Chapter 25 Flashcards
Name the major events in the history of life.
- Cellular life
- Oxygen revolution
- Nucleated cells
- Multicellularity
- Cambrian explosion
How old is Earth and how long did it take for life to start forming?
Earth is 4.6 billion years old, life started 3.5-3.8 billion years ago
What is a prokaryote?
Prokaryotes are unicellular, have no nucleus, no membrane bound organelles, have a ring of DNA, and divide by binary fission.
What were the first fossils?
A type of blue-green algae (cyanobacteria) that is called stromatolites that were most likely photoautotrophic
With the oxygen revolution, how did photoautotrophs survive?
They evolved as the number of organic molecules got smaller
What are eukaryotes?
They have a nucleus and organelles and divide by mitosis
What did multicellularity do in terms of organisms?
It allowed tissues to be unique and specialized and allowed for larger and more complex organisms.
Was the Cambrian explosion an actual explosion?
No, it was the “sudden” appearance of different species.
What is adaptive radiation?
A specific diversification event where if a species occupies an empty space, they diversify quickly to thrive in their own niches.
What is a background extinction?
Background extinctions happen naturally, due to changes in environment, new diseases, and competition.
What is a mass extinction?
An extinction that is caused by sudden outside factors.
How many mass extinctions have there been and what is the current one named?
There have been 5 major extinctions, and we are living through the 6th one, named Anthropogenic.
What are the limitations of the fossil record?
- Habitat bias
- Taxonomic and tissue bias
- Temporal bias
- Abundance bias
What is habitat bias?
Sedimentation is needed for fossils, so places with a lot of sedimentation have many more fossils.
What is the taxonomic and tissue bias?
Hard parts like bones and shells fossilize easier than soft parts.
What is the temporal bias?
Recent organisms are more abundant than older organisms
How many current species are there estimated to be?
30 million extant species
What is phylogeny?
Hypothesized evolutionary relationships between organisms.
What is a phylogenetic tree?
A graphical summary of an evolutionary history of a clade (a group of organisms believed to have evolved from a common ancestor)
What is a taxonomic tree?
A naming system that is typically based on morphological (physical) traits
What does the anatomy of a phylogenetic tree look like?
The branch connects the nodes (most recent ancestor), the tip is the end of the tree, either extinct or still living, the root is the common ancestor of all the species in the group
What is an outgroup?
An outgroup is an organism that is distant from the group of interest, but still shares some characteristics to help root the tree.
What is a sister group?
Two species that come from the same common ancestor
What is a synapomorphy?
Traits on a phylogenetic tree that are shared the most common ancestor and descendants but not in species that are more distant.
