Lab Manual Ch. 1 - 3 and Appendix A Flashcards
what two interesting features do the immature stages (nymphs) of reduviid bugs display? why?
- cover their thorax with a layer of dust, sand, or soil particles to form ‘dust particles’
- attach dead insects - mainly ants - to their thorax using elastic threads produced by glands on their back to form a ‘backpack’
-> less likely to be eaten by predators and detected by the bug’s prey
class and phylum of insects
class Insects, arthropods
define arthropods
animals with jointed legs
what is the basic insect body plan?
includes 3 main sections: head, thorax, and abdomen. from the thorax extend three pairs of legs and, usually, one or two pairs of wings
where are insects found?
in just about every habitat on Earth. 1.9m species have been identified on earth, over half of which are insects
what can an adaptation consist of?
can be a physical feature of the body or a behaviour
In each generation, new traits and combinations of traits are created by
mutations and recombination (mixing of genes through sex)
which individuals have higher fitness?
individuals that possess traits that help them to survive and reproduce better
define fitness
can be measured as the number of offspring an individual produces relative to other individuals in the population
describe causes of gene flow
influx of migrants from other population
how can we understand the evolutionary process that gave rise to a particular trait and understand whether or not a particular trait is an adaptation?
it is necessary to consult the phylogeny (evolutionary history and relationships) of the species
what do biologists do when they observe an interesting trait that appears to be an adaptation?
- come up with at least one hypothesis for how the trait may have increased the fitness of individuals (i.e. its function)
- this is inspired by some knowledge of the organism’s habitat, behaviour, and lifestyle
- test it
describe the 2 sections into which adaptations are divided
- adaptations for viability (success in survival and acquisition of food)
- adaptations for competition for mates
why must hypotheses be tested?
all scientific ideas and explanations are evaluated by how well they conform to empirical evidence
what is the name for natural selection arising from variation in viability?
viability selection
give examples of adaptations for viability and why they are important
adaptations for:
- locomotion
- predator or parasite avoidance
- food acquisition
- shelter construction
- tolerance of ambient conditions
an individual that fails to survive or obtain food will produce no offspring and have a fitness of 0
camouflage
less visible to predator
life in water
aquatic insects often have bodies and legs specially shaped to facilitate locomotion (eg oar-like hind legs of the backswimmer)
feeding
evolving specialised mouthparts to adapt to particular diets
- ants have powerful jaws = mandibles
- mosquitoes have a tube = stylet
- butterflies have a long tongue = proboscis
why are adaptations for competition for mates important?
an individual that fails to mate will produce no offspring and have a fitness of zero.
natural selection arising from variable mating success is called
sexual selection
what does sexual selection often result in?
the evolution of differences between males and females in secondary sexual characteristics (characteristics other than ovaries and testes)
define sexual dimorphism
distinct difference in size or appearance between the sexes of an animal in addition to difference between the sexual organs themselves.
why are some fully functional structures in one sex also present in a non-functional (often miniature) form in the other sex?
males and females share nearly all of their genes, so the selection acting on one sex will usually also affect the other sex to some degree
what are the two principal mechanisms of sexual selection?
intrasexual competition and mate choice
intrasexual competition
- in many species of animals, males fight with other males for access to females
- a male that is able to defeat his rivals in combat will probably sire more offspring
- for this reason, male animals often possess adaptations for fighting (eg horns, modified mandibles, or tusks)
mate choice
- mate choice is thought to increase the fitness of the ‘chooser’ by enabling it to mate only with healthy individuals (which are thus more attractive as mates and produce more offspring)
- many animals have adapted to the preferences of the opposite sex by evolving elaborate structures, colour patterns, and courtship displays that may reveal their health and vigour
life of a butterfly
complete metamorphosis
- eggs hatch into larvae (caterpillars) which feed on vegetation and grow
- when a caterpillar attains full size, it assumes a dormant and nearly immobile form called a pupa
- inside the pupa’s protective cocoon, caterpillar develops into an adult
- when transformation is complete, adult butterfly breaks out of cocoon and dries its wings
- feeds on nectar from flowers and can reproduce
water striders
- live on surface of water in small pools, streams, ocean
- order Hemiptera (true bugs)
- fine hairs covering body and legs are water-repellent to allow them to move over water without sinking
- female water striders choose their mates by engaging in pre-mating struggles which only some males can overcome
- capture small insects entrapped by water’s surface tension
- excellent eyesight to find prey
walking sticks and leaf insects
- order phasmatodea (stick insects)
- found in tropics
- adults and juveniles feed on leaves
- females capable of parthenogenesis
- parthenogenetic eggs take longer to develop than fertilised eggs
- preyed upon by birds and small animals
Madagascar hissing cockroaches
- order blattodea
- live in forested areas
- feed on variety of vegetable matter on forest floor
- males larger than females and possess prominent bumps on dorsal prothorax (anterior section of thorax) which serves as a plate which protects the head
- males defend territories
- adults hiss when handled or pursued, aggressive encounters, courtship, mating
- preyed upon by birds, animals, reptiles, amphibians
- females carry eggs in a pouch (ootheca) until they hatch
stag beetles, rhino beetles and stalk-eyed flies
- stag beetle adults and larvae live in decaying wood
- males known to use their mandibles in combat with other males
sketch a graph for:
only differences in genotype contribute to genetic variation
only differences in environment contribute to variation
interaction between genotype and phenotype contributes to variation
acclimation
- alteration of the phenotype in response to environmental variation in a manner than improves fitness
distinguish between acclimation and adaptation
individuals do not adapt but rather acclimate to their environment; populations are capable of adapting to changing environments
phenotypic plasticity
the ability of one genotype to produce different phenotypes in different environments
reaction norm
the relationship between the environment and the trait in question when phenotypic plasticity expresses itself in a continuum
why aren’t all traits phenotypically plastic?
- insufficient genetic variation exists within a particular species for a particular trait for the evolution of plasticity to occur
- costs associated with producing new phenotypes and maintaining the sensory and regulatory mechanisms required for plasticity may offer a significant selection pressure against the evolution of plasticity for a trait
- at a genetic level, linkage between genes might produce a situation whereby genes promoting plasticity might be linked to genes conferring a low fitness for other traits
2 limitations of producing new phenotypes
- if an organism incorrectly senses the environment, or the environment changes rapidly, the organism may produce a maladapted phenotype
- time difference between sensing environmental change and alteration of the phenotype
is phenotypic plasticity heritable?
in the case of a phenotypically plastic trait, the observed phenotypic variation itself is not heritable because the different phenotypes are produced by the same genotype. however the ability for a genotype to produce more than one phenotype is genetically determined
what could lead to selection for plasticity of a trait?
- heterogeneous environments, which change frequently over space and/or time
- an individual that can produce more than one phenotype is more likely to acclimate to the changing conditions than an individual who can express only one phenotype
describe Jagged ambush bugs
- males stridulate (rub rostrum against sternum) as part of courtship behaviour and to warn away rival males
- females stridulate when distrurbed
- live in meadows and fields and spend time on flowers, where they sit and wait for arthropod prey
- catch their prey and hold onto it w their raptorial claws (modified front legs) then pierce body with rostrum and inject paralysing and digestive enzymes into it
- it then sucks out liquefied body tissues
- two types of sight sensing organs: compound eyes and simple eyes (ocelli)
stereo/dissecting microscope - description + diagram
- 3d view of object
- has separate light paths for each eyepiece
- less magnification power than compound
how do you calibrate an ocular micrometer?
- find out the number of spaces on the ocular micrometer
- find the number of millimetres on the stage
- calculate the width of 1 ocular space in mm
- you can then multiply that by the length of the object
compound microscope - diagram
competition as a type of species interaction
when the interaction has a negative effect on both species
mutualism as a type of species interaction
interactions in which both species benefit
consumer-resource interaction as a type of species interaction
an interaction that has a positive effect on one species but a negative effect on the other; consumer benefits and resource suffers a cost
how can plants resist herbivory?
through tolerance or defence
tolerance
a plant’s ability to reduce the effects off herbivory on fitness (eg plant may move resources from roots to shoots following herbivory in order to stimulate shoot growth and replace lost tissue)
defense
a trait that reduces damage to a plant by herbivores
defensive traits generally fall into 3 categories:
- timing of flowering or lead production
- structural defences
- chemical defences
trichomes
hairs on stems and leaves that can trap herbivores, prevent them from laying eggs or make it difficult for them to feed on leaf tissue
two types of defences
structural and chemical
chemical defences against herbivory
secondary metabolite: a chemical produced by a plant that is not essential for growth or development
constitutive defences
the expression of some defences does not significantly fluctuate over time
induced defences
when one chemical is produced in response to wounding, which results in the production of other chemicals that spur defences (structural and chemical)
how do you measure a chemical defence in a plant?
- chemical assay to quantify the activity of polyphenol oxidase (PPO)
- PPO is an enzyme stored in the plastids of plant cells. when a plant cell is damaged, PPO is released into the cytosol of the plant cell.
- PPO can oxidise phenolic compounds to produce quinones, which can cross-link with other proteins
chemicals used for the PPO assay:
- potassium phosphate buffer: used to keep the pH of the solution constant. reaction is sensitive to pH
- PVP: absorbs phenols, so prevents reaction between PPO and phenols when trying to extract PPO
triton X-100
detergent which disrupts the chloroplast membrane, releasing PPO into the cytosol of the plant cell
caffeic acid
phenolic compound which can act as a substrate to react with PPO to produce quinones
PPO activity =
final absorbance - initial absorbance / 5 mins / leaf mass
advantages of a correlational study
- less handling time of organisms so no contamination/stress
- systems under study are more likely to be observed in their natural state
- they represent biologically relevant variation
- there are situations where experimental manipulation is not practical or ethical
advantages of experimental manipulation
- more likely to control for confounding variables
- we know the direction of causation
