Final Review questions Flashcards
What are the possible outcomes of secondary contact between populations?
How does hybrid fitness affect these outcomes?
possible outcomes include no contact/continued divergence, the fusion of the populations, reinforcement of divergence, the founding of hybrid zones (extinction of one population), and finally the formation of a new species. If two populations substantially diverged and are genetically distinct the fitness of the hybrid offspring will be lower than the parent’s fitness.
- Secondary contact - they were in contacts, then diverged, then came back into contact. Reinforement of species barriers, mating signals are not compatible between populations now, zygote failures…
- Hybrids could form a third species, delusion of a population’s barriers
What are cladograms and how are they constructed?
A phylogenetic tree based on shared derived characteristics.
cladograms are phylogenetic tree diagrams that show the most probable sequence of divergence in clades. They are constructed by using ancestral traits, derived traits, and an outgroup. steps to construct a cladogram:
1)choose an outgroup to establish ancestral traits and root the tree
2)sort members of the ingroup according to traits
What is a synapomorphy? What does it define? Can a synapomorphy also be a symplesiomorphy?
Synapomorphy = shared derived
Symplesiomorphy = shared ancestral
Depends on what group you are looking at; it may be possible for a synapomorphy to also be a symplesiomorphy.
A synapomorphy is a shared derived trait that indicates two or more taxa belong in the same group. A symplesiomorphy is a shared ancestral trait. It is a trait that is shared by all members of the taxa of interest as well as with members of the related groups. A trait can be a synapomorphy and a symplesiomorphy if different nodes are considered.
What is the principle of parsimony? How does this principle help us build phylogenetic trees?
the principle of parsimony is “entities are not to be multiplied without necessity” in other words simpler solutions are more likely to be true rather than more complex one. The tree with the least number of evolutionary changes is likely to be the one that most accurately reflects the actual evolutionary history. It helps build a phylogenetic tree by grouping taxa together in ways that minimize the number of evolutionary changes that had to have occurred in the characters.
The simplest answer is probably the right one. Fewer changes
What is the difference between homologous and homoplasious traits? How can homoplasious traits lead to incorrect phylogenies?
Homologous are similar traits that are present due to ancestry. Homoplasy is similar traits but not inherited by a common ancestor. Homoplasious traits can lead to incorrect phylogenies because they may have similar traits but is not due to the inheritance through lineages.
How does fossilization occur and what are some biases in the fossil record?
fossils occur when something is rapidly buried and is slow decomposes under layers of sand, mud, and sediment, then over a long period of time habitat dries out. biases of the fossil record are: rarity (the process of forming and finding fossils is rare), Fossils only form under ideal conditions (rapid burial, rapid decomposition), and preservation bias. preservation bias is the habitat bias (fossilization is more likely in environments with active sediment deposition ie beaches and wetlands, and burrowing organisms under the ground) Taxonomic and tissue bias (organisms with hard parts ie bones, shells, or with tough layers ie pollen are slow in decaying), and finally Abundance bias (organisms that were abundant and wide spread are more likely to be fossilized)
- What is the geologic time scale? How are intervals on the scale defined? What are some important developments in life on Earth?
is Geologic time divided into a nested hierarchy of Eons, Eras, Periods, and Epochs. Intervals are determined based on the appearance of new lineages or innovations. Originally, geologists used distinctive rock formations or fossilized organisms to identify boundaries of intervals, radiometric dating allows us to assign absolute dates to events and species in the fossil record. Precambrian Interval (4.6 Ba-541 Ma) includes the formation of earth, origin of life, and oxygenic photosynthesis. Phanerozoic Eon (541- present) is also important.
What is adaptive radiation? What is the difference between intrinsic or extrinsic adaptive radiation? What are some examples of both forms of adaptive radiation?
adaptive radiation is when a single lineage rapidly diversifies into many descendant lineages with a wide diversity of forms and ecological niches. there are two mechanisms of adaptive radiation. The first is Extrinsic adaptive radiation, which is an ecological opportunity (populations able to exploit favourable new environmental conditions or empty niches). The other mechanism is Intrinsic adaptive radiation which is the evolution of innovative morphological, physiological, or behavioural traits.
Couldn’t find examples
What is the Cambrian explosion? What fossil assemblages document this event? What hypotheses have been proposed to explain the Cambrian explosion?
The sudden appearance and rapid diversification of most of the animal phyla are extant today (541 Ma). fossil assemblages
-Microfossils (Changjiang, China, 570 Ma) tiny (less than one mm) sponges and coral
-macrofossils (Ediacaran Hills, Australia 565-542 Ma) small soft-bodied jellyfish and sponges, filtered organic debris from organic mats,
no appendages, mouth, limbs, or heads
-macrofossils (Burgess Shale, Canada, 508 Ma)
enormous diversity of animal forms and ecological roles
Hypothesizes:
1)higher oxygen levels
-made aerobic respieration more efficient
-at the start of the cambrian, O2 levels may have reached a threshold that could support larger more active animals
2)Evolution of predation
-predation led to selection for defences (shells, exoskeletons, rapid movement, etc.)
-drove morphological divergence among prey species
3)new niches
-once animals could move off ocean floor, they could exploit algae and other resources
-created new niches for predators, leading to more speciation and divergence
4)new genes
-Hox genes
-earliest animals had no/few hox genes
-gene duplication/divergence increased number of hox genes in animals
-made it possible for larger and more complex bodies to evolve
What is the difference between background and mass extinctions? Contrast the end-Permian and end-Cretaceous mass extinctions. What are the likely causes of each?
in background extinction 0.1-1 extinctions per million species per year (rate depends on taxa) mass extinction is when at least 60% of species go extinct within one million years. end-Permian extinction was the extinction of most forms of multicellular life, 90% of all species went extinct. caused by Siberian Trap flood basalts (no oxygen). the end-cretaceous extinction was the extinction of non-avian dinosaurs, 60-80% of multicellular species went extinct. caused by asteroid 10 Km wide.
What factors are contributing to the current increase in extinction rates?
habitat loss and fragmentation, overexploitation, climate change, and invasive species
How can we distinguish between bacterial, archaeal, and eukaryotic organisms?
Bacteria: cells do not contain a nucleus.
Archaea: cells do not contain a nucleus; they have a different cell wall from bacteria.
Eukarya: cells do contain a nucleus.
What is metagenomics and how are “species” defined using metagenomic analysis?
Metagenomics is a discipline that enables the genomic study of uncultured microorganisms. Species are defined as having greater than 97% similarity as marker genes
What are the six different metabolic pathways employed by prokaryotic organisms?
photoautotrophs
chemoorganoautotrophs
chemolithoautotrophs
photoheterotrophs
chemoorganoheterotrophs
chemolithoheterotrophs
What was the oxygen revolution and what are its consequences for cellular respiration?
an event stretching over the Proterozoic eon when molecular oxygen levels in the atmosphere rose and carbon dioxide levels decreased
