systematic biology post lab on dichotomous key copy

Systematic Biology Laboratory

Post Lab

Classification of OrganismsSystematics - refers to the study of the

diversity of animals and their evolutionary relationships

Linnaean system of Classification

documentation by systematists

Taxonomyconcerned with identifying, naming, and classifying organisms.

Main tasks of Systematics

Identification

Nomenclature

Classification

Binomial System

Guidelines in Writing Dichotomous Keys

1. Initially, divide the set of organisms to two groups based on the most obvious character/feature. The key should be dichotomous.

2. Construct a couplet by identifying and describing a property that some organisms have but that none of the other objects have. The property may either be QUANTITATIVE or QUALITATIVE.

Quantitative – ex. Has eight legsQualitative – ex. Blue eyes

3. Avoid distinction on the basis of geographic distribution.

4. The first choice must always be positive.

5. Group all objects displaying that property in one set and all of the remaining objects in another couplet.

6. LEADS of a couplet must start with the same initial word.

7. Leads of a couplet must be mutually exclusive to each other.

8. Statements of the leads should not be overlapping. Statements of the leads should not be vague generalities (the words small, large, long, short).

9. Two consecutive couplets should not begin with the same word. If it is necessary to repeat the same word, use the article “the”

• 10. Arriving an answer with the key, do not accept it as absolutely reliable.

• Comparison with TYPE SPECIMEN• Ask Authorities

• Learn where to look for the descriptive characteristic– generic labeled pictures help!

• Know WHERE the samples were collected• Know the habitat type• Have measuring instruments in hand• Once you can identify key features of groups,

you can skip over the early parts of the key, and jump straight to Family, for instance.

Keying Out Individuals

Plant Anatomy

Leaf Anatomy

Types of Leaves

Leaf Arrangement

Shape of Leaf Blade

Leaf Venation

Shape of Leaf Margin

Shape of Leaf Apex

Shape of Leaf Base

Example

• Leaves compound or simple?• Leaves needle-shaped or broad and flat?• Leaves opposite or alternate?• Shape of the leaf and veins?

ACER

• Yoked/Indented Key• Bracketed or Parallel Key• Serial or Numbered Key – can be derived from

Yoked/Indented Key

Types of Dichotomous Keys

Yoked Key

Bracketed/Parallel Key

TYPE SPECIMENS

• Type specimens are the objective standard of reference for the application of zoological names. When a new species or subspecies is described, the specimen(s) on which the author based his description become the type(s) (Article 72.1).

ICZN’s definition of TYPE SPECIMENS

• A particular specimen of an organism where to which the scientific name of that organism is formally attached.

• Serves as a baseline to centralize and define the characteristics/features of a particular taxon.

Type

• NO.• Purely for Nomenclature.• Types do not need to be typical in the sense of

representing an average of the range of variation of a taxon, nor do they need to be a particular sex or life stage, or even a whole specimen.

Do types have to be typical of a species?

• Syntypes – where a description has been based on a series of specimens, these collectively constitute the name-bearing type (Article 72.2-72.4; 73.2).

What kinds of types are there?

• Lectotype – One of a number of syntypes which has been designated later as the single name-bearing type of a species, the remaining syntypes become paralectotypes and have no further name-bearing function (Article 74).

• Holotype – A single specimen designated or otherwise fixed as the name bearing type of a species name when it was first described (Article 73).

• Paratype – Where there is a holotype, the other specimens in the type series are paratypes (Rec. 73D), and they have no name-bearing function.

• Hapantotype – A special kind of holotype in the case of extant protistans, which can consist of more than one individual (Article 73.3).

• Neotype – A single specimen designated as the name-bearing type of a species name when the original type(s) is lost or destroyed and a new type is needed to define the species. Under exceptional circumstances the Commission may use its plenary powers to designate neotypes for example if an existing name bearing type is not in accord with prevailing usage (Article 75)

• Allotype – a designated specimen of opposite sex to the holotype. This term has no name bearing function and is not regulated by the code (Rec. 72A).

Plant Dichotomous Key

1Vascular…………………………………………………..21’Non-Vascular………………………………….. Moss2 Spore Producing………………………………………32’Seed Producing……………………………………….63Spores found in sori…………………………………43’Spores found in strobilus…………………Horsetail4Rhizome creeping, with marginal indusium absent……………………………………………………….54’Rhizome non-creeping, with marginal indusium present……………………………………………….Pteris tripartite

5 Sori linear in arrangement…………………………Asplenium nidus

5’ Sori scattered in arrangement …………..........Microsorum sp.

6 Seed naked……………………………………………76’ Seed enclosed………………………………………107 Leaves pinnate,coriaceou………………………

Zamia pumila7’ Leaves broad to acicular or linear, spiral, whorl ………………………………..………………………………..8

8 Leaves w/ strong fragrance………………………….98’ Leaves w/o fragrance…………….Podocarpus sp.9 Flat-lik……………………………………………Thuja sp.9’ Whorl-like………………………………..Juniperus sp.10 Inflorescence solitary…………………..……..

Hibiscus rosasinensis10’ Inflorescence raceme………………………..

Malphigia sp.

Plant Divisions

Plants

Non-vascular (bryophytes)

vascular

Hepatophyta

Bryophyta

Anthocerophyta

liverworts

moss

hornworts

seedless

seed-bearing

Psilotophyta

Lycopodophyta

Equisetophyta

Pteridophyta

whisk fern

club/spike mosses

horsetail

ferns

Pinophyta

Cycadophyta

Gnetophyta

Ginkgophyta

pines/conifers

cycads/palms

gnetophytes

maidenhair tree

Division Examples

naked

Magnoliophyta Magnoliopsida (dicots)

Liliopsida (monocots)enclosed

Definition

a. Homology refers to features of two or more organisms sharing common ancestry.

b. Analogy refers to features of two or more organisms sharing common function

• Features may or may not be homologous• eg. Fin of a fish and the flipper of a whale

c. Parallelism is evolutionary change in two or more lineages such that corresponding features undergo equivalent alterations without becoming markedly more or less similar

d. Convergence is evolutionary change in two or more lineages such that corresponding features that were formerly dissimilar

Monophyletic clade is one that includes an ancestor and all descendants

Paraphyletic clade is one that includes a common ancestor and some, but not all, of its descendants

Polyphyletic clade is one that does not share an immediate common ancestor

Yun lang !

Salamat!