Outline:

-Characteristics of eukaryotes-Protists-Fungi-Plants-Animals

Evolution of the nuclear envelope

Fig 20_1

-The nuclear envelope may have evolved gradually from the cell membrane

-As cells got bigger folded cell membranes allowed better access to external environment

-Eukaryote DNA is more similar in structure to archea than bacteria (introns)

Endosymbiotic theory: Mitochondria and Chloroplasts are derived from once free-living bacteria

Fig 20_2

-Mitochondria were free living aerobic bacteria

-Chloroplasts were free living photosynthetic bacteria (cyanobacteria)

-Each became incorporated into a eukaryotic cell, formed a symbiotic relationship, can no longer live outside of cells

Evidence that mitochondria were once free living bacteria

-Mitochondria are similar in size to bacteria

-Have their own DNA, circular without introns

-Use ribosomes that are similar to bacterial ribosomes for translation of RNA to proteins

-Divide by simple fusion

-Have a double layered membrane

Evidence that chloroplasts were once free living bacteria

-Posses circular DNA

-Use prokaryotic machinery

-Photosynthesis occurs using the 3 systems found in prokaryotes

The protists are the most basal eukaryotes

-Every eukaryrote that is not a plant, animal, of fungus is a protist (negative definition)

-Phylogeny not well resolved

-Evolved mitochondria and chloroplasts

-Evolved sex

-Evolved multicellularity

Sex evolved in protists

What is sex?

- Fusion of haploid gametes to form a diploid individual. Sex combines genomes from 2 parents

What is the advantage of sex?

- Greatly increases genetic diversity of a population, which improves adaptive ability of a population. In asexual populations diversity can only arise by mutation

What selection pressures lead to the evolution of sex?

- Stress

Protists have independently evolved multicellularity several times

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Fig 20_8

Phylogeny of protists - 5 major groups are not shown because their phylogenetic position is uncertain

Ancestors of plants

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Pg 385

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Fig 20_16

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Fig 20_17

-Red algae live in deeper marine environments

-Green algae are direct ancestors of plants, most are marine, few exceptions

-Exhibit alternating life cycle

Ancestors of animals

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Pg 387

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Fig 20_19QuickTime™ and a

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-Choanoflagellates are the ancestors of animals

-Single celled heterotrophs

-Filter feed bacteria from water

-May be colonial, resemble sponges

-Genetically closest group to animals

Is this organism multicellular?

My brothers dog Nada

Is this organism multicellular?

A sponge

Is this organism multicellular?

Stromatolites in Shark Bay Aus.

http://www.youtube.com/watch?v=tpdIvlSochk

The road to multicellularity - cooperation in dictyostelium discoideum

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Fig 20_24

Multicellularity

What is the advantage of being multicellular?

-Cell sizes are limited by surface to volume dynamics and physical-structural issues

-Cells can specialize

What is multicellularity?

-Multiple cells that are permanently associated with integrated activities

Colonial organisms

-Permanently associated cells with no coordinated activities

Aggregates

-Single cells that group together