Goal 3 - Evolution (The Origin of Life)
The Origins of Life
The process of evolution involves a series of natural changes that cause species (populations of different organisms) to arise, adapt to the environment, and become extinct.
All species or organisms have originated through the process of biological evolution.
In populations, there are variations or differences between individual members because of the variety of genes (alleles).
Evolution occurs when there is a change in the genes (the chemical molecule, DNA) inherited from the parents and especially in the proportions of different genes in a population.
These variations in genes arose for either 1) recombination of alleles when they sexually reproduce or 2) mutations
Recombining genetic material can happen in three ways
Mutations are usually neutral or harmful. Sometimes they can be beneficial if the environment is under a state of change.
Evolution does not change any single individual. Instead it changes the inherited means of growth and development that typify a population (a group or part of individual of the same species living in a particular habitat).
Human evolution took place as new genetic variations in early ancestor populations favored new abilities to adapt to environmental changes and so altered the human way of life.
The process of evolution involves a series of natural changes that cause species (populations of different organisms) to arise, adapt to the environment, and become extinct.
- EVOLUTION = CHANGE
All species or organisms have originated through the process of biological evolution.
- In animals that reproduce sexually, including humans, the term species refers to a group whose adult members regularly interbreed, resulting in fertile offspring (offspring themselves capable of reproducing).
- Scientists classify each species with a unique, two part scientific name. In this system, modern humans are referred to as Homo sapiens.
In populations, there are variations or differences between individual members because of the variety of genes (alleles).
- Examples skin color in humans, coat color in foxes
Evolution occurs when there is a change in the genes (the chemical molecule, DNA) inherited from the parents and especially in the proportions of different genes in a population.
These variations in genes arose for either 1) recombination of alleles when they sexually reproduce or 2) mutations
Recombining genetic material can happen in three ways
- Independent assortment
- Crossing over during meiosis
- Combining egg and sperm when fertilization occurs
Mutations are usually neutral or harmful. Sometimes they can be beneficial if the environment is under a state of change.
- Point mutation – change in a single base pair in DNA.
- Frame shift – a single base pair is added or deleted from DNA.
- Chromosome Mutations – mistakes that affect the whole chromosome.
- Deletion Mutation – chromosome segments breaks off and does not reattach itself à new cell lacks genes carried by the segment that broke off.
- Duplication or insertion Mutation – Chromosome segments attaches to a homologous chromosome that has lost the complementary segment. Result one chromosome carries two copies of one gene.
- Inversion Mutations – A segment of chromosome breaks off and then reattaches itself to the original chromosome backwards.
- Translocation Mutations – A chromosome segment attaches itself to a nonhomologous chromosome.
Evolution does not change any single individual. Instead it changes the inherited means of growth and development that typify a population (a group or part of individual of the same species living in a particular habitat).
- Parents pass adaptive genetic changes to their offspring, and ultimately these changes become common throughout the population.
- As a result, the offspring inherit those genetic characteristics that enhance their chances of survival and ability to give birth, which may work well until the environment changes.
- Over time, the genetic changes can alter a species overall way of life, such as what it eats, how it grows, and where it can live.
Human evolution took place as new genetic variations in early ancestor populations favored new abilities to adapt to environmental changes and so altered the human way of life.
Theories for Origin of Life
Spontaneous generation or Abiogenesis
Early theory that held that some organisms originated from nonliving materials
Life comes from other living things
Early theory that held that some organisms originated from nonliving materials
- Generation of life from nonliving matter
- They spontaneously are alive.
- POOF they appear!
- Examples decaying meat produced maggots, mud produced fishes, and grain produced mice.
Life comes from other living things
- Life originated from preexisting life
Experiments to Disprove Abiogenesis or Spotaneous Generation
Pasteur
Experiment 2
- Louis Pasteur: Designed an experiment using an S-shaped flask that disproved abiogeneis in microorganisms. Set up experiment in which air, but no microorganisms, was allowed to contact broth that contained nutrients. His experiment showed that microorganisms do not arise in the broth, even in the presence of air. Proved biogenesis that living organisms come from other living things.
Oparin
Early Atmosphere and Conditions on Earth
- In early 1920’s AI Oparin proposed that the atmosphere of the early Earth was a reducing one, containing very little oxygen. The atmosphere contained water vapor, carbon dioxide, nitrogen, methane and ammonia.
- Because there was no protective ozone layer in the atmosphere, a much higher percentage of ultraviolet radiation reached the surface of the earth.
- Lightening strikes were probably more frequent in the early atmosphere.
- Oparin hypothesized that these condition were favorable for the spontaneous, abiotic synthesis of organic molecules. He hypothesized that life began in the oceans. He suggested that energy from the sun, lightening and Earth’s heat triggered chemical reactions to produce small organic molecules from the substances present in the atmosphere. The rain probably washed the molecules into the oceans to form what is often called the primordial soup.
Urey and Miller
The Miller-Urey Experiments
Stanley Miller and Harold Urey tested the reducing atmosphere hypothesis of Oparin. They simulated the conditions of early Earth by constructing an apparatus, which contained water, hydrogen, methane and ammonia (to simulate early atmosphere).
These constituents were subjected to heat (to simulate earths internal heat) and an electric charge (to simulate lightening) for a number of days. They cooled the mixture of gases to simulate rain and collected the liquid (distillate) in a flask. A week later, the distillate was checked to determine whether any complex organic molecules were present. They found some amino acids, sugars and lipids.
Stanley Miller and Harold Urey tested the reducing atmosphere hypothesis of Oparin. They simulated the conditions of early Earth by constructing an apparatus, which contained water, hydrogen, methane and ammonia (to simulate early atmosphere).
These constituents were subjected to heat (to simulate earths internal heat) and an electric charge (to simulate lightening) for a number of days. They cooled the mixture of gases to simulate rain and collected the liquid (distillate) in a flask. A week later, the distillate was checked to determine whether any complex organic molecules were present. They found some amino acids, sugars and lipids.