Module 1 - Intro Flashcards
What is the difference between vertebrates and invertebrates?
Vertebrates: animals with internal skeletons that have backbones aka their support structure exists within the organism and is called an endoskeleton
Invertebrates = 90% of animal species: animals that lack a backbone and instead have an external supportive structure called an exoskeleton
What are anthropods?
Invertebrates (have exoskeletons) and a defining feature of jointed appendages that form legs, antennae, mouthparts, and repro organs
What are the 6 unique characteristics of anthropods?
- exoskeletons
- jointed appendages
- bilateral symmetry (can be split only along a single plane)
- tagmata (segmented bodies
- ventral nerve cord
- dorsal blood vessel
What are the 3 important axes to know for bilateral symmetry?
- dorsal-ventral axis (top to bottom)
- anterior-posterior axis (front to back)
- lateral axis (one side to the other)
What are tagmata?
Fused regions of body segments of anthropods with specialized biological fxns
Where is the nerve cord located in an anthropod?
ventral side
- unlike vertebrates where the cord is located on the dorsal side of the body
What are the 3 tagmata of insects?
- Head
- Thorax
- Abdomen
How does blood circulate in anthropods?
- blood vessel known as the dorsal blood vessel
- open circulatory system in which blood is pooled within the body cavity’ tissues are essentially in direct contact with the blood
Simply put, what 2 things make up the exoskeleton?
- Cuticle
- Epidermis
What is the cuticle of the exoskeleton?
A non-living structure that is secreted by the underlying epidermis, and is made up primarily of CHOs in the form of CHITINS as well as proteins
What are the 3 major layers of the cuticle of the exoskeleton?
- epicuticle
- exocuticle
- endocuticle
What is the epicuticle and its fxn?
Outermost layer of the cuticle.
- waxy, thin, no chitin (made up of wax and cement)
- fxns as a barrier to prevent water loss and the entry of disease-causing pathogens
What is the exocuticle and its fxn?
Portion of cuticle of the exoskeleton that carries pigments and is often hardened for protection and support
What is the endocuticle and its fxn?
Innermost layer of the cuticle, it is much softer and more flexible.
What is the fxn of the exoskeleton as a whole?
Provides protection and support for the animal and acts as a framework to which muscles and organs can be anchored
What is tanning? What happens to exoskeletons as a result of tanning?
The hardening of the exocuticle. In insects, tanning involves the cross-linking of proteins within the chitin matrix of the exocuticle in a process known as SCLEROTIZATION (unique to insects)
Exoskeletons become more opaque and darker.
How have anthropods evolved to register sensations through its exoskeleton?
SENSILLIA which perceive and transmit stimuli across the exoskeleton
What is the biggest disadvantage of the exoskeleton of arthropods?
It restricts growth since it does not grow with the organism so arthropods need to MOULT
Why do arthropods need to moult?
Exoskeleton doesn’t grow with them. As they grow in size they need to moult in order to replace their old exoskeleton with a new one. This process is regulated by hormones.
What is apolysis?
The beginning of the moulting process; separation of the old cuticle from the underlying epidermis.
To allow the old cuticle to separate, the underlying epidermal cells replicate in response to the release of ecdysteroid moulting hormone.
What hormone regulates moulting? How?
Ecdysteroid Moulting Hormone
- synthesized and released into the insect’s system by the prothoracic glands
- it causes underlying epidermal cells to replicate in order for the old cuticle to separate
What does apolysis achieve?
Creates an open space btw the cuticular layers into which digestive fluid is secreted. This breaks down the inner endocuticle into metabolites reabsorbed by the epidermal cells to form new cuticle.
What is Ecdysis?
The process of an arthropod shedding its old exoskeleton after the new cuticle has been fully formed following apolysis
How do arthropods increase it body volume to increase the size of the new exoskeleton it has gained through moulting?
- contract muscles to increase fluid pressure
- swallow air or water to inflate gut and body
New cuticle is initially pale and soft until it undergoes tanning
When did the first arthropods appear?
during the Cambrian period
- fossils suggest arthropods were the first animals to colonise land
Why did arthropods have an advantage to be the first animals to colonise land?
- stiff exoskeleton gave protection from desiccation and support against gravity
- jointed appendages provided locomotion not dependant on water
Taxonomy
the branch of science that deals with classifying and naming organisms
- research the discovery, description, and identification of an organism
What are the 5 classes under the Phylum Anthropoda?
- Trilobita (extinct)
- Chelicerata
- Myriapoda
- Crustacea (we don’t cover these)
- Hexapoda
What are the 4 main ways to tell an insect from other arthropods?
- # of body regions
- # of legs
- # of antennae
- presence of wings
What are the differences between Chelicerata, Myriapoda, and Hexapoda?
of Antennae: 0, 1, 1
#of Tagmata: 2, 2, 3
Pairs of legs: 4, 8+, 3
Wings: no, no, insects only
What are the only invertebrates with wings?
Insects!
What separates insects from non-insect hexapods?
MOUTHPARTS
Non-insects: entognathous mouthparts
- mouthparts lie in a cavity within the head
Insects: ectognathous
- mouthparts are visible and external to the head
What is the main factor restricting the body size of arthropods?
The lower oxygen content in the atmosphere today compared to the Carboniferious bc an arthropod’s gas exchange system operates based on simple diffusion
- a high O2 content would have allowed O2 that enters the tracheal network to reach further cells before the O2 is absorbed and depleted
What is the tracheal system?
The body of an insect has a network of tubes from the exterior that branch within the body to lead to individual cells.
- Tracheae = larger tubes
- Tracheoles = smaller branching tubes which exchange gasses with individual cells
What are the benefits of small body size?
- Need few resources to survive
- Short generation times = evolution can occur at a rapid rate bc of the opportunity for selection to act
- Can make use of microhabitats
- Insects are ectotherms; body size allows them to absorb heat faster
- Takes advantage of passive dispersal
- Efficiency of muscular activity
Insects are ectotherms, what does this mean?
They rely on external sources of heat to regulate their body temp. The small size of insects is also advantageous in this case, as small animals have a high surface area to volume ratio = absorb heat faster
What is passive dispersal?
When animals use a mode of locomotion not dependent on their own musculature to move within or between habitats.
What are the drawbacks of small body size?
- Greater risk of predation
- Greater risk of damage from natural forces
- High risk of water loss through evaporation due to high SA to volume ratio
What is metamorphosis? What does it allow for?
The radical transformation in body form btw developmental stages during an organism’s life cycle.
Extreme changes caused by metamorphosis allow for specialization at different life stages.
What are insects that do not undergo metamorphosis called?
Ametabolous
- juveniles look and act like smaller versions of adults; once developed into adults they grow and moult unlike insects that undergo metamorphosis
What is the only difference btw adult and juvenile ametabolous insects?
presence of functional repro organs in adults
What are the 2 main categories of metamorphosis?
- Incomplete metamorphosis = the change is relatively minor
- Complete metamorphosis = more complicated and more radical changes in body form
What is Hemimetabolous Development?
Most insects that develop through incomplete metamorphosis have adults and juveniles that occupy the same habitat and use similar resources
Ex. cockroaches, grasshoppers, true bugs
What is typically the only difference btw adults and juveniles in hemimetaboulous insects?
presences of wings and fxnl repro structures in the adult stage
Their wings develop externally to the body in pouches called “wing buds”
What is the juvenile stage of hemimetabolous insects called?
NYMPHS or if they are aquatic like dragonflies NAIADS
What are exopterygots?
Insects that undergo incomplete metamorphosis that develop wings in wing buds
What is another term for complete metamorphosis?
Holometabolic Development
What is the characteristic life stage of insects that undergo complete metamorphosis?
PUPA
- generally immobile transitional phase btw the juvenile and adult life stages
What is a cocoon, what does it do?
A cocoon, sealed with or made entirely of silk, will enclose a PUPA to protect the insect while it undergoes its final developmental changes of complete metamorphosis.
In some insects that undergo complete metamorphosis, the pupa doesn’t develop in a cocoon, what does it do instead?
The pupa develops within the exoskeleton of the final juvenile stage. The exoskeleton hardens to form a PUPARIUM which protects the pupa. An adult insect emerges from its pupal exoskeleton in a process known as ECLOSION.
What are the juveniles of holometabolous insects called?
Larvae
Where do the wings of holometabolous larvae develop?
Internally during pupation from groups of cells within the body called IMAGINAL DISCS.
Because of the internal development of wings in holometabolous insects, what are these insects also referred to as?
Endopterygotes
What is one particularly important hormone regulator of metamorphosis (both complete and incomplete)?
Juvenile Hormone (JH)
- high levels of JH inhibits the development of adult characteristics; JH controls wheter the larva remains a larva through its next moult or develops into a pupa or adult; reduced level induces pupal stage, then absence triggers adult stage
- the process is simple in hemimetabolous insects; if JH is present, the nymph will moult into a larger nymph and if absent it will moult into an adult
What is diapause?
developmental arrest; development or reproduction is halted and metabolic activity is slowed
- can happen any season when unfavourable conditions arise
What do short generation times allow?
Insects to quickly adapt to changing environmental conditionals; short generation times = fast rates of evolution
What 4 orders of hemimetabolites do we cover?
- Odonata
- dragonflies, damsel flies - Blattodea
- cockroaches, eusocial termites - Orthoptera
- grasshoppers, crickets, katydids - Hemiptera
- most diverse order of insects that undergo incomplete metamorphosis
What 4 orders of insects make up holometabola?
- Coleoptera
- beetles
- presence of elytra - Hymenoptera
- ants, bees, sawflies - largest order of insects and most species rish of all animal life - Diptera
- “true flies” - Lepidoptera
- moths and butterflies
What are type speciments?
A single particular specimen that defines the species and serves as an identification for it
- carried by museums
Why are insect collections at museums important?
- voucher specimens of insects serve as a reference and basis of study
- type specimens
- fxn in outreach and education
What tool is used most often to gather insects for collection?
sweep net
- swept through vegetation to collect species on plants
How can insects be captured?
- image
- traps (ex. a malaise trap)
- sweep net
How are most insects preserved?
PINNING
- done when insect is fresh
- first, pin inserted through insect to secure to a spreading board (often through right side of thorax)
- adjust legs and antennae
- if there are wings, use a spreading board
What type of insects can’t be preserved by pinning? How are they preserved?
Soft bodied insects and larvae
- preserved in vials of ethanol
Some insects are too small and are glued to a small triangular piece of paper called a point, pin inserted through paper = POINTING
What is POINTING?
a way to preserve insects too small for PINNING. glued to cardstock (A POINT) and pin is inserted through paper
What are the 3 steps in starting an insect collection?
- Capture
- Preserve
- Label
What must all labels include?
- location
- collection data (ex. TOD)
- Name of who collected the insect
- specimen name (included on separate piece of paper)
