EARLY EARTH
Identify the relationship between the conditions on early Earth and the origin of
organic molecules.
-
What does identify mean?
Structure your answer. Learn the content before you write an answer.
Key words
Be succinct
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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What does discuss mean?
Underline key words and identify what they mean
Know what you are going to write before you write an answer
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?
Underline key words
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 nonliving 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 understand
There 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 language
There 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 selfreplication.
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 Earth’s 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.
Things to consider:
- 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
CAUSE
EFFECT
 The change in atmosphere from
 Anaerobic organisms declined
anoxic to oxic.
due to the presence of oxygen
which affected their growth and
metabolism. Photosynthetic
organisms began to evolve.

Oxygen levels increased in the
atmosphere.


Evolution of photosynthesis and
respiration (oxygen required)

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.
Nitrogen–fixing 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.
ADVANTAGES
DISADVANTAGES
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

CAUSE
Scientists classify organisms by
using a classification process
known as the hierarchal system



EFFECT
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 attenuate
COMPARED 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

CAUSE
Classifying present day organisms


Classifying past life on Earth


Classifying assists in developing
an understanding of past and
present life on Earth

EFFECT
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
animals
Things 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