Transcript Topic 3: The Evolution of Life on Earth

Life on Earth
Topic 7: Procaryotic Organisms
Part of the Evolution of Australian Biota Module
Biology in Focus, Preliminary Course
Glenda Childrawi and Stephanie Hollis
DOT Point
 Describe technological advances that have increased
knowledge of procaryotic organisms
 Describe the main features of the environment of an
organism from one of the following groups and identify its
role in that environment
 Archaea
 Bacteria
uhh.hawaii.edu
Introduction
Procaryotes are singlecelled organisms. They are
the smallest, simplest
organisms. They are
abundant in the air, water,
soil, and on most objects.
It’s believed that live as we
know it has evolved from
these organisms
bio.m2osw.com
Technology
Structural methods of classifying procaryotic organisms in the
past have been very valuable however, these methods did not
always reflect the organisms’ possible evolution.
textbookofbacteriology.net
Technology
New technological advances have changed the way procaryotic
organisms are now classified, and increased our understanding
and knowledge of biological structures, chemical composition
and biochemical (genetic) characteristics.
uhsecho.com
Technology
The light microscope has
allowed us to identify cells as
being unicellular and small
with a cell membrane and cell
wall. The electron
microscope allowed us to see
fine details including
organelles and DNA.
microscope-microscope.org
Technology
Chemical analysis has allowed
us to determine the chemical
composition of cytoplasm and
membranes. Genetic
sequencing has allowed us to
determine the number of
chromosomes and further
explore genetic material.
nhchemicalanalysis.com
Technology
These developments, due to technology, in our knowledge of
present day organisms allows for a better understanding of the
origins of life and the processes involved in the evolution of
living things.
nrc-cnrc.gc.ca
Technology
For example, we now know that bacteria have evolved along
two main evolutionary lines, classified as kingdoms-Bacteria
and Archaea
wired.com
Bacteria
Bacteria are an enormously
diverse group that share many
environments with, or live on
and in humans and other animals
and plants. These are habitats of
moderate temperature with
water freely available, low in salt
and where sunlight and organic
compounds are plentiful.
answersingenesis.org
Bacteria
Oxygen is not so important
since many of the bacteria have
powerful fermentation
capabilities, producing ATP
(energy) under anerobic
conditions. The group bacteria
contains almost every variety
and combination of
biochemical energy extraction
and carbon-fixation thought to
be possible.
science.howstuffworks.com
Bacteria
However, this group also contains some of the most specialised
and sensitive cellular organisms known. These are often
pathogens that have become highly adapted to particular
environments within animal or plant hosts.
herryyudha.com
Bacteria
Cyanobacteria resemble algae and plants in that they contain
chlorophyll and generate oxygen during photosynthesis. They
occur as individual cells or as filamentous aggregates of many
individual cells joined end to end.
serc.carleton.edu
Bacteria
Cyanobacteria contains pigment called phycobilins which give
them a blue-green appearance. They often form dense mats of
growth in shallow marine or estuarine environments.
futurity.org
Scientists believe this bacteria is responsible for the oxygen in
our atmosphere.
Bacteria
Endospore-forming bacteria are the most resistant form of
life known. Endospores form inside the mother cell rather than
budding from it. They form under conditions of nutrient
depletion or as a result of other environmental signals
forewarning difficult times ahead for the bacterium.
www2.raritanval.edu
Bacteria
Endospores appear to have evolved as a resistant, virtually
metabolically inactive cell type, increasing the probability of
survival under extreme conditions such as cold, heat or
desiccation.
kswfoodworld.wordpress.com
Bacteria
Bacterial endospores are remarkably resistant to high
temperature, high radiation and many chemicals which would
rapidly destroy all other living cells.
en.wikipedia.org/wiki/Endospore
Clostridium tetani lives in anerobic environments
Archaea
Archaea are still commonly referred to as archaebacteria,
however, this term has been discarded as they are not bacteria.
Archaea are a more specialised group than bacteria and its
members are therefore more restricted to the environments
they inhabit.
microbiologyonline.org.uk
Archaea
Archaea are single-celled, microscopic organisms which do not
contain any membrane bound organelles. They do not require
sunlight for photosynthesis, nor do they require oxygen.
scienceline.org
Archaea
Most live in extreme environments and are called
extremophiles, however, some still live in ordinary
temperatures, salinities and acid levels.
 Thermophiles live in water temperatures greater than 50C
 Halophiles live in hypersaline environments greater than 9%
and up to 32% salt concentration
 Acidophiles live in acidic environments lower than pH 2 and
as low as pH 0.9
green-buzz.net
Archaea
By studying these
organisms that presently
live in extreme conditions
on Earth, we are able to
infer what the organisms
were like that survived
during the extreme
conditions of early Earth.
news.sciencemag.org
Homework
-Students to complete DOT Point 3.5
**Hand out Holiday Research Activity and discuss**
green-buzz.net