What keys do you know about?

EPISD Middle School Science Standards Based Curriculum 2015-2016

Dichotomous Keys are:

•hierarchical•mutually exclusive• exhaustive

EPISD Middle School Science Standards Based Curriculum 2015-2016

Mutually Exclusive

• There are only two choices • If it is in one group, it cannot be in another

• Example:– Organism has a hard exoskeleton– Organism has a hard endoskeleton

The organism cannot have both a hard exoskeleton and a hard endoskeleton.

EPISD Middle School Science Standards Based Curriculum 2015-2016

Hierarchical

EPISD Middle School Science Standards Based Curriculum 2015-2016

Exhaustive

• Includes ALL possible variation combinations• It has already been broken down to its

smallest group

• What happens when a new species is discovered or bred?

EPISD Middle School Science Standards Based Curriculum 2015-2016

Example of how to build your own Dichotomous key using office supplies

Uses electricity Does not use electricity

EPISD Middle School Science Standards Based Curriculum 2015-2016

Dichotomous Key*ALWAYS start at question 1

1. a. uses electricity………...................................go to 2 b. does not use electricity………………………..….go to 32. a. has letter, symbols, and number keys……..keyboard b. has number and symbol keys ………………….calculator3. a. long, slender objects………………………………..go to 4 b. not long, slender objects………………………….go to ?4. a. made from plastic…………………………………….go to? b. made from something other then plastic….go to?

EPISD Middle School Science Standards Based Curriculum 2015-2016

EPISD Middle School Science Standards Based Curriculum 2015-2016

Example of a Dichotomous key for insects

Image taken from http://www.rivercenter.uga.edu/education/watersheds2006/gps.htm

Is it an Ant or a Grasshopper? 1. a. has six legs……………………………….….go to 2

b. does not have six legs…………………..go to 4 2. a. has an antennae…………………………..go to 3

b. does not have an antennae…………..go to 53. a. large hind legs for hopping…….grasshopper

b. no large hind legs for hopping………….Ant

EPISD Middle School Science Standards Based Curriculum 2015-2016

Common Names vs. Scientific Namesmountain lion Felis concolor

gray wolf Canis lupus

humans Homo sapiens

saguaro Cactus Carnegiea gigantea

dog Canis familiaris

EPISD Middle School Science Standards Based Curriculum 2015-2016