Mid-Sem Exam: Prac Book Questions Flashcards
What can phylogeny tell us about the past? (3 dot points)
- Tells us about evolutionary relationships between species and groups of species
- Usually has a root; common ancestor
- Tells us how species are related and allows inferences to be made about how and when evolution has occurred
What are some examples of random factors?
Mutation, gene flow, finite population size (genetic drift)
How can random factors affect individuals/populations?
Can cause changes in relative allele frequencies (genetic drift) and can be precursors to speciation events, e.g. allopatric (geo) speciation and sympatric (non-geo) speciation
What is the principle of parsimony?
Proposes that the simplest explanation, when supported by evidence, is most likely to be the correct one.
How does the principle of parsimony relate to evolutionary biology?
The phylogenetic tree that requires the least amount of evolutionary change between branches is most likely to be correct.
What evolutionary conditions might lead to long-term evolutionary stasis? (2 dot points)
- Little or no competition for an occupied niche
- New traits that randomly occur in individuals are unlikely to be selected over traits that already benefit an organism
What evolutionary conditions might lead to the rapid diversification of a lineage? (3 dot points)
- Predation
- Competition for resources/a niche
- The availability of new niches that select for different traits
What factors might increase the probability of a species going extinct? (2 dot points, one summary point)
Changes that occur quickly, e.g.
- natural disasters
- introduction of new, non-native species
What are two real-world examples of convergent evolution?
- Gliding mechanisms in squirrels (rodent) and sugar gliders (marsupials)
- Thylacine (dog-like, marsupial carnivore) and dingo (canine)
What is the fundamental difference in the developmental biology/form between sponges and Cnidarians?
Cnidarians have basic true tissues, sponges do not.
What do sponges have instead of true tissues?
Three main types of cells with specialist functions (choanocytes, pinacocytes, amoebocytes)
In what scenario may a sponge and Cnidarian interact directly?
Competition for substrate between sponges and anthozoans.
What are three examples of morphological differences between Poriferans and Cnidarians?
- Symmetry
- Cnidarians have cnidocytes (stinging cells). Sponges may have other physical or chemical defences.
- Sponges lack true tissues
If oscula are visible on most sponges, why are ostia sometimes not?
Oscula are larger pores through which water and waste products are expelled, Ostia are smaller and do the opposite. Size/visibility of ostia can indicate age/species of a sponge.
Are ostia and oscula sometimes difficult to distinguish?
Yes, in some species oscula are reduced or ostia appear larger than normal.
What can we infer from the sizes of ostia on a sponge?
May be indicators of age or species.
What are some morphological differences between Schyphozoans and (colonial) Hydrozoans?
Scyphozoans have clear radial symmetry, Hydrozoan may appear asymmetric but is actually a colony of radially symmetric organisms.
What are some similarities between hexacorals and octocorals? (3 points)
- Colonial organisms with many polyps fixed to surface
- Both are anthozoans
- Both have structures that would have served as attachment to a substrate (fixed in place)
What are some differences between hexacorals and octocorals?
- Octocorals have branching, tree-like structures that extend away from substrate
- Hard corals have bone-like calcium carbonate skeleton
- Solid structures of hexacorals indicate six tentacles or multiples of six, octo have eight
Are anemonies single or colonial organisms?
Anemones are usually colonial organisms, but will begin life as a single polyp Whether an anemone is colonial or solitary is deduced by looking at symmetry of the organism.
How can you tell whether a Cnidarian is colonial or solitary?
Symmetry; since we know that cnidarians have radial symmetry, any cnidarian that doesn’t is likely to be colonial, comprised of many individual polyps.
