Basic Concepts in Phylogenetics Flashcards

Questions and Answers

What is synamorphology?

A trait unique to an ancestor

A trait found only in one species

A homologous trait shared by some members of a group (correct)

An evolutionary innovation

What are synapomorphies?

Often evolutionary innovations

What distinguishes a synapomorphy?

A shared, derived characteristic that is common between an ancestor and its descendants.

How are synapomorphies useful?

They are useful in building a phylogenetic tree. Signup and view all the answers

Provide an example of a synapomorphy.

The change from 5 toes to a single hoof in the ancestor of horses and donkeys. Signup and view all the answers

When defining birds, wings are considered to be:

A synapomorphy. Signup and view all the answers

What are lobe-fins in tetrapods considered?

A synapomorphy. Signup and view all the answers

What does the increase in the number of thoracolumbar vertebrae in the Afrotheria clade represent?

A synapomorphy. Signup and view all the answers

What are feathers classified as?

A synapomorphy in birds. Signup and view all the answers

What is a plesiomorphy?

An ancestral character shared by two or more taxa. Signup and view all the answers

Define taxa.

A group or rank in a biological classification where related organisms are classified. Signup and view all the answers

The trait of a bird species having a mask is considered to be:

A plesiomorphy. Signup and view all the answers

Why can't a plesiomorphic character reveal information about relationships?

It can appear anywhere within the phylogenetic tree. Signup and view all the answers

In a clade including lizards and dinosaur crocodiles, having legs is:

Plesiomorphic. Signup and view all the answers

In respect to grouping the evolution of living things, how are plesiomorphies compared to synapomorphies?

Not as useful. Signup and view all the answers

Why is hair considered a plesiomorphy and a symplesiomorphy in primates?

Hair is an ancestral mammalian character shared by all primates. Signup and view all the answers

What constitutes a monophyletic group?

A common ancestor and all of its descendants. Signup and view all the answers

What are aves classified as?

Monophyletic. Signup and view all the answers

What does the 'scissor test' determine?

The group is monophyletic. Signup and view all the answers

What defines a polyphyletic group?

Lacks a common ancestor. Signup and view all the answers

What is a paraphyletic group?

A monophyletic group where some descendants have been removed. Signup and view all the answers

How is the identification of a paraphyletic group shown using the 'scissor test'?

By needing to trim away the part of the separated branch. Signup and view all the answers

What does the difference between monophyletic, polyphyletic, and paraphyletic groups pertain to?

Variation in common ancestry. Signup and view all the answers

What is convergent evolution?

The process where unrelated species evolve similar physical characteristics. Signup and view all the answers

Provide an example of convergent evolution.

Falcon: ancestral bird -> Bat: ancestral mammal -> Pterodactyl: ancestral reptile. Signup and view all the answers

What happens to analogous characteristics due to convergent evolution?

They are similar. Signup and view all the answers

Match the following organisms with their analogous features:

Bat = Wings similar to birds Butterfly = Wings similar to birds Beetle = Similar body shape to other insects Dragonfly = Wings similar to other insects Signup and view all the answers

What is the shared physical structure of bats and birds most likely due to?

Convergent evolution. Signup and view all the answers

What role does convergent evolution play in producing analogous traits?

Sources from the cladistic term of homoplasy. Signup and view all the answers

Study Notes

Basic Concepts in Phylogenetics

Synapomorphology refers to a homologous trait shared by some members of a group but not all.
Synapomorphies are commonly evolutionary innovations that help identify relationships among species.
A synapomorphy is a shared, derived trait that distinguishes a clade from other organisms, demonstrating common ancestry.
Synapomorphies are essential in constructing a phylogenetic tree, which maps evolutionary relationships.

Examples of Synapomorphies

Transition from five toes to a single hoof is an example of a synapomorphy in horses and donkeys.
In mammals, features like hair, milk, and a four-chambered heart contrast with reptiles and serve as synapomorphies.
Wings are considered a synapomorphy when defining birds.
Lobe-fins in tetrapods are recognized as a synapomorphy.

Features in Clades

The vertebral column in mammals is often conserved, but an increased number of thoracolumbar vertebrates in the Afrotheria clade (including elephants) represents a derived trait.
Feathers are identified as a synapomorphy specifically for birds.

Plesiomorphies and Taxa

A plesiomorphy is an ancestral trait shared by multiple taxa, which does not provide specific information about relationships in phylogenetic trees.
Taxa refer to groups classified in biological hierarchy based on related organisms.

Functional Trait Examples

The mask trait in bird species is categorized as a plesiomorphy.
Plesiomorphies are generally less useful in determining evolutionary relationships compared to synapomorphies.

Clades and Group Definitions

A monophyletic group includes a common ancestor and all its descendants.
Aves (birds) form a monophyletic group.
The "scissor test" is used to assess monophyly; a single cut should suffice.
A polyphyletic group lacks a direct common ancestor.
A paraphyletic group consists of a monophyletic section with some descendants excluded.

Testing Group Types

Identifying a paraphyletic group using the "scissor test" requires trimming part of a derived branch.
Differences among monophyletic, polyphyletic, and paraphyletic groups revolve around variations in common ancestry.

Evolutionary Processes

Convergent evolution describes how unrelated species develop similar traits due to analogous lifestyles.
An illustration of convergent evolution includes the similarities between falcons (birds), bats (mammals), and pterodactyls (reptiles).
Analogous characteristics, like those found in bats and birds, arise from convergent evolution rather than shared ancestry.

Characteristics of Analogous Structures

Due to convergent evolution, analogous characteristics appear similar across different species despite dissimilar evolutionary backgrounds.
Examples of organisms exhibiting analogous structures include bats, butterflies, beetles, and dragonflies.

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Description

This quiz features flashcards designed to help you understand fundamental concepts in phylogenetics, including terms like synapomorphology and synapomorphies. Test your knowledge on how these traits relate to evolutionary relationships among organisms. Perfect for students looking to grasp the basics of evolutionary biology.