Section 19.2Modern Evolutionary

Classification

Standards

• LS 4.1 Evaluate scientific data collected from analysis of molecular sequences, fossil records, biogeography, and embryology. Identify chronological patterns of change and communicate that biological evolution is supported by multiple lines of empirical evidence that identifies similarities inherited from a common ancestor (homologies).

Key Questions

1. What is the goal of evolutionary classification?

2. What is a cladogram?

3. How are DNA sequences used in classification?

4. What does the tree of life show?

Vocabulary

• Phylogeny

• Clade

• Cladogram

• Derived character

Evolutionary Classification

• Phylogeny- the study of the evolutionary history of lineages of organisms

• The goal of evolutionary classification is to group species into larger categories that reflect lines of evolutionary descent, rather than overall similarities and differences.

• Clade- a group of species that includes a single common ancestor and all descendants of that ancestor—living and extinct

Cladograms

• Cladistic analysis compares carefully selected traits to determine the order in which groups of organisms branched off from their common ancestors.

• A cladogram links groups of organisms by showing current hypotheses about how evolutionary lines, or lineages, branched off from common ancestors.

Building Cladograms

1 2

3

Derived Characters

• Derived character-a trait that arose in the most recent ancestor of a lineage and was passed to its descendants

Losing Traits

• Snakes are reptiles, which are tetrapods (four limbs).

• But, snakes do not have four limbs.

• However, the ancestors of snakes did have four limbs.

• Somewhere in the lineage leading to modern snakes, that trait was lost.

• Because distantly related groups can sometimes lose a character, systematists are cautious about using the absence of a trait as a character in their analyses.

Interpreting a Cladogram

DNA in Classification

1. Genes as Derived Characters

2. New Techniques Suggest New Trees

1. Genes as Derived Characters

• In general, the more derived genetic characters two species share, the more recently they shared a common ancestor and the more closely they are related in evolutionary time.

• DNA analysis suggests that these two vultures are more closely related to storks than they are to other vultures.

Hooded vulture

Jabiru stork

Turkey vulture

2. New Techniques Suggest New Trees

• Giant pandas and red pandas puzzles taxonomists for years.

• DNA analysis revealed that the giant panda shares a more recent common ancestor with bears.

• DNA places red pandas, however, outside of the bear clade.

Raccoon Red panda Giant panda Bear

The Tree of All Life

• The tree of life illustrates current hypotheses regarding evolutionary relationships among the taxa within the three domains of life.

• Domain Bacteria

• Domain Archaea

• Domain Eukarya

Bacteria

Archaea

Eukarya

Domain Bacteria

• Unicellular

• Prokaryotic

• Autotroph or heterotroph

• Cell wall made of peptidoglycan

• Can be found in many places (soil, water, on and inside the human body)

Domain Bacteria

Streptococcus pyogenes

Escherichia coli

Domain Archaea

• Unicellular

• Prokaryotic

• Autotroph or heterotroph

• Cell wall lacks peptidoglycan

• Cell membrane contains lipids that are not found in any other organism

• Live in extreme environments (high temp, high salt, high pressure, etc.)• Volcanic hot springs • Brine pools• Black organic mud (absence of oxygen)

Domain Archaea

Domain Eukarya

• Domain Eukarya • Kingdom Protista

• Kingdom Fungi

• Kingdom Plantae

• Kingdom Animalia

Kingdom Protista

• Unicellular, colonial, or multicellular

• Eukaryotic

• Autotroph of heterotroph

• Some- cell wall made of cellulose

• Some- chloroplasts

• Very diverse

• Scientists usually classify these organisms by what they are not

Kingdom Protista

Amoeba

Paramecium

cilia

Kingdom Protista

Algae

Kingdom Protista

Slime molds

Kingdom Protista flagellum

Euglena

Kingdom Fungi

• Most multicellular, some unicellular

• Eukaryotic

• Heterotroph (obtain nutrients from organic matter)

• Cell wall made of chitin

Kingdom Fungi

Kingdom Fungi

Kingdom Plantae

• Multicellular

• Eukaryotic

• Autotroph

• Cell wall made of cellulose

• Chloroplasts

Kingdom Plantae

Kingdom Animalia

• Multicellular

• Eukaryotic

• Heterotroph

• No cell wall

• No chloroplasts

Section 19.2 Exit Ticket

1. How can a cladogram/phylogenetic tree depict evolutionary relationships between organisms of different species?

The End