Name ________________
D.5 Clades, Cladogram and Phylogeny
1. Define the term clade.
a group of related organisms sharing a common ancestor / a
group of organisms containing an ancestor and all of its
descendants /
2. Suggest two reasons for using cladograms for the classification of organisms.
methods used to prepare cladograms use a different approach from
traditional classification/taxonomy;
show ancestral relationships;
reflect how recently two groups shared a common ancestry;
cladograms are (objective/accurate because they are usually) based
on molecular differences;
they should be considered as a good complement to traditional
classification
3. The table below lists five animals along with four physical characteristics. A plus sign (+) indicates that
the animal has this characteristic while a minus sign (–) indicates that the characteristic is absent.
Animal
Jaws
Limbs
Hair
Placenta
Salamander
+
+
–
–
Mouse
+
+
+
+
Jellyfish
–
–
–
–
Koala
+
+
+
–
Salmon
+
–
–
–
a. Based on the features above, a student constructed a evolutionary tree. State the names of
the organisms missing in the following tree.
4. The below Evolutionary tree shows the evolutionary history of species A to D. Discuss the
evolutionary relationships between species A to species B, C and D.
A is most similar to B;
A is equally similar to C and D;
A is least similar to both C and D;
5. Cladograms show evolutionary relationships among organisms. Comparative morphology investigates
characteristics for similar physical characteristics to determine which organisms share a recent common
ancestor. An Cladogram will begin by grouping organisms based on a characteristics displayed by ALL the
members of the group. Subsequently, the larger group will contain increasingly smaller groups that share
the traits of the groups before them. However, they also exhibit distinct changes as the new species evolve.
Further, molecular evidence from genes which rarely mutate can provide molecular clocks that tell us how
long ago organisms diverged in to different species .
b. Which organisms in the above Cladogram in figure 1 have fur and mammary glands?
Mouse and chimp
c. Which organisms in the evolutionary tree in figure 1 have jaws?
Every animal but a hagfish
d. Based on the evolutionary tree in figure 1, which shared a common ancestor most recently – a
mouse and a lizard or a mouse and a perch?
Mouse and Lizard
e. Which two organisms would you expect to have a closer matching DNA sequence for a gene that is
NOT under natural selection pressure in nature – Hagfish and Pigeon or Hagfish and Salamander?
Hagfish and salamander
6. Part II Molecular Evidence: Cytochrome c is a protein located in the cell and is involved with cellular
respiration.
a. Compare each organism’s DNA sequences for the gene Cytochrome c with the ancestor cell and each
other.
b. Circle or highlight the differences (mutations) present in the cytochrome c DNA sequences from
ancestor cell.
c. Record the differences between the Ancestor DNA and the other organisms DNA.
d. Based on the number of differences and similarities, which organism is the closest living relative to the
ancestor cell.
Sponge
e. Based on the number of differences and similarities in DNA sequences, which organisms are more
closely related Dolphins and sharks OR dolphins and cats?
They are equal in differences and similarities
7. Outline how variations in specific molecules can lead to phylogeny. In your answer be sure to include
the following: (3)
Phylogeny is the evolutionary line of descent;
Many living organisms have the same molecules (i.e. DNA, mitochondrial DNA, Hemoglobin,
cytochrome c. These molecules have some variations between species. Scientist use
these difference to determine the phylogenies of species.
These variations in molecules are due to random mutation
The greater the differences between proteins (i.e. hemoglobin, cytochrome c) and DNA gene
sequences the longer the time span since the two species had a common ancestor;
However, mutations are chance events so caution must be taken when interpreting
these;
8. Discuss how biochemical variation can be used as an evolutionary clock (3).
Many living organisms have the same molecules (i.e. DNA, mitochondrial DNA, Hemoglobin,
cytochrome c). These molecules have some variations between species. These variations in
molecules are due to random mutation. Random mutations accumulate steadily and gradually
overtime at a constant rate. Consequently these changes can be used as a clock to estimate how
far back a species split from a common ancestor.
For example comparing homologous molecules from related species it is possible to count the
number of difference. If the mutation rate for a molecule is known, you can use these differences
and this known rate to estimate how long ago a species share a common ancestor.
However, mutations occur randomly and their rates are not always constant, so caution must be
taken when interpreting these.
Part 3: Make TWO Cladograms
9. Cladogram of Plants:
a. Fill in the below table to help you make a cladogram. Put a plus sign (+) if the organism has it and a
negative sign (-) if the organism does not have it.
b. On a white board or a piece of paper make a cladogram of the below species, using some or all of
the characteristics below. (hint: you do NOT need to use all of the below characteristics in your
cladogram)
Plant
Bryophytes
Filicinophyta
Coniferaphyta
Angiospermaphyta
Vascular
Tissue
(xylem &
phloem)
Seeds
Cones
Spores
True
Roots
Flowers and
fruits
10. Cladogram of Aminal:
a. Fill in the below table to help you make a cladogram. Put a plus sign (+) if the organism has it and a
negative sign (-) if the organism does not have it.
b. On a white board or a piece of paper make a cladogram of the below species, using some or all of
the characteristics below. (hint: you do NOT need to use all of the below characteristics in your
cladogram)
animal
Bilateral
symmetry
Radial
symmetry
segments
Hard
exoskeleton
One opening
for waste and
nutrients
Two openings
for 1 waste
and 1
nutrients
Jointed
appendages
Porifera
Cnidaria
Mollusca
Arthropods
Annelida
Platyhelmithes
11. Discuss the relationship between cladograms and the classification of living organisms.(6)

Classification traditionally based on morphology/ physical characteristics ;

And Cladistics is based on molecular differences/base sequences/amino acid sequences. This is a
strength of cladistics because it maintain objectivity;

Cladistics is based on probability but improbable events do occur, so relationships can be wrong;
and this is thus a weakness of cladistics;

Clades includes ancestral species/descendants from that species;

The Members of clade share set of features not found in more distant relatives;

Cladogram is a tree-like diagram where nodes/branches represent the splitting of (two) new groups
from a common ancestor;

Different cladograms can represent same relationships in a group;

Cladogram timescale not necessary;

Classification based on cladograms is often same as traditional classification;

However, in some groups, cladograms have led to revised classification;
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