5.4 CLADISTICS Flashcards
CLADOGRAM
is a tree diagram showing the similarities and differences between different species
NODES
Branching points on the cladgram
CLADE
groups of species that evolved from a common ancestor and that have shared characteristics
WHAT DO NODES DENOTE?
Nodes denote a speciation event when a common ancestor splits into two or more
species
CLADE EVIDENCE
Evidence for which species are part of a clade can be obtained from the base sequences of a gene or the corresponding amino acid sequence of a protein
DIFFERENCES AND TIME
Sequence differences accumulate gradually so there is a positive correlation between the number of differences between two species and the time since they
diverged from a common ancestor.
TRAITS CAN BE
analogous or homologous
ANALOGOUS STRUCTURE
Some animals belonging to different groups live in the same or similar habitat
This can lead to development of similar superficial structures for organisms that live in a similar manner
The structures look comparable anatomically from the outside; however, are not alike on the inside (do not share a common ancestor)
They are similar traits but not from a common ancestor
HOMOLOGOUS STRUCTURES
Common internal structures that are similar in seemingly dissimilar animals that have evolved from a common ancestor.
The standard example of homologous structures is the “pentadactyl limb” which is the five digit limb found in animals such as humans, dolphins, bats,
and dogs.
Even though the shape, size and function of this structure vary between species, the general structure and position of the bones in these limbs are the same.
RECLASSIFICATION
Evidence from cladistics has shown that classifications of some groups based on structure did not correspond with the evolutionary origins of a group or species
Reclassification of the figwort family using evidence from cladistics
