Lab 8 Flashcards
(12 cards)
Why we do preservation
Inverts are preserved in ways that are appropriate for the taxonomic group so that they can be studied for purposes like research on systematics, ecological relationships such as predator/prey and various symbioses, as well as conservation.
This also reduces the need for increased mortality, as long-term preservation of a single specimen can be used as an educational tool for many students to learn from.
dissect preserved specimens
The ability to dissect preserved specimens allows us to gain information about them with the benefit of increasing knowledge about morphology and functionality of particular parts and organs, as well as visually compare and contrast between different individuals and species.
preserved whole specimen or preserved dissection
Contrastingly, a preserved whole specimen, or preserved dissection if possible, allows for the specimen to be educational over the long term.
We see this in insect collections, where, when specimens are properly prepared and stored, they can be part of a collection like that in a museum for multiple generations
Motile predators and the need for defense
Often predators need fewer defense-specific mechanisms than their prey do, as they are well-adapted to capturing prey - which comes with characteristics that can aid in defense.
In this way, there is definite overlap between predatory adaptations and defensive ones.
Most characteristics of an organism take energy to produce or maintain, so sometimes there is a trade-off due to limited resources – remember that the evolution that allows for adaptations is focused on survival and reproduction – so if a feature is costly to have then there needs to be a (reproductive) benefit.
If features for predation increase survival because defense is not as necessary (there are fewer predators or the organism is less vulnerable to predation due to features necessary for its own acts as a predator) then the cost of defense mechanisms is too great for any added benefit to be worthwhile.
Phylum Mollusca
triploblastic, coelomates.
Their bodies include a head, a muscular foot and the internal organs or visceral mass.
Characteristically, parts of molluscs are enclosed by a secretory epithelium (called the mantle) which defines a space called the mantle cavity.
The mantle secretes a calcareous shell that often has an outer organic layer (the periostracum).
Most molluscs have a radula (flexible ribbon of chitinous teeth) and a distinct gill type (ctenidium) that may be used for filter-feeding as well as respiration.
Gills may be numerous (chitons); paired (most molluscs); single or absent (some gastropods); or large (some bivalves).
Cephalopods
have reduced or absent shells (except for Nautilus) and are fast, intelligent predators.
Squid have a reduced, internal ‘shell’ called a pen that is used for some support – but due to their predatory nature, an external shell would be heavy and cumbersome and allow for much less flexibility.
They have a closed circulatory system, unlike other members of the Phylum Mollusca that rely on open systems, and are able to move quickly through the water, partly due to the use of their siphon.
The mantle (which excretes the shell in molluscs) is thickened in the squid, due to the lack of an external shell, and the mantle cavity is between this mantle and the internal organs.
This cavity fills with water and through muscular action can shoot water out through the siphon to create propulsion through the water.
Squid, although able to move away from danger, still have a defense mechanism in the form of an ink sac.
If threatened, they can release ink to obscure the view of the offending organism.
Being a predator themselves, squid have the common mollusc radula for scraping, along with a beak for biting into their prey, to start off their digestive system.
Since they are motile, it is easier for squid to find mates and undergo internal fertilization
Adaptations to a motile and predatory lifestyle
Squid are adapted to being highly motile being light and flexible, and having musculature and a siphon to give bursts of propulsion.
Their closed circulatory system improves oxygenation to aid in the movement.
Their beak aids in their predatory nature, as do their tentacles.
They have a highly modified nervous system (including cephalization, of course!) and are highly intelligent.
Are there any others you can think of?
Phylum Arthropoda: Class Insecta and preservation
The chitinous exoskeleton, allows many insects to keep their shape when drying out.
Pinning is a common method of preservation, to allow for the insect to be viewed properly for ID and then stored.
If an insect is exceptionally large, the additional step of removing the insides and stuffing with cotton can help prevent bad odours and drooping or dented bodies.
If an insect is soft-bodied, generally preservation in ethanol is a better choice than pinning.
If they are too small to be pinned, many can be attached to a small, pointed piece of paper that is then suspended on a pin.
This is called ‘pointing’.
To have maximum utility, it is imperative that pinned or otherwise preserved specimens are properly labeled.
For insects, this generally includes the location and date of collection and the name of the collector, and then usually an ID for the specimen.
Normally, the ID would be included on a separate, lower label, as this information may need to be switched out if there are taxonomic changes or more information is gathered and the ID needs to be updated.
These labels have a somewhat standardized format.
Insects are much less useful without collection data, as this can have a big impact on things like identifications and range estimates of individual species.
In a larger insect collection, each specimen would be given a unique identification number and its information would be included in a database as well as on the specimen itself.
This allows someone interested in the specimen to access the specimen information and then locate the insect within the collection, or use just the database to gather information related to the collection as a whole.
Class Insecta key characteristics and terminology
Flight
Insecta there has also been the evolution of flight, so they are largely terrestrial with some freshwater groups.
This has greatly increased the available niches for various species and has contributed to diversification of this large group.
many of them have four wings.
of Legs, antennae, tagmata
Class Insecta key characteristics and terminology
Insects have six legs.
And two antennae.
They have 3 tagmata (head, thorax, and abdomen) which are each multiple segments that are fused into distinct body regions.
Head, leg and antennal characteristics can be helpful for identification within various orders, as can wing venation.
Class Insecta key characteristics and terminology
Their complex behaviours have allowed for many interesting and common adaptations
grasshoppers with jumping hindlegs,
beetles with protective forewings (elytra),
bees and other pollinators with hairy bodies for carrying pollen.
Moths and butterflies have wings covered in scales that are thought to perform multiple functions: colourful signals to mates, protection from sticking in spiderwebs or resin, and improved flight (through improvement of lift and thermoinsulatory properties).
Mosquitoes have piercing mouthparts for taking bloodmeals from (usually) vertebrates.
Class Insecta key characteristics and terminology
Adaptations to diverse environments
Exoskeletons are an important adaptation for all arthropods – protection from predation and desiccation,
as well as an attachment site for muscles, which supports their complex behaviours (there are also many sensory adaptations for this reason!).
Tagmatization has created fused body regions in arthropods, to allow for specialized tasks to occur (ie. feeding/sensory functions/locomotion, etc.).
Flight is an adaptation in insects that allows for increased habitat options and the ability to disperse populations (to find new resources, and to escape from poor habitats or from predators).
There are multiple others, often specific to smaller groupings of arthropods.
