1.
• Identify the relationship between the conditions on early Earth and the origin of organic molecules:
- Conditions of early Earth:
_ Massive oceans existed
_ Only small landmasses above the surface of the water
_ No ozone layer
_ Large amounts of radiation reached the Earth
_ No free oxygen in the air
_ Large amounts of volcanic activity; heat, ash, dust and gases into atmosphere
_ Violent electric storms common
_ Atmosphere contained some water vapour (H2O), hydrogen (H2), hydrogen cyanide (HCN), a lot of carbon dioxide (CO2), nitrogen (N2), possibly ammonia (NH3) and methane (CH4).
- The chemicals of life are contained within the following basic organic compounds: water, carbohydrates, lipids, proteins, and nucleic acids.
- These compounds are made up of hydrogen (H), oxygen (O), carbon (C), nitrogen
(N) and some other common elements.
- As you can see, the elements needed to create the basic organic compounds were already present in the atmosphere; i.e., H, O, C and N were already there.
- The lack of an ozone layer, the frequent violent electric storms, and the volcanic activity of early Earth could have provided the energy for molecules to be formed.
• Discuss the implications of the existence of organic molecules in the cosmos for the origin of life on Earth:
- For life to have originated, the following events need to have happened:
_ The required chemicals need to have been formed
_ These chemicals need to have come together in a self-replicating body
_ This body would need to have a form of protection for its contents
_ It had to be able to use an energy source to replicate itself
- The first step needed for life to be formed would be that the organic molecules needed for life would have to be present
- These organic molecules could have been formed here on Earth, or been sent to Earth from outer space (the cosmos)
• Describe two scientific theories relating to the evolution of the chemicals of life and discuss their significance in understanding our origin of life:
- Theory 1: The chemicals for life came from outer space:
_ Before an atmosphere was formed, nothing stopped meteorites hitting the
Earth
_Scientists believe Earth was heavily bombarded with meteorites during formation _ Certain types of meteorites, called carbonaceous chondrites, have been found, which contain organic molecules, like amino acids
_ This provided evidence of organic molecules somewhere else in the universe
_ This means that the chemicals for life could have come from outer space
- Theory 2: The chemicals for life were formed on Earth:
_ Haldane and Oparin suggested that early Earth contained all the basic chemical components necessary for life
_ They hypothesised that complex organic molecules, like nucleic acids and carbohydrates, could have been created using inorganic molecules through slow reactions using energy from lightning or UV rays.
_ These complex organic molecules could have collected together on the surface of the oceans, forming a “soup”, which later could have formed cells
_ The theory was untested until the 1950s, when Urey and Miller tested it in the lab
• Discuss the significance of the Urey and Miller experiment in the debate on the composition of the early atmosphere:
- Urey and Miller performed the following experiment to prove Haldane and
Oparin’s theory:
_ A closed system was set up and powerful electrical sparks were passed through a chamber containing ammonia, hydrogen, and methane.
_ These chemicals were used because the scientists wanted to recreate the atmosphere of early Earth.
_ Steam was recycled and passed through the chemicals
_ After a week, the steam collected was red and turbid. When this water was tested, it was found to contain some amino acids.
- This experiment proved that, if early Earth did contain those chemicals, life could have formed from inorganic molecules.
• Identify changes in technology that have assisted in the development of an increased understanding of the origin of life and evolution of living things:
- The Urey/Miller experiment has been improved using modern technology
- UV radiation and carbon dioxide is used instead of electricity and ammonia and methane, to make the conditions in the closed chamber more like that of early Earth.
- Advances in technology that has increased our knowledge of the origin of life and evolution are the changes in chemical analysis, biochemistry and molecular biology.
- Other technological advances:
Technology Uses
-Microscope which Enabled the discovery or micro-organisms
-Radiometric Dating enabled to assign absolute dates to rocks/fossils
Has established age of the Earth as 4.5 billion years old
-Electron Microscopy which enabled scientists to study minerals, microbes and nature of rocks in detail.
Gas and Liquid Chromatography
Radioactive Tracing
Amino Acid and Nucleotide
Sequencing
Spectrophotometry
Enabled the comparisons between ancient organic material and biological material today • Gather information from secondary sources to describe the experiments of Urey and Miller and use the available evidence to analyse the:
_ Reason for the experiment:
- To test the hypothesis of Haldane and Oparin
- i.e. organic molecules could have been created on the surface of early
Earth, from inorganic molecules using energy from UV rays and lightning
_ Result for their experiment:
- After a week of electrical discharge and recycling steam through their apparatus, they analysed the condensed liquid
- It was found to contain amino acids, the building blocks of proteins
_ Importance of their experiment in illustrating the nature and practice of science:
- It showed that hypotheses and theories are welcomed in science, but are only accepted when backed up with scientific proof, that is, experiments.
_ Contribution to hypotheses about the origin of life:
- The results supported Haldane and Oparin’s theory that early Earth contained the basic chemical components for life
- It proved that complex organic molecules can be produced from basic chemical components or inorganic molecules
2.
• Identify the major stages in the evolution of living things, including the formation of:
_ Organic molecules
- The first stage of the evolution of life was the creation of organic molecules, either through synthesis from inorganic molecules, or from outer space
- These organic molecules began to clump together in a “soup”
_ Membranes
- A membrane had to be developed to protect the internal environment of the large organic molecule
- The internal environment, i.e. the contents began to evolve into nucleic acids and the primitive cell could now replicate
- RNA was thought to be the first genetic material
_ Procaryotic heterotrophic cells
- The first and simplest types of cells, like bacteria
- No membrane-bound nucleus or membrane-bound organelles
- These consumed other organic molecules to provide energy (heterotrophic)
_ Procaryotic autotrophic cells
- Some of the heterotrophic procaryotic cells developed pigments
- These pigments allowed them to use the energy from the sun to create food _ Eucaryotic cells
- These cells had membrane-bound nuclei and organelles
- Examples include animals, fungi, plants
_ Colonial organisms
- Colonial organisms are groups or colonies of similar cells, eg, stromatolites - All the cells in the colony have the same function; no differentiation
- They form when daughter cells from cell division become bound together
_ Multicellular organism
- These are groups of cells, where some cells have differing functions from others - Each cell has its own specialised function and all cells depend on each other - The organism functions as a coordinated whole
• Describe some of the paleontological and geological evidence that suggests when life originated on Earth paleontological evidence
- Fossils are found in sedimentary rocks, the oldest of which are 3800 million years old
- The earliest fossils are of 2 types:
_ Microfossils, these are similar to present day unicellular, anaerobic (does not need oxygen) procaryotic organisms
_ Stromatolites, layered clumps or photosynthetic cyanobacteria
- Modern stromatolites are found in Western Australia, Shark Bay
- Microfossil and stromatolite fossils are found in 3 places:
_ 3400 – 3500 mya rocks from Warrawoona Group, Western Australia
_ 2800 – 3000 mya rocks from Fig Tree Group, South Africa
_ 2000 mya rocks from Gunflint Chert rocks, Lake Superior, North America
Geological evidence
- ancient rocks contain chemical evidence that metabolism by bacteria was underway. Geologists have described ancient (2.5 billion years) rocks called banded iron formations. The alternate bands of iron rich and silicon based sediments are believed to have derived from seasonal fluctuations of the activity of several types of bacteria.
- geologists have also used sedimentary records of pyrite, a form of iron. Evidence from these old rocks has been used to suggest that oxygen started to build up in the atmosphere, which suggests of photosynthesis in living organisms.
• Explain why the change from an anoxic to an oxic atmosphere was significant in the evolution of living things: the change from anoxic to oxic atmosphere was gradual as a result of photosynthesis, releasing more free oxygen in the atmosphere. This change in the environment was significant in the evolution of living things due to the following consequences:
-expansion of eukaryotes, resulting in an explosion of diverse forms of plants and animals.
-development of the ozone shield protecting life against UV radiation, as a result of increasing levels of atmospheric oxygen.
-the evolution of life forms able to carry out aerobic respiration, this has enabled multicellular organisms to develop and leave a much more active and complex existence.
• Discuss the ways in which developments in scientific knowledge may conflict with the ideas about the origins of life developed by different cultures: - Science: Evolution; all organisms are constantly changing, not created, but evolved. - Christians: They believe in Biblical creationism; all organisms created as they are by God, no change over time
- Chinese: Believe the first organism was P’an Ku, who evolved in a giant cosmic egg. All elements of the universe were in the egg, all mixed. In the egg, he separated the opposites, then 18,000 years later the egg hatched, and P’an Ku died from the effort of creation.
- Greek: Aristotle’s ideas that the whole universe had a hierarchy and that it started from rocks, up through plants and animals, to humans, and finally to God.
- Romans: Lucretius, a Roman philosopher believed there was no God, because the universe was so imperfect. It was made of particles all squeezing together.
- As you can see, science contradicts with the belief of many people.
-Aboriginals: Dreamtime; great supernatural beings existed in the dreamtime and created the Earth and everything in it