saccone is the coolest chapter 30 the theory of evolution

SACCONE IS THE COOLEST

Chapter 30

The Theory of Evolution

http://www.nationalgeographic.com/features/outpost/ http://www.discovery.com/news/features/humanorigins/humanorigins.html

http://www.pbs.org/wgbh/nova/odyssey/debate/

http://www.nationalgeographic.com/features/outpost/



http://www.discovery.com/news/features/humanorigins/humanorigins.html











Evolution

• A process of change through time


Theory of Evolution1. Suggests that existing forms of life

on earth have evolved from earlier forms over long periods of time

2. Evolution accounts for the differences in structures, function, and behavior among life forms as well as changes that occur in populations over many generations


(I) Evidence of Evolution• Observations supporting the theory

of organic evolution can be made through the study of:

1. Geologic record

2. Comparative Cytology, Biochemistry, Anatomy, and Embryology


(A) Geologic Record1. Earth is between 4.5 to 5 billion

years old (age was determined by radioactive dating of rocks)

2. Fossils- are the remains of traces of organisms that no longer exist.

Fossils have been preserved in ice, sedimentary rock, amber, and tar


Tyrranosaurus rex


3. Other fossils have been formed from petrification, a process by which the tissues are gradually replaced by minerals that produce a stone replica of the original material

4. Imprints, casts, and molds of organisms or parts of organisms are frequently found in sedimentary rock

5. In undisturbed layers (strata) of sedimentary rock, the lower strata contain old fossils while the upper strata contain younger fossils


(B) Comparative Anatomy1. Evidence supports that

similarities of basic structures exist between different organisms

2. Homologous structures are anatomical parts found in different organisms in origin and structure

3. The presence of such homologous structures suggest that these organisms have evolved from a common ancestor


(B) Comparative Anatomy

Paranthropus boisei

Homo sapiens


(C) Comparative Embryology• Although certain adult

organisms may be different from each other, a comparison of the earl stages of their embryonic development may show similarities that suggest a common ancestor


(C) Comparative Embryology


(D) Comparative Cytology

1. All living things are made up of cells

2. Cell organelles including the cell membrane, ribosome's, and mitochondria are structurally and functionally similar in most organisms


Mitochondrion DNA and can replicate


(E) Comparative Biochemistry

• All living things contain similar biochemical compounds

• Examples would include: structure and function of DNA, RNA, and proteins (including enzymes) are similar in all organisms


(II) Theories of Evolution1. Attempts to explain the similarities

and differences among species2. Adaptations- are a major component

to these theories. Adaptations are features which make a species better suited to live and reproduce in its environment


(A) Jean Baptiste Lamark


(A) Lamark

• The evolutionary theory of Jean-Baptiste Lamark was based on the principle of:

1. Use and Disuse

2. Inheritance of acquired traits


Principle of Use and Disuse• For an organism, new structures appeared

in the course of evolution because they were needed. Structures that were present and were used became better developed and increased in size; structures that were not used decreased in size and eventually disappeared

Ex: muscles of an athlete vs. appendix


Inheritance of Acquired Traits• Useful characteristics acquired by an

individual during its lifetime can be transmitted to its offspring

• These acquired traits results in species that are better adapted to their environment

• Ex: a giraffe’s neck became longer as a result of stretching to reach higher branches. This acquired trait was then passed down to the offspring


Inheritance of Acquired TraitsArnold’s kids wouldn’t be “pumped”


(B) Weisman1. August Weisman did not agree with

Lamark’s theory of acquired traits2. In a series of experiments, Weisman removed

the tails of mice3. The mating of these tailless mice produced

offspring with tails of normal length4. Weisman removed the tails of these mice and

allowed them to mate5. Again, offspring were produced with tails of

normal length6. The acquired condition of “taillessness” was

not inherited


(C) Charles Darwin


(C) Darwin’s Ship the HMS Beagle


(C) Darwin• Charles Darwin devised a theory of evolution

based on variation and natural selection as seen in the Galapagos islands.

• Included in hid theory were five main ideas:

1. Overpopulation

2. Competition

3. Survival of the Fittest

4. Reproduction

5. Speciation


Overpopulation

• Within a population, there are more offspring produced in each generation than can

possibly survive


Competition• Natural resources; like food, water, and space available to a

population is limited• Because there are many organisms

with similar nutritional requirements, there must be

competition between them for the resources needed to survive


Survival of the Fittest• Variations among

members of a population make some of them better adapted to the environment than others

• It is generally the best-adapted individuals that will survive

• The environment is the agent of natural selection determining which species will survive


Reproduction

• Individuals that survive and then reproduce transmit these

variations to their offspring


Speciation

• The development of a new species occurs as variations or adaptations

accumulate in a population over many generations

• Ex: caveman present man


(III) Modern Theories of Evolution

• The modern theory of evolution includes both Darwin’s ideas of variation and natural selection

and the current knowledge of the sources of variations


(A) Sources of Variations

1. Segregation and the recombination of alleles during sexual reproduction

2. Gene mutation occurs spontaneously and at random


(B) Natural Selection1. Natural selection involves the struggle of organisms to

survive and reproduce in a given environment2. Traits which are beneficial to the survival of an

organism in a particular environment tend to be retained and passed on, and therefore, increase in frequency within a population

3. Traits which have low survival value to an organism tend to diminish in frequency from generation to generation

4. If environmental conditions change, traits that have low survival value may now have a greater survival value. Therefore, traits that prove to be favorable under new environmental conditions will increase in frequency


Ex: Insects resistant to insecticides1. Genetic make-up of some insects make them resistant

to the effects of insecticides

2. Before the widespread use of insecticides, this trait was of no particular survival value

3. With the increased use of insecticides, this trait developed a very high survival value

4. Therefore, insects with resistance to insecticides survived and reproduced much more successfully than those lacking the trait

5. As a result, the frequency of insecticide resistance has increased greatly in insect populations


(C) Geographic Isolation• Gene frequency- the percentage of organisms in a

population that carry an allele

1. Isolation of a population increases the chances for speciation (the development of a new species) by separating a small group of organisms from the main population with its large gene pool (inheritable traits)

2. Changes in gene frequency are more likely to occur in small populations than in large ones

3. Geographic isolation of a population is caused by natural barriers like mountains, large bodies of water, and deserts


4. The evolution of an isolated population into a new species may involve the following factors:

a) the gene frequency in the isolated population may have been different than the gene frequency in the main population to begin with

b) different mutations occur in the isolated population and in the main population

c) different environmental factors may also have exerted different selection pressures on each population (natural selection was different)


(D) Reproductive Isolation

• If the isolated population becomes so different from the main population that members of the two cannot interbreed and produce fertile offspring, then they have become two distinct species


(E) Time Frame for Evolution• There are two different theories proposed

by scientists to address the rate of evolution:

1. Gradualism- proposes that evolutionary change is slow, gradual, and continuous

2. Punctuated Equilibrium- proposes that species have long periods of stability (several million years) interrupted by geologically brief periods of significant change during which a new species may evolve


(IV) Heterotroph Hypothesis

• Is one proposed explanation for how life arose and evolved on primitive earth

• According to this hypothesis, the first life forms were heterotrophic and had to obtain their nutrients from the environment


(A) Primitive Earth• Based on assumption1. Earth was very hot consisting of inorganic

substances in all states: solid, liquid, and gas2. Many sources of energy including heat,

lightning, solar radiation(x-rays and U.V. rays), and radiation from radioactive rocks

3. The atmosphere consisted of water vapor, hydrogen, methane gas, and ammonia

4. As the earth cooled, water condensed in the atmosphere and rain fell forming seas described as “hot, thin soup”


(B) Synthesis of Organic Compounds

1. In the seas, (primordial soup) chemical bonds formed between the dissolved substances

2. Eventually, various types of organic molecules formed in the seas, including amino acids and simple sugars

3. More complex organic compounds were then formed by the interactions between the simpler molecules


(C) Nutrition1. Some of the large. Complex molecules

formed groupings or clusters called aggregates

2. These aggregates developed a surrounding “membrane”

3. It is believed that aggregates absorbed simple organic molecules from the environment for food

4. Therefore, they carried on a form of heterotrophic nutrition


(D) Reproduction

1. In time, as these aggregates became more complex and highly organized, they developed the ability to reproduce

2. At the point where the ability to reproduce had evolved, the aggregates were considered to be living cells


(E) Heterotroph to Autotroph1. It is thought that these early heterotrophic life

forms carried on a form of anaerobic respiration known as fermentation

2. As a result of the extended periods of fermentation, carbon dioxide was added to the atmosphere

3. Eventually, as a result of evolution, some heterotrophic forms developed the capacity to use carbon dioxide from the atmosphere to form organic compounds (food)

4. These organisms were the first autotrophs


(F) Anaerobes to Aerobes 1. Autotrophic activity (photosynthesis) added

free oxygen to the atmosphere

2. Over time, the capacity to use oxygen in respiration (aerobic) evolved in both autotrophs and heterotrophs

3. Present day organisms may be heterotrophic or autotrophic; aerobic or anaerobic

saccone is the coolest chapter 30 the theory of evolution

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