Biology

The Origins of Life: How did it begin?



Evolution attempts to answer the same questions using science.



Some interesting things to consider:

-At present: there are 30-40 million species alive today

• this constitutes about 1% of all the species that have EVER lived on this planet


• this means about 99% of species that have ever lived are extinct

In the beginning: 1 species

Evolution=change/time

There are two components: change and time

• Is there evidence that life has changed througout the history of this planet?


• How long did this take? Is there evidence to support this?

SOME EARLY IDEAS AND IMPORTANT CONTRIBUTIONS:

1. Charles Bonet: 1720-1793

• Proposes that evolution occurs through a series of catastrophes

Minerals --> Plants --> Animals --> Intelligent Beings (humans) --> angels

• One of the first to use term evolution in a scientific sense

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Jean Baptiste Lamarck: 1744-1829

• A naturalist has made significant contributions in the areas of botany and invertebrate zoology


• One of the first to proponents of the idea that evolution occurs in accordance with natural laws


• Developed the famous evolutionary idea: "The Inheritance of Acquired Traits"

1. The Principle of Use and Disuse- the more a particular organ or structure is used, the more it will develop. The less an organ is used, the more it will deteriorate over time

2. In a struggle for survival, an individual's traits will be pushed to improve via this force

3. Once structure is modified via use and disuse, the modification is passed on to the offspring.

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August Weisman: 1834-1914

• Disproved Lamarck's idea of the inheritance of acquired traits


• Cut the tails off of mice (an acquired characteristic) for 21 generations


• 22nd generation still had tails

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Charles Lyell: 1797-1875

• 1830- Wrote "Principles of Geology"


• suggests earth was formed via a slow and gradual process: uniformitaranism
• contrasted catastrophism, which went hand-in-hand with biblical chronology
• in summary...it suggests that the earth is much older than we thought

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Charles Darwin: 1809-1882

• came from a prestigious family in England; father was a well known surgeon
• father wanted him to follow in his footsteps, but Charles could not stand the brutality of current medicine
• preferred the work of a naturalist: geology, botany, zoology, taxonomy, etc.
• father sent him to Cambridge University to become a clergyman
• at Cambridge, Darwin continued his studies as a naturalis and became well respected in this field
• 1831: Darwin takes the unpaid position as ship naturalist aboard the HMS Beagle
• the expedition's purpose is to chart the coast line of South America
• the voyage took 5 years
• Darwin's job was to study and collect specimens of the native plants, animals, and geology

SOME IMPORTANT INFLUENCES ON DARWIN:

• Charles Lyell: Geologist that wrote "Principles of Geology"

-suggests the earth is very old (contrary to popular belief)

• Thomas Malthus: Economist that wrote a paper on human population growth

-populations grow faster than the environments ability to support them

-this leads to competition

• Physical Environment and Wildlife:

-the geology of the earth and the variety of plant and animal life is like nothing he's ever

seen before

GALAPAGOS ISLANDS:

• series of small volcanic islands 600 miles off the coast of Ecuador
• located along the equator
• amazing variety of wildlife
• home to many endemic species (found no where else in the world)
• many species vary from island to island (similar but different)
• variations seem to fit with the physical environment in which the organisms live
• each island had a slightly different species of finch
• beak size and shape was one difference that interested Darwin
• the beak structure fit with the food source that was available on each island

DARWIN'S CONTROVERSIAL BOOK: ON THE ORIGIN OF SPECIES

• although it was not his passion, Darwin was trained as a clergyman and was still a religious person
• before his voyage, he was a strong proponent of devine design (a literal explanation of earth's history and evolution based on biblical standards)
• as the voyage progressed, he began to form new opinions on this matter
• 1838: he formed the theory of natural selection
• for fear of religious and social prosecution he did not publish this idea
• 1858: Darwin learns that Alfred russel Wallace has independently developed a similar theory; this persuades Darwin to publish jointly with Wallace

DARWIN'S THEORY: NATURAL SELECTION

1. Variation: there is genetic variation within a population

• every individual is slightly different from the next
• examples: some cheetahs are faster or larger than other cheetahs

2. Adaptation: some of these variations are favorable - 'adaptations'

• a characteristic that is genetically controlled
• gives the organism some advantage - increases the chance of survival
• example: walking stick's shape and color hides it from predators

3. Survival: not all offspring can survive

• organisms produce far more offspring than can possibly survive
• why can't they all survive? living factors-predators, disease, weather, competition for food and space, etc.
• overpopulation leads to competition
• who will survive? individuals with adaptations "survival of the fittest"
• fitness: an individual's ability to reproduce and pass on its genes

4. Reproduction: organisms that DO survive will reproduce and pass on its adaptations to their offspring

• organisms with favorable traits are more likely to survive and mate with organisms that have similar traits
• this produces offspring that also produce these favorable traits

5. Change/Time: Over long periods of time, these characteristics will increase in a population and the nature of the population will gradually change

• these changes accumulate within the population generation after generation
• this process takes an extremely long amount of time
• individuals DO NOT evolve in their lifetime! a species will evolve over many generations

KEY POINTS TO REMEMBER:

• the organisms have no control over this process! we cannot choose to evolve
• the natural environmental conditions and resources are what drive this process. hence the name: natural selection