Modern Classification Lesson

Modern Classification

By Kerry Dabbs

Scientists classify living things according to their relatedness based on things like:

*homologous structures - body arrangements that are similar

​These vertebrates are all fairly closely related in evolutionary terms.
They share the same basic arrangement and number of limb bones

Multiple Choice

Looking at the homologous bone structures, which 2 organisms appear to be most closely related?

• dolphin and bat

• horse and cat

• human and cat

• human and horse

Scientists classify living things according to their relatedness based on things like:

*embryology - similarities in development of their embryos

​These vertebrates are all fairly closely related in evolutionary terms. They show very similar embryological development.

Scientists classify living things according to their relatedness based on things like:

*fossil record - layers of earth reveal fossils that are similar but show gradual changes over time

​These "horse" fossils organized from top (newest),
to bottom (oldest), show very similar structure but definite changes in size an proportions over millions of years.

Multiple Choice

Older fossils from similar species will be found ___________ newer fossils

• above

• below

Scientists classify living things according to their relatedness based on things like:

*DNA sequences - the more closely related a species is, the more similar their DNA sequences will be, and the more similar the resulting proteins they build will be

​These vertebrate amino acid/protein sequences show similarities indicating level of relatedness. The more similar the sequence, the more closely related 2 species are.

Multiple Choice

According to the protein sequence chart, the most related organisms are

• mouse, rat, chicken

• human, pig, dog

• human, pig, dog, frog

​All living things fit into one of the 3 DOMAINS of life:

Archaea and Eukarya are connected on the same evolutionary line after Bacteria branch off, indicating that they are more closely related to each other

The black vertical line at the bottom represent s a single common ancestor that all of them arose from

​Domains

​Kingdoms

​This is another representation of the same information about domains.
This one shows the kingdoms inside each domain

Multiple Choice

How many kingdoms are there in Domain Bacteria?

• 1

• 2

• 4

• 6

Multiple Choice

How many kingdoms are there in Domain Eykarya?

• 1

• 2

• 4

• 6

Multiple Select

Which 2 domains have organisms that don't have a nuleus?

• Bacteria

• Archaea

• Eukarya

• Animals

​This graphic shows another way to display the modern classification model.

Time would be moving left to right, with present day being represented as the 6 kingdoms on the right and the oldest common ancestor that they all evolved from, on the left.

Multiple Choice

Which 2 domains appear to be the most closely related?

• Bacteria, Archaea

• Bacteria, Fungi

• Bacteria, Eukarya

• Eukarya, Archaea

Multiple Choice

What is it that indicates a close evolutionary relationship?

• a more recent branch, indicating a recent common ancestor

• a similar color on the chart

• a similar sounding name

Phylogenetic Trees and Cladograms

• are ways to show evolutionary relationships

• can be interpreted in a similar way

Phylogenies

Each lineage has a part of its history that is unique to it alone and parts that are shared with other lineages.​

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Phylogenies trace patterns of shared ancestry between lineages!

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Shared lineage = common ancestry!

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Phylogenies

The process of evolution produces a pattern of relationships between species.

​

As species evolve and adaptations are inherited, their evolutionary paths split.

Phylogenies

When a lineage splits (speciation), it is represented as branching on a phylogeny.

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When a speciation event occurs, a single ancestral lineage gives rise to two or more daughter lineages.

Multiple Choice

Which group of animals on this tree are most closely related to birds?

• Saurischian dinosaurs

• Ornithischian dinosaurs

• Crocodiles

• None of these are related to birds

Multiple Choice

According to this tree, which of these animal phyla are most closely related?

• Arthropoda & Mollusca

• Arthropoda & Chordata

• Chordata & Mollusca

Multiple Choice

Where is the alligator and T. rex's common ancestor?

• Point A

• Point B

• Point C

• Point D

Cladograms

​A cladogram is similar, but shows relationships based on shared physical homologies.

The starting point of the branch represents the common ancestor of all the organisms shown.
Characteristics listed are common to all organisms beyond that point on the branch.

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For this class, we will treat phylogenies and cladograms as the same.

Multiple Choice

Which letter represents the most recent common ancestor of sponges and mushrooms?

• A

• B

• C

• D

• E

Clades

A clade is a grouping that includes a common ancestor and all the descendants (living and extinct) of that ancestor. 

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Imagine clipping a single branch off the phylogeny — all of the organisms on that clipped branch make up a clade.

Multiple Choice

Which trait(s) do conifers have?

• vascular tissue only

• vascular tissue and seeds

• vascular tissue, seeds and flowers

• seeds only

Multiple Choice

All the animals to the right of the hagfish would have the common characteristic of -

• Fur
• Claws or nails
• Lungs
• Jaws

Multiple Choice

What do both the squirrel and lion have in common that the other animals do not?

• They are both vertebrates

• They both have lungs

• They are both mammals

• They both lose their canine teeth.

Multiple Select

What do amphibians, birds, prosimians and humans all have in common? Check all that apply.

• Hair

• Endothermic

• Eukaryotic

• Tetrapod

• Vertebrate