Dichotomous Key Reading


okay now we're gonna learn how to read a

dichotomous key

there are dichotomous keys out there for

everything you can get one for reptiles

that are found in South Carolina it is

something that scientists use out in the

field to identify living things so here

is a plant example for discovering the

identity of a leaf so you can identify a

tree from its leaf okay so dichotomous

keys has that prefix die what is that

prefix mean again

hopefully you said to sew a dichotomous

key is called that because there are two

options at each question to help you

move on to the next one okay so first we

need to the very first thing you do when

you are ready to use the dichotomous key

is to choose what you're identifying and

focus on it so let's pick one leaf to

focus on and we're gonna focus on this

one okay and we're not gonna worry about

the other ones right now or just gonna

focus on this one so when we're ready to

start identifying we're focusing in on

one organism we are always always going

to start at the very top with one a and

when you do a new organism

once again you start at the top at one a

and so one a needle leaves okay

needle leaves are like pine tree leaves

they look like little needles this one

does not have needle leaves so the

answer to a is no so we go to be non

needle leaves when the answer is yes you

go across

okay so needle leaves no so we go down

non needle leaves yes so we're gonna go

across and this says go to three so

that's what we're gonna do we're gonna

come down to question three now okay a

simple leaf as in a single leaf well

this looks like it has one two three

four five six seven leaves so that's not

right so go down to be compound leaves

made of leaflet yes it has multiple

small Leafs making it up so we're gonna

go to seven come on down to seven it

says leaflets attached at one single

point well it looks like they're all

coming from right here so yes well since

it's yes we're gonna go across chestnuts

so this leaf belongs to the chestnut

tree okay all right so we have

identified a leaf let's do another one

for practice let's try this one okay so

now we're starting over with the new

organism so that means

gotta go back all the way up to start

with one a hay needle leaves no go down

non needle leaves

yes go to three simple leaves a single

leaf yes go to four smooth edge no

jagged edge yes go to six leaf edge is

small and too tight no I don't think so

leaf edge is large and thorny yes this

is a holly leaf okay so the clues to

remember one focus on one organism at a

time to always start at one a with a new

organism three if the answer to a is no

go to be okay

when the answer is yes move over and do

what it tells you to do

all right so get out your worksheet and

time to practice on your own