5.3 Classification of biodiversity
Understanding:
- The binomial system of names for species is
universal among biologists and has been agreed
and developed at a series of congresses
- When species are discovered they are given
scientific names
- Taxonomists classify using taxa
- All organisms classified into 3 domains
- Principal taxa for classifying eukaryotes are:
kingdom, phylum, class, order, family, genus,
species
- In a natural classification the genus and higher
taxa have all evolved from one common ancestor
- Taxonomists sometimes reclassify groups of
species when new evidence shows a previous
taxon contains species evolved from a different
ancestor
- Natural classifications help in identification of
species and allow the prediction of
characteristics shared by species within a group
Nature of science:
- Cooperation and collaboration between
groups of scientists: scientists use the
binomial system to identify a species rather
than the many different local names
Applications
- Classification of one plant and one animal
species from domain to species level
- External recognition features of
bryophytes, filicinophytes, coniferophytes
and angiospermophytes
- Recognition features of porifera, cnidaria,
platyhelminthes, annelide, mollusca and
arthropoda, chordata
- Recognition of features of birds, mammals,
amphibians, reptiles and fish
Skills
- Construction of dichotomous keys for use
in identifying specimens
Why are supermarkets organised like
this?
Classification…
All living things arranged into
groups according to their
similarities
HOW DO WE IDENTIFY LIVING
THINGS?
Living things…
Nutrition
Metabolism
Growth
Response
Excretion
Homeostasis
Reproduction
The 3 domains
1. Eukaryotes
2. Eubacteria (prokaryote)
3. Archaea (prokaryote)
What is the difference?
Feature
Bacteria
Archaea
Eukaryota
Histones associated
with DNA
Absent
Proteins similar to
histones bound to
DNA
Present
Presence of introns
Rare or absent
Present in some
genus
Frequent
Structure of cell
walls
Made of chemical
called
peptidoglycan
Not made of
peptidoglycan
Not always present
Not made of
peptidoglycan
Cell membrane
differences
Glycerol-ester
lipids; unbranched
side chains; d-form
of glycerol
Glycerol-ether
lipids; unbranched
side chains; l-form
of glycerol
Glycerol-ester
lipids; unbranched
side chains; d-form
of glycerol
Classification
Eukaryotes are classified using principal taxa
Kingdom
Phylum
Class
Order
Family
Genus
Species
K
P
Crisps
Only
For
Good
Students
Who am I?
Try to guess who this is…
Kingdom
Phylum
Class
Order
Family
Genus
Species
Animalia
Chordata
Mammalia
Carnivora
Canidae
Canis
lupus
Naming species
The same species can have many different local
names.
Lords and ladies
Cuckoo pint
Devils and angels
Cows and bulls
Willy Lily
Snakes meat
Arum maculatum
Naming species
Cooperation and collaboration between
scientists
Ensures all
scientists use same
names
Decided by
different animal
and plant
congresses
Binomial system
Use two names: the genus and species
Rules:
1. Genus name begins
with upper case
letter and species
name with lower
case
2. Italics
3. Can be abbreviated
once if used already:
A.maculatum
Natural classification
Classify organisms in a way that closely follows
evolution
Members of a genus should have a common ancestor
Members of the group share many characteristics
Unnatural classification – grouping birds, bats and
insects because they fly
Flight evolved separately in these groups and they have
very big differences otherwise
Advantages of natural
classification
1. Identification of species is easier
Go through each taxa step by step – assign a kingdom,
then a phylum etc…
Dichotomous keys can be used to help with the process
Could do no easily with unnatural classification
2. Prediction of characteristics
Inherited similar characteristics from common ancestor
Could not do this if we used unnatural classification
E.G find a new species of bat – we know it has
mammalian features (could not do if grouped with
birds)
Reclassification
New evidence may show that members do not share a
common ancestor
Split group up into more taxa
(or two groups are found to be more similar – merge
the groups)
Creating the dichotomous key
All living things are grouped due to their
similarities…
What are
these?
BIRDS
What are
these?
MAMMALS
What are
these?
FISH
We can create a dichotomous key to split these animals
up.
To do this we need to ask questions about them to find
their differences.
How are fish, mammals and birds different?
BIRDS
Feathers
MAMMALS
Fur
FISH
Scales
This is how we construct a dichotomous key…
Does it
have
scales?
yes
no
Does it
have
feathers?
yes
no
Your task
You need to be able to read both types of
dichotomous key and be able to create your
own.
1. Complete the classification worksheet
2. Create your own classification key using 5
animals of your choice
3. Look at page 265 in your book turn your key
from part 2 into the second type of key.