Phylogeny

Question 1

What is the number of species on Earth?

Answer 1

• No accurate estimate
• Estimates over six decades are variable (2-100 million)
• Current best estimate: 8 million species
• Eukaryotes only

Question 2

Life on Earth

Answer 2

• Scientists have classified over 1.5 million species of animals
• Thousands more are described each year
• Less than 20% of all extant species know
• Less than 1% are known for extinct species

Question 3

How do you discover a new species?

Answer 3

• No form rules
• Compare morphological, genetic features, physiological features to known specimens
• Publish in scientific journal

Question 4

What is microevolution?

Answer 4

pertains to evolutionary changes in frequencies of variant forms of genes within populations

Question 5

What is macroevolution?

Answer 5

pertains to evolution on a long timescale. Origins of new structures, species, mass extinctions

Question 6

What are the patterns of macroevolution?

Answer 6

• Stasis
• Lineage splitting
• Extinction

Question 7

What is stasis?

Answer 7

some lineages don’t change much, even over millions of years

Question 8

What is lineage-splitting?

Answer 8

• Speciation
• Various patterns
  frequent lineage splitting
  low rate go lineage splitting
  bursts of lineage splitting

Question 9

What is extinction?

Answer 9

• Frequent or rare within a lineage
• Can occur simultaneously across many lineages (mass extinction)
• Two possible evolutionary fates for every species (give rise to new species and become extinct)
• Over 99% of the species that have ever lived on Earth are extinct

Question 10

What is phylogeny?

Answer 10

the origin and diversification of any taxon, or the evolutionary history of its origin and diversification

Question 11

What is a phylogenetic tree?

Answer 11

a tree diagram whose branches represent current or past evolutionary lineages and which shows the hypothesized patterns of common descent among those lineages

Question 12

How are these relationships determined?

Answer 12

classification is based on common evolutionary descent

Question 13

What are their shared characters?

Answer 13

• Homology: character similarity resulting from common ancestry
• Homoplasy: non-homologous similarities that may be found in various organisms (not inherited from a common ancestor)

Question 14

What is cladistics?

Answer 14

• An approach or methodology for classifying organisms based on common evolutionary descent
• Goal: infer the evolutionary tree (phylogeny) that relates all extant and extinct species
• Accomplished by comparing characters
  characters can be morphological, chromosomal or molecular
  sometimes behavioural and ecological features are also used
• Analysis of ancestral and derived characters used to construct a cladogram

Question 15

What is a cladogram?

Answer 15

a diagram used in cladistics to show evolutionary relationships between organisms

Question 16

What is a clade?

Answer 16

a unit of evolutionary common descent that includes ancestral lineage and all descendants

Question 17

What is a character?

Answer 17

organismal feature that varies between species

Question 18

What is an ancestral character?

Answer 18

character state present in the common ancestor

Question 19

What is a derived character?

Answer 19

all other variant forms of the character that arose later within the group

Question 20

What are the types of clades?

Answer 20

monophyletic clade
paraphyletic clade
polyphyletic clade

Question 21

What is a monophyletic clade?

Answer 21

includes the most recent common ancestor and all descendants of that ancestor

Question 22

What is a paraphyletic clade?

Answer 22

includes the most recent common ancestor and some but not all descendants of that ancestor

Question 23

What is a polyphyletic clade?

Answer 23

does not include the most recent common ancestor of all members of a group (the group has at least two separate evolutionary origins)