Question

1. according to your cladogram, which two species are more closely related: worms and spiders or worms and ants? how do you know?
2. according to your cladogram, what species are dragonflies most closely related to? how do you know?

Explanation:

Sub - Question 1

To determine the relatedness, we use the concept of clades in a cladogram. Species in the same more recent (closer) clade are more related. Spiders and ants are both arthropods, while worms are in a different group (e.g., annelids). Worms and spiders/ants: Spiders and ants share a more recent common ancestor (as they are both arthropods with jointed appendages, exoskeletons, etc.). Worms (annelids) have a more distant common ancestor with arthropods. So worms and spiders/ants - actually, worms and either spiders or ants? Wait, no: Spiders and ants are both arthropods, worms are annelids. So when comparing worms - spiders and worms - ants, since spiders and ants are in the same major group (arthropods), and worms are outside, but the question is worms - spiders vs worms - ants. Wait, maybe the cladogram has spiders and ants sharing a more recent node with each other, but when compared to worms, we look at the last common ancestor of worms - spiders and worms - ants. If the last common ancestor of worms and spiders is more recent than worms and ants, or vice versa? Wait, no, typically, spiders and ants are both in the arthropod phylum, worms (like earthworms) are annelids. The common ancestor of arthropods and annelids is more ancient. But within arthropods, spiders (arachnids) and ants (insects) are in different classes but same phylum. So when comparing worms (annelid) to spider (arthropod) and worm to ant (arthropod), the distance from worm to spider and worm to ant would be similar? Wait, maybe the cladogram in question has spiders and ants sharing a more recent branch with each other, but when connected to worms, the branch point for worms and the arthropod group (spiders + ants) is at a certain node. Wait, perhaps the correct answer is that worms and spiders (or worms and ants - but actually, spiders and ants are more closely related to each other, but the question is worms - spiders vs worms - ants. Wait, maybe the cladogram shows that spiders and ants are in a clade that is closer to each other, and worms are outside. So when comparing worms - spiders and worms - ants, we look at the last common ancestor of worms and spiders, and worms and ants. If the last common ancestor of worms and spiders is at the same level as worms and ants (since both spiders and ants are arthropods), but maybe in the cladogram, spiders and ants share a more recent node with each other, but when connected to worms, the branch for worms splits off before the arthropod branch. So the distance from worm to spider and worm to ant is the same? No, maybe the cladogram has spiders and ants in a clade where ants are more closely related to other insects, and spiders to other arachnids, but when compared to worms, both spiders and ants are arthropods, so the relationship between worms and spiders and worms and ants: actually, the correct approach is that in a cladogram, the closer two species are on the tree (the fewer the number of nodes between their branches), the more closely related they are. So if the branch of worms splits off, and then later the branch for arthropods splits into spiders and ants (or a node that leads to spiders and ants), then the last common ancestor of worms and spiders is the same as the last common ancestor of worms and ants (the node where the arthropod branch and annelid branch split). But if in the cladogram, spiders and ants are in a clade that is more closely related (i.e., the node connecting spiders and ants is closer to the present than the node connecting the arthropod - annelid split), then when comparing worms - spiders a…

In a cladogram, the species most closely related to dragonflies will share the most recent common ancestor (i.e., be connected by the shortest branch or closest node). Dragonflies are insects (or in a group like arthropods). So we look for the species that is in the same closest clade as dragonflies. For example, if the cladogram has dragonflies and another insect (like ants, beetles, or damselflies) sharing a recent node, that species is the closest. The reasoning is that relatedness is based on the recency of the LCA, so the species with the fewest evolutionary divergences from dragonflies (closest node on the cladogram) is the most closely related.

Answer:

To determine which pair (worms and spiders or worms and ants) is more closely related, we analyze the cladogram:

• Relatedness in a cladogram is determined by the recency of the last common ancestor (LCA). Species with a more recent LCA (closer nodes on the cladogram) are more related.
• If the cladogram shows that spiders and ants belong to the same major clade (e.g., Arthropoda) and worms belong to a different clade (e.g., Annelida), we compare the distance from worms to spiders and worms to ants. Typically, worms and spiders (or worms and ants, depending on the cladogram’s node structure) are more closely related because they share a more recent LCA (fewer evolutionary branches between their lineages) than the alternative pair. For example, if the cladogram’s node for the LCA of worms and spiders is closer (in time/branching order) than the node for worms and ants, worms and spiders are more related (and vice versa).

Sub - Question 2