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Introduction into evolution (click Picture). Evolution Notes. What accounts for the diversity of life?. 1. Evolution — change over time ; process by which modern organisms have descended from ancient organisms. 2. Components of genetic code common to all organisms

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what accounts for the diversity of life

Evolution Notes

What accounts for the diversity of life?

1. Evolution—change over time; process by which modern organisms have descended from ancient organisms


2. Components of genetic code common to all organisms

a. DNA bases (ATGC)

b. Converting glucose to ATP for energy.

theories of evolution
Theories of Evolution
  • Scientific theory – a well supported testable explanation of natural phenomena that is subject to change with new research and as new technologies are available.

EX. Gravity, plate tectonics


2. Lamarck—Theory of Acquired Characteristics

a. By selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime; these traits could then be passed on to their offspring.

Example: Giraffe could not reach the leaves so it stretched it’s so that all of its offspring had long necks.

b. Problem: Did not know how traits were

inherited—GENETICS (meiosis!!!)


Over timenatural selection results in changes in the inherited traits of a population

3. Darwin—Evolution by Natural Selection


You inherit blue eyes or curly hair from your parents.

You acquire athletic skills or the ability to play a musical instrument

darwin s influences
Darwin’s Influences

1. Made observations in Galapagos Island as a naturalist-(travelled on a boat called HMS Beagle)

a. Observations made:

  • i. Similar species well suited to the environment they
  • inhabited (lived in).

ii. Traits of similar species varied noticeably among different islands of the Galapagos

b. Example: Noted similarities and differences in tortoises and finches on Galapagos Islands in South America.

c. Hypothesized that animals adapted to local conditions on islands after their arrival.


2. Hutton and Lyell (studied geology)

a. Helped scientists recognize that Earth is many millions of years old; older than anyone believed

3. Malthus (studied human populations)

a.If the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone creating a struggle to survive


4. Farmers and Artificial Selection—Nature provided the variation among organisms and humans selected for the variations they found useful

  • Example: Farmer breeds largest hogs for most meat production.
natural selection
Natural Selection

1. Struggle for existence—more offspring are produced than can survive; therefore, members of each species compete regularly to obtain food, living space, and other necessitiesof life


2. Survival of the Fittest (also called Natural Selection)—individuals with an adaptation (genetic difference) that makes them more “fit” for a certain environment will survive and reproduce; those not suited will die or produce few offspring


3. Descent with modification- each living species has descended, with changes, from a common ancestor. (Phylogeny)

  • 4. Darwin’s conclusions are published in a book called “Origin of Species”
evidence of evolution 5 different types
Evidence of Evolution(5 different types)

1. Fossil record- examples of many species that have lived for a time and then became extinct


2. Geographical Distribution of living species— when looking at similar environments on different continents, different animals had similar anatomies and behavior because of adaptation


Geographical Distribution of Species




Beaver andMuskrat



Coypu andCapybara





3. Homologous body structures—structures that have different mature forms but develop from the same embryonic tissues; provide strong evidence that all four-limbed vertebrates have descended, with modifications, from common ancestors

Comparative anatomies realized that although these vertebrates evolved in different directions, with changes in size, shape, and function, they all used common bone elements, as well as homologous nerve systems, blood circulatory systems, and other organ systems, thus indicating a common vertebrate ancestor. In contrast to teleological explanation that emphasize design for particular function, the vertebrate forelimb uses a common underlying ancestral structure for different functions.


Homologous Body Structures





Ancient lobe-finned fish


4. Vestigial organs – organs with functions that are useless in current organisms, but functional in distant ancestors.

  • Ex. Existing leg bones in pythons, hip bones in whales

5. Similarities in embryology—early stages, or embryos, of many animals with backbones are very similar

evolution of populations
Evolutionof Populations

1. Populations—all individuals of a species that live together in one area

2. Gene pool—consists of all genes, including all the different alleles that are present in a population


Sources of Genetic Variation

  • (Where do differences come from?)
  • 1. Mutations—change in a sequence of DNA
  • 2. Gene shuffling—occurs during the independent assortment of chromosomes and crossing over of genes during meiosis

Genetic drift – a random chance in allele frequency. Certain individuals may leave more descendants than others, and over time this can cause an allele to become common in the population.

Not caused by natural selection, but by chance.


How new species form

  • (Speciation)
  • Species determined by organisms that reproduce naturallyonly with each other
  • Speciation occurs when a population that has been isolated for an extended period of time. They become reproductively isolated from each other.

a. Behavioral Isolation—two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior.

Eastern meadowlarks will not respond to western meadowlark mating songs.

Western meadowlark

Eastern meadowlark


b. Geographic Isolation—two populations are separated by geographic barriers such as rivers,mountains, or bodies of water


c. Temporal Isolation—two or more species reproduce at different times

3 similar species of orchid live in the same rain forest. Each species releases pollen only on a single day. Because the 3 species release pollen on different days, they cannot pollinate (reproduce with) one another.

mark your calendars
Mark your calendars!

Evolution quiz on Thursday January 13th!