Learning Objectives Living things can be classified based on

structural evidence

embryological evidence

evolutionary evidence

molecular (relatedness of DNA sequence) evidence

Carolus Linnaeus developed the system of taxonomy and binomial nomenclature that is still in use today.

Classification Method of organizing plants and animals into

categories based on their appearance and the natural relationships between them

DNA composition is most reliable method for identifying the relationships among organisms

Taxonomy

science of classifying organisms

makes sense of the diversity of life in order to study it better

Aristotle Began arranging organisms according to their physical

similarities (previously – useful vs. harmful)

animals: red blood (vertebrates) vs. no red blood

plants: size; herbs, shrubs, trees

Benefits of Classification Helps biologists

keep track of living things

study their differences and similarities

learn how living things are related to one another through evolution (the process by which living things change over generations)

save time and effort

Benefits of Classification Today’s system:

natural system since it represents genuine relationships between organisms

the more closely organisms are related to each other, the more features they have in common

hierarchical – categories are grouped according to size in a series of successively larger ranks

Carolus Linnaeus Swedish physician and naturalist (1707-1778)

“Father of taxonomy”

Established 1st orderly system of classifying living things

Introduced binomial nomenclature

His system was able to impose a much-needed order on the study of life

Classification Groups Taxons (groups) range in order of specificity

General to specific Domain

Kingdom

Phylum

Class

Order

Family

Genus

Species

Dichotomous Key A dichotomous key is a tool that allows the user to

determine the identity of organisms in the natural world, such as trees, wildflowers, mammals, reptiles, rocks, and fish.

"Dichotomous" means "divided into two parts". Therefore, dichotomous keys always give two choices in each step.

1. a. wings covered by an exoskeleton – go to step 2 b. wings freely observed – Go to step 3 2. a. body has a round shape ……….ladybug a red beetle with black spots b. body has an elongated shape ……….grasshopper a green insect that hops 3. a. wings point out from the side of the body ……….dragonfly an insect that

is 10- 15 cm long and lives in marshes b. wings point to the posterior of the body ……….housefly a flying insect with

red eyes and an annoying buzz

Hints: Use constant characteristics rather than variable ones. (Flowers change with

the seasons) Use measurements in centimeters or meters rather than terms like "large"

and "small". If possible, start both choices of a pair with the same word.

NOTE: Finish the dichotomous key with a description of the organism

Dichotomous Key for conifers

This key is not a dichotomous key

Broad leaved versus coniferous trees

Conifers have needles or scales

Broad leaved examples

Branching

Simple and Compound leaves

Simple and compound leaves

Simple leaves

Leaf Shapes

Lobed leaves

Palmately compound leaf

Pinnately Compound Leaf

Bipinnately Compound Leaf

State if the leaf is simple, compound, needles or scales

Leaf shapes

Leaf margins

Evaluate this key

Evaluation of the key The characteristics are not constant. Flowers bloom

and seed pods are visible at different seasons

The trees are not described at the end of the key

Large and small are used instead of real measurements

Yes and no questions are used.

Therefore, this dichotomous key is not as good as it should be!