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.
What are some reasons for the adaptations of non-colonial corals, compared with colonial corals?
Hard skeletons and plate-like structures (septa) provide physical protection in the absence of colony.
What is the current accepted taxonomy for the phylum Cnidaria to class level?
Includes Cubozoa (box jellies), Scyphozoa (true jellies), Anthozoa (anemones and corals) and Hydrozoa (hydra, port. man-o-war).
What do parasitic trematodes and free-living planarians have that parasitic cestodes do not?
A mouth enabling attachment to substrate and ALSO through which food and nutrients are absorbed.
What do parasitic cestodes have in place of a mouth?
Absorb nutrients directly through tegument.
How did terrestrial invertebrates adapt to breathing air on land?
Book lungs; flattened respiratory surfaces that function in aquatic and terrestrial environments, as long as they are kept moist.
How do springtails keep themselves moist?
Special grooming fluid, as well as residing in moist environment
How do molluscs keep themselves moist?
Some molluscs have shells that can be clamped down to retain moisture.
Why doesn’t external, indirect fertilisation work on land?
Requires water as a medium through which reproductive material can travel.
How is terrestrial slug reproduction similar to reproduction in aquatic environments?
Pheremone laced scent trails; similar to when marine invertebrates release pheromones to initiate mating.
How do some terrestrial invertebrates care for their young?
- Nest building
- Defending of young from predation
Why advantages does the defending of young confer on offspring?
A greater percentage of young will survive to hatching.
Why can scorpions survive in a desert while spiders can’t?
Watertight exoskeletons.
What are some advantages to parasitism as a viable life history method?
- Uninterrupted access to food source
- Protective environment for the incubation of offspring
- Host provides mechanisms for progression of the parasite’s life cycle (dispersal in faeces)
In what hosts do F. hepatica live? Where are they found?
Mostly in the livers of mammals (liver fluke)
Where do planaria occur?
In freshwater, amidst rocks and debris.
What do planaria eat and how do they do it?
Carnivorous, consume other aquatic invertebrates. Suck up food with muscular mouth, passes through eversible pharynx.
(Nematodes) are vinegar eels parasitic or free-living? What morphological feature are they missing that suggests parasitism? (2 points)
Vinegar eels lack suckers, hooks or teguments that suggest parasitism
What is a hydrostatic skeleton?
A fluid-filled cavity that activates longitudinal and circular muscles to aid in movement.
Which phyla have a hydrostatic skeleton?
Most invertebrate phyla have a hydrostatic skeleton, excluding poriferans and some invertebrate phyla with chitinous exoskeletons.
Can leeches swim? Comment on the movement of leeches.
Some swim by moving side to side, others move by delooping (attach with sucker and propel forward)
What are some morphological similarities between leeches and earthworms? (3 points)
- Both have clitella
- Nervous system
- Hydrostatic skeleton
What are some morphological differences between leeches and earthworms? (5 points)
- Reduced setae in leeches
- Reduced or absent segmentation in leeches
- Leeches have jaws
- Leeches have eyespots
- Leeches have posterior sucker
(Annelids) what are some benefits of having a closed circulatory system?
- Blood transfers faster in a closed system = faster metabolism
- More energy efficient
Why are earthworms called ‘ecosystem engineers’?
As detritivores, earthworms recycle organic material and produce nutrients in the soil that benefit other organisms.
What are the scolex, hooks, and suckers of parasitic cestodes?
The scolex is the head portion of a cestode, which includes the hooks and suckers and is used to attach to a host.
What are the strobila and proglottids of parasitic cestodes?
The proglottids are the male/female sex organs, housed in each segment of the cestode. All of the proglottids collectively form the strobila.
Of Nematodes and Platyhelminthes, which group belongs in the group Ecdyozoa? What is another phylum that belongs in this group?
Nematodes. Arthropods share this classification also. Ecdyozoans have the ability to shed exoskeleton several times throughout their lifespan.
What morphological adaptations to parasitic life do liver flukes (F. hep) have that free-living planarians do not?
- Oral and ventral suckers
- Anaerobic respiration for oxygen-poor environment
Compare and contrast Platyhelminthes and Nematodes.
- Nematodes lack circular muscles
- Platyhelminthes have an incomplete digestive system
- Nematodes have pseudocoelom, Platy are acoelomate
How are the dorsal and ventral surfaces of Annelids different?
Dorsal = darker Ventral = lighter
Why do leeches and polychaetes have small coeloms compared to earthworms?
Because of reduced segmentation, the coeloms of leeches and SOME polychaete worms can expand more relative to body size.
What structures of annelids are repeated in each segment?
Setae, nephridia
What structures of annelids run throughout the whole body?
Circulatory system, nervous system, excretory system, longitudinal muscles.
