A 90 page summary (lecture notes) of all information covered in the lectures of Biology 144 in Semester Two, Term Three about Plant Diversity. This summary contains extra definitions, explanations and diagrams. Tables and bullet points are used to aid memorisation. Leave a 5 star rating if you like...
Vocabulary Monophyletic: A group of organisms that are in the same
taxon and share the most common recent ancestors.
Paraphyletic: A group of organisms from a common
evolutionary ancestor or ancestral group, but not including all
the descendant groups.
Phylogenetic Trees These “trees” provide a standard organisation of organisms into
three broad groups: Archaea, Bacteria and Eukarya.
Note: Most of life on Earth is made up of bacteria.
Nodes & Branches
These inform the reader of the changes in genetic sequences
that have occurred and when groups showed enough changes
to be separated in different taxa.
Separations between the three groups are not clear cut. It has
been theorized that modern eukaryotic cells were formed when
some prokaryotic cells were consumed by amoeba-like early
form of the eukaryotic cell in a process known as phagocytosis.
Endosymbiotic Theory This theory is that some of the organelles in eukaryotic cells
were once prokaryotic microbes.
Example: a eukaryotic cell would have engulfed a few
cyanobacterium. The cell membrane would have formed a
phagosomal membrane around the bacterium once engulfed.
Over time this membrane becomes the membrane of the
chloroplast which is now part of the cell. Evidence for this
arises from size, DNA, ribosomes and method of division of
these organelles.
Phylogeny Phylogeny - pattern of shared ancestry.
How to Read Phylogenies:
● Root = ancestor
● Tips = descendents
As you move from root to tips, you are moving forward in time.
, Image: Source Unknown
Branching: This represents a single evolutionary lineage
splitting two lineages. This is speciation.
Phylogenies are not indicating which species are more
advanced than others.
Lineage Each lineage has some history that is shared with other
lineages but some history that is unique.
In this same way, each lineage has shared and unique
ancestors.
Clades A clade is a group which includes a common ancestor and all
the descendents of that ancestor (living or dead). This is a
monophyletic group.
A clade can be recognized as the group you would get if you
“cut” the tree anywhere with a single line.
Clades are embedded within one another, hierarchically.
Building a Phylogenetic 1. Gather data about characteristic of the group interested
Tree in,
2. Characters are inherited, genetically controlled and
comparable between organisms (homologous).
Typical characters: morphology, genetics (DNA
, sequence), physiology and behavioural.
3. Researchers look for similarities between organisms,
specifically similarities resulting from a shared common
ancestry, eg: homologous ancestry
4. By using these shared derived characters, organisms
can be hierarchically divided into smaller and smaller
groups.
5. These shared derived characteristics need to be
suitable for differentiation.
Examples: Turtles, lizards, snakes, crocs, mammals and birds
all have/had four limbs - this shared derived trait is not a good
way to determine relationships as most members of the clade
may share that trade.
Eukarya makes up 4 kingdoms in total: plants, fungi, animals
and protists.
Protists Characteristics of Protists:
● Very diverse.
● Can cause diseases in humans such as malaria.
● Can be unicellular, colonial or multicellular groups.
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