, and plasma membrane |
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tissue: |
a group of similar cells specialized for the purpose of a common function. There are four animal tissue types: epithelial, connective, muscle, and nervous tissue |
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organ: |
specialized structure made up of more than one type of tissue, often organized into organ systems, e.g., digestive |
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organ system: |
for overall function, e.g., digestive |
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organism: |
the individual |
Analogy vs. homology. Analogy is common function without regards to origin. Often used example of analogy: wings of insect an extension of exoskeleton, while wing of bird a modified forelimb. Homology is a structural similarity (morphological equivalence from sharing a common evolutionary origin) regardless of present day function. Therefore, the wing of a bird is homologous to the foreleg of a lizard, or the arm (upper extremity) of a human being.
Three major criteria of homology (not in the book but important):3
A) position; where the organ is borne
B) special qualities; e.g., internal anatomy
C) serial homology or connection of divergent structures by intermediates, as you saw with the crayfish appendages in Invertebrate Zoology, or by similar structures in related organisms.
Evolution: change over time; the process by which the genetic composition of a population changes over time in response to natural selection.
DARWIN AND THE BASIS FOR THE THEORY OF EVOLUTION BY NATURAL SELECTION
Charles Darwin was a curious observer of nature as a boy in the 1820s. His physician father sent him off to Edinburgh to become a doctor, which was not his interest. He dropped out, and went to Cambridge to become a minister. After graduation, he went on the sailing ship Beagle at age 22 with Captain Robert FitzRoy. Up to that time Darwin had accepted special creation and the nonchanging status of species, along with the rest of European society.
Darwin was particularly impressed by the Galápagos Islands off of Ecuador. He had also read Lyell's Principles of Geology and later Malthus's Essay on the Principle of Population. By the 1840's Darwin had worked out his theory of natural selection. Darwin did not do much with it until received a letter from Alfred Wallace in 1858, expressing many of the same ideas. Then Darwin published The Origin of Species in 1859.
Main points to Darwin's line of thinking towards the theory of evolution by natural selection:2
(I am using the term"fact" here for a readily repeatable observation)
FACT #1: all species have great fertility
FACT #2: most populations are stable in size, with seasonal fluctuation
FACT #3: resources are limited
inference 1: Only a fraction of offspring survive from a struggle for existence in the limited resources
FACT #4: individuals vary, no two alike
FACT #5: much of this variability is inherited
inference 2: Survival in the struggle is not random, but depends on part in individuals' heredity. Those individuals whose inherited characteristics fit them best to their environment are likely to leave more offspring than others.
inference 3: This unequal survival rate will lead to a gradual change in the population, with favorable characteristics accumulating over the generations.
From this combination of fact (observation) and inference has sprung EVOLUTION, the unifying theme of the great diversity of living organisms. Fervent discussion and testing of evolutionary theory has continued for the last 140 years among scientists. The observations highlighted above, along with evidence from the fossil record and current animal/plant populations, have been best explained by evolution in the form of natural selection, as initially proposed by Darwin and since modified to account for additional data.
Vertebrates have a reasonable fossil record, especially compared to the invertebrates (why?), and so throughout the semester we will be making references to fossils and the geologic times that they have been found. From longest to shortest unit, geologic time is measured in eons, eras, periods, and epochs. Let's see which are most applicable for vertebrate zoology (mya: million years ago). I am not expecting you to memorize these, but to be aware of the general framework.1
Cenozoic Era (65 mya to today)
Quaternary Period (1.8 mya to today)
Holocene Epoch (11,000 years to today)
Pleistocene Epoch (1.8 mya to 11,000 yrs)
Tertiary Period (65 to 1.8 mya)
Pliocene Epoch (5 to 1.8 mya)
Miocene Epoch (23 to 5 mya)
Oligocene Epoch (38 to 23 mya)
Eocene Epoch (54 to 38 mya)
Paleocene Epoch (65 to 54 mya)
Mesozoic Era (245 to 65 mya)
Cretaceous Period (146 to 65 mya)
Jurassic Period (208 to 146 mya)
Triassic Period (245 to 208 mya)
Paleozoic Era (544 to 245 mya)
Permian Period (286 to 245 mya)
Carboniferous Period (360 to 286 mya)
Devonian Period (410 to 360 mya)
Silurian Period (440 to 410 mya)
Ordovician Period (505 to 440 mya)
Cambrian Period (544 to 505 mya)
|main page| |background| |03028: Physiology| |03048: Anatomy|
|03050: Invertebrate Zoology| |03051: Vertebrate Zoology| |03074: Economic Botany|
Please send comments and questions to: cronewil@hvcc.edu
Copyright 1999, 2000 by Wilson Crone
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This web page last updated on January 28, 2000