Preliminary BiologyModule 3 – Life on Earth

Kim Hua

1. Analysis of the oldest sedimentary rocks provides evidence for the origin of life.

Identify the relationship between the conditions of early Earth and the origin of organic molecules. Scientists argue that the universe was created 10-21 billion years ago which arose by a big bang,

causing universe to expand. Matter in the universe condensed into solar system. Earth believed to have formed around 4.5 billion years ago.

Early Earth Clouds of water vapour that had

originally surrounded the Earth condensed to form the oceans and seas but still hot.

One or two large landmasses existed. There was lots of volcanic activity.

Volcanoes poured out lava and ash. Atmosphere consisted of the gases

hydrogen, carbon monoxide, methane and ammonium but no oxygen (anoxic).

No ozone layer. Lots of electrical storms and Cosmo rays

producing explosive energy which was able to penetrate the thin atmosphere.

Believed first organic chemicals (organic substances) originated around 4 billion years ago.

Primitive cells originated abound 3.5 billion years ago.

Discuss the implications of the existence of organic molecules in the cosmos for the origin of life on Earth.Discovery of organic molecules on meteorites implies there are organic molecules in the cosmos. This means early Earth may have been ‘seeded’ with organic molecules from the cosmos and the first cells may have arrived from the cosmos. This has led to research in other areas to detect chemicals in outer space and the analysis of interstellar dust.

Describe two scientific theories relating to the evolution of the chemical of life and discuss their significance in understanding the origin of life.

There were three theories made by scientists relating to the evolution of chemical of life, of which one was proven incorrect.

Theory Description SignificanceSpontaneous generation For centuries humans believe

life spontaneously arises from non-living matter.

Proven incorrect through experiment made by Redi, Spallanzani and Pasteur.

Was believed for many years, until several scientists carried out an experiment.

Panspermia ‘Seeds’ from outer space led to life on Earth.

Scientists believed that meteorites (seeds) heavily bombarded Earth in early years. Some meteorites known as ‘carbonaceous’ were found containing amino acid, the building block of life.

Led to further research of meteorites into places like Mars e.g. NASA probes found extent of organic molecules in the cosmo and its potentioal role in origin of life.

Found that meteorites in Mars also contained amino acids.

Chemosynthetic theory Oparin and Haldane in the Urey and miller did an experiment to

Figure 1 - what early Earth may have looked like.

1920s, proposed theory that the conditions of early Earth’s atmosphere were able to form organic molecules, amino acid.

Slowly these led to life on Earth.

test Oparin and Haldane’s theory. Since then, many more experiments

have been performed to prove first life on earth.

Gather information from secondary sources to describe the experiments of Urey and Miller and use available evidence to analyse the:

- Reason for their experiments- Results of their experiments- Importance of their experiments illustrating the nature and practice of science- Contribution to hypotheses about the origin of life.

Oparin and Haldane’s hypothesis about the origin of life was unproven until the 1950s when Urey and Miller decided to perform an experiment to test if the conditions of early Earth were able to react and form amino acids, the basic unit of life, therefore creating life. Reason for experiment

They set up an apparatus replicating the conditions at the time. A closed system was set up and powerful electrical sparks were discharged into a glass chamber

containing ammonia, nitrogen, methane, hydrogen, water vapour and carbon dioxide. The electrical sparks represented the electrical storms and the gases were gases found during the time.

Gases circulated between lower chamber, of water representing the oceans and the upper chamber replicating the atmosphere.

Electrical discharge passed through atmosphere chamber which stimulated the energy in early atmosphere.

Results of experiment When Urey and Miller analysed the liquid using paper chromatography techniques they found that it

contained a number of amino acids. This proved the hypothesis and hence Oparin and

Haldane’s hypothesis became a theory.

Importance of experimentIn scientific methods, first step is observation and construction of hypothesis. An experiment is then designed to test the hypothesis and the results are then analysed to see if the hypothesis is confirmed or disproved. If hypothesis is proven correct, further experiments are done and data collected. The hypothesis also becomes a theory if sufficient evidence is available.

Contribution Results show organic molecules can form in a reducing

atmosphere and thus first step in the chemosynthetic origin theory was shown as possible.

Led to further research by other scientists therefore increased knowledge that the conditions of early earth were possible to formation of organic molecules.

Discuss the significance of the Urey and Miller experiments in the debate on the composition of the primitive atmosphere.

There is debate about the composition of the early atmosphere of Earth. Urey and Miller suggested that the Earth has a reducing atmosphere and they conducted the experiment using methane, ammonia, hydrogen and water.

Identify the changes in technology that assisted in the development of an increased understanding of the origin of life and evolution of living things.

Figure 2 - apparatus setup for Urey and Miller's experiment.

Our ability to describe the origins, processes and evolution of living things has been made possible by advances in science and technology, particularly in molecular biology and biochemistry.

Scientists and engineers have developed many techniques to find out more about the Earth, its history and living organisms is occupies.

Developments in engineering have enabled both space and deep sea exploration. Some samples of all types of materials can now be analysed to the molecular level by different techniques, including chemical analysis and x-ray crystallography.

Chemical separation techniques such as chromatography help to isolate molecules for further study, the ages of rocks and fossils can be dated by radiometric dating methods. Developments in microscopy, particularly the electron microscope, have led to a new understanding of structures at the molecular level.

Biochemical analysis particularly DNA, have enabled scientists to undertake comparative studies of different organisms. Genetic engineering techniques continue to help scientists to understand how change can take place in living organisms and thus we can better understand the relationship between organisms and their possible evolutionary pathways.

2. The fossils record provides information about the subsequent evolution of living things.Fossils are the remains, traces or imprints of organisms that have been preserved over a long period of time. They are usually embedded in solid materials such as rocks, wood or amber. Vertebrates are more likely to be fossilized because they have more hard material.Paleontology is the scientific study of fossils and all aspects of extinct life.

Conditions for fossilsAlso, there are specific environmental requirements for fossils to be formed:

o No oxygen o Moist (easier for sediments to compress)o Sedimentary rockso Has to be quick before organism decays.

Identify the major stages in the evolution of living things, including the formation of:- Organic molecules- Membranes- Procaryotic heterotrophic cells- Procaryotic autotrophic cells - Eucaryotic cells- Colonial organisms- Multicellular organisms

Stage Time period EvolutionOrganic molecules 4 b.y.a First step in evolution was formation of organic molecules form

inorganic substances. The experiment of Urey and Miller and latest scientific research confirmed that it was possible.

Membranes 4 – 3.5 b.y.a Formation of boundary around cells so they would not dissolve in water.

Believed to be made from mixing proteins, polysaccharides and lipids.

Once membrane was formed, RNA inside cell was able to grow,

split and reproduce.Procaryotic heterotrophic cells

3.5 – 2.5 b.y.a

Simplest unicells on Earth; had no membrane bound organism. Cell wall maintained shape and prevent bursting when water

moves in osmosis. Scientists believed first cells were heterotrophic and used organic

molecules are food source. Procaryotic autotrophic cells

2.5 – 2 b.y.a Competition for organic molecules created selective pressure so that cells could make their own food and an adaptive advantage over those that could not make their own food.

When cyannobacteria began to photosynthesise, it started flow of energy through ecosystems.

Once oxygen was collected into atmosphere, both heterotrophic and autotrophic organisms could use aerobic respiration to release energy for use in cell.

Eucaryotic cells 1.5 b.y.a Similar to procaryotes. Suggested it had symbiotic relationship with cyannobacteria after engulfing it.

Cyannobacteria became chloroplast and mitochondria of eucaryotes.

Unicells with membrane bound organelles.Colonial organisms 1.5 b.y.a Individual cells subjected to certain environmental pressures

associated together into colonies. Often connected by strands of cytoplasms that integrate the colony.

Likely some of the colonies became permanently attached to each other and functioned more efficiently in this way than as more independent colonial cells.

Led to multicellular organisms. Multicellular organisms

1 – 0.5 b.y.a Join together to form tissues, organs and systems specializing in a specific function.

Describe some of the paleontological and

geological evidence that suggests when life originated on Earth.

Figure 3 - Table of Earth's history

Paleontological evidence refers to fossil evidence whilst geological evidence refers to evidence found in rocks and landforms.

Evidence Description of evidence Pal. or geo. DatesAge of Earth Radioactive dating of rocks using U-238 geological 4.5 b.y.aOldest fossil Cyannobacteria in stromatolites Paleontological 3.5 b.y.aEarly trilobite Trilobites in marine sediments in North America Paleontological 600 m.y.aEarliest reptile Skulls of anapsids with solid skull except for eye

socket, nasal openings, etc.Paleontological 350 m.y.a

Formation Newcastle coal measures

Coal seams in Newcastle Geological 290 m.y.a

Eastern North America splits from western Africa

Oldest rocks of mid-Atlantic ridge from offshore North America and western Africa

Geological 235 m.y.a

Archaeopteryx Transitional fossil between reptiles and birds found in south Germany.

Paleontological 150 m.y.a

Formation of Cumberland plain, NSW

Disrupted stream patterns leading to current day geography

Geological 80 m.y.a

India collided with Eurasia

Marine sediments intruded with granite and basalts in Himalayas

Geological 50 m.y.a

Oldest Homo erectus fossil

Homo erectus fossils found in Java, China and Africa in 19th century

Paleontological 1.8 m.y.a

Explain why the change from an anoxic to an oxic atmosphere was significant in the evolution of living things. Believed that atmosphere of early Earth had little or no oxygen. Evidence provided in types of rocks

formed at the time. Atmosphere changed to oxic due to photosynthesis activity. This was mainly due to the

cyannobacteria. Oxygen released into atmosphere and the accumulation of the oxygen led to an oxic atmosphere. Led to two effects on evolution of life:

o Anaerobes found themselves in a toxic environment. May have cause mass extinction but also evolution of eucaryotes.

o Mitochondria carried out aerobic respiration with procaryotes.

Discuss the ways in which developments of scientific knowledge may conflict with the ideas about the origins of life developed by different cultures.

There are distinctions between cultural beliefs, religion, philosophy and science. The theory of evolution has been and still been an area of conflict between cultural beliefs, religion and science.Science - Involves observations of natural, phenomena, the formation of a hypothesis to explain the observation, experimental testing and analysis of results to makes a conclusion.Religion – involves a set of beliefs based on faith and usually the presence of God or Gods involved in the creation of the Earth. Do not have to be scientifically tested.Philosophy – love of knowledge and the search for the truth and wisdom. Often debates about the ultimate reality, searching for the underlying causes and principles behind natural phenomena.

Belief DescriptionAborigines Believed in the ‘Dreamtime’.

Super human beings, both human and animal occupied the land and these beings were the ancestors of the Aboriginal people.

Myth of the Rainbow Serpent describes how rives and landscape of Australia was created.

Sky heroes took form as bird, fish and other objects found on Earth. Hindu Hindu Vedas, books of knowledge, have several different stories about

creation of Earth. One version states there was formless void into which one ‘breathed its

own nature’ and the world was created. Creationists All life was created at same time and each species created for particular

environment. God created all living things on Earth and they have not changed since

their creation.

3. Further developments in our knowledge of present-day organisms and the discovery of the origins of life and the processes involved in the evolution of living things.

Describe technological advances that have increased knowledge of Procaryotic organisms. Electron microscopes – allowed better magnification and resolution to determine internal structure

of procaryotes. At one stage cyannobacteria were blue-green algae; however an investigation into their cellular structure showed they are a procaryote and had no nucleus.

Submersible craft – allows scientists to investigate life forms that live near hydrothermal vents, allowing greater understanding of the conditions under which life is sustained.

Biochemical techniques – studies of metabolic pathways revealed similarities and differences previously unknown.

Describe the main features of the environment of an organism from one of the following groups and identify its roles in that environment:

- Archaea- Bacteria

Feature Eubacteria ArchaeaCell wall Peptidoglycan Mixture of polysaccharides and

proteins.Cell membrane Fatty acid linked to bacteria No fatty acid

Archaea Known as ‘extremephiles’ since they exist only in extreme conditions. Uses variety of materials as energy source.

Type of Archaea Description Methanogens Produces methane gas as waste products. Releases 2 billion tones of methane

gas per year. Live in anaerobic conditions. Inhabits digestive tracts of animals, swamps and oceans.

Halophiles Occupy salty environment Contains pink pigment to produce energy. Traps solar energy.

Thermoacidophiles Inhabits hot springs. Maintains cellular pH of 7.

Eubacteria Classified according to shape:

o Bacilli (rod-shaped)o Cocci (sphere shaped)o Spirilla (spiral shaped)o Vibrio (comma-shaped)

Lives in most environments. Inhabits anaerobic environments turning them into oxic environments.

Type of Eubacteria DescriptionCyannobacteria Blue-green algae

Photosynthetic; can fix nitrogen from air Too many cyannobacteria can lead to

Eutophication where they use up oxygen and cause water to ‘die’.

Nitrogen-fixing bacteria Converts atmospheric nitrogen into forms of nitrogen directly usable by plants – nitrates and ammonium ions.

Live on roots of plants to ensure that plants take up enough nitrogen gas.

Deep sea bacteria Found in areas like rift vents at midge ocean ridges or guts of dwelling organisms.

Releases enzymes that degrade food eaten by their host.

Comparison of Archaea, Bacteria and Eucarya

Archaea Bacteria EucaryaNucleus & membrane-bound organelles

Absent Absent Present

Cell wall material Polysaccharides & protein

Peptidoglycan Cellulose (plants)Chitin (fungi)

Membrane lipids Hydrocarbons-glycerol with an ether linkage

Fatty acids – glycerol with an ester linkage

Fatty acids – glycerol with an ester linkage

RNA polymerases (enzymes)

≥ 8 polypeptides 4 polypeptides 10-12 polypeptides

Start codon for polypeptide synthesis

Methionine Formyl methionine methionine

4. The study of present-day organisms increase our understanding of the past organisms and environment.

Explain the need for scientists to classify organisms.o Classification is the process of sorting out items into groups making it simpler to describe the item. It

is important when there are many varied items. Therefore, when items are large in number and very varied, classification is the best management system for several reasons.

o Organisms may differ in the following way: anatomy (structure), physiology (functioning), behavior (doing) and biochemistry (molecular activity).

o At the genetic level there may be differences in chromosomes number and structure. While all the criteria can be use, the most practical one to use in the field is anatomical structure.

o Whether an organism is alive or dead as fossils, structure can easily be observed. This is because structure of organism stays most constant in an organism’s lifetime compared to other features that may change seasonally or with maturity.

o Classification of plants is based on structure and means of reproduction. o Recently, from molecule structures have been used by scientists to classify organisms. This is because

it has similarities in DNA and protein.

Reasons for classification include: Enable an item to be described quickly and accurately. For example instead of saying organism X has a

hard black body covering, a segmented body, a pair of antennae and three pairs of legs, it is easier to say that it is an arthropod.

Makes communication simpler and more accurate. For example, when scientist can get straight to the point about organism X rather than a long, detailed description of the organism.

As more items are collected, they can be fitted into groups. This means that they can identify that a certain item can be identified as belong in a specific group. For example, if an organism is found in some remote place, it can be identified by matching it with the characteristics of one of the groups in the classification system.

Enables trends in a group to be observed and followed. Important for living things that have taken millions of years to evolve to their present state of great diversity. For example. Fossils may be identified and classified so that trends in evolution can then be established.

Help explain the relationships between organisms and this is also important in establishing evolutionary pathways.

Describe the selection criteria used in different classification systems and discuss the advantages and disadvantages of each system.

Selection criteria Use structural characteristics to distinguish different organisms and split them into groups. Includes feature such as presence of legs, number of legs, type of skeleton and type of internal

transport system.All organisms can be grouped into five kingdoms: Plantae, Animalia, Protista, Monera and Fungi.

Kingdom Example Key featuresPlantae (plants) All plants e.g. eucalyptus, ferns Made of procaryotes cells

Contains chlorophyll and makes their own food

Obtains energy through photosynthesisAnimalia (animals) All animals e.g. earthworms, fish Unicellular or multicellular organisms

Do not contain chlorophyll and cannot make their own food

Eucaryotic cells with no cell walls Develops from zygote produced when egg

fertilized by sperm (meiosis)Protista (Protists) Protozoan and some algae Lack of features that would allow them to be

classified as plants, animals or fungi Are either heterotrophic or autotrophic Usually single-celled organisms

Monera All procaryotes e.g. cyannobacteria Made from procaryote cells Single-celled Reproduces by binary fission with one cell

splitting into two Either heterotrophic or autotrophic

Fungi All fungi e.g. mushrooms Do not contain chlorophyll Cells are eucaryotic and surrounded by

cellulose cell wall. Either unicellular or multicellular.

The kingdom system

KingdomTwo Kingdoms Includes Plantae & AnimaliaThree Kingdoms Includes Plantae & Animalia & MoneraFour Kingdoms Includes Plantae & Animalia & Monera & FungiFive Kingdoms Includes Plantae & Animalia & Monera & Fungi & Protists

The domain system A more recent classification is the domain system. Divided into three domains:

o Archaeao Bacteriao Eubacteria

There are many kingdoms and phyla within each domain.

Figure 4 - diagram shows the relationship between the domain system and kingdom system.

Comparison between two kingdom system & five kingdom system

Feature System 1 System 2System name Two Kingdom system Five Kingdom systemAdvantage Using basic observatory ability it is

easy to classify organism as either a plant or an animal.

Variety of organisms can be classified in more accurate detail based on their cell structure, DNA, organelles and metabolism.

Disadvantage Does not accurately classify organisms such as fungi and bacteria because they do not suit the required description.

More investigation and testing is required for classifying organisms based on cell structure, DNA, organelles and metabolism. Special equipment also required e.g. electron microscope.

Explain how levels of organizations in hierarchical system assist classification. Organises organisms into different levels. Scientists use hierarchical system to classify organisms. It is effective method to classify because organisms are placed in groups that increasingly reflect their

similarities or differences. Allows scientists to determine how similar two organisms are to each other. Useful for storing and retrieving information.

Hierarchical level Feature/descriptionSpecies Fundamental unit of taxonomy.

Group of very similar individuals that have the potential to interbreed freely, to produce fertile offspring.

Cannot interbreed freely with other species. Scientific name of species consists of two parts; it is binomial, with a genus

name followed by species name. May be divided into sub-species, therefore it has three names. Most broad in detail for classification.

Genus Refers to generic name.

Groups of species closely related are known as genus.Family Related genera are groups of family

Major groups of generally similar organisms. Family names always ends in ‘ae’ e.g. Felidae. Not printed in any special

way.Order Are groups of related families.

Individual may vary in many ways. Order begins in capital letter and usually end in ‘a’ e.g. Carnivore &

ArtiodactylsClass For the basis on which most fossil study is based on.

Related group of orders are known as a class.Phylum About 30 phyla in animal kingdom.

Only about a dozen leave fossil remains. Groups of related classes form a larger group known as phylum.

Kingdom The five kingdoms: o Plantae – multicellular algae and plantso Animalia – multicellular animalso Monera - procaryoteso Protista – single-celled eucaryoteso Fungi – unique group of eucaryotes

Groups of related phylums are known as a Kingdom.

Figure 5 - example of how the hierarchy system works for the red kangaroo (Macropus rufus).

Discuss , using examples, the impact of changes in technology on the development and revision of biological classification systems.

Electron microscope DNA-DNA hybridization Due to high resolution and high

magnification of electron microscope, it has allowed scientists to get a better understanding of the internal structure organisms such as cell structure.

Helped show the difference between procaryotes and eucaryote cells, therefore introducing a new kingdom, Monera.

Also allowed reclassification of blue-green bacteria to blue-green algae.

Measures amount of hydrogen bonding between single strands of DNA from different species.

Also helps give genetic distance between two species it provides no information about the character state and distant relationships may be too difficult to find corresponding genes.

Both techniques and many other techniques have impacted the development and revision of biological classification systems. Advantages include:

Quantitative data Allows diverse organisms to be compared Indicated evolutionary relationships between organisms

Describe the main features of the binomial systems in naming organisms and relate these to the concepts of genus and species.

Taxonomy is the branch of science concerned about the classification of living things. Classification systems aim to reflect our understanding and current knowledge of the world of living things.Binomial system is for naming organisms at the genus and species level. This is their ‘scientific’ name. Genus name always comes first and starts with a capital letter. Species comes following the genus and it written in small lower-case letters. Always italicized scripted or underlined. E.g. Eucalyptus regnans which is commonly known as mountain ash. Organisms within a species are often very similar but they have individual differences. Species within a genus, however, are not very similar.

Identify and discuss the difficulties experienced in classifying extinct organisms. Scientists believe that 99% of all species that have ever existed are extinct. Evidence comes from

fossils. Seems to appear to have been six major mass extinctions during history of living organisms. Mass extinction is the rate of which extinction is much higher than the normal rate.

Figure 6 - shows the six mass extinctions which occurred over time during history of living organisms.

There are many reasons why classification of extinct organisms is difficult which include: Definition of species is a group of organisms that can interbreed to produce fertile egg but for extinct

organisms it is impossible to use this definition for extinct species. Fossils of extinct organisms are often damaged or incomplete due to natural activities occurring over

a long period of time on Earth. This means the fossils may not show all the structural features and it is likely different fossils shows different sections.

Impossible to study their biochemistry and their fine cell structure. Studies on organisms which were not extinct have shown that gross structure sometimes insufficient

to classify organisms. Cyannobacteria, a procaryote, can only be observed using a modern day electron microscope. Their

metabolism shows specific features that can only be discovered by biochemical analysis of the cyannobacteria living today.

Studying modern organisms are not always accurate as they may not be similar to their ancestors. Organisms can change over billions of years due to environmental pressure. However, there are still many structural and biochemical factors which may help scientists to get an

insight into the features of the original species.

Explain how classification of organisms can assist in developing an understanding of present and past life of Earth.

Technology has significantly affected the way that organisms have been changed. Electron microscopes have enables scientists to see the internal structure of organisms allowing

them to get a better knowledge of the organisms. This therefore allows them to classify organisms more accurately. An example is the cyannobacteria. Through the use of electron microscopes it has allowed scientists to reclassify cyannobacteria as a procaryote rather than a eucaryote.

Biochemical studies have caused the Archaea to be separated from other bacteria. The older five-kingdom system have also been largely altered to a three-domain system in which four of the five kingdoms are in one domain and the fifth kingdom is divided into two domains.

Perform a first-hand investigation and gather information to construct and use simple dichotomous key and show how they can be used to identify a range of plants and animals using live specimens using live and preserved specimens, photographs or diagrams of plants and animals.

Dichotomous key is a key that branches continuously separate objects into two based on (usually) their structural characteristics. It is a convenient method for identifying an organism.A decision is made about each of the characteristics at a branch e.g. ‘does the organism/object have this characteristics of not?’ Based on the answer, one of the two branches is followed up to the next branch. The key finishes when there is only one organism or groups of organisms in each category.

Figure 7 - this is an example of a simple dichotomous key. (a) is the table using paired statements and (b) is a dichotomous key.