Download Evolution.notebook 1 May 12, 2011

Evolution.notebook
May 12, 2011
Evolution ­ process of change over time
Theory of Evolution ­ existing forms of life on earth have evolved from earlier forms over long periods of time
Evidence of Evolution:
1. Geological Record ­ shows earth is 5 billion years old
2. Fossils ­ remains or traces of organisms that no longer exist
* Age of fossils determined by ­ dating of the rocks in which it is found
* Found preserved in ­ ice, tar, amber
* Formed by petrification ­ process where tissues are replaced by minerals that make it turn stone­like.
* Fossils found in lower strata (layer) ­ older and simpler
* Fossils found in upper strata ­ younger and more complex
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* Resemblances exist between layers of strata ­ possible link between modern and primitive species
* If no resemblances ­ organisms die out
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3. comparative anatomy­­study similarities in structure of related organisms
a. homologous structures­­body parts similar in structure even though their function may differ, suggest common ancestry ex. Bone structure in a whale's flipper, forearm of a human, and wing of a bat
b. Purpose of homologous structures: suggests a common ancestor
Analogous Structures: same function; different structure
Example: bird and insect wing
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Vestigial Structures: nonfunctional structures that are remnants of structures that were functional in ancestors
Example: tailbone­ remnant reptilian tail
appendix ­ remnant digestive sac
fly does not have bones in its wing
4. Comparative Embryology: comparison of early stages of development
Purpose: if embryos of different species are very similar, it suggests a common ancestry
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5. Comparative Cytology ­ cell organelles are compared between organisms
6. Comparative Biochemistry ­ structure and function of DNA, RNA, proteins, enzymes are similar in closely related organisms
Example: Organism # of amino acid differences
Chimp
Cow
Frog
0
10
20
THEORIES OF EVOLUTION
1. Lamark ­ Evolution has 2 principles
a. Law of Use and Disuse ­ the more you use a body part, the stronger it becomes
b. Inheritance of Acquired Characteristics ­ organisms develop characteristics by use/disuse and pass them on to their offspring
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Disproved by Weismann ­ * cut off tails of mice for 22 generations
* In each generation, mice were always born with tails
* So, acquired characteristic of no tails was not inherited.
Charles Darwin
2. Darwin ­ best known theory based on presence of variations among members of a species and natural selection
d. Adaptation ­ any kind of inherited trait that improves an organism's chance for survival
a. overpopulation ­ too many offspring produced in an area
e. Survival of the Fittest ­ only the "best fit" organisms survive and reproduce because of their adaptations and variations
b. competition ­ resources are limited c. variation ­ different characteristics of the organisms in a species. Comes from:
* meiosis/sexual reproduction
* random gene & chromosome mutations
f. Natural Selection ­ the environment determines which adaptations and variations are helpful or harmful. Nature selects which organisms survive.
* thick fur ­ helpful in cold * thin fur ­ harmful in cold
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g. Reproduction ­ organisms with helpful variations tend to survive and reproduce, passing on variations to their offspring
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http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
h. Speciation ­ development of a new species will occur as variations accumulate in a population over time
1. Industrial Melanism - development of
dark colored organisms in a population
exposed to industrial air pollution
Example: peppered moth in England
* before 1850 - moth was light colored,
a few were black
* 1850-1900 - heavy industrialization
causes smoke to darken trees
*After 1900 - moths are black
* In non-industrialized areas, light colored
moths continue to predominate
WHY DID THIS CHANGE OCCUR???
Dark gene was already
in
population
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2. Bacterial Resistance to Antibiotics
3. Insect Resistance to DDT
• Antibiotics usually kill bacteria
• Once antibiotics became common, resistant
strains of bacteria began to appear
• Antibiotics were no longer effective in killing
those strains
• DDT - insect spray
• Some insects have a natural resistance
(genetic) to DDT
• When DDT-sensitive insects were killed
by spraying, the DDT-resistant insects
survived & passed on their natural DDT
resistance to their offspring
WHY??????
Modern Theory of Evolution
includes both Darwin's ideas of variation and
natural selection and the genetic basis of
variations in populations. Change in gene
frequency over time.
2. Reproductive Isolation ­ * In time, organism will evolve into a new species
* Isolated population will eventually become so different that they cannot interbreed even if barrier is removed.
Factors that cause speciation:
1. Geographic isolation ­ * Changes in genes that lead to a new species are more likely to occur in smaller populations
* These populations can be segregated by a geographic barrier (water, mountains...)
Environment is the major cause for adaptations!
Types of Adaptations:
1. Structure ­ involve physical body of organism (wings, fins, legs...)
2. Physiology ­ involve metabolism of organism (poison venom of snake, spider web)
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3. Behavior - involve actions of organism
(mating, migration, hibernation)
* Warning Coloration - colors of animal
make it obvious to predators due to
nasty taste. Predator learns its lesson
after one bite.
4. Protection * Camoflauge - blend into background
(flounder, fawn, chameleon)
Monarch
butterfly
* Mimicry - one organism is protected
from predator by its resemblance to
another species
Snake Mimicry
http://chalk.richmond.edu/education/projects/webunits/adaptations/snake.html
Monarch
butterfly
Viceroy
butterfly
Time Frame for Evolution:
1. Gradualism - evolutionary change occurs
slowly, gradually, and continually. Small
variations accumulate and cause
reproductive isolation and a new species
2. Punctuated Equilibrium:
species have long periods of stability
interrupted by geologically brief periods
where major changes occur possibly leading
to the evolution of a new species
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Heterotroph Hypothesis ­ 1st life forms on earth were heterotrophs and had to obtain nutrients from the environment
* Supported by the Miller/Urey experiment
* devised apparatus and simulated conditions of primitive earth
* showed that in the presence of heat & electrical energy, gases could combine to form simple organic compounds
* Primitive Earth's atmosphere ­ *No free oxygen. Only H2, NH3, CH4, & H2O vapor gases
*hot, lightning, UV light, radiation from rocks
* 1st pre­cell ­ simple molecules ­> complex molecules ­> clusters ­> heterotrophic cells (anaerobic respiration)
* Rise of photosynthesis ­ anaerobic respiration resulted in buildup of CO2 in atmosphere. Some heterotrophic cells adapted to use CO2 to make organic compounds. These heterotrophic cells became the 1st autotrophs (plants). O2 was then produced.
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