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Biology 11: Domain Eukarya

Purpose: Apply the Kingdom classification system to study a diversity of organisms

Compare the characteristics of a prokaryotic cell with those of a eukaryotic cell

Understand the main characteristics of Kingdom Protista

Text: 330 and 337 *This is required reading!

What are Eukaryotes?

Introduction

The domain system of classification is based on biochemical differences, revealing that there are three different types of organisms.

Which of the domains above have prokaryotic cells? Bacteria and Archae

Which domain above has eukaryotic cells? Eukarya

Name the eukaryotic kingdoms: Plantae, Animalia, Protista and Fungi

Biology 11: Domain Eukarya, Kingdom Protista

Prokaryotes vs. Eukaryotes

What are the major differences between prokaryotic and eukaryotic cells?

Character Prokaryotic EukaryoticPlasma Membrane Y Y

Cell WallSome Only Plants

Nuclear MembraneN Y

MitochondriaN Y

Endoplasmic ReticulumN Y

RibosomesY Y

What is one error with the diagram above?

-Prokaryotic cell is much too large.

Eukaryotic Cell Evolution


Where do we think the endoplasmic reticulum and nuclear envelope came from?

-Infolding of the plasma membrane.

Mitochondria and chloroplasts most likely came from the endosymbiosis of aerobic prokaryotes. What does this mean?

-Aerobic prokaryotes (does require O2 for cellular respiration) lived symbiotically and then permanently inside cells.

Common Eukaryotic Life Cycles

Which of the three types of life cycles has a diploid adult stage and only the gametes are haploid?

-Diplontic

Which life cycle has a haploid adult and only the zygote is diploid?

-Haplontic

Which type of life cycle has a haploid adult called a gametophyte and a diploid adult called the sporophyte?

Alternation of generations.

Which life cycle is found in:

a) Humans: Diplontic b) Protists and Fungi: Haplontic

c) Plants: Alternation of Generations


Kingdom Protista

Purpose: Protists are the most primitive form of eukayotic life and provide biologists with an opportunity to investigate how eukaryotic cells were first formed.

Text Pages: 330 to 339 *This is required reading!

Kingdom Protista is a “catch-all” grouping where biologists have put eukaryote organisms that do not easily fit into the other Animal Kingdoms. For this reason, the life forms found here are very diverse:

Generally, protists can be defined as:

-Mostly unicellular (that are sometimes colonial or multicellular) eukaryotes that are not Fungi, Plants or Animals.

-Protists are usually found in aquatic habitats or inside of hosts (endosymbionts and parasites).


The great diversity of organisms found in the Kingdom Protista is organized based on two characteristics:

a) Mode of Nutrition

Autotrophic:

-Make their own food through photosynthesis

Heterotrophic:

-Engulf food using pseudopods

-Absorption of food across the cell membrane.

-Parasitic or endosymbiosis

b) Mode of Locomotion

-Flagellae

-Cilia

-Pseudopodia

*Watch Protist Movement video.


https://www.youtube.com/watch?v=NwZvfzMB2bg

Protist Diversity

The great variety of protists we have today is a product of Secondary Endosymbiosis, the process through which an autotrophic protest becomes endosymbiotic in a heterotrophic protist:

Below is a phylogenetic tree demonstrating a recent organization of protists into different groups:


Chromalveolata

This supergroup is controversial because it contains such a great diversity of protists

a) Diatoms are autotrophic unicellular algae with a silica rich cell wall.

They are key primary producers in fresh and salt water ecosystems.

b) Dinoflagellates have two flagellae (one is free and the other is wrapped in a groove around the cell).

They can be autotrophic, heterotrophic or mixotrophic and are important food sources.

Dinoflagellates cause “red tide”. What is this and why is it important to know about on the Pacific Coast?

-Dinoflagellate blooms cause the red colour and they are dangerous as they can produce toxins. These toxins can accumulate in filter feeders and cause shellfish poisoning in humans.

c) Brown Algae are multicellular and get their brown colour from photosynthetic pigment.

We know them as brown seaweeds and they create important ecosystems for marine organisms (kelp forests).

Brown algae have a “holdfast” (not roots!) that attaches to rocks. They can also have air bladders that function in reproduction and to keep the algae blades close to the surface.

Brown algae are used in sushi, cosmetics and as a stabilizer in ice cream.


d) Water Molds are unicellular decomposers, although they can also be parasitize fish skin or gills and plants (Irish Potato Famine).

e) Ciliates are heterotrophs and mixotrophs that use their cilia to move and sweep food into their mouths.

Paramecium are a good example of ciliates and you will observe them in the Protist Lab.

f) Plasmodium is a parasitic protist that is transferred to humans through mosquito bites and causes the disease Malaria. The protist feeds on red blood cells, causing them to die.

*Watch Malaria: Human Host from HHMI


http://www.hhmi.org/biointeractive/malaria-human-host

Rhizaria and Unikonta

Rhizaria and Unikonta are both controversial clades and they included together here as they both contain Amoebas.

a) Amoebas are heterotrophic or parasitic (amoebic dysentery) and reproduce by binary fission.

Amoebas move using pseudopodia, temporary extensions of the cell into which they push their cytoplasm. They engulf food material through phagocytosis.

b) Plasmodial Slime Mold and Cellular Slime Mold are important decomposers. They also have interesting puzzle solving abilities and infrastructure planning potential!


Archaeplastids

Commonly known as algae, most Archaeplastids get their nutrients through photosynthesis and are important in aquatic ecosystems because they:

1. Are primary producers

2. Extract CO2 and release O2.

a) Red Algae are autotrophic, often multicellular and gain their colour from accessory pigment that masks the green chlorophyll.

Some Red Algae look like coral as they have calcium carbonate embedded in their cell walls.

Red Algaes are used as nori in sushi, stabalizers ice cream and other products and to make Agar.

b) Green Algae can be unicellular, multicellular or colonial and gain their colour from green chlorophyll.

What are some characteristics that demonstrate Green Algae’s close relationship to land plants?

1. Contain Chlorophyll A and B

2. Cell Wall

3. Eukaryotic

4. Store starch produced through photosynthesis in a pyrenoid (found in chloroplasts).

Green Algae examples include:

1. Chlamydomonas (Unicellular)

Reproduce sexually in favourable conditions and asexually in unfavourable.

Follow the haplontic life cycle.


2. Volvox (Colonial)

Each volvox colony is a hollow ball of many algae cells and will eventually burst to release smaller daughter colonies.

All cells in the colony of identical, but functionally individuals.

3. Ulva (Multicellular)

Ulva is multicellular an exhibits cell specialization. This is very evident in its alternation of generation life cycle.


Evolution of Multicellularity

How are multicellular organisms different from unicellular organisms?

-In unicellular organisms life’s activities all occur in one cell, whereas multicellular organisms can have specialized cells dealing with particular activites.

Below is an image depicting how a unicellular protist may have eventually given rise to multicellular organisms.

1. An ancestral colony may have formed when a cell dividing and its offspring remain attached to one another.

2. Next, the cells in the colony may have become specialized and interdependent

3. Later on, additional specialization among the cells may have led to distinctions between sex cells (gametes) and non-reproductive cells (somatic cells).

Multicellular organisms have evolved in three different lineages (Brown Algae, Fungi and Animals, Red and Green Algae).

One theory suggests that 1 billion years ago two Unikot lineages divided to produce Fungi and Animals. Evidence of this division comes from molecular clocks and morphological similarities.


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