Week 5/6 Flashcards
Define: node
In a phylogenetic tree, the point where a branch splits, representing the common ancestor from which the descendant species diverged.
What is the purpose of taxonomy?
To provide us with a hierarchical classification of species in groups that are more and more inclusive.
What is the purpose of phylogeny?
To discover the pattern of evolutionary relatedness among groups of species (by comparing anatomical or molecular features).
How do we indicate shared ancestry on a phylogenetic tree?
Using a node.
Define: taxon (pl. taxa)
All the species on some taxonomic entity under discussion.
Define: monophyletic
Describes groupings in which all members share a single common ancestor not shared with any other species or group of species.
Define: paraphyletic
Describes groupings that include some, but not all, the descendants of a common ancestor.
Define: polyphyletic
Describes groupings that do not include that last common ancestor of all members.
What type of phyletic group does a phylogenetic tree hope to identify?
Monophyletic - includes all descendants of a common ancestor.
What are the three domains on the entire tree of life?
- eukarya
- bacteria
- archaea
Define: characters
The anatomical, physiological, or molecular features that make up organisms.
What are two reasons that character states may be similar between two different species?
- character state was present in a common ancestor of the two groups
- character state independently evolved in the two groups as an adaption to similar environments
Define: homologous
Characters that are similar because of descent from a common ancestor.
Define: analogous
Similarities due to independant adaptation by different species.
Define: synapomorphies
A shared derived character; a homology shared by some, but not all, members of a group.
Define: cladistics
Phylogenetic reconstruction on the basis of shared evolutionary changes in characters, often called synapomorphies.
Define: parsimony
Choosing the simpler of two or more hypotheses to account for a given set of observations.
When constructing phylogenetic trees, there are often a variety of different ways to arrange a tree for one group of organisms… how do we know which is the best tree to use?
The tree that is the simplest, has the fewest # of steps.
Why does molecular data provide more details when using it to create a phylogenetic tree?
There are more characters that can vary among species.
How is DNA used to create phylogenetic trees?
Sequences are taken from organisms and compared to one another.
- recent common ancestor = little time to develop differences
- ancient common ancestor = a lot of time to develop differences
In what way does phylogeny and fossils work together?
Phylogeny provides framework for the interpretation of fossils, and fossils provide a record of life’s history (in the context of continual planetary change).
According to the textbook, what proof do we have that helps to determine that evolution has taken place?
Two complementary but independent approaches (phylogenies and fossils) to reconstructing the evolutionary past, yield the same history.
Why is it important for plants to disperse their offspring?
To avoid/minimize competition for resources - can’t all be in one area.
Define: spore
Cells that disperse and give rise to new haploid individuals.
Define: gametophyte
In alternation of generation, describes the haploid multicellular generation that gives rise to gametes.
Define: sporophyte
Describes the diploid multicellular generation in plants that produces spores.
Define: alternation of generation
Describes the basic life cycle of all plants. The life cycle in which a haploid phase, the gametophyte, and a diploid phase, the sporophyte, follow one after the other.
Define: sporangium
A structure in which many thousands of diploid cells undergo meiosis, producing huge numbers of haploid spores.
Define: sporopollenin
A complex mixture of polymers that is resistant to environmental stresses such as ultraviolet radiation desiccation.
In what ways does dispersal enhance the reproductive fitness of plants?
- do not have to compete for resources
- allows offspring to avoid pathogens and parasites
- allows offspring to colonize new habitat
In vascular plants, which generation is the dominant one, and why?
Sporophyte
- physically larger than gametophyte
- photosynthetic production is much higher than that of the gametophyte
How do spore-dispersing vascular plants differ from bryophytes?
Both the gametophyte and sporophyte generation are free-living - they can provide their own nourishment.
