NATURAL SELECTION
Intro web assignment: http://webs.csu.edu/~biep1/Teaching/PHY321G/Lectures/W01/01_Intro.html
Natural selection web assignment: http://online.morainevalley.edu/WebSupported/BIO112/new_page_1.htm
I. Introduction
A. Lab: first lab will be a film on the Mating Game and also Sci American selections.
B. Course will be loose. Syllabus not absolute. Discussion. Thinking. Lab will be more experimental. Lab Handouts.
C. It is important to keep up with the assignments and NOT to get behind. Make sure you understand all of the figures.
II. What is PHYSIOLOGY?
A. "Physi" - "Ology" The physical or mechanical study of life.
B. Physiology is the science where you go as far as you can looking at life from the mechanists point of view.
1. Any living aspect can be considered in either one of two respects: the mechanistic or vitalistic viewpoint.
a. MECHANIST - Living organisms are made up on the basis of and governed by the chemical and physical laws.
b. VITALIST - The quality of life is something special beyond the scope of chemical and physical considerations. Such things as conscience, love, and soul are frequently approached with the vitalistic view. Scientific method can not be applied to vitalistic viewpoints.
2. In this course the mechanistic view will be taken as far as it can be taken. Living organisms will be regarded as machines. However, this does not deny vitalism. In fact, most scientists, and even physiologists, have a combination of both vitalistic and mechanistic views toward life.
a. To regard a living organism as a machine is not meant to be a demeaning statement with respect to the phenomenon of life. The simplest bacterium, a living organism, is orders of magnitude more complex, organized and fascinating that any man made machine.
b. To understand physiology it will be necessary to understand some of the basic laws of chemistry and physics.
3. Any physiology of an animal should be regarded in a problem solving fashion. You can put yourself in Mother Natures shoes and ask if you were she how could you most effectively, efficiently , and directly (easily) increase an animal's survivability, given a particular situation and the tools you have for change?
III. The level of research in animal physiology is decreasing. Why?
A. What makes science go? All of the following must exist:
1. Interest.
2. Money.
3. Methods.
B. In animal physiology the interest is high - many scientists and the common person find it exciting to ask "How does that animal do that?"
C. The money is high for any physiology that it is related to the medical field. But basic research is in severe trouble. There is little federal funding for a question like "How can seals dive down so far?"
D. The methods have been severely hampered by animal rights groups. To ask how an animal machine works the classic process was to 'take the animal apart' to figure it out. (Demo: Take apart something - Bubble monkey). That process is less and less acceptable. Also the regulations necessary to keep animals in the laboratory are highly constraining. (Note that veterinary science has greatly advanced and animals have benefited from animal research).
IV. What is an animal?
A. An animal (in fact, every cell of an animal) is a slave to a particular chemical reaction:
C6H12 O6 + 6 O2 ------> 6 CO2 + 6 H2O
B. It is because of this reaction that an animal moves, eats, breathes, has blood, needs water, is better if warm, and is responsive to the environment.
C. Why oxygen and glucose? Why not N2 and silicone? The answer is PLANTS. Animals are dependent upon plants for the two reactants of the above reaction.
V. How did these fancy, physical-chemical machines come about? What rules led to the development of these machines? :EVOLUTION
A. Evolution is based upon the conjugation of two phenomena:
DNA mutation and selection(survival of the fittest).
1. DNA mutations - only important when it happens in ova or sperm.
a. Nucleotide change ==> one amino acid change in one protein (point mutation).
b. (Jumping DNA) Sections of (repetitious) DNA can move from one area to another to give new combinations ==> new proteins with amino acid sequences similar to existing proteins and they probably carry out similar molecular functions.
c. Deletions of existing DNA ==> could be a loss of a few amino acids of a protein or it could be a loss of major functions (e.g. blind and colorless cave fish).(Sometimes a loss of a gene is caused by a jumping gene inserting into it).
d. Recombination of genes (transfer of genes from one organism species to another) (I know of no examples of this occurring in nature at the animal level - although new animals have been created by scientists in this way). ==> mixed characteristics between two animals may lead to an animal better than either of the two parental animals.
e. Hybridization and crossover - mating of two strains or closely related species ==> a gene combination that makes an animal better than either of the parents.
f. Unequal crossing over allows duplication of whole or parts of a gene=>protein. One of the two copies is not free to mutate without loss of function from the original.
2. Selection - Survival of the fittest (once the mutation has occurred, does the mutation ascribe an advantage to the organism.)
a. Survival means being better. Better relative to members of its own species. Better with respect to the way it can cope with physical environment and living environment (other competitive and predatory species).
b. A "better organism" is generally one that leads to better gene propagation. (e.g. mutations that lead to a longer life after reproductive years would not normally be considered a selective advantage).(Note that over reproduction can work against survival of the genes).
B. We often think of evolution as a process that yields an unlimited variety of mechanisms that can cope with almost any situation. But, in fact, evolution is constrained by the ways that DNA mutation and selection work. Also the mechanisms are constrained in that all of the physiological machinery must be based on organic chemistry in one way or another (e.g. we should not expect cheetahs to evolve a turbo charged internal combustion engine in order to go faster.)
1. All functional mechanisms of an organism are alterations of previously existing functional mechanisms. Wholesale innovations (other than deletions) do not occur. (For example, a dinosaur with bird like wings and feathers was not suddenly born one day)(A squirrel that jumps between trees becomes a bat like organism.)(A human would not be born tomorrow with infrared sensors) (Loss of color, extremities can be sudden and beneficial).
a. All intermediate steps in the natural selection process must be advantageous over the previous. Speculate how wing development occurred. (If the only way to get from A to D is through B and C, and B and C are disadvantageous, then D will never evolve no matter how much more advantageous it is.)
2. Even though any naturally selected mechanism must have been derived from an existing mechanism (and therefore must be related with respect to structure) the original and derived function do not have to be related. (This is because natural selection selects for better ORGANISMS from random DNA mutations; natural selection does not select for a particular better function).(e.g. the mammalian lungs evolved from a swim bladder).
3. Evolution is extremely slow (in comparison to human time scales of thinking)
a. It has not been too slow considering the rate at which the environment has changed over the past millions of years. (Man is changing the earth's environment probably faster than it has ever changed before. The evolution of many animals is not keeping up, and many have become extinct.)
b. The environment is always changing. An animal considered best at one time may not be best in another time. (e.g. we consider ourselves superior to dinosaurs - but we think of our environment as it is today in making that comparison. Would we be superior in the way the earth was then???)
4. An amazing aspect of natural selection is that it gives the word "purpose" a meaning. Although there is no intentional goal inherent in the process (it is inherently a random process), nevertheless the effect is to maximize the domination of environmental niches. It allows us, in an odd way, to legitimately start asking the question "WHY?".
C. The animal we see in the environment today is not the perfect living machine for that environment (it generally is the best, but that is not always true either). Although these animals are very far from perfection, the adaptations can still be amazing and impressive.
D. Examples
Structure: Jaws------------>teeth--->specialized teeth------->tusks
Function: food acquisition ----->digestion -------->battle ----------->mating
Structure: Swim bladder------>gas exchanging organ------>lung
Function: flotation-----------------------------------> respiration
The structure of a molecule such as Na+ - K+ ATP Pump has evolved
to be used for a variety of
functions:salt gland, osmoregulation, kidney, muscle, nerve.
Evolution of GI tract in digestion:
invagination of epidermis->double opened tube-> compartments of specialization along tube->heating to digest
1a. No organism has been found with an oven for a stomach, although cooking is a simple mechanistic way to make foods available that would normally be unusable.
convergent evolution
epidermis-------------------------->insect TYMPANIC membrane
gill slits------------------------>eardrum
3. When you think of an organ such as a heart, do not think of it as the best mechanism that could have been innovated to perform the function, but think of it as the best mechanism that could have been naturally selected.
VI. Excess reproduction is a common stratagey. By having many more offspring than can be supported by the environment, only those with the best genetics will tend to survive.
VII. Review: The development of machinery (eyes, feet, lungs, intestines, hair, etc.) is through the process of natural selection. This process has many advantages that has led to the huge diversity of successful animals found on planet earth. But natural selection also has several built in restrictions that must be respected. When considering how an animal organ works, for example, it is very valuable to understand the process by which it was made and to understand the restrictions that existed in the development of that organ.
A. Advantages:
1. Evolution has had a veeeeeeeerrrrrrrrry long time to work.
2. It yields functional systems.
B. Disadvantages:
1. There is no innovation.
2. It is very slow.
3. No negative intermediate steps are allowed.
4. The planetary environment is constantly changing.
5. Far from perfect.
VIII. Further considerations regarding natural selection (evolution) (survival of the fittest).
A. In order to be a good survival machine compared to other similar makes and models, an organism must provide an ideal environment for the multitude of chemical reactions in its body that make it go.
1. Osmotic and ion control.
2. Temperature control.
3. Waste control.
B. An organism to survive in an environment must interact well with it.
1. External environment interaction.
a. Movement.
b. Senses.
c. Nervous system - sensory evaluation..
d. Temporal control.
2. Internal environment interaction.
a. Nervous system - internal sensory detection and evaluation.
b. Endocrine system.
C. The bottom line for successful survival is successful DNA propagation. (success is measured in terms of propagating the DNA of the organism). We must be careful not to relate human standards for success (high milk production in cows, human intelligence, putting a round object through a 18 inch metal ring) to success in the natural selection process.
D. Fittest does not necessarily mean the most efficient, it means the most effective. if an animal is more successful by being more wasteful it will still be selected for. Our warm body temperature is an excellent example -it is very wasteful but it does make warm blood animals more competitive
Constraints caused by the way DNA mutates and the way natural selection works.: