Biology 2201
Unit 2- Biodiversity
Classifying Living Things
Ch. 4 – Patterns of Life
Ms. K. Morris – 2010-2011
Section 4.1 Characteristics of Life
Characteristics of Living Things (p.104)
Living Things:
• Organized systems made up of one or more
cells
• Carry out chemical reactions to get energy
(metabolize matter and energy)
• Interact with the environment and maintain
homeostasis
• Grow and develop
• Reproduce themselves (biogenesis)
• Adapt to their surroundings
• How have scientific classification systems
developed? (p. 104-105)
• The first attempt to group organisms was made
by Aristotle. He only recognized 1000 different
kinds of organisms. He divided them into two
groups which he named kingdoms: Kingdom
Plantae and Kingdom Animalia. He subdivided
each kingdom into smaller groups based on
characteristics such as type of movement.
• With the invention of the microscope,
microscopic organisms posed problems for
classification. Ernst Haeckel was forced to
develop a third kingdom which he named
Protista.
• Soon biologists identified two more kingdoms:
Fungi, which included mushrooms and moulds, and
Bacteria, which lack a nucleus.
• During the 1990's, more interest was focused on a
special group of bacteria that have been found in
extreme environments. These have a unique
structure and have been given their own kingdom
grouping called the Archaea.
• Presently, biologists are working with a six kingdom
classification: Animalia, Plantae, Protista, Fungi,
Bacteria, and Archaea.
• Refer to page 105 in the textbook for sample
organisms from each kingdom.
Section 4.2 Naming & Classifying
Organisms
• Taxonomy - the practice of classifying
organisms. It is the branch of biology that deals
with the classification and naming of living
things.
• The system used today was developed by
Carolus Linnaeus who used simple physical
characteristics to organize organisms into
groups.
• This method involves using two Latin or Greek
names which are chosen from a characteristic
of the organism or to honor a scientist.
• Binomial Nomenclature - a classification
system, a standard naming method used by
scientists when referring to organisms.
• 'Binomial' means that the scientific name of
each organism is actually the combination of
two names:
– the genus name and the species name.
• The genus name is capitalized, while the species
name is not; both are type set in italics.
– For example: Homo sapiens. (humans).
• The scientific name can be abbreviated by
using the first letter of the genus name
followed by the species name. This is usually
done when the genus name is being repeated
in a written document.
– Example: Homo sapiens becomes H. sapiens
• Common names are used in everyday
language but can pose problems for biologists.
A cat for people in Newfoundland may not be
the same as a cat for people in Africa. Why
not?
The Value of the classification system (p. 112)
Scientific names: Advantages of binomial nomenclature
• Avoids confusion- Many plants and animals have
common, local names that differ from area to area.
Even if an organism is named differently in different
languages ( or even provinces), the scientific name will
always be the same.
• e.g. In Newfoundland we have a tree that some people
call the Larch, others call it the Juniper, while other
people call it Tamarack. All scientists call this tree Larix
decidua. The common groundhog is also called the
marmot and woodchuck but all biologists call it
Marmota monax.
• It indicates evolutionary relationships between
organisms. Classification tries to show how organisms
evolved and which species are most closely related to
each other.
The Limitations of a Classification System
• Anomaly - something that does not fit a pattern
or system.
• The kingdom classification system is not perfect.
The classification system was recently changed
from a 5 kingdom system to a 6 kingdom system
to reflect new discoveries concerning bacteria.
• The discovery of halophiles, methanogens, and
thermophiles made it necessary to create a 6th
kingdom, the Archaebacteria.
• These bacteria have such unique structures that
they differ significantly from other bacteria.
• New biochemical evidence now tells us that it
is more closely related to spiders than to
crabs.
• In the kingdom protista, there are many
anomalies. Indeed, Kingdom protista is often
called the garbage bucket kingdom. The
protist Euglena is an example. It can move
(like animals) - it has flagella, but it also has
chloroplasts like a plant cell. ( see p. 147)
• The new six kingdom classification system still has its
limits and there are anomalies that don t fit nicely
into it.
• Viruses are not classified as a living organism and
therefore they are not put into any Kingdom. (see
previous note for reason why)
• Another anomaly is the horseshoe crab. It is really a
living fossil . We classify it in with arthropods
(animals with an shelled exoskeleton) but really,
there are no living arthropods like it.
• It is older than most species on the planet. Their
design has basically endured for upwards of 300
million years.
The Levels of the Classification System
(p. 108-113)
• A scientist named Linnaeus invented this
classification system.
• The classification system divides organisms of
each kingdom into smaller groups, based on
their similarities. Such a system is called
hierarchal.
• Hierarchal- a system of classification where
groups at each level are subdivided into
smaller groups below it.
• The seven major levels of the classification
system are, from largest group to most
specific are:
• Kingdom
• Phylum
• Class
• Order
• Family
• Genus
• Species
• A memory device for memorizing the order of
the levels is remembering the sentence:
• King Phillip Cried Out, For Goodness Sake !
• Each group is smaller than the last. Organisms
placed into the lower groups together are very
closely related while organisms placed into
groups at the higher levels share some common
characteristics but are not necessarily similar.
– e.g. Both humans and worms are placed into the
same Animalia kingdom. They are both
heterotrophic, eukaryotic, and multicellular but after
that, they are numerous differences!
• Animals placed into the same genus would be
very closely related.
– e.g. Dogs and wolves belong to the same genus - not
only are they animals but they have very similar
features.
• Kingdoms are divided into smaller groups
called taxon.
• A species is a natural group or population of
similar organisms that interbreed in nature. It
is the basic identifying level and would include
a single type of organism.
• Demonstrate how to use a taxonomic key to
group and identify an organism.
– Core Lab #3: “Creating a Dichotomous Key”
• p. 110-111
When classifying organisms, taxonomists use a
combination of information, including: (p. 113-116)
1.
2.
3.
4.
5.
Fossil Information (radioactive dating)
Structural Information (anatomy)
Embryological Information
Biochemical Information
Evidence from DNA
1. Radioactive Dating (Fossils)
• Many fossils contain radioactive isotopes
which can be tested to give the
approximate age of a fossil.
• Many radioactive isotopes decay at
known rates. Scientists use the decay of
carbon-14 in a process called
radiocarbon dating to find the ages of
some objects up to about 50 000 years
old.
2. Structural Information
• comparisons of the physical structures are
made between species to determine if they
are similar or not.
• The more physical similarities they have, the
more closely related they probably are. e.g. a
bats wing, a whales flipper and a humans arm
don’t appear alike but the bone structure and
arrangement are very similar under the skin –
this indicates a common ancestor.
• see p. 114 diagram
3. Embryological Information
• Comparing the earliest stages of embryonic
development can show who may be related to
who.
• e.g. Sea squirts don’t look like vertebrates or
even have a backbone but their larvae have a
very simple backbone so they are classified
into the vertebrates.
• Only a very skilled scientist can tell the early
embryos of apes and humans apart.
4. Biochemical Information
• DNA/protein comparisons. New technology
allows us to compare the structure of protein
molecules between organisms.
• Since proteins are made from the instructions
on DNA (genes), the closer the biochemical
similarity between proteins in animals means
the more closely they are related.
• e.g. although a mouse and a guinea pig look
similar, comparison of the structure of their
insulin, a protein, tells us that they are not
closely related.
Continued…
• Proteins are important molecules in organisms
• they are made by their cells by following instructions
on genes
• Protein structures can vary greatly in different
species.
• If two organisms have very similar or identical
protein structure such as the protein insulin, then
they are very closely related.
• e.g. guinea pigs and mice look very much alike but a
comparison of their insulin reveals that their insulin
protein is 35% different which means they are not
that closely related.
5. Evidence from DNA
• This is the most modern, powerful and precise
classification tool available.
• DNA analysis can easily tell who is related to
who.
• Matching the structure of DNA and comparing
the differences tells us who is related to who.
• For example, DNA analysis has shown that we
are very closely related to chimpanzees - 98%
of our genes match those of a chimpanzee!
• Classification systems improved as a result of
the development of modern techniques.
• Through the use of these techniques,
organisms once thought to be closely related
were found to be unrelated and vice versa.
• For example: Echinodermata (sea stars and
sea urchins) are more closely related to the
chordates than to any invertebrate.
• Note: The use of common or local names for
species can be confusing.
Section 4.3 Viruses
p. 122-125
• There is one group of organisms that are not
considered to be living things and that is the
viruses.
• Viruses have no cellular structure, no cytoplasm,
organelles or cell membrane. They carry out no
life processes. They are made up of strands of
DNA or RNA surrounded by a protein coat called
a capsid.
- Refer to page 122 in textbook for examples.
• Viruses are usually classified by the size and
shape of their capsid or by the types of disease
they cause. They are not able to be classified into
a Kingdom.
Virus Reproduction (ref. p. 122) see fig 4.20 p. 122
• Viruses classified as non-living because they lack many of the
cell structures and do not carry out basic life processes.
– don’t feed, excrete wastes, do cellular respiration, etc. Have no
cytoplasm, organelles, etc. All they seem to do is reproduce, so
they are not classified into any kingdom of living things.
Have only two things in common with living things:
– 1. ability to reproduce
– 2. genetic material ( nucleic acid - DNA or RNA)
• Lifestyle is parasitic. It uses host cells to reproduce, often
destroying them in the process.
• 1st identified in 1935 (more than 160 major groups are now
known - 21 of these groups infect humans).
Virus Structure: Two sections:
1. Capsid - outer protein capsule which protects
the genetic material. It helps to anchor the
virus to the host cell during reproduction.
Capsids vary in shape with the type of virus:
(see fig 4.20, p. 122)
– e.g. ( 1) polyhedral - polio virus ( 2 ) spherical - HIV
virus ( 3) cylindrical - tobacco mosaic virus)
2. Genetic material (nucleic acid DNA or RNA the genes of the virus)
Life cycle
Generally:
1. attach to a host cell
2. get inside of the host cell
3. use the energy and organelles of the host cell
to reproduce new viruses. The viral genetic
material attaches to the cells genetic material,
then commands the cells organelles to start
manufacturing viruses.
Entry into the host cell
Two methods to enter:
1. Attach and inject its nucleic acid (genetic
material) into the host cell.
2. Attach and let the host cell form a vesicle
around it. The cell takes it in by phagocytosis.
• Once inside, the virus breaks out of the
vacuole and injects its DNA into the nucleus of
the host cell.
Specificity of Viruses:
Viruses often only infect certain species they
are adapted to. Viruses may infect
(a) only a particular species
(b) only plants and animals
(c) only plants and fungi
(d) only certain cell types in an organism
(e.g. the polio virus only infects nerve cells
and intestinal cells)
T4 Viruses
• infects only bacterial cells
• also called a bacteriophage
• life cycle is called the Lytic Cycle
• See figure 4.21 p. 123
T4 Virus Reproduction - Lytic Cycle - see diagram p. 123.
A. Virus attaches to host cell.
B. Injects it nucleic acid into the host.
C. Viral genes take over the cells nucleus, forcing the cell
to replicate virus genetic material. The host cells
energy and organelles complete the task.
D. Assembly of new viruses. The cells organelles form
protein capsids around viral nucleic acid.
E. Lysis and release. The cell eventually bursts, releasing
new viruses. (Lysis = burst)
• the lytic cycle takes about 30 minutes to complete
• each host cell usually produces about 200
bacteriophages per cell
• End of Ch. 4 Notes
–Test #3 on Monday Dec. 13th