PHYLOGENY AND EARLY LIFE

Question 1

When did the first prokaryotes show up?

Answer 1

3.5 bya

Question 2

When did the first eukaryotes show up?

Answer 2

~1.8 bya

Question 3

What led to the evolution of eukaryotes?

Answer 3

Endosymbiosis, the theory that a prokarytic cell engulfed a smaller cell which would later evolve into an organelle found in eukaryotes

Question 4

When did multicellularity appear?

Answer 4

Early multicellular eukaryotes appeared 1.2 bya - smaller multicellular eukaryotes appeared 1.8 bya and larger, diverse multicellular eukaryotes appeared 600 years ago

Question 5

What are the benefits to multicellularity?

Answer 5

1. Larger in size
   
   1. Prey to fewer predators
2. Longer life
   
   1. Not restricted to the lifespan of a single cell
3. Specialization
   
   1. Increases efficiency

Question 6

How do multicellular cells stay attached?

Answer 6

Cadherins, or glycoproteins in cell-cell adhesion, which are crucial in development

Question 7

When was land colonized?

Answer 7

Cyanobacteria and other photosynthetic eukaryotes coated terrestrial surfaces over 1 bya

Animals, plants, and fungi didn’t colonize until 500 mya

Question 8

When did primates show up?

Answer 8

6-7 mya

Question 9

What was the Cambrian Explosion?

Answer 9

Prior to the Cambrian Explosion, large organisms were soft-bodied and there was little evidence of predation

After the explosion, defensive adaptations began to arise

Question 10

What is phylogeny?

Answer 10

Phylogeny is the evolutionary history of a species/group of species

Question 11

What is the hierarchial classification?

Answer 11

Domain, kingdom, phylum, class, order, family, genus, species

Question 12

What is a problem with the Linnaean system

Answer 12

Species may be places into a genus to which it may not be closely related. It distinguishes groups but does not tell about the group’s evolutionary relationship to one another

Question 13

What are phylogenetic trees used for?

Answer 13

Phylogenetic trees represent a hypothesis about evolutionary relationships, and are depicted as a series of dichotomies, or 2-way branching points

Question 14

What are sister taxa?

Answer 14

Sister taxa are groups of organisms which share an immediate common ancestor that is not shared with another group

Question 15

What are problems with the phylogenetic tree?

Answer 15

1. Shows patterns of descent but not phenotypic similarities
2. Cannot infer ages
3. Shouldn’t assume that a taxon evolved from the taxon next to it

Question 16

What does a clade consist of?

Answer 16

A clade consists of ancestral species and their descendents

Question 17

What is a monophyletic group?

Answer 17

A monophyletic group (“single tribe”) consists of ancestral species and all its descendents

Question 18

What is a paraphyletic group?

Answer 18

A paraphyletic group (“beside the tribe”) consists of an ancestral species and some, but not all, descendents and the most recent common ancestor

Question 19

What is a polyphyletic group?

Answer 19

A polyphyletic group (“many tribes”) consists of distantly related species but does not include the most common ancestor

Question 20

What is adaptive radiation?

Answer 20

Adaptive radiation occurs when a common ancestor divides into multiple species with time which are adapively specialized to a specific environmental niche

Question 21

What is divergent evolution?

Answer 21

Divergent evolution is the development of a new species fro a pre-existing species

Question 22

What is convergent evolution?

Answer 22

Convergent evolution is the process whereby organisms not closely related independently evolve similar traits as a result of having to adapt to similar environments or ecological niches

Question 23

What are ancestral traits?

Answer 23

Ancestral traits are traits inherited from a common ancestor and have undergone little change since

Question 24

What are derived traits?

Answer 24

Derived traits are present in that organism but are absent in the last common ancestor