EARLY EARTH

EARLY EARTH

Identify the relationship between the conditions on early Earth and the origin of organic molecules. What does identify mean?

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Key words

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Early Earth was formed approximately 4.5 billion years ago. During its early years the Earth underwent many changes. Clouds of water vapour that originally surrounded the Earth began to form the seas. The seas were quite warm. There were only one or two large land masses. Volcanoes were continually active spewing ash and lava into the atmosphere. The original atmosphere was thought to only contain hydrogen and helium. However due to the lack of gravity these gases escaped the atmosphere. This gave rise to the secondary atmosphere which contained hydrogen, carbon monoxide, carbon dioxide, nitrogen, methane and ammonia. There was no free oxygen making this environment anoxic. These gases on the early Earth had the main constituents to form organic molecules (C, H, and O) which in turn led to the origin of organic molecules around 4 billion years ago. Once these organic compounds arose primitive cells began to emerge around 3.5 billion years ago.

Discuss the implications of the existence of organic molecules in the cosmos for the origin of life on earth.

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Some scientists have suggested that our DNA and RNA (C, H, O, N, P) could have come from outer space. This theory arose due to the fact that early Earth was bombarded with meteorites/asteroids for approximately 500 years. Fred Hoyle stated that small microbes and other micro-organisms came to Earth from outer space via meteorites/asteroids. Astronomers have detected carbon compounds in meteorites and comets, however there is not enough concrete evidence to support that the cosmos was the soul cause for the origin of life.OTHER KEY FACTS:

Chemicals make up cells.

Proteins: (made up from building blocks of 20 amino acids) C, H, O, N, P, S.

74 amino acids have been found in meteorites.

75% of molecules detected in space are organic

Fossil bacteria in Martian rocks

Organic materials widespread in cosmos

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

What does describe and discuss mean?

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Research your answer before you decide to answer the question.

Chemosynthetic theory- this theory states that the origin of life arose from the organic molecules that were present on the early Earth. Early Earth contained many simple elements which formed simple compounds. These compounds contained the building blocks for life. Scientists believe that these compounds must have converted into the building blocks of life under the right conditions, and therefore the beginning origins of life.

Scientists have replicated early Earth conditions to identify whether or not chemicals from the early Earth yielded any life. Their findings are quite significant and have led to a better understanding of the origins of life.

Outer space theory- states that the origins of life originated from outer space and made their way to Earth via meteorites/asteroids as elements, compounds and even simple cells. Space material has been found to contain organic molecules. These molecules make up living matter. The outer space theory shows the possibility that life arose from space material coming to earth. This theory is also significant in our understanding of the origin of life. Discuss the significance of the Urey and Miller experiments in the debate on the composition of the primitive atmosphere.

What does discuss mean?

Outline the experiment performed by Urey and Miller

Link what they found to the origin of life

Link what they found relating to the composition of the early atmosphere

Urey and Miller simulated the early conditions on Earth. The main reason for this was to test the chemosynthetic theory that chemicals from the early Earth could covert to biological chemicals under the right conditions. Miller set up an apparatus that was symbolic of the primitive atmosphere. The atmosphere chamber contained the early gases including methane, carbon dioxide, ammonia, nitrogen, hydrogen and water vapour. An electrical discharge was passed through the atmosphere chamber to simulate energy. When samples were taken from the fluid they found organic molecules, the main chemicals that make up living matter. Other experiments used UV light which yielded nitrogenous bases, ribose, amino acids and nucleotides (genetic material). This experiment has not proved that biological compounds were formed from non-living matter under these early Earth conditions. The biological compounds could have evolved from the sea floor from volcanic vents or even from heat and chemical energy. However this experiment does prove that non-living matter under the right conditions can form organic matter (living), and thus supporting the chemosynthetic theory.

Identify changes in technology that have assisted in the development of an increased understanding about the origin of life and the evolution of living things.Things to consider: - What does identify mean?

Underline key words

Know what the question is asking

Write an answer in which you understandThere have been many changes in technology which have assisted in the development of an increased understanding about the origin of life and the evolution of living things. Technology changes include seismology (seismographs), radiometric dating, microscopy and biological studies.

SEISMOLOGY Geologists have developed our understanding of the Earth and its structure through the use of seismology, which is the study of pressure and shock waves produced by earthquakes. Seismographs are produced to record the wave patterns and strength of such crustal movement. There is such a large amount of interest in seismology/seismographs because the changing structure of the surface layers may have influenced the origin and evolution of life.

RADIOMETRIC DATING: This type of technology uses radioisotopes to date rocks and fossils. Radiometric dating is an important piece of technology as it identifies how old the Earth may be as well as dates the origin of life and the evolution of living things.

MICROSCOPY and BIOLOGICAL STUDIES. Developments in microscopy, particularly the electron microscope, have led to a new understanding of structures at the molecular level. Biochemical analysis particularly of 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.

The use of these new technologies has led to a better understanding of the origins of life and the evolution of living things.

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

Things to consider: - What does identify mean?

Underline key words

Know what you are going to write before you write your answer.

Use scientific languageThere are many stages which have contributed to our understanding of the evolution of living things. These stages are as follows:The formation of organic molecules (4.0 BYA)

Complex organic molecules formed in water on the early Earth, from pre-existing chemicals.

The formation of biological membranes (4.0 3.5 BYA)

Membranes developed to isolate and protect the system of large complex organic molecules which evolved to include nucleic acids and became capable of self-replication.

Procaryotic heterotrophic cells (3.5 2.5 BYA)First cells with simple structures. These cells used up biological molecules in their environment for sustainability.

Procaryotic autotrophic cells (2.5 2.0 BYA)

First type of cells which used energy from the environment to survive. If autotrophs did not evolve life might not have evolved.

Eucaryotic cells (1.5 BYA)

These cells evolved and contained a membrane bound nucleus and cell organelles. Believed to initially evolve from procaryotes.

Colonial organisms (1.5 BYA)

Multicellular organisms may have originated when daughter cells became bound together after cell division to form an aggregation of similar cells or colony. Stromatolites provide an example of this both as fossils and as present-day colonial cells.

Multicellular organisms (1.5 0.5 BYA)

There are two methods as to how multicellular organisms evolved one being that the unicellular organism underwent many repeated cell divisions without cytoplasmic division, or the cell underwent cytokinesis. This would have led to the multicellular organism having many cells each with a specialised function. Each cell with a different function is dependent on other cells. However the organism functions as a whole.

Describe some of the palaeontological and geological evidence that suggests when life originated on Earth.

Things to consider:

What does describe mean?

What does palaeontological and geological mean?

Be succinct in your answer and include scientific terminology

The study of rocks and fossils can provide us with the evidence for early life forms and their activities. Firstly palaeontological evidence refers to fossils. Fossil evidence is scarce in ancient rock with the abundance of fossils being mainly found in the past 600 million years. The earliest fossils found are of two types: microfossils which are similar to present day anaerobic procaryotes and stromatolites which are made up of cyanobacteria. These two types of fossils suggest that life may have originated approximately 3.5 bya.

Geological evidence is the study of rocks and the Earths crust. The first cells were heterotrophic. After time autotrophic cells emerged to feed heterotrophs as well as to photosynthesise. As we know oxygen is a by-product of photosynthesis. The oxygen had a dramatic effect on the Earth. The oxygen produced did not at first build up in the atmosphere but was taken up by rocks. These oxidised rocks can be seen today in the ancient banded iron and red bed rock formations (2.8 2.0 BYA). These rocks have also led scientists to hypothesise about when life first originated on Earth.

Explain why the change from an anoxic to an oxic atmosphere was significant in the evolution of living things.

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What does explain mean?

Underline key words

Understand the question before you write an answer, be succinct and use scientific terminology.The change from an anoxic to an oxic atmosphere was significant in the evolution of living things. Firstly oxygen began to build up in the atmosphere after most free oxygen had been absorbed by surface rock. Some of this oxygen reacted with U.V. light to form ozone. This in turn enabled the ozone layer to form high in the atmosphere. The ozone layer then acted as a shield and protected organisms from damaging U.V. light. This protecting enabled living things to colonise the land.

We will now look at explaining the change

CAUSEEFFECT

The change in atmosphere from anoxic to oxic.

Oxygen levels increased in the atmosphere.

Evolution of photosynthesis and respiration (oxygen required)

Anaerobic organisms declined due to the presence of oxygen which affected their growth and metabolism. Photosynthetic organisms began to evolve.

Living systems developed. Used oxygen to produce chemical energy. Aerobes produced energy using respiration. Greater metabolic activity. More active. Result was increase in size/complexity of organisms.

Life on Earth changed forever. Plants and animals became more complex. Presence of oxygen in the atmosphere limits the formation of complex organic molecules such as amino acids.

We can now see that these changes in the atmosphere were significant in the evolution of living things.Process and analyse information to construct a timeline of the main events that occurred during the evolution of life on Earth. (Pg 161 of text)

Things to consider:

What does process and analyse mean?

What does construct mean?

Relate the question to the evolution of life.10 BYA the universe began

5 BYA the galaxies began to form

4.5 BYA The Earth was formed

4 BYA The early evolution of organic molecules. Biological membranes evolve to protect organic molecules

3.5 BYA procaryotic heterotrophs form. First known stromatolites found in WA

2.5 BYA procaryotic autotrophs emerge and begin to photosynthesise

2.3 BYA first cyanobacteria found in stromatolites, production of oxygen by these cyanobacteria by the means of photosynthesis

2 BYA Anoxic to Oxic atmosphere

1.5 BYA first eucaryotic cells appear in turn forming colonies

1 BYA multicellular organisms evolve

600 MYA most animal phyla present, diverse algae

500 MYA diversification of animal phyla. First jawless fish

440 MYA first bony fish, plants and animals evolve on land

400 MYA first insects and amphibians

345 MYA extensive forests, first reptiles

290 MYA many types of insects, increase in reptiles, amphibians decline

225 MYA first dinosaurs, first mammals, diverse marine invertebrates

180 MYA diverse dinosaurs, first birds

138 MYA flowering plants and mammals diversify

66 MYA increasing numbers of birds, mammals, flowering plants

2 MYA humans evolve

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

Things to consider:

What does discuss mean?

Identify what you need to write before answering the question.

What cultures are we going to consider?

Discussion:Gather first hand or secondary information to make observations of a range of plant and animal fossils.

Things to consider:

Underline key words

Answer all questions

(Refer to the photocopied worksheet, from Heinemann to answer this dot point)

Identify data sources, gather, process, analyse and present information from secondary sources to evaluate the impact of increased understanding of the fossil record on the development of ideas about the history of life on earth.

Things to consider:

What does identify, gather, process, analyse, process and evaluate mean?

What does impact mean?

In this question you need to relate the impact of increased understanding..to your answer.

(Refer to the photocopied worksheet, from Heinemann to answer this dot point or refer to your textbook pages 130 135)

Describe technological advances that have increased knowledge of procaryotic organisms.

Things to consider:

What does describe mean?

Underline key words and make sure you understand their meaning before you answer the question

There are two main technological advances that have increased our knowledge of procaryotic organisms. Firstly the electron microscope which has extremely high magnification (300000x) has enabled scientists to identify the ultrastructures and functions of procaryotic organisms. This in turn has increased our knowledge of procaryotic organisms. Secondly biochemical studies have lead to a further understanding of procaryotic cell metabolism and function. Scientists have also used biochemical studies to compare DNA and RNA sequences in procaryotes. The more similar the nucleotide the more similar the two procaryotes are genetically. Therefore through the use of the electron microscope and biochemical studies we have an increased knowledge of procaryotic organisms.Describe the main features of the environment occupied by one of the following and identify the role of this organism in its ecosystem:

Archaea

Eubacteria

Cyanobacteria, including those that form stromatolites

Nitrogen fixing bacteria

Methanogens

Deep-sea bacteria

Things to consider:

What does describe mean?

What does identify mean?

Underline key words, and understand what the question is asking before you answer the question.

Archaea These are extreme types of procaryotes. The methanogens which can be found in swamps, digestive tracts and on the ocean floor are obligate anaerobes which use methane production as a key step in the generation of biological energy. They use carbon dioxide and hydrogen from the surrounding environment and convert it to methane.

Eubacteria Diverse group of procaryotes which inhabit nearly every environment on Earth including inside other organisms. They include photosynthetic green and purple bacteria which are found in anaerobic lake and ocean sediments. They produce sulphur from hydrogen sulphide. Pseudomonas which are present in most aquatic and terrestrial environments. Lactic acid bacteria used in the manufacture of foods. Decomposers found in aquatic and terrestrial environments break down dead matter into simpler compounds.

Cyanobacteria Cyanobacteria live in a variety of terrestrial and aquatic environments. The role of cyanobacteria in a terrestrial environment can either be mutualistic or free-living. This means that the cyanobacteria can live separately to all other organisms whereby it fixes nitrogen for nutrients or it can live in a mutual relationship with lichen a type of fungi which protects the cyanobacteria. In an aquatic environment, high phosphorus levels stimulate excess growth in cyanobacteria known as eutrophication. This in turn means that there is high production of oxygen, however dead cyanobacteria cause depletion of oxygen levels, affecting fish and other aquatic organisms.

Nitrogenfixing bacteria Nitrogen fixing bacteria come in the forms of bacteria and cyanobacteria. They live in terrestrial and aquatic environments where they fix the nitrogen in the atmosphere or the soil into directly usable products by plants and other organisms. E.G. Rhizobium lives in the root nodules of legumes where they fix nitrogen and obtain nutrients in exchange for protecting the bacteria.

Methanogens Methanogens can be found in swamps, wetlands, ruminant stomachs, and human stomachs and in extreme conditions. Methanogens are anaerobes meaning they can not live in an oxygen rich environment. Their principle role in any environment is to break down organic material and to convert it into methane gas.

Deep sea bacteria Chemosynthetic bacteria are found deep within the ocean near vents; oceanic drop offs as well as cracks in the sea bed floor. These areas are unusually high in temperature and are high in hydrogen sulphide. Chemosynthetic bacteria synthesise this hydrogen sulphide and turn it into nutrients and energy. Symbiotic relationships also exist in marine environments between clams, tube worms, mussels and cyanobacteria.Use the available evidence to outline similarities in the environments past and present for one of the following: Archaea

Eubacteria

Cyanobacteria, including those that form stromatolites

Nitrogen-fixing bacteria

Methanogens

YOUR TASK:

Choose one of the above bacteria, not the same one from the previous lesson and use the internet to outline similarities in the environment past and present. Your research should include at least half a page of information. Underneath your research include a bibliography of what resources you used.

Analyse information from secondary sources to discuss the diverse environments that living things occupy today and use available evidence to describe possible alternative environments in which life may have originated

YOUR TASK:

You are to use the internet to research the diverse environments organisms occupy today as well as describing alternative environments where life may have originated. Your research should include at least half a page of information as well as citation of the sites you used in your answer.

Explain the need for scientists to classify organisms

Things to do:

What does explain mean?

Underline key words

Understand the question

Classification is the process whereby items are sorted into groups based on their characteristics. The need to classify is important because if we had a large amount of organisms how would we distinguish organisms from one organism to the next. Classification of organisms is needed for the following reasons. It enables the items to be described quickly and accurately. It makes communication simpler and precise. Organisms can be identified as belonging to a particular group. Classifying enables trends to be studied further within a group. Finally it enables scientists to explain relationships between organisms.

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

Things to do:

What does describe and discuss mean?

Underline key words

Understand what you are going to write before you write an answer.

The main selection criteria used in different classification systems is the comparison of structural characteristics. Structural characteristics can show how similar or different organisms are. For example structurally a dog and a cat walk on four legs while humans walk on two. Structural characteristics in most cases are continual. That means a dog is always born with four legs from one generation to the next. There are also many types of structural characteristics therefore it is easier to compare diverse organisms.

Morphology is another word for structural characteristics and indicates the evolutionary relationships between species.

Another selection criteria used in different classification systems is the use of biochemical studies. Scientists compare protein sequences, DNA, RNA and nucleotide sequences between organisms to identify which organisms are similar or different in genetic terms.

ADVANTAGESDISADVANTAGES

Explain how levels of organisation in a hierarchal system assist classification

Things to consider:

What does explain mean?

Underline key words

Understand what the question is asking before you answer it

CAUSEEFFECT

Scientists classify organisms by using a classification process known as the hierarchal system

The effect of using a hierarchal classification system is that organisms are placed into groups that either closely reflect each other or are totally different.

This can be seen when organisms that are dissimilar are usually separated at the kingdom level while organisms that are similar in features are usually grouped up to or including the species level.

Classifying systems also aids scientists in the storage and retrieval of information on such organisms

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

Things to consider:

What does discuss mean?

What does impact mean?

Underline key words

Understand what this question is asking before answering

The development of the light microscope first revealed that living things were made up of cells. Improvements in light microscopy and the introduction of the electron microscope have also revealed more and more levels of detail of a cells internal structure. This knowledge increased our knowledge of the number of kingdoms from 2-5.

Advances in molecular biology and biochemistry have also enabled scientists to compare and contrast certain organisms. For example Woese an American biologist discovered two major groups within the monera at the molecular level. DNA sequencing also enables scientists to analyse evolutionary relationships between organisms as well as redefine the classification system. Describe the main features of the binomial system in naming organisms and relate these to the concepts of genus and species

Things to consider:

What does describe mean?

What does relate mean?

Underline key words

Understand what the question is asking before you answer it

The classification of living things is known as taxonomy. Taxonomy arose in the 18th century when Carolus Linnaeus developed the binomial system for naming organisms at the genus and species level. Binomial refers to two, meaning that every organism is classified with two names. A number of species make up a genus where the organism shows similar characteristics on some level. Species are very similar in characteristics but still have some individual differences.

For example the Banksia coccinea. The first word Banksia is always written in italics and has a capital letter. The first word always refers to the genus level. The second word coccinea refers to the species name. Genus and species are written in Latin because it was the language of science and medicine. Latin is still used today to classify organisms. E.G. Banksia refers to the explorer who found the flower, and coccinea refers to the colour meaning scarlet.

COMPARED TO:

Banksia attenuateCOMPARED TO:

Banksia sphaerocarpa

Note that the flowers have the same genus name but different species name due to their differing characteristics.Identify and discuss the difficulties experienced in classifying extinct organisms

Things to consider:

What does identify and discuss mean?

Underline key words

Understand what you are going to write before you answer the question

It is difficult in classifying extinct organisms in two major ways. Firstly it is impossible to study their biochemical make up. That means organisms that were extinct millions of years ago are almost impossible to classify because scientists have no information on their biochemical make up. Secondly it is near impossible to classify extinct organisms because scientists do not have access to cell structure and function. Cells hold the key to certain functions as well as metabolic activities within organisms which could show evolutionary relationships between organisms previously unknown. Even today comparing structurally between organisms may not necessarily prove whether or not an organism is closely related to another. For example cyanobacteria to be distinguished from other types of bacteria need to be studied under the electron microscope to identify its metabolic processes being different from others.

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

Things to consider:

What does explain mean?

What is the question asking?

Be succinct in your answer and use scientific terminology

CAUSEEFFECT

Classifying present day organisms Classifying past life on Earth

Classifying assists in developing an understanding of past and present life on Earth This shows how similar or different species are from one to the next. Scientists classify on the basis of structural characteristics (morphology) and biochemical analysis showing evolutionary relationships between organisms To classify life previously on Earth scientists look at the organisms structural characteristics and if possible biochemical analysis. This enables scientists to determine evolutionary relationships between current and past life

Classifying between past and present life on Earth has increased our understanding of life on Earth. This is evident as scientists compare past and present day life forms which shows structurally and biochemically the evolutionary relationships between species. E.G. Classification of birds and crocodiles showing more similarities compared to that of the crocodile and snakes.

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

This is an experiment whereby you will gather information to understand classification as well as classification keys.

AIM:

To analyse plant and animal samples and place them into a range of keys

MATERIALS:

Plant samples

Animals samples

METHOD:

1. Observe a range of plant and animal specimens.

2. With each specimen look for structural characteristics that differentiate from other specimens

3. Once observed place all the specimens into a shorthand key

4. Once you have finished your shorthand key construct a dichotomous key to show the differences between the species

RESULTS:

Construct your two keys here:

QUESTIONS:

1. What is the purpose of classification keys

2. Briefly outline how to construct a shorthand key and a dichotomous key

3. Write a conclusion to the experiment