It is estimated that humans lost their body hair______ years ago.
2 answers:
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Dichotomous keys are useful to identify organisms according to their morphological traits. The given key provides enough macroscopic morphological traits to identify these Arachnida species.
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A dichotomous key is a significantly useful tool to classify organisms. The key provides an easy and fast way for identification by describing different morphological traits, leading you to the correct taxonomic classification.
The key provides morphological descriptions about different taxonomic groups in an easy way to identify these traits in your individual.
The term <em>dichotomous</em> refers to how information is provided. You will always have two options (a and b, or 1 and 2), and you will have to choose one of them according to the characteristics of your organism.
In the exposed example, as the key provides morphological traits, we will separate the organisms<u><em> into two groups</em></u>:
- the group that has the trait
- the group that does not have it.
By recognizing each trait in each of the individuals, we will get to identify the species.
1
(a) Abdomen <u>with a </u><u>tail</u> --------------------------- The only option is E
(b) Abdomen <u>without a </u><u>tail</u><u> </u>---------------------- All the others A, B, C, D, F, G
2 ---<em>Only for group A, B, C, D, F, G---</em>
(a) <u>Legs</u><u> much longer </u>than abdomen and cephalothorax ----------A and G
(b)<u> </u><u>Legs</u><u> not much longer</u> than abdomen and cephalothorax----- B, C, D, F
3 ---<em>Only for group A, G---</em>
(a) <u>Hairs</u> on the legs -----------------------------------The only option is A
(b) <u>No hairs</u> on the legs ------------------------------ G
4 ---<em>Only for group B, C, D, F---</em>
(a) Cephalothorax or <u>abdomen</u><u> segmented</u> ----------------The only option is D
(b) Cephalothorax or a<u>bdomen not segmented</u> ----------- B, C, F
5 ---<em>Only for group B, C, F---</em>
(a) Abdomen and cephalothorax <u>of the same size</u> --------The only option is F
(b) Abdomen and cephalothorax <u>of different size</u> -------B, C
6 ---<em>Only for group B, C---</em>
(a) Body <u>covered with long</u><u> hair</u><u> </u>----------------------------------The only option is C
(b) Body<u> </u><u>not covered with</u><u> hair</u> ------------------------------------B
A → <em>Tegenaria domestica</em>
B → <em>Ixodes hexagonus</em>
C → <em>Tyroglyphus longior</em>
D → <em>Chelifer tuberculatus</em>
E → <em>Abaliella dicranotarsalis</em>
F → <em>Poecilotheria regalis</em>
G → <em>Odielus spinosus</em>
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