CH. 16 - Evolution

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Keywords

1. General

1. Adaptive advantage - a variation in genetic that imparts an advantage

2. Evolution - change in genetic makeup in a population over time

2. Evidence of Evolution

1. Actual remains - with teeth, bones, etc found in rock, tar pits, ice, amber

2. Amber - fossilized resin of tree

3. Analogous Structure - similar structure, different origin.  Wing of insect vs wing of bird

4. Cast - minerals deposited in molds

5. Homologous structure - similar structure, similar origin

6. Imprints - impressions left by an organism

7. Molds - form in hollow spaces of rocks with the organism decayed

8. Petrification - minerals replace the cells of an organism

9. Reproductive isolation - interbreeding impossible after enough changes accumulated

10. Vestigial structures - structures appear to be useless but had ancestral functions

3. Theories of Evolution

1. Natural selection - the fittest survive

2. Use and disuse - Lamarckian Evolution that's disproved

4. Forces of Evolution

1. Adaptive Radiation - emergency of number of lineages from single species to adopt to different niches

2. Allopatric speciation - geographic barrier that leads to speciation

3. Bottleneck effect - majority of population died, resulting gene pool not representative

4. Convergent Evolution - unrelated species becoming more similar in feature to adapt to same environment

5. Deme - small local population that breed with each other only

6. Divergent Evolution - two or more similar species becoming more dissimilar

7. Dominant allele - letter p is used to represent this gene locus

8. Founder Effect - small colonizing population that leads to genetic drift

9. Gene flow - migration of individuals between different populations

10. Gene frequency - decimal fraction representing the presence of an allele

11. Gene pool - sum of all the alleles for any given trait in population

12. Genetic Drift - changes in composition of gene pool due to change

13. Hardy-Weinberg Principle - certain equilibrium exist in all genes in gene pool with conditions that must be met

14. Parallel Evolution - predators and prey coevolve

15. Phylogeny - study of the evolutionary history

16. Population - all members of a particular species in a given location

17. Recessive allele - letter q is used to represent this gene locus

18. Sympatric Speciation - 1 mutation causing a reproductive barrier

5. Origin and Early Evolution of Life

1. Primordial soup - early molecules that are miscible with one another and formed simple monomeric molecules after years

2. Coacervate droplets - colloidal protein molecules that absorbs substances from surrounding

  

Evidence of Evolution

1. Fossil record

1. General

1. Most direct evidence of evolutionary change

2. Represent the remains of extinct ancestor

3. Generally found in sedimentary rocks

2. Types of fossils

1. Actual remains - with teeth, bones, etc found in rock, tar pits, ice, amber

2. Petrification - minerals replace the cells of an organism

3. Imprints - impressions left by an organism

4. Molds - form in hollow spaces of rocks with the organism decayed

5. Cast - minerals deposited in molds

3. Significant fossil remains found

1. Trilobite - primitive crustacean in early Paleozoic era

2. Dinosaurs - ancient animals similar to birds and reptiles in Mesozoic era

3. Eohippus - primitive horse the size of fox

4. Woolly mammoth - hairy elephant in Siberian ice

5. Saber-tooth tigers - found in asphalt tar-pit

6. Insects - preserved in amber (fossilized tree resin)

7. Archaepteryx - missing links between reptiles and birds

2. Comparative Anatomy

1. Homologous structures

1. Same basic anatomical features and evolutionary origin

2. Same evolutionary origins

2. Analogous structures

1. Similar functions

2. Different evolutionary origins and entirely different patterns of development

3. Example: wings of fly versus wing of birds

3. Comparative Embryology

1. Stages of development that shows common ancestry

2. The earlier in stage that the development of embryo diverge, the more dissimilar the adult form will be.

1. Thus, embryo of monkey and human can't be differentiated until much later in development

3. Examples of Evolution: Avian embryo has teeth, mollusks resemble annelids, human embryo has a tail

4. Comparative Biochemistry (physiology)

1. Organisms with the same basic needs and metabolic processes

2. The closer the two organisms in comparison, the closer the genetic makeup

3. Bloods of closely related organisms are very similar

4. The more different the biochemical characteristics, the earlier the divergence of two species

5. Vestigial Structures

1. Structures that appear useless but had ancestral function

2. Appendix

1. Small and useless in humans

2. In herbivores, it assists in digestion of cellulose

3. Tail - Human, tail is reduced to few useless coccyx

4. Splints - horse has them as vestigial remains of 2 side toes of Eophippus

5. Python - has legs which are reduced to useless bones

6. Geographic Barriers

1. Some species migrate after multiplication

1. Lessens intraspecie competition

2. When barrier happens, genetic adaptation on either side of barrier might happen

2. Each population would evolve specific adaptation to the environment in addition to other neutral changes

3. If interbreeding doesn't happen (from geographic barrier), eventually, the species won't be able to interbreed even if barrier were removed

Theories of Evolution

1. Lamarckian Evolution

1. Discredited

2. New organs or changes in existing ones arose because of the need

3. "use or disuse"

4. Inheritance of acquired characteristics

1. The more muscle mass my daddy has, the more I'd have

2. Disproved - only changes in the DNA of sex cells, can changes be inherited

2. Darwin's Theory of Natural Selection

1. General

1. Survival of the fittest

2. Many basic agents that'd lead to evolutionary change

2. Overpopulation

1. More offspring are produced than can survive, thus the fittest of the brood survive

3. Variations

1. Offspring showing different characteristics that parents and might have an advantage for survival

4. Competition

1. Struggle for survival, competing for necessities of life

5. Natural Selection

1. Some organisms have adaptation that allows it to survive

6. Inheritance of the variations

1. The individuals that survive live to reproduce

2. When reproduce, the favorable variation is passed on

7. Evolution of new species

1. Favorable changes are perpetuated

2. Eventually, enough changes lead to a new specie

Forces of Evolution

1. Population Genetics

1. General

1. Population includes all members of a particular species in a given location

2. Gene pool - sum of all the alleles for any given trait in population

3. Gene frequency - decimal fraction representing the presence of an allele

4. Dominant allele - letter p is used to represent this gene locus

5. Recessive allele - letter q is used to represent this gene locus

6. For any gene locus, p + q = 1

2. Hardy-Weinberg Principle

1. When conditions are met, then the Hardy-Weinberg Equation can be used

1. Population is very large

2. No mutations that affect the gene pool

3. Mating between individuals is completely random

4. No net migration into or out of the population

5. The genes in the population are all equally successful at reproduction

2. p + q = 1

3. p2 + 2pq + q2 = 1

1. p2 = frequency of dominant homozygote

2. 2pq = frequency of heterozygote

3. q2 = frequency of recessive homozygote

2. Microevolution

1. Hardy-Weinberg condition does not persist for long in nature

2. Real populations suffers from unstable gene pool, and migrating populations

1. Natural Selection

1. phenotype with favorable variations are selected

2. Mutation

1. Gene mutations change allele frequency in population

2. Gene equilibrium is altered

3. Assortive Mating

1. Mates not randomly chosen

2. Selected via proximity and phenotypes

1. Relative genotype ratios will be affected

1. Depart from the Hardy-Weinberg equilibrium

3. On the whole, the frequencies in the gene pool is unchanged

4. Genetic Drift

1. Changes in composition of gene pool due to change

2. Bottleneck effect - population drastically reduced

1. Some alleles over-represented, some under-represented, some disappeared

3. Founder effect -

1. Gene pool doesn't represent the original population

2. Few individuals colonize new habitat

4. Gene flow - migration of individuals between populations resulting in loss or gain of genes, thus changing the population's gene pool

3. Speciation

1. Evolution of new species that can no longer interbreed

2. Demes

1. Small local population

2. Members of a deme resemble each other more than other demes nearby

3. Mating between same deme occurs more frequently

3. Development of New Species

1. Gene flow impossible between two idifferenet species

2. Events that lead to speciation

1. Genetic variation

2. Environmental changes

3. Migration to new environment

4. Adaptation to new environment

5. Natural selection

6. Isolation

3. Allopatric speciation - physical barrier

4. Sympatric speciation - no barrier

4. Adaptive Radiation

1. Emergency of a number of lineages from a single ancestral species

2. Each specie adapts to a distinct niche

3. Such speciation minimizes competition

5. Evolutionary History

1. Phylogeny - study of evolutionary history between species

1. Ancestor at the trunk

2. Modern species at the tip of branches

2. Convergent Evolution

1. Groups within the branches develop in similar ways to adopt to similar environments

2. Fishes and dolphin both developed same features but came from different classes of vertebrate

3. Parallel Evolution

1. Groups that faced similar though geographically separate environment with a similar ancestor

2. Example - placental wolf, anteater, mouse and mole

4. Divergent Evolution

1. Two or more related species becoming more dissimilar due to environmental factors

5. Isolation

1. Genetic isolation that results in speciation

Origin and Early Evolution of Life

1. The Heterotroph Hypothesis

1. General

1. First form of life lacked ability to synthesize their own nutrients

2. Molecules must already exist

3. Primitive sea of inorganic and organic compounds

1. Energy like lightning might have led to synthesis of simple organic molecules such as sugar, amino acids, purines, and pyrimidines

2. Evidence of Organic Synthesis

1. Stanley L Miller in 1953

1. Application of UV radiation, heat with methane, hydrogen, ammonia, and water

1. Forms complex organic compounds

2. After one week, the liquid in the apparatus contained

1. Urea, hydrogen cyanide, acetic acid, lactic acid

3. Formation of Primitive Cells

1. Coacervate droplets

1. Colloidal protein molecules that clump up to form coacervate droplets

1. Collodial molecules surrounded by shell of water

2. absorb and incorporate substances from surrounding environment

3. developed on early Earth

4. Possess properties that associated with living organisms

2. Most of these coacervate droplets were unstable

1. Few might be stable enough to survive and probably mutated into first primitive cells with nucleic acid polymers that became capable of reproduction

2. Development of Autotrophs

1. The primitive heterotrophs evolved complex biochemical pathways

2. Evolved anaerobic respiratory processes

1. Not enough nutrients produced/existed

3. Autotrophic nutrition developed

1. Pioneer autotrophs developed primitive photosynthetic pathways to synthesize carbohydrates

3. Development of Aerobic Respiration

1. Primitive autotrophs fixed CO2 and released oxygen as waste

2. Oxygen turned the atmosphere from reducing to oxiding one

1. Some oxygen converted to ozone to block high energy radiation

2. The living organisms at the time destroyed the conditions that made their development possible

1. They must evolve to survive, thus aerobic pathways developed

4. General Categories of Living Organisms

1. All living organisms can be divided into four categories

1. Autotrophic anaerobes - chemosynthetic bacteria

2. Autotrophic aerobes - green plants and photoplankton

3. Heterotrophic anaerobes - yeasts

Heterotrophic aerobes - amoebas, earthworms, humans