Lab 2

phenotypic plasticity

a single genotype can produce different phenotypes in response to its environment

phenotype

outward appearance or observable manifestation of a genotype

overall phenotype

an organism’s overall phenotype is composed of its morphology, behaviour, and physiology

variation in phenotypes

the result from variation among genotypes and the environment

• as well as interactions between the two

genotype

complete genetic constitution of an organism

continuous traits

also known as polygenic or quantitative traits

• height, skin colour, intelligence

• controlled by multiple genes and environmental influences

discrete traits

also known as qualitative traits

• blood type, tongue rolling, hitchhiker’s thumb

• controlled by one or few genes

acclimitation

altering the phenotype in response to environmental variation to gain higher fitness

onnis sicula

produces yellow (dormant) seeds under long-day growth conditions

produces green (non-dormant) seeds under short-day growth conditions

reaction norm

the relationship between the environment and the trait in question

why phenotypic plasticity does not evolve in all traits

1. insufficient variation

2. cost and limitations

insufficient variation

If there’s no genetic variation in how a trait responds to the environment, then phenotypic plasticity for that trait can’t evolve — because natural selection has nothing to "work with."

costs and limitations

There are inherent costs and limitations to phenotypic plasticity.

• costs associated with producing new phenotypes and maintaining the regulatory mechanisms necessary for it to occur

observed phenotypic variation

the observed phenotypic variation for a phenotypically plastic trait cannot be inherited itself

• the phenotype variation is produced by the same genotype

how plasticity evolves

in heterogenous environment, which can change frequently

• plasticity evolves (ability for an organism to change its phenotype in response to different environmental conditions)

phymata americana

specimens observed in lab are wild

• phenotypic variation due to interaction b/w genetic and environmental variation

stridulate

making a shrill sound by rubbing the legs, wings, or other parts of the body together

• precopulatory courtship behaviour in male Phymata americana

• warn rival males

• both males and females stridulate when disturbed

promiscuous

having or characterized by many transient sexual relationships

• male and female Phymata americana

phymata americana growth

Phymata americana go through 5 stages of incomplete metamorphosis

• start off as nymph

• sheds exoskeleton 5 times before reaching adult form

rostrum

beak-like sucking mouth part

phymata americana hunting

sit and wait on flowers

• waits for prey (flies, moths, butterflies, wasps, bees) before striking them when they are within range

• while holding prey, they pierce its body with their rostrum (injecting paralyzing and digestive enzymes)

• sucks out liquefied body tissues

phymata americana sensory organs

two types of light sensing organs:

• compound eyes

• simple eyes (ocelli)

also possesses:

• clubbed antennae (for smelling)

• Johnston’s organs (for hearing)

stereo microscope

dissecting microscope

• provides 3D view of the object

• separate light paths for each eyepiece

• less magnification than compound microscopes

distance

the greater distance b/w the objective lens housing and the stage plate

• allows for better viewing and better manipulation of a wide variety and size of specimens

impatiens waleriana

all plants observed in lab are clones

• plant being shaded from sunlight

  • reduced amounts of red light illicit morphological, physiological, and biochemical characteristics in plants

• induces phytochrome molecule response

observation

comes from our senses

• allows us to formulate predictions which we can investigate

if we are more familiar with the subject, papers and books can also become observations

questions

comes from our observations

• best questions are relevant and have the capacity to be answered

• different questions form the type and scope of the study

influences our hypotheses, experiments, and our answer

hypothesis

a possible explanation for our observations

• proposes a relationship between potential factor(s) and observed phenomenon

• informed by all relevant observations

proving hypotheses

hypotheses can only be disproven—not proven

• you can find evidence against a hypothesis (disprove or reject it)
  but you can’t confirm it's true in all cases

null hypothesis

proposes no relationship between the factor being studied and the observed phenomenon

• the default stance we take when trying to explain the observed phenomenon

good hypotheses

generates specific, testable predictions that rejects or fails to rejects null hypothesis

• not overly complicated but not vague either

• includes a factor that can be measured that results in observed phenomenon

experimental manipulation

investigator actively alters the system and measures the effects of the manipulation

• factor being controlled = independent variable

• phenomena responding to the factor = dependent variable

level of independent variable being administered = treatments

correlational study

uses naturally occurring variation to investigate the effect of one factor on another

• no manipulation, just observations

• no classification of “independent/dependent” variables

experiment vs correlational study

some hypotheses can be tested by either manipulation or correlation

correlational advantages

• less handling of organisms

• systems observed in their natural state

• represent biologically relevant variation

• more practical/ethical

experimental advantages

• controls for confounding variables

• establishes direction of causation

control

reference to which results of an experimental manipulation can be compared

• must be identical to the treatment groups

confounding variables

factors that the researcher failed to control or eliminate

• can damage the validity of the experiment

controlled variables

variables that are held constant in a study

• e.g giving animals in different groups the same amount of food so as to not affect the results by inability to find food

statistical techniques

provides a quantifiable measure of how confident we should be in rejecting the null hypothesis

discussion

knowing the results is different from interpreting them

• if more students attend a seminar with cookies than one without what does this mean?

• are students hungry? do they like cookies? are they opportunistic feeders and the type of food served at seminars is actually irrelevant?

putting hypotheses in theories

when a hypothesis is supported by a substantial amount of evidence from many studies and is shown to be reliable within specified limits

• hypothesis may be accepted as part of a general theory

theory

has been tested and shown to be universally valid

• sometimes described as natural laws (e.g law of gravity)

1. must accurately describe a large class of observations

2. must make definite predictions about the results of future observations