Bio lab quiz

Know how to use a dichotomous key to identify an unknown organism

Always read both choices in a couplet, even if the first choice initially appears

correct

2. Make sure you understand the terminology in the couplets

3. When measurements are given, be sure to measure the characteristics yourself

4. Living organisms are somewhat variable, so do not base your conclusion on a

single observation study several specimens

5. If a choice is not clear, try both choices  if you end up with two possible

answers, research the two possible organisms to help you decide

6. Even if you arrive at an answer, research the organism you arrive at to see if it

agrees with the unknown specimen you are trying to identify  if it does not

agree, an error has been made in the key or its use

Know the names of the two types of dichotomous keys and how to distinguish between them

Bracketed keys:Numbered by the number of the first statment in the couplet that is followed by a period and the number to the second statement. The lead directs you to the next couplet or name of the unknown organism

Indented Keys: Numbering in indented key is similar to bracket key.But instead of using numbers to indicate the selected lead, the couplets are subdivided until the unknown organism is identified

Know how to draw a phylogenetic tree.

1)Choose your species and traits:

2)Identify the outgroup

3)group by shared derived traits

4)draw the branches starting with earliest shared traits then breaking off into subsequent organisms.

know the parts of a phylogenetic tree

Root: the common ancestor of all taxa

Node: represents a taxonomic unit or a branching point

Branch: defines the relationship between the taxa and changes in traits over time

Outgroup: a taxon that shares ancestral traits with the rest of the group, but is distinct

Polytomy: a node with more than two branches, often occurs when differences are not known

Reading a phylogenetic tree

Be familiar with phylogenetic terms (synapomorphy, etc…) and identify parsimonious trees.

Phylogenetic groups

Monophyletic group (clade): group of organisms descended from a common ancestor

Polyphyletic group: group of organisms descended from different common ancestors

Paraphyletic group: group of organisms descended from a common ancestor but does

not include all descendants of the common ancestor

Symplesiomorphies: traits that are shared between all organisms in a given phylogenetic tree.

Parsimonious tree:a phylogenetic tree that requires the fewest possible evolutionary changes—such as genetic mutations or physical trait shifts—to explain the observed data

Make sure you can identify the different parts of a microscope.

Optical System

• Eyepiece (Ocular Lens): The top lens you look through, usually with 10x magnification.

• Objective Lenses: A set of lenses (commonly 4x, 10x, 40x, and 100x) that provide the primary zoom.

• Head (Body Tube): Connects the eyepiece to the objective lenses and holds the internal mirrors.

• Revolving Nosepiece: A rotating turret that holds the objective lenses so you can switch power levels.

Mechanical System

• Stage: The flat platform where you place the microscope slide.

• Mechanical Stage / Stage Clips: Secure the slide and use X-Y knobs to move it smoothly.

• Arm: The curved vertical frame used to support the head and carry the device safely.

• Base: The heavy bottom platform that keeps the microscope stable.

• Coarse Focus Knob: The larger dial for quick, major adjustments to clarity.

• Fine Focus Knob: The smaller dial for sharp, precise final focusing.

Illumination System

• Illuminator: The light source, such as a built-in LED/halogen lamp or a mirror.

• Condenser: A lens beneath the stage that focuses light directly onto the sample.

• Iris Diaphragm: A rotating disk or lever that controls how much light passes through the slide.

compare and contrast the different kinds of microscope

A compound microscope uses visible light and multiple lenses for magnification, typically up to 1,000x or 2,000x, ideal for viewing thin, transparent samples like cells. A dissection microscope provides a 3D view with lower magnification (10x to 100x), suited for larger, opaque objects. In contrast, an electron microscope employs electrons for ultra-detailed imaging, achieving magnifications of 100,000x or more, but cannot view live specimens due to sample preparation requirements.

be sure that you know how to focus on a specimen

• Look at the stage from the side—not through the eyepiece—and use the large coarse adjustment knob to bring the lens as close to the slide as you safely can.

• Look through the eyepiece.

• Slowly turn the coarse adjustment knob to move the lens away from the slide until the sample comes into view.

• Use the smaller fine adjustment knob to make the image sharp and clear.

• Adjust the iris diaphragm or light dial underneath the stage if the view is too bright or too dark

how do you calculate total magnification

multiply the power of objective lens by the power of the ocular lenses(Ex. objective lens :10 xPower of the ocular lenses: 10= 100)

Understand the concept of Hardy-Weinberg equilibrium and the conditions required for a population to maintain this

Developed models indicate that heredity alone does not influence the genetic structure of a population. The frequency of alleles remains constant under specific conditions, meaning a new genotype won't drive evolution if five criteria are satisfied: no gene mutation, complete random mating, a large population size, and no gene flow.

know how to use the hardy Weinberg equations for allelic and genotypic frequency what do each of the variables represent?

Allelic Frequency

p+q= 1

p is the frequency for the

dominant allele (R)

 q is the frequency for the

recessive allele (r)

 Allele: R or r 

Genotypic Frequency

p2 + 2pq + q2 = 1p + q = 1

 p2 is the frequency for homozygous dominant (RR)

 q2 is the frequency for homozygous recessive (rr)

 2pq is the frequency for the heterozygote (Rr)

 Genotype: RR, Rr, or rr  Individual Organism

population

Example: R = freckles, r = no freckles

So, RR = freckles, Rr = freckles, and rr = no freckles

Allelic Frequencies

If p = 0.7, then q = 0.3 70% of the alleles in the population give freckles, 30% do not give freckles

know the different evolutionary forces

Genetic drift: significant evolutionary force under conditions known as the bottleneck effect and the founder effect.

Bottle neck effect: A bottleneck occurs when a population undergoes a drastic reduction in size because of chance events, such as a volcanic eruption or a hurricane. Bad luck, not bad genes!

know the concept of evolution and why it occurs

the change in the inherited traits of a population over successive generations